Table 18 — Reading and Changing

Chilled Fluid Set Point Transducer Calibration — Press and scroll down to
view the transducer calibration information. See Table 19
KEYPAD ENTRY DISPLAY RESPONSE COMMENTS for a complete list, and the Pressure Transducers section on
COOLING Change set point from page 59 for a description of this subfunction.
default to 48 F.
Cool Set point 1 Manual Control Mode — This control allows the user to
44.0 F default have full control over the compressors, loaders, and the mini-
Cool Set point 1 Set point change mum load valve (if installed) of the machine. Normal safe-
48.0 F complete ties such as high pressure, oil level and pressure, and CPM
related alarms are NOT bypassed in this control mode. The
SERVICE FUNCTION — This function allows the techni- capacity control function and overrides ARE bypassed when
cian to view and input configuration data. Factory configu- using the manual control mode. To enter this mode, switch
ration data, field configuration data, and service configura- the LOR switch to OFF. Press at the HSIO. The dis-
tion data may be viewed or entered through the keypad and
display module. See Table 19 for a complete listing of con- play will read Manual Control Enable - Disable. Press
figurable items. Whenever a processor module is replaced in and switch the LOR switch to Local. The display will change
the field, the complete list of configuration codes should be to Manual Control Enable - Enable. The Disable and Enable
checked for correct settings. The current software version will appear on the second line of the display. See Table 19
can be displayed. See Table 20. for a complete list of this function.
Scroll down in this function to display configuration in- Scroll down and press to start the desired com-
formation including number of compressors, tonnage, and pressor. The control will start the compressor if the pre-lube
compressor must-trip amps. cycle is passed, just as in normal operation. Press to
Password Protection of HSIO Configurable Service Points
add loaders as desired and press to turn off loaders
— To modify configurations and values and to use the manual
control subfunction, the password must be entered before the and compressors. The Minimum Load Valve can be ener-
first change can be made. The default password is set to gized using the same procedure.
. See Table 21 for an example of how to Dual Chiller Configuration — Press to enter the Dual
enter the password to change the Lead/Lag configuration. Chiller control configuration. This method of control is for
a stand-alone Master/Slave combination of chillers and will
Options Configuration Tables 1 and 2 — These subfunc- NOT work with the Flotronic™ System Manager (FSM).
tions can be accessed by pressing or and scroll- The Minus One Pass Cooler option is required for this
ing down to display the configuration options. See Table 19 configuration.
for a complete list of these options. The chillers should be piped for series flow through the
coolers. The Master chiller must be downstream from the
Temperature Reset, Demand Limit and Head Pressure PID Slave chiller leaving water. Both the Master and Slave chiller
Configurations — Press and scroll down to view the must be connected to the same CCN Level II communica-
configuration information. See Table 19 for a complete list. tions bus with different addresses. To enable the dual chiller
Factory Configuration Codes — Pressing allows configuration the CCN Enable function must be set
entry into the factory and service configuration codes to Enable for each chiller, otherwise each chiller will oper-
subfunction. Under this subfunction, there are 5 configura- ate independently. This value can be activated through the
tion codes that are downloaded at the factory. Each code is HSIO or through a CCN device. Both chillers should be con-
made up of 8 digits. If the processor module is replaced in figured for Close Control and require flow switches
the field, these 5 configuration codes should be checked us- to be installed. For cooler pump control, wire both Master
ing the keypad and HSIO display module. See Table 22 for and Slave chiller outputs to the cooler pump starter. All sