80MGF

Service Literature 80MGF SERIES UNITS

80MGF series units are midefficiency gas furnaces manufactured with tubular heat exchangers formed of aluminized or stainless steel. 80MGF units are available in heating capacities of 45,000 to 140,000 Btuh and cooling applications up to 5 tons. Refer to Engineering Handbook for proper sizing. Units are factory equipped for use with natural gas. A kit is available for conversion to LPG operation. All 80MGF units built proir to September 98 use electronic (direct spark) ignition. 80MGF11 model units are equipped with the Lennox SureLight ignition system. The 80MGFX unit meets the California Nitrogen Oxides (NOx) Standards and California Seasonal Efficiency requirements. All units use a redundant gas valve to assure safety shutoff as required by A.G.A. or C.G.A. The heat exchanger, burners and manifold assembly can easily be removed for inspection and service by simply disconnecting gas, unplugging wiring harness and spark wires and removing four screws holding the heat exchanger in place. Then the heat exchanger slides out of the cabinet. All specifications in this manual are subject to change. Procedures outlined in this manual are presented as a recommendation only and do not supersede or replace local or state codes. In the absence of local or state codes, the guidelines and procedures outlined in this manual (except where noted) are recommended only and do not constitute code. Units may be installed in upflow, downflow or horizontal position. The heat exchanger is designed for upright or horizontal use only. When the unit is installed in the downflow position, the heat exchanger is field removed and reinstalled so it is upright when the cabinet is inverted. No field conversion is required when the unit is installed in the horizontal position. Introduction . . . . . . . . . . . . . . . . . . . . . . . . Specifications . . . . . . . . . . . . . . . . . . . . . . Blower Data . . . . . . . . . . . . . . . . . . . . . . . Parts Identification . . . . . . . . . . . . . . . . . . I Unit Components . . . . . . . . . . . . . . . . . . II Installation . . . . . . . . . . . . . . . . . . . . . . . 1 2 5 7 9 19 TABLE OF CONTENTS III Start Up . . . . . . . . . . . . . . . . . . . . . . . . . Preliminary Seasonal Checks . . . . . Heating Start Up . . . . . . . . . . . . . . . . IV Heating System Service Checks . . . V Typical Operating Characteristics . . . VI Maintenance . . . . . . . . . . . . . . . . . . . . VII Wiring and Sequence of Operation . VIII SureLight Control Troubleshooting . 19 20 20 20 22 24 26 40
Corp. 9801L2 Revised 082004

Page 1

1998 Lennox Industries Inc.

SPECIFICATIONS
Model No. Input Btuh (kW) Output Btuh (kW) lA.F.U.E. California Seasonal Efficiency Flue size connection diameter Temperature rise range in. (mm) round 30 - 60 (17 - 33) in wg. (Pa) 80MGF2(X)-45 45,000 (13.2) 36,900 (10.8) 80.1% 75.4% 76.4% 3 (76) 45 - 75 (25 - 42) .50 (125) 1/2 (13) 9x7 229 x 178 1/4 (187) Tons kW 1, 1-1/2 or 2 3.5, 5.3 or 7.0 130 (59) 120 volts b LPG/propane kit Twinning Kit Up Flow/Horizontal UpFlow/Horizontal Filter and Filter Rack Kits }No. }N & size of filt i f filters in. ( i (mm) )
Down flow
Down-flow Filter Filt Kit Catalog No. No. & Size of Filters in. (mm) 60 hertz 10 x 7 254 x 178 1/3 (224) 2, 2-1/2 or 3 7.0, 8.8 or 10.6 9x7 229 x 178 1/4 (187) 1, 1-1/2 or 2 3.5, 5.3 or7.0 135 (61) 1 phase (less than 12 amps) All models 10 x 7 254 x 178 1/3 (224) 2, 2-1/2 or 3 7.0, 8.8 or 10.6 80MGF2-60 80MGF3(X)-60 80MGF2-75 80MGF3(X)-75 60,000 (17.6) 49,200 (14.4) 80.5% 75.9% 80.1% 76.8% 4 (102) 75,000 (22.0) 61,700 (18.1) 80.0% 76.8%

_F (_C)

High static certified by A.G.A./C.G.A.

Gas Piping Size I.P.S. Natural or LPG/propane Blower wheel nominal diameter x width di t idth Blower motor output hp (W) in. mm

Nominal cooling that th t can b added be dd d Shipping weight lbs. (kg) 1 package

Electrical characteristics

Optional Accessories (Must Be Ordered Extra) b LB-69845L (38K84) 15L3801 5 lbs. (2 kg)

Single (32J02) Ten Pack (66K64) (1) 16 x 20 x 1 (406 x 508 x 25) LB-69843A (32J01) 3 lbs. (1 kg)

(2) 16 x 20 x 1 (406 x 508 x 25) LB-79239A (67J91) 79J15 10 lbs. (4 kg)

Down-flow Combustible Floor Base Sidewall Power Venting Kit Hanging Bracket Kit
lAnnual Fuel Utilization Efficiency based on U.S. furnaces. }Polyurethane frame type filter is furnished with kit.
Filters are not furnished with kit and must be ordered extra. DOE test procedures and according to FTC

25 lbs. (11 kg) 15 lbs. (8 kg)

combustion system rating for non-weatherized

LB-69957 (46J66)
labeling regulations.

Isolated

Page 2

SPECIFICATIONS continued
Model No. Input Btuh (kW) Output Btuh (kW) lA.F.U.E. California Seasonal Efficiency Flue size connection diameter Temperature rise range in. (mm) round 45 - 75 (25 - 42) in wg. (Pa) .50 (125) 1/2 (13) 12 x 8 305 x 203 1/2 (373) Tons kW 2, 2-1/2, 3, 3-1/2 or 4 7.0, 8.8, 10.6, 12.3 or 14.1 140 (64) 120 volts b LPG/propane kit Twinning Kit Up Flow/Horizontal UpFlow/Horizontal Filter and Filter Rack Kits }No. & size of filters in. (mm) Down flow Down-flow Filter Kit Catalog No. No. & Size of Filters in. (mm) LB-79239A (67J91) Single (32J02) Ten Pack (66K64) (1) 16 x 20 x 1 (406 x 508 x 25) 60 hertz 12 x 9 305 x 229 3/4 (560) 3-1/2, 4, 5 or 6 12.3, 14.1, 17.6 or 21.1 175 (79) 1 phase (less than 12 amps) All models 80MGF4(X)-75 75,000 (22.0) 61,700 (18.1) 80.0% 76.3% 80.1% 76.5% 4 (102) 35 - 65 (19 - 36) .65 (162) 80MGF3/4(X)-100 80MGF4/5(X)-100 100,000 (29.3) 82,000 (24.0) 80.0% 77.0%

_F (_C)

High static certified by A.G.A./C.G.A.

Gas Piping Size I.P.S. Natural or LPG/propane Blower wheel nominal diameter x width di t idth Blower motor output hp (W) in. mm

Nominal cooling that th t can b added be dd d Shipping weight lbs. (kg) 1 package

Electrical characteristics

Optional Accessories (Must Be Ordered Extra) b LB-69845L (38K84) 15L3801 LB-69845K (81J14) 5 lbs. (2 kg) Single (46J14) Ten Pack (66K65) (1) 20 x 20 x 1 (508 x 508 x 25) 3 lbs. (1 kg)

LB-69843A (32J01)

(2) 16 x 20 x 1 (406 x 508 x 25) 10 lbs. (4 kg) 79J15 LB-79239B (67J92) 25 lbs. (11 kg) 15 lbs. (8 kg)
combustion system rating for non-weatherized

Down-flow Combustible floor Base Sidewall Power Venting Kit Hanging Bracket Kit
lAnnual Fuel Utilization Efficiency based on U.S. furnaces. }Polyurethane frame type filter is furnished with kit.
Filters are not furnished with kit and must be ordered extra. DOE test

10 lbs. (4 kg)

LB-69957 (46J66)
procedures and according to FTC labeling regulations.

Isolated

Page 3

SPECIFICATIONS continued
Model No. Input Btuh (kW) Output Btuh (kW) lA.F.U.E. California Seasonal Efficiency
Flue size connection diameter Temperature rise range _F (_C) in wg. (Pa) .50 (125) 1/2 (13) 12 x 8 305 x 203 1/2 (373) Tons kW 2, 2-1/2, 3, 3-1/2 or 4 7.0, 8.8, 10.6, 12.3 or 14.1 175 (79) 120 volts b LPG/propane kit Twinning Kit UpFlow/Horizontal Filter and Filter Rack Kits }No. & size of filters in. (mm Catalog No. Down-flow Filter Rack No. & Size of Filters in. mm LB-79239B (67J92) 60 hertz 12 x 9 305 x 229 3/4 (560) 3-1/2, 4, 5 or 6 12.3, 14.1, 17.6 or 21.1 190 (86) 1 phase (less than 12 amps) All models in. (mm) round 80.0% Not Available 4 (102) 45 - 75 (25 - 42) .65 (162) 80MGF3/4-120 80MGF4/5(X)-120 80MGF4/5-140 140,000 (41.0) 114,800 (33.6) 80.1% 75.5% 80.0% Not Available 5 (127) 120,000 (35.2) 98,400 (28.8)

High static certified by A.G.A./C.G.A.

Gas Piping Size I.P.S. Natural or LPG/propane in. (mm) Blower wheel nominal diameter x width Blower motor output hp (W) in. mm

Nominal cooling that can be added Shipping weight lbs. (kg) 1 package

Electrical characteristics

Optional Accessories (Must Be Ordered Extra) b LB-69845K (81J14) 15L3801 Single (46J14) Ten Pack (66K65) (1) 20 x 20 x 1 (508 x 508 x 25) LB-69843A (32J01) 5 lbs. (2 kg) Single (58J93) Ten Pack (66K66) (1) 20 x 20 x 1 (508 x 508 x 25) 3 lbs. (1 kg)

(2) 16 x 20 x 1 (2) 406 x 508 x 25 10 lbs. (4 kg) 79J15 LB-79239C (67J93) 12 lbs. (5 kg)

Down-flow Combustible Floor Base Sidewall Power Venting Kit Hanging Bracket Kit

25 lbs. (11 kg) 15 lbs. (8 kg)

LB-69957 (46J66)

lAnnual Fuel Utilization Efficiency based on U.S. DOE test procedures and according to FTC labeling regulations. Isolated combustion system rating for non-weatherized furnaces. }Polyurethane frame type filter is furnished with kit.
2 in. x 5 in. (51 mm x 127 mm) flue adaptor furnished with -140 input furnaces for connection to furnace induced draft blower. Filters are not furnished with kit and must be ordered extra.

Page 4

BLOWER PERFORMANCE DATA

80MGF2-45, 80MGF2-60 AND 80MGF2-75 BLOWER PERFORMANCE
External Static Pressure in. w.g. 0 .05 .10 .15 .20 .25 .30 .40 .50 .60 .70
NOTE

Air Volume at Various Blower Speeds High cfm 1270 1245 1220 1195 1170 1140 1110 1060 990 900 800 L/s 600 590 575 565 550 540 525 500 465 425 380 Medium-High cfm 980 975 975 965 960 950 940 910 880 810 740 L/s 460 460 460 455 455 450 445 430 415 380 350 Medium-Low cfm 770 770 770 765 760 760 760 750 740 690 630 L/s 365 365 365 360 360 360 360 355 350 325 295 cfm 570 565 565 560 560 555 550 545 540 530 520 Low L/s 270 265 265 265 265 260 260 255 255 250 245

Pa 0 12 25 37 50 62 75 100 125 150 175

All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished) in place. Also see Filter Air Resistance table

80MGF3-60 AND 80MGF3-75 BLOWER PERFORMANCE

External Static Pressure in. w.g. 0 .05 .10 .15 .20 .25 .30 .40 .50 .60 .70
NOTE

Air Volume at Various Blower Speeds High cfm 1425 1415 1400 1385 1370 1350 1330 1280 1210 1135 1070 L/s 670 670 660 655 645 635 630 605 570 535 505 Medium-High cfm 1240 1230 1220 1200 1180 1160 1140 1095 1040 985 920 L/s 585 580 575 565 555 545 540 515 490 465 435 Medium-Low cfm 1000 995 990 985 980 970 955 925 900 860 800 L/s 470 470 465 465 460 460 450 435 425 405 380 cfm 800 800 795 795 790 780 770 750 720 680 630 Low L/s 380 380 375 375 375 370 365 355 340 320 300

Pa 0 12 25 37 50 62 75 100 125 150 175

All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished) in place. Also see Filter Air Resistance table

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80MGF4-75, 80MGF3/4-100 AND 80MGF3/4-120 BLOWER PERFORMANCE

External Static Pressure in. w.g. 0 .05 .10 .15 .20 .25 .30 .40 .50 .60 .70
NOTE

Air Volume at Various Blower Speeds High cfm 1830 1815 1800 1875 1750 1725 1700 1650 1600 1550 1480 L/s 865 855 850 885 825 815 800 780 755 730 700 Medium-High cfm 1600 1585 1570 1550 1530 1515 1500 1460 1420 1380 1330 L/s 755 750 740 730 720 715 710 690 670 650 630 Medium cfm 1325 1320 1315 1310 1300 1290 1275 1245 1210 1170 1130 L/s 625 625 620 620 615 610 600 590 570 550 535 Medium-Low cfm 1070 1070 1070 1065 1060 1050 1040 1020 1000 980 960 L/s 505 505 505 505 500 495 490 480 470 460 455 cfm 880 880 880 875 875 870 870 860 840 820 790 Low L/s 415 415 415 415 415 410 410 405 395 385 375

Pa 0 12 25 37 50 62 75 100 125 150 175

All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished) in place. Also see Filter Air Resistance table

80MGF4/5-100, 80MGF4/5-120 AND 80MGF4/5-140 BLOWER PERFORMANCE

External Static Pressure in. w.g. 0 .05 .10 .15 .20 .25 .30 .40 .50 .60 .70
NOTE

Air Volume at Various Blower Speeds High cfm 2450 2440 2430 2415 2400 2380 2360 2310 2260 2180 2100 L/s 1155 1150 1145 1140 1135 1125 1115 1090 1065 1030 990 Medium-High cfm 2160 2155 2150 2135 2120 2105 2090 2050 2000 1950 1890 L/s 1020 1015 1015 1010 1000 995 985 965 945 920 890 Medium cfm 1970 1965 1960 1950 1940 1930 1915 1870 1810 1750 1700 L/s 930 925 925 920 915 910 905 880 855 825 800 Medium-Low cfm 1700 1695 1690 1685 1680 1675 1670 1650 1610 1560 1520 L/s 800 800 800 795 795 790 790 780 760 735 715 cfm 1500 1500 1495 1495 1490 1480 1470 1440 1410 1370 1330 Low L/s 710 710 705 705 705 700 695 680 665 645 630

Pa 0 12 25 37 50 62 75 100 125 150 175

All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished) in place. Also see Filter Air Resistance table

FILTER AIR RESISTANCE

cfm (L/s) 0 (0) 200 (95) 400 (185) 600 (280) 800 (375) 1000 (470) 1200 (560) 1400 (655) 1600 (750) 1800 (845) 2000 (935) 2200 (1030) 2400 (1125) 2600 (1220) in. w.g. (Pa) 0.00 (0) 0.01 (2) 0.03 (7) 0.04 (10) 0.06 (15) 0.09 (22) 0.12 (30) 0.15 (37) 0.19 (47) 0.23 (57) 0.27 (67) 0.33 (82) 0.38 (95) 0.44 (110)

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80MGF PARTS IDENTIFICATION and ORIENTATION

VENT ADAPTER

CABINET TOP

HEAT EXCHANGER ASSEMBLY FLUE BOX

COMBUSTION AIR BLOWER

PRESSURE SWITCH PRIMARY LIMIT 80MGF CABINET

FRONT ACCESS PANEL BURNER ASSEMBLY TRANSFORMER

NOx TURBULATOR

CONTROL BOARD

SECONDARY LIMITS

CABINET BOTTOM

BLOWER ASSEMBLY DOOR INTERLOCK SWITCH

FIGURE 1

HEATING COMPONENTS (shown in horizontal position)

ROLLOUT SWITCH (2)

PRIMARY LIMIT

COMBUSTION AIR PROVE SWITCH

MANIFOLD Left Bottom Back

BURNERS

Front Right HEAT EXCHANGER GAS VALVE COMBUSTION AIR BLOWER COLLECTOR

Top

FIGURE 2 Page 7

80MGF BURNER ASSEMBLY (Shown With SureLight ignitor)

SURELIGHT IGNITOR BURNER BOX TOP VEST PANEL UPPER BURNER MOUNTING RAIL LOWER BURNER MOUNTING RAIL FLAME SENSOR ROLLOUT SWITCHES

BURNER

HEAT EXCHANGER PRIMARY LIMIT Top

ORIFICE GAS VALVE

Back Left Right BURNER BOX Front Bottom

MANIFOLD

FIGURE 3 80MGF BLOWER DOOR COMPONENTS BLOWER ACCESS (SureLight MODEL SHOWN)
To Access Blower: 1 Turn off power to unit and disconnect L1 and L2 line voltage power. 2 Disconnect thermostat wiring connections from furnace control board. 3 Disconnect blower leads from control board. 4 Disconnect J1 from P1. 5 Disconnect 6 pin P156 from control board. 6 Disconnect 9 pin P58 from control board. 7 Disconnect sensor wiire from center of board. 8 Remove screws (2) and lift panel from unit.

7 3

5
Top

6 8 2 1
FIGURE 4 Page 8
Back Left Bottom

Right

Front

IUNIT COMPONENTS (Figures 1, 2, 3)

80MGF unit components are shown in figure 1. The blower controls, gas valve and burners can be accessed by removing the front access panel. A separate blower access door is located behind the front access panel. Electrical control components are mounted to the blower access door. 80MGF units are factory equipped with bottom return air panels. The panels are designed to be field removed as required for bottom air return. Indentations on side of units, show where side air return opening should be cut during installation.

ditions. The diagnostic LED lights red (not flashing) to indicate control board failure. Table 3 shows how to interpret the other LED modes. Pre-Purge On a call for heat, the combustion air blower begins operating. If the combustion air prove switch closes, the combustion air blower continues to operate for 45 seconds (pre-purge) before allowing ignition. Pre-purge allows the heat exchanger to be cleared of combustion products and to introduce fresh air for combustion. If the combustion air prove switch does not close, the combustion air blower continues to run indefinitely (until the prove switch closes). Post-Purge After a demand, the combustion air blower continues to operate for 5 seconds (post-purge) before stopping. Postpurge allows the heat exchanger to be cleared of combustion products. Ignition Control The ignition control is a direct spark ignition control module integral to the furnace control. See figure 5. When there is a call for heat, the control delays ignition until combustion air blower operation has been proved and pre-purge period has elapsed. It then opens the gas valve and generates a spark to ignite the burners. Trial for ignition lasts for 7 seconds. At the same time, the control begins monitoring the flame sensor. If the flame current is too weak (less than 1 microamp) or if the burners do not ignite (within the 7 second ignition trial), the control will shut off spark and the combustion air blower and de-energize the gas valve. Flame current should be between 1 and 5 microamps to keep the gas valve open. See figure 23. The control will attempt to ignite the burners up to two more times. Each time the control restarts the ignition sequence, it begins with a 45 second pre-purge. If flame is not sensed after the third trial, the control locks out. Lockout means that the control shuts off the gas valve, spark and combustion air blower for 60 minutes. At the end of 60 minutes the control completely resets and will attempt ignition up to three times. The control can be manually reset before the end of 60 minutes by momentarily turning off power to the unit.

ABlower Door Components (Figure 4)

Electrical burner control and blower control components are located on the outside surface of the blower access door. Jackplugs allow the blower door to be easily removed for blower service. Located on the blower door are the unit transformer (T1), the furnace control (A3) and door interlock switch (S51). Furnace control (A3) combines the function of a burner ignition control and blower control.

1 Control Transformer (T1)

A transformer located on the blower door provides power to the low voltage section of the unit. Transformers on all models are rated 30VA with a 120V primary and a 24V secondary.

2Door Interlock Switch (S51)

A door interlock switch rated 16A at 125VAC is located on the blower access door. The switch is wired in series with line voltage. When the blower door is removed the unit will shut down.

3 Ram Control (A3)

The furnace control combines burner ignition functions with blower control functions. Some early model 80MGF units utilize a furnace control manufactured by RAM Electronics Corporation. The RAM" board is a printed circuit board which controls the blower, gas valve, combustion air blower and ignition spark. It also monitors the flame, limit and gas valve operation. The control has a nonadjustable, factory preset on" fan timing (45 seconds). Fan off" timings are adjustable. The board utilizes both 120 and 24VAC. See figure 5. The board is also equipped with a diagnostic LED for use when troubleshooting the unit. When the furnace is idle (blower off and no heating or cooling demand), the diagnostic LED flashes at a slow steady rate. On a call for heat, the diagnostic LED begins flashing at a fast rate and the combustion air blower is energized. The LED flashes different codes to indicate problem con-

DANGER
Shock hazard. Spark related components contain high voltage. Disconnect power before servicing. Control is not field repairable. If control is inoperable, simply replace entire control. Can cause injury or death. Unsafe operation will result if repair is attempted.

Page 9

RAM CONTROL (A3)

SPARK OUTPUT

LINE VOLTAGE TERMINAL CONNECTIONS

24VAC VOLT TERMINAL CONNECTIONS

See Table 2 for Terminal Functions

See Table 2 for Terminal Functions FAN-OFF TIMING SWITCHES THERMOSTAT CONNECTIONS

DIAGNOSTIC LED

FIGURE 5 TABLE 1
Furnace Control A3 Limit Response During Operation Response Condition Combustion Air Blower Gas Valve Supply Air Blower Diagnostic LED

Loss of Flame Sensed Before End of 45 second Blower On Delay (3 or Fewer Trials for Ignition) Loss of Flame Sensed After 45 second Blower On Delay (3 or Fewer Trials for Ignition) Loss of Flame Sensed (More Than 3 Trials for Ignition) Flame Sensed Without Demand Primary or Secondary Limit Open Rollout Switch Open Combustion Air Prove Switch Open

On

On (Spark Starts Within 0.8 seconds)

When flame is sensed, the indoor blower starts after a 45 second delay. Gas valve remains open and blower continues to run until demand stops, flame sensor senses loss of flame, a limit opens or the prove switch opens. If any of these events occur during a thermostat demand, the gas valve closes and the diagnostic LED registers the error condition (table 1). Blower Control and Timings

On

Fast Flash

DANGER
On Fast Flash

On

Off Then On With Spark After PrePurge

Electrical Shock Hazard. This control contains field adjustable switches and also contains line voltage. Make sure power is disconnected before making any field adjustments or performing any service procedure. NOTE If fan off" time is set too low, residual heat in heat exchanger may cause primary limit S10 to trip resulting in frequent cycling of blower. If this occurs, adjust blower to longer time setting. Fan ON" timing (time that the burners operate before the supply air blower starts) is fixed at 45 seconds and cannot be adjusted.

Off

Off

Off

2 Flashes

On

Off

On

5 Flashes

On On On

Off Off Off

On On On

4 Flashes 4 Flashes 3 Flashes

Page 10

Fan OFF" timings (time that the blower operates after a heating or cooling demand has been satisfied) are determined by the arrangement of switches on the furnace control board. See figure 5. To adjust fan off " timings, gently reposition the switches to a new timing position. Figure 6 shows the various fan off" timings and how switches should be positioned. 80MGF1, 2, 3, 4 and 6 units are shipped with a factory fan off" setting of 180 seconds. 80MGF5 and 7 units are shipped with factory "off" setting of 60 seconds. Fan off" time will affect comfort and efficiency and is adjustable to satisfy individual applications. The fan off" timing is initiated after a heating or cooling demand but not after a blower demand (that is, when indoor thermostat switch is changed from ON to AUTO and heating/cooling demand is not present, the blower stops immediately). TABLE 2
FURNACE CONTROL A3 TERMINAL DESIGNATIONS Terminal Type Function Y G R W C 120VAC HOT AUX CMB BLWR ACB HEAT ACB COOL VALVE 24VAC HOT GROUND FLAME SENSE PSW Screw Strip Screw Strip Screw Strip Screw Strip Early Units 1/4" Spade Later Units Screw Strip 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade Cooling Demand Blower Demand 24VAC to Thermostat Heating Demand 24VAC Common Line Voltage In Line Voltage Out (Switched) Switched 120VAC to Combustion Air Blower Switched 120VAC to Blower Heating Tap Switched 120VAC to Blower Cooling Tap 24VAC to Gas Valve 24VAC In From Transformer To Cabinet Ground Flame Microamp Sensing 24VAC In From Pressure Switch Switch Open: Prohibits Ignition Switch Closed: Allows Ignition 24VAC In From Limits Limit Open: Closes Gas Valve Limits Closed: Allows Ignition 24VAC to Limit Train and Pressure Switch 24VAC In From Rollout Switches

FAN-OFF TIME ADJUSTMENT SWITCHES

LOCATED ON FURNACE CONTROL (A3) Fan-Off Timings Switch 1 2 Off Off On On Off On Off On Timing Seconds 90 120 180 240

FIGURE 6 Diagnostic LED The furnace control is equipped with a diagnostic LED used for troubleshooting the unit and the control. LED functions are shown in table 3. TABLE 3
Furnace Control A3 Diagnostic LED LED State Steady On Slow Flash Fast Flash Meaning Control Failure Normal Operation and No Call For Heat Normal Operation with Call For Heat Remedy Replace Control ------Failed to Sense or Sustain Flame. Check Gas Valve, Burners, Spark Electrode and Wire, Flame Sensor. Replace Control If All OK. Failed to Prove Combustion Blower Operation or Blocked Vent. Repair or Replace as Necessary. Check Primary Limit, Rollout Switches and Secondary Limits. Find source of Overtemperature. If all OK, Reset or Replace Limits as Necessary. Check Gas Valve. If OK, Check Flame Sensor.

Two Flashes

Control Lockout

Three Flashes

Pressure Switch Open

Four Flashes

Open Limit

Five Flashes

Flame Sensed and Gas Valve Not Energized.

HI LIMIT IN HI LIMIT OUT ROLLOUT IN

1/4" Spade 1/4" Spade 1/4" Spade

Page 11

4 EGC Control (A3)

Some early model 80MGF units are equipped with an integrated ignition/blower control (EGC1 or EGC2) which controls ignition, safety circuits, blower operation, fan off timing, and allows for thermostat connection and troubleshooting. The EGC is a printed circuit board which is divided into two sections, 120 and 24VAC. Line voltage comes into the board on the 120VAC side. See figure 8. Terminal designations are listed in tables 5 and 6. Ignition Control 80MGF units use the EGC direct spark integrated ignition control. The EGC controls and monitors the entire sequence of operation. On a call for heat from the thermostat the control monitors the combustion air blower pressure switch. The control will not begin the heating cycle if the pressure switch is closed (by-passed). Once the pressure switch is determined to be open, the combustion air blower is energized. When the differential in pressure across the pressure switch is great enough, the pressure switch closes and a 15 second pre-purge period begins. After the pre-purge period, the gas valve will open and ignition (spark) will be attempted for 10 seconds. After ignition, the control initiates a ten second flame stabilization period. The flame stabilization period allows the burners to heat up and the flame to stabilize. Once flame is established, the control will constantly monitor the burner flame using flame rectification. Flame failure response time is 0.8 seconds. If the initial attempt for ignition fails, the sequence is repeated up to five times. After the fifth trial, the control goes into Watchguard"*. During watchguard mode, the entire unit will be de-energized for one hour. After one hour the control will repeat the ignition sequence. Watchguard may be manually reset by breaking and remaking thermostat demand. *NOTEIf flame is established beyond the 10 second flame stabilization period then lost, the control resets for five more ignition trials. The control can be reset five times during one unsatisfied thermostat demand, providing a maximum of 25 trials for ignition. Safety Circuits During the entire heating demand the control monitors the safety circuits. If the primary or secondary heating limits open, the control de-energizes the main gas valve and combustion air blower while the indoor blower remains energized. When the limit automatically resets, the ignition sequence also resets. If either of the limits trip five consecutive times during one unsatisfied thermostat demand, the control will go into watchguard for one hour. The control monitors main valve voltage. If voltage is sensed

when no voltage should be present, the control de-energizes the combustion air blower which terminates voltage to the valve. The system goes into hard lock-out which is reset only by removing power to the unit. If flame is sensed when no flame should be present, the control will energize the combustion and indoor blowers. The unit will remain locked in this sequence until the flame is no longer sensed or the main power is turned off to reset the control.

DANGER
Shock hazard. Avoid personal injury. Make sure to disconnect power before changing fan off" timing.

Blower Operation / Fan Off Timings Fan off" timing (time that the blower operates after the heat demand has been satisfied) can be adjusted by moving the jumper on the EGC blower control board. Figure 7 shows the various fan off" timings and how jumper should be positioned. To adjust fan off " timing, gently disconnect jumper and reposition across pins corresponding with new timing. Unit is shipped with a factory fan off" setting of 180 seconds. Fan on" time is factory set at 45 seconds following the opening of the main gas valve and is not adjustable. Fan off" time will affect comfort and efficiency and is adjustable to satisfy individual applications. The fan off" timing is initiated after a heating demand but not after a cooling demand. NOTE If fan off" time is set too low, residual heat in heat exchanger may cause primary limit S10 to trip, resulting in frequent cycling of blower. If this occurs, adjust blower to longer fan off" time setting. FAN-OFF TIME ADJUSTMENT
TIMING JUMPER To adjust fan-off timing: Remove jumper from EGC and select one of the other pin combinations to achieve the desired time.

180

60

TIMING PINS (seconds) Leave jumper off for 240 second fan-off timing.

120

90 FIGURE 7

Thermostat Connection Thermostat wires are connected to the terminal strip found on the EGC control board.

Page 12

Troubleshooting The EGC control board is equipped with two diagnostic green LEDs to indicate the mode of failure. The LED lights are marked DIAG #1 and DIAG #2. The codes are given in table 4. On the EGC1 only, the last failure code is stored in memory and may be retrieved by depressing and holding the memory recall button. When this button is depressed, the LEDs will signal the last failure code in memory. Power must be restored to the control (depress blower interlock switch) within one minute of blower access panel removal in order to retain memory. To clear the memory of the stored failure code, remove main power and short the jumper next to the diagnostic button for five seconds.
DIAG #2 Simultaneous Flash On

TABLE 4
EGC DIAGNOSTIC CODES DIAG #1 DIagnostic Condition Simultaneous Flash Flash Power ON". Normal Operation. Increased flash rate indicates there is a heating demand. Primary or Secondary Limit Switch Open. Auto-Reset Switch. Pressure Switch Watchguard, pressure switch opened during operation or condensate drain blocked. Watchguard, burners failed to ignite. Flame sensed without valve energized. Roll-out Switch Open. Manual-Reset Switch. Circuit board self-check failure or ignition/blower control is wired incorrectly.

Flash Alternate Flash Off Flash Continuous On

Off Alternate Flash Flash On Continuous On

EGC2 INTEGRATED CONTROL

8 9 10 11 12 13 14

*
15

* *
16

* * *

NOTE: EGC1 board will have terminal (#15) for 7 ACB low speed. NOTE: EGC1 board will have terminal (#16) for ACB Heat speed. 6 5 4 DIAGNOSTIC LEDS

DIAGNOSTIC MODULE

BLOWER TIME ADJUSTMENT JUMPER

THERMOSTAT TERMINAL STRIP (DETACHABLE)

7 8

EDGE CONNECTION

24VAC PLUG P20

3 2 1 RED DIAGNOSTIC BUTTON DIAGNOSTIC CODE ERASE JUMPER (EGC1 only. Depress button and hold (Remove power to control and short pins for for display of last failure code.) 10 seconds to erase previous code.)

FIGURE 8

Page 13

TABLE 5
BLOWER CONTROL A15 TERMINAL DESIGNATIONS Terminal Designation Type Function (See fig. 8) R G W Y C 1 2 3 4, 5, 6 7 8 9 10 11 12, 13 14 15 16 Screw Strip Screw Strip Screw Strip Screw Strip Screw Strip 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade 24VAC to Thermostat (Red) Manual Fan Input from Thermostat (Green) Heat Demand Input from Thermostat (White) Cool Demand Input from Thermostat (Yellow) Common Ground to Thermostat 24VAC Hot from Transformer 24VAC Return to Transformer 24VAC Ground 120VAC Return 120VAC Common 120VAC Return 120VAC Common Input Combustion Blower (Line Voltage) Heat Only Accessory (Line Voltage) 120VAC Hot to Transformer 120VAC Hot Input Accessories (Line Voltage) ACB Cool Speed (Line Voltage) EGC1 ACB Low Cont. Speed (Line Voltage) EGC2 ACB Heat Speed (Line Voltage) ACB Heat Speed (Line Voltage)

5Flame Sensor (11 models)

A flame sensor is located on the left side of the burner support. See figure 9. The sensor is mounted on a bracket in the burner support and the tip protrudes into the flame envelope of the leftmost burner. The sensor is fastened to burner supports and can be removed for service without removing any part of the burners. During operation, flame is sensed by current passed through the flame and sensing electrode. The SureLight control allows the gas valve to remain open as long as flame signal is sensed.
NORMAL FLAME SIGNAL u 0.7 MICROAMPS LOW FLAME SIGNAL v 0.7 MICROAMPS MINIMUM FLAME SIGNAL v 0.15 MICROAMPS

1/4 in. 7 mm  1/32 in. 0.79 mm BURNER

11/16 in. 18 mm  1/32 in. 0.79 mm 3/16 in. 4.7 mm

FLAME

SIDE VIEWSENSOR

END VIEW

TABLE 6
EGC CONTROL JACK/PLUG 20 TERMINAL DESIGNATIONS Pin # Function 1 2 3 4 5 6 7 8 9 Rollout Switch Out Spare Gas Valve Common Pressure Switch Return Hi Limit Return / Pressure Switch Out Flame Sensor Gas Valve Out High Limit Out Rollout Switch Return

FIGURE 9 NOTE The 80MGF furnace contains electronic components that are polarity sensitive. Make sure that the furnace is wired correctly and is properly grounded.

6 SureLight Ignition System A3 (11 models)

All 80MGF11 model units are equipped with the Lennox SureLight ignition system. The system consists of ignition control board (figure 11 with control terminal designations in table 10) and ignitor (figure 12). The board and ignitor work in combination to ensure furnace ignition and ignitor durability. The SureLight integrated board controls all major furnace operations. The board also features two LED lights for troubleshooting and two accessory terminals rated at (4) four amps. See table 9 for troubleshooting diagnostic codes. Table 7 and 8 show jack plug terminal designations. Units equipped with the SureLight board can be used with either electronic or electromechanical thermostats without modification. The SureLight ignitor is made of durable siliconnitride. Ignitor longevity is also enhanced by voltage ramping by the control board. The board finds the lowest ignitor temperature which will successfully light the burner, thus increasing the life of the ignitor.

DANGER
Shock hazard. Disconnect power before servicing. Control is not field repairable. If control is inoperable, simply replace entire control. Can cause injury or death. Unsafe operation will result if repair is attempted.

Page 14

TABLE 7
SureLight BOARD J156 (J2) TERMINAL DESIGNATIONS PIN # 1 FUNCTION Ignitor Not Used Ignitor Neutral Combustion Air Blower Line Voltage Not Used Combustion Air Blower Neutral

2 3 4 5 6

TABLE 8
SureLight BOARD J58 (J1) TERMINAL DESIGNATIONS PIN # 1 FUNCTION Primary Limit In Gas Valve Common Roll Out Switch Out Gas Valve 24V Pressure Switch In Pressure Switch and Primary Limit Out Not Used Roll Out Switch In Ground

2 3 4 5 6 7 8 9

ELECTROSTATIC DISCHARGE (ESD) Precautions and Procedures

CAUTION
Electrostatic discharge can affect electronic components. Take precautions during furnace installation and service to protect the furnaces electronic controls. Precautions will help to avoid control exposure to electrostatic discharge by putting the furnace, the control and the technician at the same electrostatic potential. Neutralize electrostatic charge by touching hand and all tools on an unpainted unit surface, such as the gas valve or blower deck, before performing any service procedure.

aElectronic Ignition On a call for heat the SureLight control monitors the combustion air blower pressure switch. The control will not begin the heating cycle if the pressure switch is closed (by passed). Once the pressure switch is determined to be open, the combustion air blower is energized. When the differential in the pressure switch is great enough, the pressure switch closes and a 15second prepurge begins. If the pressure switch is not proven within 21/2 minutes, the control goes into WatchguardPressure Switch mode for a 5minute reset period. After the 15second prepurge period, the SureLight ignitor warms up for 20 seconds after which the gas valve opens for a 4second trial for ignition. 80MGF units with board 63K89, 24L85 or 56L83: the ignitor stays energized for the first second of the 4second trial. Units with board 97L48: ignitor stays energized for the full 4second trial for ignition. If ignition is not proved during the 4second period, the control will try four more times with an inter purge and warmup time between trials of 35 seconds. After a total of five trials for ignition (including the initial trial), the control goes into WatchguardFlame Failure mode. After a 60minute reset period, the control will begin the ignition sequence again. The SureLight control board has an added feature that prolongs the life of the ignitor. After a successful ignition, the SureLight control utilizes less power to energize the ignitor on successive calls for heat. The control continues to ramp down the voltage to the ignitor until it finds the lowest amount of power that will provide a successful ignition. This amount of power is used for 255 cycles. On the 256th call for heat, the control will again ramp down until the lowest power is determined and the cycle begins again. bFan Time Control The fan on time of 45 seconds is not adjustable. Fan off time (time that the blower operates after the heat demand has been satisfied) can be adjusted by flipping the dip switches located on the SureLight integrated control. The unit is shipped with a factory fan off setting of 90 seconds. Fan off time will affect comfort and is adjustable to satisfy individual applications. See figure 10. FAN-OFF TIME ADJUSTMENT
60sec. 90sec. 120sec. 180sec.

To adjust fanoff timing, flip dip switch to desired setting.

FIGURE 10

Page 15

The SureLight board is equipped with two LED lights for troubleshooting. The lights are found just above the 24VAC terminal strip see figure 8. The diagnostic codes are listed below in table 9. TABLE 9 DIAGNOSTIC CODES
MAKE SURE TO ID LEDS CORRECTLY: REFER TO INSTALLATION INSTRUCTIONS FOR CONTROL BOARD LAYOUT.

LED #1
SIMULTANEOUS SLOW FLASH SIMULTANEOUS FAST FLASH

LED #2
SIMULTANEOUS SLOW FLASH SIMULTANEOUS FAST FLASH

DESCRIPTION
Power Normal operation Also signaled during cooling and continues fan. Normal operation signaled when heating demand initiated at thermostat. Primary or Secondary limit open. Units with board 63K8901 or 24L85: Limit must close within 5 trials for ignition or board goes into one hour limit Watchguard. Units with board 56L83 or 97L48: Limit must close within 3 minutes or board goes into one hour limit Watchguard. Pressure switch open or has opened 5 times during a single call for heat; OR: Blocked inlet/exhaust vent; OR: Condensate line blocked; OR: Pressure switch closed prior to activation of combustion air blower. Watchguard burners fail to ignite. Flame sensed without gas valve energized. Rollout switch open. OR: 9 pin connector improperly attached. Circuit board failure or control wired incorrectly. Main power polarity reversed. Switch line and neutral. Low flame signal. Measures below .7 microAmps. Replace flame sense rod. Improper main ground or line voltage below 75 volts; OR: Broken ignitor; OR: Open ignitor circuit.

SLOW FLASH

ON

OFF ALTERNATING SLOW FLASH SLOW FLASH ON ON ON OFF FAST FLASH SLOW FLASH ALTERNATING FAST FLASH

SLOW FLASH ALTERNATING SLOW FLASH OFF SLOW FLASH ON OFF ON SLOW FLASH FAST FLASH ALTERNATING FAST FLASH

NOTE Slow flash equals 1 Hz (one flash per second). Fast flash equals 3 Hz (three flashes per second). Drop out flame sense current < 0.15 microAmps

SURELIGHT INTEGRATED CONTROL BOARD

SureLight Ignitor
SURELIGHT IGNITOR

FIGURE 12 TABLE 10
TERMINAL DESIGNATIONS ACB COOL Blower Cooling Speed (Line Volt) ACB HEAT Blower Heating Speed (Line Volt) PARK Alternate Blower Speeds (Dead) Continuous Low Speed Blower ACB LOW Accessory Terminal (Line Volt) ACC TX 120VAC Hot to Transformer HOT 120VAC Hot Input HTG ACC Heat Only Accessory (Line Volt) 120VAC Neutrals NEUTRALS 24VAC Hot from Transformer 24VAC HOT 24VAC RTN 24VAC Return from Transformer FLAME SENSE Flame Sense Terminal

FIGURE 11 Page 16

BBlower Motors and Capacitors

All 80MGF units use direct drive blower motors. All motors used are 120V permanent split capacitor motors to ensure maximum efficiency. See table 11 for ratings. TABLE 11 80MGF BLOWER RATINGS 120V 1PH
BLOWER MOTOR 80MGF2 80MGF3 80MGF3/4 80MGF4 80MGF4/5 80MGF5/6 HP 1/4 1/3 1/2 1/2 3/4 3/4 CAP 5MFD 370V 5MFD 370V 7.5MFD 370V 7.5MFD 370V 40MFD 370V 40MFD 370V

tive. If pressure becomes less negative (signifying an obstruction) the pressure switch opens. When the pressure switch opens, the furnace control (A3) immediately closes the gas valve to prevent burner operation.

DFlame Rollout Switches (S47)

Flame rollout switch is a high temperature limit located on top of the burner box. Each furnace is equipped with two identical switches. One switch is located over the leftmost burner and the other switch is located over the rightmost burner. The limit is a N.C. SPST manual-reset limit connected in series with the ignition control A3. When S47 senses rollout, the ignition control immediately stops ignition and closes the gas valve. If unit is running and flame rollout is detected, the gas valve will close and ignition control will be disabled. Rollout can be caused by a blocked flue or lack of combustion air. The switch is factory set and cannot be adjusted. The setpoint will be printed on the side of the limit. The switch can be manually reset. To manually reset a tripped switch, push the reset button located on the control. ROLLOUT SWITCH (S47)

SUPPLY AIR BLOWER AND SECONDARY LIMITSSECONDARY

LIMITS (S21)

Top Left Front Bottom

Back Right

BLOWER MOTOR MOTOR CAPACITOR To Remove Blower From Unit: Remove Bolts and Wiring Jackplugs. Then Slide Out Front of Unit.

MANUAL RESET BUTTON

FIGURE 14

EPrimary Limit Control (S10)

LIMIT CONTROL FOR 80MGF SERIES UNITS
THIS TYPE AUTO-RESET LIMIT IS USED FOR THE PRIMARY LIMIT (S10) AND RIGHT SECONDARY LIMIT (S21) (see FIGURE 13)

FIGURE 13

CCombustion Air Blower (B6)

All 80MGF units use a combustion air blower to move air through the burners and heat exchanger during heating operation. The blowers will use either a shaded pole 120V motor or a Cframe 120V motor. Shaded pole and Cframe motors do not use run capacitors. The motor operates during all heating operation and is controlled by furnace control A3. The motor also operates for a period before burner ignition (prepurge). The prepurge time is 45 seconds for 80MGF units equipped with the RAM control and 15 seconds for units equipped with the EGC control. With either the RAM, EGC or SureLight control board, the motor will operate 5 seconds after the gas valve closes (post-purge). A pressure switch connected to the combustion air blower housing is used to prove combustion air blower operation. The switch monitors air pressure in the blower housing. During normal operation, the pressure in the housing is nega-

FIGURE 15 The primary limit (S10) on 80MGF units is located in the middle of the heating vestibule panel. When excess heat is sensed in the heat exchanger, the limit will open. If the limit is tripped, the furnace control energizes the supply air blower and closes the gas valve. The limit automatically resets when unit temperature returns to normal. The switch is factory set and cannot be adjusted. The switch may have a different setpoint for each unit model number. However, the setpoint will be printed on the side of the limit. There are two types of primary limit. See figures 15 and 16.

Page 17

FSecondary Limit Controls (S21)

The secondary limit (S21) on 80MGF units is located in the blower compartment in the back side of the blower housing. When excess heat is sensed in the heat blower compartment, the limit will open. If the limit is tripped, the furnace control energizes the supply air blower and closes the gas valve. The limit automatically resets when unit temperature returns to normal. The switch is factory set and cannot be adjusted. Two limits are supplied in each furnace and each limit is a different style (figures 15 and 16). The setpoint will be printed on the side of the limit. If stick limit (Figure 16) suffers from nuisance trips and the furnace is in the horizontal position, replace with limit kit no. 50L98. LIMIT CONTROL (S21) (S10) FOR 80MGF SERIES UNITS
INSULATING COVER SPADE CONNECTORS

GSpark Electrode and Flame Sensor (Models with EGC or Ram control only)
Figure 17 shows the arrangement of flame sensor, spark electrode and burners. The Ram and EGC ignition control uses direct spark to ignite the rightmost burner and the burners cross-light to the left. The flame sensor uses flame rectification to sense combustion. A flame retention ring in the end of each burner is used to maintain correct flame length and shape and to keep the flame from lifting off the burner head. Figure 18 shows the gap between tip of the electrodes and the burner surface.

HGas Valve
The 80MGF uses a gas valve manufactured by Honeywell or WhiteRodgers. The valve is internally redundant to assure safety shutoff. If the gas valve must be replaced, the same type valve must be used. 24VAC terminals and gas control knob are located on top of the valve. All terminals on the gas valve are connected to wires from the electronic ignition control. 24V applied to the terminals energizes the valve. Inlet and outlet pressure taps are located on the valve. A regulator adjustment screw is located on the valve. Refer to figures 19 or 20 for location of valve features. An LPG changeover kit is available from Lennox. The kit includes burner orifices and a regulator conversion kit.

THIS TYPE AUTO-RESET LIMIT IS USED FOR THE LEFT SECONDARY LIMIT (S21) (see FIGURE 13)

LIMIT

SPARK ELECTRODE

LIMIT

INSULATING COVER (s)

FIGURE 16

TYPICAL BURNER/ELECTRODE ORIENTATION DIRECT SPARK MODELS ONLY

1/8"(+1/64") UPPER BURNER MOUNTING RAIL BURNER MANIFOLD ORIFICE

23/32 in. (18 mm)

Top Right Bottom Left

GROUND

FLAME RETENTION RING

LOWER BURNER MOUNTING RAIL

FLAME SENSOR

FIGURE 17

Page 18

SPARK ELECTRODE TO BURNER GAP

BURNER

5/16 in. (7 mm)

The switch is a single-pole single-throw pressure switch electrically connected to the furnace control. The purpose of the switch is to prevent burner operation if the combustion air blower is not operating. PROVE SWITCH
COMBUSTION AIR BLOWER PROVE SWITCH Normally Open Closes on Negative Pressure

SPARK ELECTRODE SPARK ELECTRODE

FLAME SENSOR TO BURNER GAP

BURNER

5/16 in. (7 mm)

Sensing Tube Attaches to Top Side Of Blower Top Right

Back FLAME SENSOR PROVE SWITCH

FIGURE 18 WHITE RODGERS 36E SERIES GAS VALVE

MANIFOLD PRESSURE ADJUSTMENT SCREW MANIFOLD PRESSURE OUTLET

Left

Front Bottom

FIGURE 21 On start-up, the switch senses that the combustion air blower is operating. It closes a circuit to the furnace control when pressure inside the combustion air blower increases above pressure switch set point (In. negative w.c.). The pressure sensed by the switch is relative to atmospheric pressure. If the flue becomes obstructed during operation, the switch senses a loss of negative pressure (pressure becomes more equal with atmospheric pressure) and opens the circuit to the furnace control and gas valve. The switch trip pressure is different depending on unit model number. The trip pressure is printed on the side of the limit. The switch is factory set and is not field adjustable. It is a safety shut-down control in the furnace and must not be bypassed for any reason.

GAS VALVE SHOWN IN OFF POSITION

FIGURE 19 HONEYWELL VR8205 SERIES GAS VALVE

MANIFOLD PRESSURE ADJUSTMENT SCREW MANIFOLD PRESSURE OUTLET

IIPLACEMENT AND INSTALLATION

ON

Make sure unit is installed in accordance with installation instructions and applicable does.

OFF

IIISTART-UP
BEFORE LIGHTING smell all around the appliance area for gas. Be sure to smell next to the floor because some gas is heavier than air and will settle on the floor. Use only your hand to turn the gas control knob. Never use tools. If the knob will not turn by hand, do not try to repair it, call a qualified service technician. Force or attempted repair may result in a fire or explosion.

GAS VALVE SHOWN IN OFF POSITION

FIGURE 20

ICombustion Air Blower Prove (Pressure) Switch (S64)

80MGF series units are equipped with a combustion air prove switch located on the vestibule panel. The switch is connected to the combustion air blower housing by means of a flexible silicone hose. It monitors air pressure in the combustion air blower housing.

Page 19

APreliminary and Seasonal Checks

1 Inspect electrical wiring, both field and factory installed for loose connections. Tighten as required. 2 Check voltage at disconnect switch. Voltage must be within range listed on the nameplate. If not, consult the power company and have voltage condition corrected before starting unit.

CSafety or Emergency Shutdown

Turn off unit power. Close manual and main gas valves.

DExtended Period Shutdown

Turn off thermostat or set to UNOCCUPIED" mode. Close all gas valves (both internal and external to unit) to guarantee no gas leak into combustion chamber. Turn off power to unit. All access panels, covers and vent caps must be in place and secured.

BHeating Start-Up
1 STOP! Read the safety information at the beginning of this section. 2 Set thermostat to lowest setting. 3 Turn off all electrical power to appliance. 4 This appliance is equipped with an ignition device which automatically lights the burners. Do not try to light the burners by hand. 5 Remove access panel.

IVHEATING SYSTEM SERVICE CHECKS AA.G.A./C.G.A. Certification

All units are A.G.A. and or C.G.A. design certified without modifications. Refer to the 80MGF Operation and Installation Instruction Manual Information.

BGas Piping
Gas supply piping should not allow more than 0.5"W.C. drop in pressure between gas meter and unit. Supply gas pipe must not be smaller than unit gas connection. Compounds used on gas piping threaded joints should be resistant to action of liquefied petroleum gases.

WARNING
Shock and burn hazard. 80MGF units are equipped with a direct spark ignition system. Do not attempt to light manually. 6 White Rodgers 36E Gas Valve Switch gas valve lever to OFF. See figure 19. Honeywell VR8205 Gas Valve Turn knob on gas valve clockwise to OFF. Do not force. See figure 20. 7 Wait five (5) minutes to clear out any gas. If you then smell gas, STOP! Immediately call your gas supplier from a neighbors phone. Follow the gas suppliers instructions. If you do not smell gas go to next step. 8 White Rodgers 36E Gas Valve Switch gas valve lever to ON. Honeywell VR8205 Gas Valve Turn knob on gas to ON. Do not force. valve counterclockwise 9 Replace access panel. 10 Turn on all electrical power to unit. 11 Set thermostat to desired setting. 12 If the appliance will not operate, follow the instructions To Turn Off Gas To Unit" and call your service technician or gas supplier. Turning Off Gas To Unit 1 Set thermostat to lowest setting. 2 Turn off all electrical power to unit if service is to be performed. 3 Remove access panel. 4 Switch lever on White Rodgers gas valve to OFF; turn knob on Honeywell valve clockwise to OFF. Do not force. 5 Replace lower access panel.

CTesting Gas Piping

IMPORTANT
In case emergency shutdown is required, turn off the main shut-off valve and disconnect the main power to unit. These controls should be properly labeled by the installer. When pressure testing gas lines, the gas valve must be disconnected and isolated. Gas valves can be damaged if subjected to more than 0.5psig (14" W.C.). See figure 22. If the pressure is equal to or less than 0.5psig (14"W.C.), use the manual shutoff valve before pressure testing to isolate furnace from gas supply. GAS PIPING TEST PROCEDURE
MANUAL MAIN SHUTOFF VALVE WILL NOT HOLD TEST PRESSURE IN EXCESS OF 0.5 PSIG (14"W.C.)

CAP GAS VALVE FIELD PROVIDED LINE PRESSURE TAP

FIGURE 22

Page 20

When checking piping connections for gas leaks, use preferred means. Kitchen detergents can cause harmful corrosion on various metals used in gas piping. Use of a specialty Gas Leak Detector is strongly recommended. It is available through Lennox under part number 31B2001. See Corp. 8411L10, for further details. Do not use matches, candles, flame or any other source of ignition to check for gas leaks.

The gas valve is factory set and should not require adjustment. All gas valves are factory regulated. See table 12. Manifold Adjustment Procedure: 1 Connect a test gauge to outlet pressure tap on gas valve. Start unit and allow 5 minutes for unit to reach steady state. 2 While waiting for the unit to stabilize, notice the flame. Flame should be stable and should not lift from burner. Natural gas should burn blue. L.P. gas should burn mostly blue with some orange streaks. 3 After allowing unit to stabilize for 5 minutes, record manifold pressure and compare to values given in table 12. NOTEShut unit off and remove manometer as soon as an accurate reading has been obtained. Take care to replace pressure tap plug.

DTesting Gas Supply Pressure

When testing supply gas pressure, connect test gauge to inlet pressure tap (field provided). See figure 22. Check gas line pressure with unit firing at maximum rate. Low pressure may result in erratic operation or underfire. High pressure can result in permanent damage to gas valve or overfire. For natural gas units, operating pressure at unit gas connection must be a minimum of 4.5" W.C. For L.P. gas units, operating pressure at unit gas connection must be a minimum of 9.0" W.C. On multiple unit installations, each unit should be checked separately, with and without other units operating. Supply pressure must fall within range listed in previous paragraph.

F Proper Gas Flow (Approximate)

Furnace should operate at least 5 minutes before checking gas flow. Determine time in seconds for two revolutions of gas through the meter. (Two revolutions assures a more accurate time.) Divide by two and compare to time in table 13 below. Adjust manifold pressure on gas valve to match time needed. NOTE To obtain accurate reading, shut off all other gas appliances connected to meter. TABLE 13 GAS METER CLOCKING CHART Seconds for One Revolution Natural LP 80mgf g Unit 1 cu ft 2 cu ft 1 cu ft 2 cu ft Dial Dial Dial DIAL 45 80 160 200 400 60 60 120 150 300 75 48 96 120 240 100 36 72 90 180 120 30 60 75 150 140 25 50 64 128
Natural1000 btu/cu ft LP2500 btu/cu ft

ECheck Manifold Pressure

After line pressure has been checked and adjusted, check manifold pressure. Move pressure gauge to outlet pressure tap located on unit gas valve (GV1). Checks of manifold pressure are made as verification of proper regulator adjustment. Manifold pressure for the 80MGF can be measured at any time the gas valve is open and is supplying gas to the unit. Normal manifold pressure for natural gas units is 3.5 in. w.c. For LP/propane gas the correct manifold pressure is 9.0 in. w.c.

IMPORTANT
For safety, connect a shut-off valve between the manometer and the gas tap to permit shut off of gas pressure to the manometer. TABLE 12 GAS VALVE REGULATION
Unit (Fuel) Natural L.P. Operating Pressure (outlet) in. W.C. 3.5 +0 0.3 9.0 + 0.5

Page 21

GHigh Altitude Derate

NOTEIn Canada, certification for installation at altitudes over 4500 ft. (1372m) above sea level is the jurisdiction of the local authorities. 80MGF1 through 8 Models This unit does not require gas pressure adjustment, or pressure switch change when operating at elevations of 0 to 7500 ft. (0 to 2248m). Check gas line pressure with unit firing. The minimum pressure as shown on the nameplate for natural and propane gases must be maintained. No orifice change is required. NOTEThis is the only permissible field derate for this appliance. 80MGF9, 10 and 11 Models Table 14 shows manifold pressure settings for installations at different altitudes. Refer to table 15 for pressure switch replacement for models at elevations of 4500 feet (1372m) and greater. TABLE 14
ALTITUDE feet (m) 0 4500 (0 1372) 4500 5500 (1372 1676) 5500 6500 (1676 1981) 6500 7500 (1372 2286) GAS FUEL Natural Propane/LP Natural Propane/LP Natural Propane/LP Natural Propane/LP MANIFOLD PRESSURE in. W.C. (kPa) 3.5 (0.87) 9.5 (2.36) 3.4 (0.86) 9.2 (2.29) 3.3 (0.82) 8.9 (2.21) 3.2 (0.80) 8.6 (2.14)

the ignition control sensor connection and the negative () lead of the meter to the sensor wire. See figure 23. 2 Set thermostat for a heating demand and check flame signal with unit operating. See table 16 for microamp reading for the various control boards used. FLAME SIGNAL TEST
D.C. MICROAMP METER FLAME SENSOR SENSOR WIRE IGNITION CONTROL SENSE" TERMINAL

FIGURE 23 TABLE 16 MICROAMP SIGNAL 1.0 to 5.0 1.0 to 5.0 w.70 DROP OUT SIGNAL t1.0 v.45 v.15

CONTROL Ram EGC SureLight

Flame signal may rise above 5 microamps for the first few seconds after ignition then level off within the range.

WARNING
Fire and explosion hazard. These instructions MUST be followed exactly. Can cause a fire or explosion resulting in property damage, personal injury or loss of life.

Unit Model 80MGF45 80MGF60 80MGF75 80MGF100 80MGF120 80MGF140

TABLE 15 Pressure Switch Part Number No Change No Change 88J8001 18L2401 18L2401 No Change

VTYPICAL OPERATING CHARACTERISTICS ABlower Operation and Adjustment

NOTE The following is a generalized procedure and does not apply to all thermostat controls. 1 Blower operation is dependent on thermostat control system. 2 Generally, blower operation is set at thermostat subbase fan switch. With fan switch in ON position, blower operates continuously on heating speed. With fan switch in AUTO position, blower cycles with demand or runs continuously while heating or cooling circuit cycles. 3 Depending on the type of indoor thermostat, blower and entire unit will be off when the system switch is in OFF position.

HFlame Signal
A microamp DC meter is needed to check the flame signal on the primary ignition control. Flame (microamp) signal is an electrical current which passes from the furnace control through the sensor electrode during unit operation. Current passes from the sensor through the flame to ground to complete a safety circuit. To Measure Flame Signal: 1 Place meter in series between furnace control and sensor wire. Connect the positive (+) lead of meter to

BTemperature Rise
Temperature rise for 80MGF units depends on unit input, blower speed, blower horsepower and static pressure as marked on the unit rating plate. The blower speed must be set for unit operation within the range of AIR TEMP. RISE F" listed on the unit rating plate.

Page 22

To Measure Temperature Rise: 1 Place plenum thermometers in the supply and return air plenums. Locate supply air thermometer in the first horizontal run of the plenum where it will not pick up radiant heat from the heat exchanger. 2 Set thermostat to highest setting. 3 After plenum thermometers have reached their highest and steadiest readings, subtract the two readings. The difference should be in the range listed on the unit rating plate. If the temperature is too low, decrease blower speed. If temperature is too high, first check the firing rate. Provided the firing rate is acceptable, increase blower speed to reduce temperature. To change blower speed taps see the Blower Speed Taps section in this manual.

TABLE 17
BLOWER SPEED SELECTION Unit Factory Connected Speed Taps Cool (Black) 80MGF2-45 80MGF2-60 80MGF3-60 80MGF2-75 80MGF3-75 80MGF4-75 80MGF3/4-100 80MGF4/5-100 80MGF3/4-120 80MGF4/5-120 80MGF4/5-140 2 2 2 2 2 2 2 2 2 2 2 Heat (Red) 4 4 4 3 4 4 4 5 3 5 3 4 4 4 4 4 5 5 5 5 5 5 Speeds Available

CExternal Static Pressure

1 Measure tap locations as shown in figure 24. 2 Punch a 1/4" diameter hole STATIC PRESSURE in supply and return air pleTEST nums. Insert manometer MANOMETER hose flush with inside edge of hole or insulation. Seal around the hose with per80MGF UNIT magum. Connect the zero end of the manometer to the FIGURE 24 discharge (supply) side of the system. On ducted systems, connect the other end of manometer to the return duct as above. For systems with nonducted returns, leave the other end of the manometer open to the atmosphere. 3 With only the blower motor running and the evaporator coil dry, observe the manometer reading. Adjust blower motor speed to deliver the air desired according to the job requirements. 4 External static pressure drop must not be more than 0.5" W.C. 5 Seal around the hole when the check is complete.

TABLE 18
BLOWER SPEED SELECTION HI LOW TAPS AVAILABLE 3 5 5 6 4

2 3 3

3 4 4

5 MOTOR PLUG SPEED TAP DESIGNATION

5 Depress harness connector tab to release wire terminal. Select connector location for new speed (refer to unit wiring diagram). Insert wire terminal until it is securely in place. See figure 25. 6 Replace harness connector to motor. BLOWER SPEED TAP SELECTION Leadless motors only

HARNESS CONNECTOR

DBlower Speed Taps Leadless Motors

Blower speed tap selection is accomplished by changing the taps at the blower motor harness connector. Disconnect harness connector from motor to expose speed selectors. Blower speed selections are listed in table 17. To Change Blower Speed: 1 Turn off electric power to furnace. 2 Remove front panel and blower access door. See figure 4. 3 Disconnect blower motor harness from motor. 4 Select desired speeds for heating and cooling. (Red = heating, Black = cooling, White = common). See table 17.
DEPRESS TAB TO RELEASE WIRE TERMINAL. SELECT CONNECTOR LOCATION FOR NEW SPEED (REFER TO UNIT WIRING DIAGRAM). INSERT WIRE UNTIL IT IS SECURELY IN PLACE.

MOTOR

FIGURE 25

Page 23

EBlower Speed Taps Leaded Motors 11 Models

Blower speed tap changes are made on the SureLight control board. See figure 8. Unused taps must be secured on dummy terminals "PARK M1" and or "PARK M2" on the SureLight board. The heating tap is connected to the "ACB HEAT " terminal and the cooling tap is connected to the "ACB COOL" terminal. The continuous blower tap is connected to the "ACB LOW" terminal. To change existing heat tap, turn off power then switch out speed tap on "ACB HEAT" with tap connected to "PARK M1" or "PARK M2". See table 19 for blower motor tap colors for each speed. TABLE 19

ACleaning Heat Exchanger and Burners

NOTEUse papers or protective covering in front of furnace while cleaning furnace. Due to dimples designed in the heatexchanger, cleaning is not recommended. Removal is for inspection only. Burners Burners and burner flame should be inspected at the beginning of each heating season. Clean burners, if necessary, as outlined below: 1 Turn off electrical and gas supply to unit. 2 Remove burner box top. 3 Remove burner retaining bracket. 4 Remove burners. 5 Clean burner insert with bottle brush as shown in figure 26. NOTEUse papers or protective covering in front of furnace while cleaning furnace. CLEANING BURNERS
BURNER BOTTLE BRUSH

VIMAINTENANCE
At the beginning of each heating season, the system should be checked as follows: Filters All 80MGF filters are installed external to the unit. Filters should be inspected monthly and cleaned or replaced when necessary to assure proper furnace operation. See table 20 for filter sizes. Replacement filters for 80MGF-45/60/75 units must have a minimum velocity rating of 400 FPM. Replacement filters for 80MGF-100/120/140 units require a minimum velocity rating of 625 FPM. TABLE 20
MODEL NUMBER 80MGF45/60/75 80MGF100/120/140 FILTER SIZE 16" X 20" X 1" 20" X 20" X 1"

FIGURE 26 6 Use bottle brush to clean inside of each burner. 7 Replace burners and burner retaining bracket, making sure burners are properly seated in slots on tray and orifice in manifold. 8 Check electrode gap using appropriately sized twist drills or feeler gauges. Gap should be between 2.79 to 3.56mm (0.110 and 0.140 inches). 9 Reinstall burner box top.

CAUTION
Some soaps used for leak detection are corrosive to certain metals. Carefully rinse piping thoroughly after leak test has been completed. Do not use matches, candles, flame or other sources of ignition to check for gas leaks. 10 Restore electrical power and gas supply. Follow lighting instructions on front of unit. Check the following: appearance of burner flame, burner pressure, gas flow and temperature rise. Make adjustments, if necessary. See adjustments section.

WARNING
Blower door must be securely in place when blower and burners are operating. Gas fumes, which could contain carbon monoxide, can be drawn into living space resulting in personal injury or death.

BSupply Air Blower

1 Check and clean blower wheel. 2 Motors used on the Lennox 80MGF series units are permanently lubricated and need no further lubrication.

Page 24

CFlue and Chimney

Flue must conform to all AGA/GAMA venting requirements. Flue pipe deteriorates from the inside out and must be disconnected in order to check thoroughly. Check flue pipe, chimney and all connections for tightness and to make sure there is no blockage or leaks.

CAUTION
Potential for gas leaks, fire or explosion. Some soaps used for leak detection are corrosive to certain metals. Carefully clean piping thoroughly after leak detection has been completed. Can cause damage to piping resulting in gas leaks, fire or explosion.

DElectrical
1 Check all wiring for loose connections. 2 Check for correct voltage. 3 Check ampdraw on blower motor.

HEAT EXCHANGER REMOVAL (unit shown in horizontal position)

REMOVE SCREWS (4)

Left Bottom Front Right SLIDE ENTIRE ASSEMBLY OUT OF CABINET Back Top

FIGURE 27

Page 25

VIIWIRING AND SEQUENCE OF OPERATION

5 2 3

4 8

80MGF WITH RAM CONTROL 1- When disconnect is closed, 120V is routed through door interlock switch (S51) to feed the line voltage side of the furnace control (A3) and transformer T1 primary. Door interlock switch must be closed for A3 and T1 to receive voltage. 2- T1 supplies 24VAC to terminal 24VAC" on A3. In turn, terminal R" of A3 supplies 24VAC to terminal RC" of the indoor thermostat (not shown). 3- When there is a call for heat, W1 of the thermostat energizes W of the furnace control with 24VAC. 4- CMB BLWR of the blower control energizes the combustion air blower (B6). When the combustion air blower nears full speed, combustion air prove switch (S18) closes.

5- When S18 closes, assuming the flame rollout switch (S47) primary limit (S10) and secondary limits (S21) are closed, the furnace control begins a 45 second time-delay (pre-purge). 6- At the end of the pre-purge cycle, the furnace control simultaneously opens the gas valve and sends high voltage to the spark electrode. 7- When flame is sensed, the furnace control begins a 45 second delay before energizing the indoor blower. 8- When heat demand is satisfied, W1 of the thermostat de-energizes W of the furnace control and the furnace control immediately de-energizes the gas valve. The combustion air blower runs for 5 seconds (post-purge) before being de-energized. Also, the indoor blower runs for a designated period (90240 seconds) as set by switches on furnace control.

Page 26

80MGF TROUBLESHOOTING SEQUENCE NORMAL HEATING MODE

LED: SLOW FLASH RATE THERMOSTAT CALLS FOR HEAT LED: FAST FLASH RATE FLAME OFF? YES CONTROL SELFCHECK OKAY? YES HI LIMIT SWITCH CLOSED? YES PRESSURE SWITCH OPEN? YES COMBUSTION AIR BLOWER ON? PRESSURE SWITCH CLOSED? YES PREPURGE (45 seconds) IGNITION TRIAL (7 seconds) START IGNITION SPARK, OPEN MAIN GAS VALVE. INCREMENT TRIAL REGISTER. HAS FLAME BEEN REGISTERED WITHIN 7 SECONDS? YES SYSTEM FAN ON. (Fixed 45second delay) FLAME SENSE OKAY? YES FLAME CONTINUOUSLY CHECKED? ROLLOUT SWITCHES CLOSED YES HI LIMIT SWITCH CLOSED? YES PRESSURE SWITCH CLOSED? YES THERMOSTAT OPENS LED: SLOW FLASH RATE COMB. AIR BLOWER OFF (5 sec. delay) FAN OFF (After selected 90, 120, 180, or 240 delay)? NO NO NO SEQUENCE HOLDS. MAIN VALVE OFF. COMBUSTION AND SYSTEM FANS ON. RESET OR REPLACE ROLLOUT SWITCH. LED: 4 flashes. MAIN VALVE OFF. COMBUSTION & SYSTEM FANS ON. SEQUENCE HOLDS UNTIL SWITCH CLOSES. LED: 4 flashes for hi limit. LED: 3 flashes for pressure switch. SWITCH CLOSED YES COMBUSTION FAN ON. SYSTEM FAN OFF. (AFTER DELAY TO OFF INTERVAL COMPLETED.) LED: Fast flash rate. NO MAIN VALVE AND SPARK ARE OFF. INCREMENT TRIAL REGISTER THREE TRIALS COMPLETED? YES IGNITION RESET PERIOD COMBUSTION & SYSTEM FANS OFF. IS 60 MIN. RESET PERIOD COMPLETE? LED: Fast flash rate. MAIN VALVE AND SPARK OFF. NO START IGNITION SPARK (IN 0.8 SEC. MAXIMUM). HAS FLAME BEEN DETECTED WITHIN 7 SEC.? YES YES NO NO NO NO NO NO

ABNORMAL HEATING MODE

LOCKOUT: MAIN VALVE OFF COMB. AIR AND SYSTEM FANS ON RESET THERMOSTAT LED: 5 flash if flame sensed with valve off LED: Steady on if control board failure CHECK TO SEE IF MAIN VALVE IS OFF. SEQUENCE HOLDS UNTIL HI LIMIT CLOSES. LED: 4 flashes. CHECK TO SEE IF MAIN VALVE IS OFF. SEQUENCE HOLDS UNTIL PRES. SWITCH OPENS. LED: 3 flashes. CHECK TO SEE IF MAIN VALVE IS OFF. SEQUENCE HOLDS UNTIL PRES. SWITCH CLOSES. LED: Fast flash rate.

NO

Page 27

80MGF TROUBLESHOOTING SEQUENCE COOLING

LED: Slow flash rate. REMAINS UNCHANGED THROUGHOUT COOLING CYCLE.

THERMOSTAT CALLS FOR COOLING.

COMPRESSOR CONTACTOR AND SYSTEM FAN ENERGIZED AT COOLING SPEED AFTER 1 SECOND DELAY.

THERMOSTAT OPENS.

COMPRESSOR OFF.

SYSTEM FAN OFF AFTER COMPLETING SELECTED DELAY INTERVAL (At dip switches).

80MGF TROUBLESHOOTING SEQUENCE FAN ONLY

LED: Slow flash rate. REMAINS UNCHANGED THROUGHOUT SEQUENCE.

MANUAL FAN SELECTION MADE AT THERMOSTAT. CONTROL ENERGIZES SYSTEM FAN AT HEATING SPEED.

THERMOSTAT CALLS FOR HEAT. NO YES SYSTEM FAN REMAINS ON HEATING SEQUENCE AND RUNS THROUGH COMPLETION.

THERMOSTAT CALLS FOR COOLING. YES SYSTEM FAN SWITCHED TO COOLING SPEED. COOLING SEQUENCE RUNS TO COMPLETION. NO

SYSTEM FAN ON AT HEATING SPEED UNTIL MANUAL FAN IS SWITCHED OFF AT THERMOSTAT.

SLOW FLASH FAST FLASH 2 FLASH 3 FLASH 4 FLASH 5 FLASH STEADY ON

LED CODES NORMAL OPERATION. NO CALL FOR HEAT. NORMAL OPERATION. CALL FOR HEAT. . SYSTEM LOCKOUT. FAILURE TO DETECT OR SUSTAIN FLAME. PRESSURE SWITCH OPEN OR CLOSED. HIGH LIMIT OR ROLLOUT SWITCH OPEN. FLAME SENSED AND GAS VALVE NOT ENERGIZED. CONTROL BOARD FAILURE.

Page 28

80MGF WITH EGC2 IGNITION CONTROL 1 When disconnect is closed, 120V is routed through door interlock switch (S51) to feed the line voltage side of the ignition control (A3) and transformer T1 primary. Door interlock switch must be closed for A3 and T1 to receive voltage. 2 T1 supplies 24VAC to terminal 24VAC" on A3. In turn, terminal R" of A3 supplies 24VAC to terminal R" of the indoor thermostat (not shown). 3 When there is a call for heat, W1 of the thermostat energizes W of the ignition control with 24VAC. 4 CAB of the ignition control energizes the combustion air blower (B6). When the combustion air blower nears full speed, combustion air prove switch (S18) closes.

5 When S18 closes, assuming primary limit (S10) and secondary limit (S21) are closed, a 15 second prepurge begins. After the prepurge period the ignition control starts ignition spark and opens main gas valve. 6 After 45 seconds, ignition control (A3) energizes the indoor blower (B3). 7 When heat demand is satisfied, W1 of the thermostat deenergizes W of the ignition control and the gas valve is immediately de-energized. The combustion air blower immediately stops. The indoor blower runs for a designated fan off" period (60240 seconds) as set by jumper on ignition control.

Page 29

80MGF WITH EGC2 HEATING SEQUENCE OF OPERATION NORMAL HEATING MODE

CONTROL MAIN POWER ON" FLAME OFF? YES CONTROL SELFCHECK OKAY? YES ROLLOUT SWITCH CLOSED YES LED: SLOW FLASH RATE THERMOSTAT CALLS FOR HEAT LED: FAST FLASH RATE COMB. AIR BLOWER PRESSURE SWITCH OPEN? YES COMBUSTION AIR BLOWER ON? HTG ACC. TERM. ENERGIZED. YES PRESSURE SWITCH CLOSED WITHIN 2.5 MIN.? YES COMB. AIR BLOWER PREPURGE (15 seconds) IGNITION TRIAL (10 seconds) START IGNITION SPARK, OPEN MAIN GAS VALVE. HAS FLAME REGISTERED WITHIN 10 SECONDS AFTER IGNITION TRIAL? YES IS FLAME SENSED AFTER 10 SECOND FLAME RECTIFICATION PERIOD? YES INDOOR AIR BLOWER ON. (Fixed 45second delay) NO NO NO GAS VALVE, COMB. BLOWER AND INDOOR BLOWER (WITH DELAY) OFF. SEQUENCE HOLDS UNTIL PRESSURE SWITCH CLOSES OR THERMOSTAT RESETS CONTROL. DIAG. CODE: 1OFF; 2FLASHING (C.A.B. PRESSURE SWITCH OPEN) YES PRESSURE SWITCH WATCHGUARD CONDITION: GAS VALVE, COMB. BLOWER AND INDOOR BLOWER (WITH DELAY) OFF. DIAG. CODE: 1OFF / 2FLASHING (C.A.B. PRESSURE SWITCH OPEN) IS 5 MINUTE RESET PERIOD COMPLETE? GAS VALVE OFF. COMB. BLOWER ON. INDOOR BLOWER (WITH 45 DELAY) ON. HAS CONTROL FAILED FLAME SENSE 5 TIMES DURING ONE HEAT DEMAND? IF YES, SYSTEM GOES INTO 60 MIN.WATCHGUARD. DIAG. CODE: 1ALT. FLASHING / 2ALT. FLASHING IF NO, GO TO COMB. AIR BLOWER ON?" HAS CONTROL RESET IGNITION SEQUENCE 5 TIMES IF YES, SYSTEM GOES INTO 60 MIN. WATCHGUARD. DIAG. CODE: 1ALT. FLASHING / 2ALT. FLASHING IF NO, GO TO COMB. AIR BLOWER ON?" GAS VALVE OFF. COMB. BLOWER OFF. INDOOR BLOWER ON UNTIL LIMIT CLOSES. DIAG. CODE: 1FLASHING / 2ON (LIMIT OPEN) IS LIMIT NOW CLOSED? YES HAS PRIMARY LIMIT OPENED 5 TIMES DURING ONE UNSATISFIED HEAT DEMAND. IF YES, SYSTEM GOES INTO 60 MIN.WATCHGUARD. DIAG. CODE: 1FLASHING / 2ON IF NO, GO TO COMB. AIR BLOWER ON?" GAS VALVE, COMB. BLOWER AND INDOOR BLOWER (WITH DELAY) OFF. DIAG. CODE: 1OFF / 2FLASHING NO (C.A.B. PRESSURE SWITCH OPEN) HAS C.A.B. PRESSURE SWITCH CLOSED IN 2.5 MINUTES? YES GAS VALVE, COMB. BLOWER AND INDOOR BLOWER (WITH DELAY) OFF. SEQUENCE HOLDS UNTIL ROLLOUT SWITCH IS MANUALLY CLOSED. DIAG. CODE: 1ON; 2FLASHING (FLAME ROLLOUT OPEN) NO GAS VALVE, COMB. BLOWER AND INDOOR BLOWER (WITH DELAY) OFF. REMOVE POWER TO RESET CONTROL. DIAG. CODE: BOTH ON (CONTROL SELFCHECK FAILURE OR INCORRECT WIRING) NO

ABNORMAL HEATING MODE

GAS VALVE OFF. COMB. BLOWER ON. INDOOR BLOWER ON HEAT SPEED. SEQUENCE HOLDS UNTIL NO FLAME SENSED OR MAIN POWER IS INTERRUPTED AND RESET. DIAG. CODE: 1 FLASHING; 2OFF (FLAME SENSED WITHOUT VALVE ENERGIZED)

NO

NO

NO

PRIMARY/SECONDARY LIMITS MONITORED IN HEAT CYCLE. ARE SWITCHES CLOSED? YES PRESSURE SWITCH CLOSED? YES THERMOSTAT OPENS LED: SLOW FLASH RATE COMB. AIR BLOWER OFF (5 sec. delay) HTG ACC. TERM.DEENERGIZED. INDOOR AIR BLOWER OFF (After selected 60, 90, 120, 180, or 240 delay)?

NO

Page 30

80MGF WITH EGC2 COOLING SEQUENCE OF OPERATION

LED: Slow flash rate. REMAINS UNCHANGED THROUGHOUT COOLING CYCLE.

THERMOSTAT CALLS FOR COOLING.

COMPRESSOR CONTACTOR AND SYSTEM FAN ENERGIZED AT COOLING SPEED AFTER 1 SECOND DELAY. ACC TERMINAL ENERGIZED.

THERMOSTAT OPENS.

COMPRESSOR OFF.

SYSTEM FAN AND ACC TERMINAL OFF AFTER 0 SECONDS.

80MGF WITH EGC2 MANUAL CONTINUOUS FAN SEQUENCE OF OPERATION

LED: Slow flash rate. REMAINS UNCHANGED THROUGHOUT SEQUENCE.

CONTINUOUS FAN SELECTION MADE AT THERMOSTAT. CONTROL ENERGIZES SYSTEM FAN AT HEAT SPEED. ACC TERMINAL ENERGIZED. HTG ACC. TERM. ENERGIZED WITH COMB. AIR BLOWER.

THERMOSTAT CALLS FOR HEAT. NO YES

THERMOSTAT CALLS FOR COOLING. YES SYSTEM FAN SWITCHED TO COOLING SPEED. ACC TERMINAL REMAINS ENERGIZED. NO

SYSTEM FAN REMAINS ON HEATING SPEED AFTER SELECTED DELAY. ACC TERM. REMAINS ENERGIZED.

THERMOSTAT OPENS.

THERMOSTAT OPENS.

SYSTEM FAN SWITCHED OFF AFTER DELAY. ACC TERMINAL DEENERGIZED. SYSTEM FAN SWITCHES TO CONTINUOUS SPEED AND ENERGIZES ACC TERMINAL. BOTH REMAIN ON UNTIL CONTINUOUS FAN IS SWITCHED OFF AT THERMOSTAT.

Page 31

80MGF WITH EGC1 IGNITION CONTROL 1 When disconnect is closed, 120V is routed through door interlock switch (S51) to feed the line voltage side of the ignition control (A3) and transformer T1 primary. Door interlock switch must be closed for A3 and T1 to receive voltage. 2 T1 supplies 24VAC to terminal 24VAC" on A3. In turn, terminal R" of A3 supplies 24VAC to terminal R" of the indoor thermostat (not shown). 3 When there is a call for heat, W1 of the thermostat energizes W of the ignition control with 24VAC. 4 CAB of the ignition control energizes the combustion air blower (B6). When the combustion air blower nears full speed, combustion air prove switch (S18) closes.

5 When S18 closes, assuming primary limit (S10) and secondary limit (S21) are closed, a 15 second prepurge begins. After the prepurge period the ignition control starts ignition spark and opens main gas valve. 6 After 45 seconds, ignition control (A3) energizes the indoor blower (B3). 7 When heat demand is satisfied, W1 of the thermostat deenergizes W of the ignition control and the gas valve is immediately de-energized. The combustion air blower immediately stops. The indoor blower runs for a designated fan off" period (60240 seconds) as set by jumper on ignition control.

Page 32

80MGF WITH EGC1 HEATING SEQUENCE OF OPERATION NORMAL HEATING MODE

CONTROL MAIN POWER ON" FLAME OFF? YES CONTROL SELFCHECK OKAY? YES ROLLOUT SWITCH CLOSED YES LED: SLOW FLASH RATE THERMOSTAT CALLS FOR HEAT LED: FAST FLASH RATE COMB. AIR BLOWER PRESSURE SWITCH OPEN? YES COMBUSTION AIR BLOWER ON? HTG ACC. TERM. ENERGIZED? YES PRESSURE SWITCH CLOSED WITHIN 2.5 MIN.? YES COMB. AIR BLOWER PREPURGE (15 seconds) IGNITION TRIAL (10 seconds) START IGNITION SPARK, OPEN MAIN GAS VALVE. HAS FLAME REGISTERED WITHIN 10 SECONDS AFTER IGNITION TRIAL? YES IS FLAME SENSED AFTER 10 SECOND FLAME RECTIFICATION PERIOD? YES INDOOR AIR BLOWER ON. (Fixed 45second delay) NO NO NO YES PRESSURE SWITCH WATCHGUARD CONDITION: GAS VALVE, COMB. BLOWER AND INDOOR BLOWER (WITH DELAY) OFF. DIAG. CODE: 1OFF / 2FLASHING (C.A.B. PRESSURE SWITCH OPEN) IS 5 MINUTE RESET PERIOD COMPLETE? GAS VALVE OFF. COMB. BLOWER ON. INDOOR BLOWER (WITH 45 DELAY) ON. HAS CONTROL FAILED FLAME SENSE 5 TIMES DURING ONE HEAT DEMAND? IF YES, SYSTEM GOES INTO 60 MIN.WATCHGUARD. DIAG. CODE: 1ALT. FLASHING / 2ALT. FLASHING IF NO, GO TO COMB. AIR BLOWER ON?" HAS CONTROL RESET IGNITION SEQUENCE 5 TIMES IF YES, SYSTEM GOES INTO 60 MIN. WATCHGUARD. DIAG. CODE: 1ALT. FLASHING / 2ALT. FLASHING IF NO, GO TO COMB. AIR BLOWER ON?" GAS VALVE OFF. COMB. BLOWER OFF. INDOOR BLOWER ON UNTIL LIMIT CLOSES. DIAG. CODE: 1FLASHING / 2ON (LIMIT OPEN) IS LIMIT NOW CLOSED? YES HAS PRIMARY LIMIT OPENED 5 TIMES DURING ONE UNSATISFIED HEAT DEMAND. IF YES, SYSTEM GOES INTO 60 MIN.WATCHGUARD. DIAG. CODE: 1FLASHING / 2ON IF NO, GO TO COMB. AIR BLOWER ON?" GAS VALVE, COMB. BLOWER AND INDOOR BLOWER (WITH DELAY) OFF. DIAG. CODE: 1OFF / 2FLASHING NO (C.A.B. PRESSURE SWITCH OPEN) HAS C.A.B. PRESSURE SWITCH CLOSED IN 2.5 MINUTES? YES NO GAS VALVE, COMB. BLOWER AND INDOOR BLOWER (WITH DELAY) OFF. SEQUENCE HOLDS UNTIL PRESSURE SWITCH CLOSES OR THERMOSTAT RESETS CONTROL. DIAG. CODE: 1OFF; 2FLASHING (C.A.B. PRESSURE SWITCH OPEN) GAS VALVE, COMB. BLOWER AND INDOOR BLOWER (WITH DELAY) OFF. SEQUENCE HOLDS UNTIL ROLLOUT SWITCH IS MANUALLY CLOSED. DIAG. CODE: 1ON; 2FLASHING (FLAME ROLLOUT OPEN) NO GAS VALVE, COMB. BLOWER AND INDOOR BLOWER (WITH DELAY) OFF. REMOVE POWER TO RESET CONTROL. DIAG. CODE: BOTH ON (CONTROL SELFCHECK FAILURE OR INCORRECT WIRING) NO

ABNORMAL HEATING MODE

GAS VALVE OFF. COMB. BLOWER ON. INDOOR BLOWER ON HEAT SPEED. SEQUENCE HOLDS UNTIL NO FLAME SENSED OR MAIN POWER IS INTERRUPTED AND RESET. DIAG. CODE: 1 FLASHING; 2OFF (FLAME SENSED WITHOUT VALVE ENERGIZED)

NO

NO

PRIMARY/SECONDARY LIMITS MONITORED IN HEAT CYCLE. ARE SWITCHES CLOSED? YES PRESSURE SWITCH CLOSED? YES THERMOSTAT OPENS LED: SLOW FLASH RATE COMB. AIR BLOWER OFF (5 sec. delay) HTG ACC. TERM. DEENERGIZED. INDOOR AIR BLOWER OFF (After selected 60, 90, 120, 180, or 240 delay)?

NO

Page 33

80MGF WITH EGC1 COOLING SEQUENCE OF OPERATION

LED: Slow flash rate. REMAINS UNCHANGED THROUGHOUT COOLING CYCLE.

THERMOSTAT CALLS FOR COOLING.

COMPRESSOR CONTACTOR AND SYSTEM FAN ENERGIZED AT COOLING SPEED AFTER 1 SECOND DELAY. ACC TERMINAL ENERGIZED.

THERMOSTAT OPENS.

COMPRESSOR OFF.

SYSTEM FAN AND ACC TERMINAL OFF AFTER 0 SECONDS.

80MGF WITH EGC1 MANUAL CONTINUOUS FAN SEQUENCE OF OPERATION

LED: Slow flash rate. REMAINS UNCHANGED THROUGHOUT SEQUENCE.

CONTINUOUS FAN SELECTION MADE AT THERMOSTAT. CONTROL ENERGIZES SYSTEM FAN AT LOW SPEED. ACC TERMINAL ENERGIZED. HTG ACC. TERM. ENERGIZED WITH COMB. AIR BLOWER.

THERMOSTAT CALLS FOR HEAT. NO YES

THERMOSTAT CALLS FOR COOLING. YES SYSTEM FAN SWITCHED TO COOLING SPEED. ACC TERMINAL REMAINS ENERGIZED. NO

SYSTEM FAN SWITCHES TO HEAT SPEED AFTER SELECTED DELAY. ACC TERM. REMAINS ENERGIZED.

THERMOSTAT OPENS.

THERMOSTAT OPENS.

SYSTEM FAN SWITCHED OFF AFTER DELAY. ACC TERMINAL DEENERGIZED. SYSTEM FAN SWITCHES TO CONTINUOUS SPEED AND ENERGIZES ACC TERMINAL. BOTH REMAIN ON UNTIL CONTINUOUS FAN IS SWITCHED OFF AT THERMOSTAT.

Page 34

80MGF WITH SURELIGHT IGNITION CONTROL 1 When there is a call for heat, W1 of the thermostat energizes W of the furnace control with 24VAC. 2 S10 primary limit switch and S47 rollout switch are closed. Call for heat can continue. 3 SureLight control energizes combustion air blower B6. Combustion air blower runs until S18 combustion air prove switch closes (switch must close within 21/2 minutes or control goes into 5 minute Watchguard Pressure Switch delay). Once S18 closes, a 15second prepurge follows. 4 SureLight control energizes ignitor. A 20second warmup period begins.

5 Gas valve opens for a 4second trial for ignition. 6 Flame is sensed, gas valve remains open for the heat call. 7 After 45second delay, SureLight control energizes indoor blower B3. 8 When heat demand is satisfied, W1 of the indoor thermostat deenergizes W of the SureLight control which deenergizes the gas valve. Combustion air blower B6 continues a 5second postpurge period, and indoor blower B3 completes a selected OFF time delay.

Page 35

SURELIGHT CONTROL HEATING SEQUENCE OF OPERATION

NORMAL HEATING MODE
POWER ON CONTROL SELFCHECK OKAY? NO COMBUSTION AIR BLOWER ON FOR 1 SECOND.

ABNORMAL HEATING MODE

GAS VALVE OFF. COMBUSTION AIR BLOWER ON. INDOOR BLOWER ON. LED #1 ALTERNATING FAST FLASH LED#2 ALTERNATING FAST FLASH CHECK FOR BROKEN IGNITOR OR OPEN IGNITOR CIRCUIT GAS VALVE OFF. COMBUSTION AIR BLOWER OFF. INDOOR BLOWER DELAY OFF. LED #1 ON LED #2 ON (RESET CONTROL BY TURNING MAIN POWER OFF.)

TURN INDUCER ON FOR 1 SECOND. IS POLARITY REVERSED? SIGNAL IMPROPER GROUND AT LED. SIGNAL HOLDS UNTIL UNIT IS PROPERLY GROUNDED. NO NO YES IS THERE PROPER GROUND?

YES

POLARITY REVERSED. LED #1 FAST FLASH LED #2 SLOW FLASH

IS VOLTAGE ABOVE 75 VOLTS? YES NO

NO

LOW VOLTAGE SIGNAL AT LED HOLDS UNTIL VOLTAGE RISES ABOVE 75 VOLTS.

ROLLOUT SWITCH CLOSED? YES

GAS VALVE OFF. COMBUSTION AIR BLOWER OFF. INDOOR BLOWER OFF WITH DELAY. LED #1 ON. LED #2 SLOW FLASH. SEQUENCE HOLDS UNTIL ROLLOUT SWITCH CLOSES. GAS VALVE OFF. COMBUSTION AIR BLOWER ON. INDOOR BLOWER ON HEATING SPEED. LED #1 SLOW FLASH LED #2 OFF

BURNER OFF? (CONTINUOUS FLAME CHECK) YES NORMAL OPERATION: LED #1 SLOW FLASH LED #2 SLOW FLASH THERMOSTAT CALLS FOR HEAT: LED #1 FAST FLASH LED #2 FAST FLASH YES IS COMBUSTION AIR PRESSURE SWITCH OPEN? YES IS COMBUSTION AIR BLOWER ENERGIZED? (HTG ACC TERMINAL IS ENERGIZED WITH C.A.B.) YES HAS COMBUSTION AIR PRESSURE SWITCH CLOSED IN 2.5 MINUTES? YES 15-SECOND COMBUSTION AIR BLOWER PREPURGE INITIATED BY CLOSED PRESSURE SWITCH. YES CONTINUED NEXT PAGE

NO

NO

GAS VALVE OFF. COMBUSTION AIR BLOWER OFF. INDOOR BLOWER OFF WITH DELAY. LED #1 OFF LED #2 SLOW FLASH (Sequence holds until pressure switch closes or thermostat resets control.)

NO

PRESSURE SWITCH IS IN WATCHGUARD MODE. GAS VALVE OFF. COMBUSTION AIR BLOWER OFF. INDOOR BLOWER OFF WITH DELAY. LED #1 OFF. LED #2 SLOW FLASH. IS 5-MINUTE RESET PERIOD COMPLETE?

Page 36

NORMAL HEATING MODE

15-SECOND COMBUSTION AIR INDUCER PREPURGE INITIATED BY CLOSED PRESSURE SWITCH. YES IGNITOR WARM-UP 20 SECONDS. YES 4-SECOND TRIAL FOR IGNITION. GAS VALVE OPENS. IGNITOR ENERGIZED FOR 1 SECOND AFTER VALVE OPENS. NO FLAME SENSED DURING THIS PERIOD. BOARD 97L48 ONLY: IGNITOR ENERGIZED FOR THE FULL 4SECOND TRIAL FOR IGNITION. YES FLAME STABILIZATION PERIOD. 4 SECONDS FLAME RECTIFICATION CURRENT CHECK. CAN FLAME BE PROVEN WITHIN 4 SECONDS AFTER GAS VALVE OPENS? (u0.15 microamps) YES NO FLAME PRESENT? YES FLAME SIGNAL ABOVE 0.7 MICROAMPS? YES INDOOR BLOWER ON DELAY BEGINS (45 seconds.) YES PRIMARY AND SECONDARY LIMIT SWITCHES CLOSED? NO NO NO

ABNORMAL HEATING MODE

IS VOLTAGE ABOVE 75 VOLTS? YES IS THERE A PROPER GROUND? YES YES NO NO NO LEDS SIGNAL ALTERNATING FAST FLASH

IS IGNITOR INTACT AND CONNECTED? GAS VALVE OFF. COMBUSTION AIR INDUCER ON. INDOOR BLOWER OFF. NO HAS CONTROL FAILED TO SENSE FLAME FOR FIVE CONSECUTIVE TRIES DURING A SINGLE HEAT DEMAND?

NO

YES

IGNITION WATCHGUARD MODE. GAS VALVE OFF. COMBUSTION AIR INDUCER OFF. INDOOR BLOWER OFF WITH DELAY LED 1 ALT. SLOW FLASH LED 2 ALT SLOW FLASH IS 60-MINUTE RESET PERIOD COMPLETE? YES HAS CONTROL RESET IGNITION SEQUENCE FOUR TIMES? LOW FLAME SIGNAL (Does not affect operation of control) LED #1 SLOW FLASH LED #2 FAST FLASH GAS VALVE DEENERGIZED. COMBUSTION AIR INDUCER DEENERGIZED.INDOOR BLOWER ON UNTIL SWITCH CLOSES.LED #1 SLOW FLASH. LED #2 ON. IS LIMIT SWITCH CLOSED? YES NO NO

YES

LIMIT SWITCH WATCH GUARD MODE. GAS VALVE OFF. COMB. AIR INDUCER OFF. INDOOR BLOWER OFF WITH DELAY. LED#1SLOW FLASH LED#2 ON. IS 60MINUTE RESET PERIOD COMPLETE.?

YES

HAS PRIMARY/SECONDARY LIMIT RESET. (See table 9 DIAGNOSTIC CODES for limit reset operation) NO

YES

ROLLOUT SWITCH CLOSED? YES COMBUSTION AIR PRESSURE SWITCH CLOSED? YES THERMOSTAT DEMAND SATISFIED. YES LED #1 & #2 SIMULTANEOUS SLOW FLASHES. YES COMB. AIR INDUCER CONTINUES 5-SECOND POST PURGE AFTER TSTAT DEMAND IS SATISFIED. INDOOR AIR BLOWER COMPLETES SELECTED OFF" DELAY BEFORE SHUTTING OFF. ACB.HEAT SPEED, HTG ACC TERM. AND ACC TERM. OFF. NO

GAS VALVE POWER OFF. COMBUSTION AIR INDUCER POWER OFF. INDOOR BLOWER OFF WITH DELAY LED #1 ON. LED #2 SLOW FLASH. SEQUENCE HOLDS UNTIL ROLLOUT SWITCH IS RESET

YES GAS VALVE DEENERGIZED. COMBUSTION AIR INDUCER ON. INDOOR BLOWER OFF WITH DELAY LED #1 OFF. LED #2 SLOW FLASH. HAS CAB SWITCH CLOSED IN 2.5 MINUTES? NO 5-MINUTE PRESSURE SWITCH WATCHGUARD MODE. YES

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SURELIGHT CONTROL COOLING SEQUENCE OF OPERATION

NORMAL COOLING MODE
POWER ON IGNITION CONTROL MAIN POWER ON. NO GAS VALVE OFF. COMBUSTION AIR BLOWER OFF. INDOOR BLOWER OFF WITH NORMAL DELAY. SIGNAL CIRCUIT BOARD FAILURE AT LED. INTERRUPT MAIN POWER TO RESET CONTROL.

ABNORMAL COOLING MODE

CONTROL SELF DIAGNOSTIC CHECK. IS CONTROL OPERATING NORMALLY? YES TURN INDUCER ON FOR 1 SECOND.

YES IS POLARITY REVERSED? SIGNAL IMPROPER GROUND AT LED. SIGNAL HOLDS UNTIL UNIT IS PROPERLY GROUNDED. NO NO YES IS THERE PROPER GROUND? IS VOLTAGE ABOVE 75 VOLTS? NO LOW VOLTAGE SIGNAL AT LET HOLDS UNTIL VOLTAGE RISES ABOVE 75 VOLTS. SIGNAL POLARITY REVERSED AT LED.

ROLLOUT SWITCH MONITORED CONTINUOUSLY. IS ROLLOUT SWITCH CLOSED? YES

NO

GAS VALVE OFF. COMBUSTION AIR BLOWER OFF. INDOOR BLOWER OFF WITH NORMAL DELAY. SIGNAL CIRCUIT BOARD FAILURE AT LED. SEQUENCE HOLDS UNTIL ROLLOUT SWITCH CLOSES. GAS VALVE OFF. COMBUSTION AIR BLOWER OFF. INDOOR BLOWER OFF WITH NORMAL DELAY. SIGNAL CIRCUIT BOARD FAILURE AT LED. SEQUENCE HOLDS UNTIL FLAME IS NOT SENSED.

NO CHECK FOR MAIN BURNER FLAME SENSE. IS MAIN BURNER FLAME OFF?

LED: SLOW FLASH RATE REMAINS UNCHANGED THROUGHOUT COOLING CYCLE. THERMOSTAT CALLS FOR COOLING. COMPRESSOR CONTACTOR AND SYSTEM FAN ENERGIZED WITH 0-SECOND DELAY. ACB COOL SPEED AND ACC. TERMINAL IS ENERGIZED.

THERMOSTAT OPENS.

COMPRESSOR OFF.

SYSTEM FAN AND ACC. TERM. OFF WITH 0-SECOND DELAY.

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SURELIGHT CONTROL CONTINUOUS LOW SPEED FAN SEQUENCE OF OPERATION

LED: SLOW FLASH RATE REMAINS UNCHANGED THROUGHOUT SEQUENCE. MANUAL FAN SELECTION MADE AT THERMOSTAT. CONTROL (G) ENERGIZES SYSTEM FAN AT ACB LOW SPEED. ACC. TERMINAL IS ENERGIZED. HTG ACC. TERM. ENERGIZES WITH COMB. AIR BLOWER.

THERMOSTAT CALLS FOR HEAT (W). NO YES

BOARD NO. 63K8901 SYSTEM FAN DEENERGIZED. SYSTEM FAN ENERGIZES ON ACB HEAT SPEED AFTER NORMAL DELAY.

THERMOSTAT CALLS FOR COOLING. YES SYSTEM FAN SWITCHED TO ACB COOL SPEED. ACC. TERM. REMAINS ON. THERMOSTAT OPENS. NO

BOARD NO. 24L85, 56L83, 97L48 SYSTEM FAN SWITCHES TO ACB HEAT SPEED AFTER NORMAL DELAY (fan remains energized)

THERMOSTAT OPENS. COMBUSTION AIR AND HTG ACC TERMINAL DEENERGIZE.

BOARD 63K89: SYSTEM FAN OFF. ACC. TERM. OFF. (AFTER OFF DELAY COMPLETED).

BOARDS 24L85, 56L83 AND 97L48: SYSTEM FAN SWITCHES TO LOW SPEED AFTER NORMAL DELAY. (fan remains energized)

MANUAL FAN SELECTION MADE AT THERMOSTAT. CONTROL (G) ENERGIZES SYSTEM FAN AT ACB LOW SPEED. ACC. TERM. ENERGIZED.

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VIIITroubleshootingSureLight Control
PROBLEM: 1 UNIT FAILS TO OPERATE IN THE COOLING, HEATING, OR CONTINUOUS FAN MODE
Condition Possible Cause Corrective Action / Comments
ACTION 1 Check 120V main voltage. Determine cause of main power failure.

1.1 1.1.1 Both diagnostic lights fail to light up. Main voltage 120V not supplied to unit. LED#1Off LED#2Off 1.1.2 Miswiring of furnace or improper connections. 1.1.3 Circuit breaker tripped or fails to close. 1.1.4 Door interlock switch failure. 1.1.5 Transformer Failure. 1.1.6 Failed control board. 1.2 Diagnostic lights flash the rollout code. 1.2.1 Rollout switch open. 1.2.2 Rollout switch failure. LED#1On, LED#1 O LED#2 Slow LED#2Slow Flash 1.2.3 Miswiring Mis iring or improper connections at rollout switch. 1.2.4 Nine pin connector failure 1.3 On initial powerup the comb. air blower does not energize. Diagnostic lights flash the reverse polarity code. LED#1Fast Flash, LED#2Slow Flash. 1.4 1.4.1 On initial power up the combustion Open combustion air blower motor air blower does not energize. Diagnostic lights flash normal power circuit. on operation. LED#1Slow Flash LED#2Slow Flash 1.4.2 Failed combustion air blower motor.

ACTION 1 Check for correct wiring of 120V to power make up box and transformer. ACTION 2 Check 24V wiring to control board. ACTION 1 Replace circuit breaker if it is reset but does not have continuity. ACTION 2 If circuit breaker still trips, check for short. ACTION 1 Check that door switch is activated when door is closed. ACTION 2 Check wire connections to switch, replace loose connectors. ACTION 3 Check continuity of switch in closed position. Replace if malfunctioning ACTION 1 Check that transformer output is 24V. Replace if malfunctioning ACTION 1 If all the above items have been checked, replace board. ACTION 1 Manually reset the rollout switch by pushing the top button. ACTION 2 Determine the cause of the rollout switch activation before leaving furnace. ACTION 1 Check continuity across rollout switch. Replace rollout switch if switch is reset but does not have continuity.

ACTION 1 Check wiring connections to switch. switch

ACTION 1 Check 9pin connector for proper connection to control board. ACTION 2 Check continuity of the multi plug pin.

1.3.1 120V main power polarity reversed.

ACTION 1 Check the 120V has line and neutral correctly input into control. ACTION 2 Reverse the line and neutral at the 120V field connection.

ACTION 1 Check for 120V to combustion air blower. If no power, check wire and connections.

ACTION 1 If power is present at blower, replace blower.

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PROBLEM 1: UNIT FAILS TO OPERATE IN THE COOLING, HEATING, OR CONTINUOUS FAN MODE
Condition 1.5 On initial powerup the combustion air blower remains energized. g Di Diagnostic li ht fl h th i ti lights flash the improper main ground. LED#1Alternating Fast Flash LED#2Alternating Fast Flash Possible Cause 1.5.1 Improper ground to the unit. 1.5.2 6Pin connector is improperly attached to the circuit board. 1.5.3 Line voltage is below 75V. Corrective Action / Comments
ACTION 1 Check that the unit is properly grounded. ACTION 2 Install a proper main ground to the unit ACTION 1 Check 6pin connector for proper installation. Correctly insert connector into control. ACTION 1 Check that the line voltage is above 75V. Determine cause of voltage drop and supply correct voltage to the control.

PROBLEM 2: UNIT FAILS TO OPERATE IN THE COOLING OR HEATING MODE, BUT COMBUSTION AIR BLOWER OPERATES CONTINUOUS. UNITS WITH CONTROL BOARDS DATE CODED AFTER NOV.1 1997, WILL OPERATE IN COOLING WITH COMBUSTION AIR BLOWER CYCLING 5 SECONDS ON 55 SECONDS OFF, BUT NOT IN THE HEATING MODE.
Condition 2.1 On initial powerup the combustion air blower remains energized. Diagnostic lights flash the improper main ground. Units with control boards date coded after Nov.1 1997; combustion Nov 1 air blower will cycle 5 seconds on 55 seconds off. LED#1Alternating Fast Flash LED#2Alternating Fast Flash Possible Cause Corrective Action / Comments

2.1.1 Open ignitor circuit.

ACTION 1 Check for correct wiring and loose connections in the ignitor circuit. Check multi plug connections for correct installation.

2.1.2 Broken or failed ignitor.

ACTION 1 Unplug ignitor and read resistance across ignitor. If resistance does not read between 10.9 and 19.7 ohms, replace the ignitor.

PROBLEM 3: UNIT FAILS TO FIRE IN THE HEATING MODE, COMBUSTION AIR BLOWER DOES NOT ENERGIZE
Condition 3.1 Unit operates with a cooling or continuous fan demand. Combustion air blower will not start with a Heating demand. Diagnostic lights flash the limit failure g g mode. d LED#1Slow Flash, LED#2On Possible Cause 3.1.1 Primary or secondary (if equipped) limit open. Corrective Action / Comments
ACTION 1 Check continuity across switch(es). Switches reset automatically upon cool down. ACTION 2 Check for restrictions on blower inlet air (including filter) and outlet air. Determine cause for limit activation before placing unit back in operation.

3.1.2 Miswiring of furnace or improper connections at limit switch(es).

ACTION 1 Check for correct wiring and loose connections. Correct wiring and/or replace any loose connections.

3.2 3.2.1 Unit operates with a cooling and continuous fan demand. Miswiring of furnace or improper con Combustion air blower will not start nections to combustion air blower. with a Heating demand. Diagnostic lights flash the pressure switch failure code. LED#1Off, LED#2Slow Flash 3.2.2 Pressure switch stuck closed.

ACTION 1 Check for correct wiring and loose connections. Correct wiring and/or replace any loose connections.

ACTION 1 Check that the pressure switch is open without the combustion air blower operating. Replace if malfunctioning

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PROBLEM 3: UNIT FAILS TO FIRE IN THE HEATING MODE, COMBUSTION AIR BLOWER DOES NOT ENERGIZE (CONT.).
Condition Possible Cause Corrective Action/Comments 3.3 Unit operates with a cooling and con3.3.1 tinuous fan demand. Miswiring of furnace or improper con Combustion air blower will not start nections to combustion air blower. with a Heating demand. Diagnostic lights flash the pressure switch failure code 2.5 minutes after 25 heating demand. 3.3.2 Combustion air blower failure. LED#1Off, LED#2Slow Flash

ACTION 1 Check for correct wiring and loose connections. Correct wiring and/or replace any loose connections.

ACTION 1 If there is 120V to combustion air blower and it does not operate, replace combustion air blower.

PROBLEM 4: UNIT FAILS TO FIRE IN THE HEATING MODE, COMBUSTION AIR BLOWER ENERGIZES, IGNITOR IS NOT ENERGIZED.
Condition 4.1 Unit operates with a cooling and continuous fan demand. Combustion air blower energizes with a heating demand demand. Diagnostic lights flash the pressure switch failure code 2.5 minutes after heating demand. LED#1Off LED#2 Slow LED#2Slow Flash Possible Cause 4.1.1 Pressure switch does not close due to incorrect routing of the pressure switch tubing. 4.1.2 Pressure switch does not close due to obstructions in the pressure tubing. 4.1.3 Pressure switch tubing damaged Corrective Action/Comments
ACTION 1 Check that the pressure switch tubing is correctly routed. Correctly route pressure switch tubing.

ACTION 1 Remove any obstructions from the pressure tubing and/or taps.

ACTION 1 Check pressure switch tubing for leaks. Replace any broken tubing. ACTION 1 Check the differential pressure across the pressure switch. This pressure should exceed the set point listed on the switch. ACTION 2 Check for restricted inlet and exhaust vent. Remove all blockage. ACTION 3 Check for proper vent sizing and run length. See installation instructions. ACTION 4 Check voltage to combustion air blower. ACTION 1 Check that the proper pressure switch is installed in the unit. Replace pressure switch if necessary.

4.1.4 Pressure switch does not close due to a low differential pressure across the pressure switch.

4.1.5 Wrong pressure switch installed in the unit, or pressure switch is out of calibration. 4.1.6 Miswiring of furnace or improper connections at pressure switch. 4.1.7 Pressure switch failure.

ACTION 1 Check for correct wiring and loose connections. Correct wiring and/or replace any loose connections. ACTION 1 If all the above modes of failure have been checked, the pressure switch may have failed. Replace pressure switch and determine if unit will operate.

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PROBLEM 5: UNIT FAILS TO FIRE IN THE HEATING MODE, COMBUSTION AIR BLOWER ENERGIZES, IGNITOR IS ENERGIZED. (CONT.)
Condition 5.1 Unit operates with a cooling and continuous fan demand. Combustion air blower energizes with Heating demand. Ignitor is energized but unit fails to light. Possible Cause 5.1.1 Check that gas is being supplied to the unit. 5.1.2 Miswiring of gas valve or loose connections at multipin control amp plugs or valve. 5.1.3 Malfunctioning gas valve or ignition control. Corrective Action/Comments
ACTION 1 Check line pressure at the gas valve. Pressure should not exceed 13" WC for both natural and propane. Line pressure should read a minimum 4.5" WC for natural and 8.0"WC for propane. ACTION 1 Check for correct wiring and loose connections. Correct wiring and/or replace any loose connections. ACTION 1 Check that 24V is supplied to the gas valve approximately 35 seconds after heat demand is initiated. ACTION 2 Replace the valve if 24V is supplied but valve does not open (check for excessive gas line pressure before replacing gas valve). ACTION 3 Replace the control board if 24V is not supplied to valve.

LED#1Alternating Slow Flash LED#2Alternating Slow Flash

PROBLEM 6: BURNERS LIGHT WITH A HEATING DEMAND BUT UNIT SHUTS DOWN PREMATURELY
Condition 6.1 Burners fire with a heating demand. Burners light but unit shuts off prior to satisfying Tstat demand. Diagnostic lights flash the pressure switch code. LED#1Off LED#2Slow Flash 6.2 Combustion air blower energizes with a heating demand. Burners light but fail to stay lit B li ht b t f il t t lit. After 5 tries the control diagnostics flash the watchguard burners failed to ignite code. LED#1Alternating Slow Flash LED#2Alternating Slow Flash 6.2.1 Sensor or sense wire is improperly installed. 6.2.2 Sensor or sense wire is broken. 6.2.3 Sensor or sensor wire is grounded to the unit.
ACTION 1 Check that sensor is properly located (page 10) and that the sense wire is properly attached to both the sensor and the control. ACTION 1 Check for a broken sensor. ACTION 2 Test continuity across the sense wire. If wire or sensor are damaged replace the component. ACTION 1 Check for resistance between the sensor rod and the unit ground. ACTION 2 Check for resistance between the sensor wire and the unit ground. ACTION 3 Correct any shorts found in circuit. ACTION 1 Check the microamp signal from the burner flame. If the microamp signal is below 0.70 microamps, check the sense rod for proper location or contamination. ACTION 2 Replace, clean, or relocate flame sense rod. If rod is to be cleaned, use steel wool or replace sensor. DO NOT CLEAN ROD WITH SAND PAPER. SAND PAPER WILL CONTRIBUTE TO THE CONTAMINATION PROBLEM. NOTE: Do not attempt to bend sense rod.

Possible Cause

Corrective Action/Comments

6.1.1 Low pressure differential at the pressure switch.

ACTION 1 Check for restricted vent inlet or exhaust. Remove all blockage. ACTION 2: Check for proper vent sizing. See installation instructions.

6.2.4 Control does not sense flame.

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PROBLEM 6: BURNERS LIGHT WITH HEATING DEMAND BUT UNIT SHUTS DOWN PREMATURELY (CONT.)
Condition 6.3 Combustion air blower energizes with a heating demand. Burners light. Rollout switch trips during the heating demand. Diagnostic lights flash rollout failure. LED#1On LED#2Slow Flash Possible Cause Corrective Action/Comments
ACTION 1 Check that the manifold pressure matches value listed on nameplate. See installation instructions for proper procedure. ACTION 2 Verify that the installed orifice size match the size listed on the nameplate or installation instructions. ACTION 3 Check gas valve sensing hose to insure no leaks are present. ACTION 4 Check the input rate to verify rate matches value listed on nameplate. ACTION 1 Tighten orifice until leak is sealed. NOTE: Be careful not to strip orifice threads. ACTION 2 Check for gas leakage at the threaded orifice connection. Use approved method for leak detection (see unit instructions). ACTION 1 Check for sooting deposits or other restrictions in the heat exchanger assembly. Clean assembly as outlined in instruction manual. ACTION 2 For 80MGF gas furnaces, check for proper combustion and flow. CO2 should measure between 6.0% and 8.0% for natural and 6.5% and 8.5% for L.P. CO should measure below .04% (400PPM) in an airfree sample of flue gases. ACTION 1 Check that the burners are firing into the center of the heat exchanger openings. Correct the location of the burners if necessary.

6.3.1 Unit is firing above 100% of the nameplate input.

6.3.2 Gas orifices leak at the manifold connection.

6.3.3 Insufficient flow through the heat exchanger caused by a sooted or restricted heat exchanger.

6.3.4 Burners are not properly located in the burner box. 6.4 Combustion air blower energizes with a heating demand. Burners light roughly and the unit fails to stay lit. Diagnostic lights flash watchguard flame failure. LED#1Alternating Slow Flash LED#2Alternating Slow Flash 6.4.1 Recirculation of flue gases. This condition causes rough ignitions and operation. Problem is characterized by nuisance flame failures.

ACTION 1 Check for proper flow of exhaust gases away from intake vent. Remove any obstacles in front of the intake and exhaust vent which would cause recirculation. ACTION 2 Check for correct intake and exhaust vent installation. See instructions

6.4.2 Improper burner crossovers

ACTION 1 Remove burner and inspect the crossovers for burrs, or any restriction or if crossover is warped. Remove restriction or replace burners.

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PROBLEM 6: BURNERS LIGHT WITH HEATING DEMAND BUT UNIT SHUTS DOWN PREMATURELY (CONT.)
6.5 Combustion air blower energizes with a heating demand. Burners light. Diagnostic lights flash watch guard flame failure. NOTE" Unit might go into 60 minute Watchguard mode depending on intermittent nature of sensor signal. LED#1Alternating Slow Flash LED#2Alternating Slow Flash

6.5.1 Loose sensor wire connection causes intermittent loss of flame signal.

ACTION 1 Check that the sensor is properly located. ACTION 2 Check that the sense wire is properly attached to both the sensor and the control. Pay extra attention to the pin connectors.

PROBLEM 7: CONTROL SIGNALS LOW FLAME SENSE DURING HEATING MODE

Condition 7.0 Unit operates correctly but the diagnostic lights flash low flame sense code code. LED#1Slow Flash LED#2Fast Flash Possible Cause 7.1.1 Sense rod is improperly located on the burner. Corrective Action/Comments
ACTION 1 Check the sense rod for proper location on the burner. Properly locate the sense rod or replace if rod cannot be located correctly. ACTION 1 Check sense rod for contamination or coated surface. Clean the sense rod with steel wool or replace sensor. DO NOT USE SAND PAPER TO CLEAN ROD. SAND PAPER WILL CONTRIBUTE TO THE CONTAMINATION PROBLEM.

7.1.2 Sense rod is contaminated.

PROBLEM 8: INDOOR BLOWER FAILS TO OPERATE IN COOLING, HEATING, OR CONTINUOUS FAN MODE
Condition 8.0 Indoor blower fails to operate in continuous fan, cooling, or heating mode. Possible Cause 8.1.1 Miswiring of furnace or improper connections at control or indoor blower motor. 8.1.2 120V is not being supplied to the indoor air blower or blower motor failure. 8.1.3 Defective control board Condition 9.0 AM radio interference Possible Cause 9.1.2 Ignitor operation Corrective Action/Comments
ACTION 1 Correct wiring and/or replace any loose connections. Check for correct wiring and loose connections. ACTION 1 Check for 120V at the various calls for indoor blower by energizing "Y", "G", and "W" individually on the low voltage terminal strip. Note that when "W is energized, the blower is delayed 45 seconds. If there is 120V to each motor tap but the blower does not operate, replace the motor. ACTION 1 If there is not 120V when "Y", "G", or "W" is energized, replace the control.

PROBLEM 9: RF STATIC DURING TIME FOR IGNITION

Corrective Action/Comments
ACTION 1 Call Technical Support, Dallas

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SERVICE NOTES

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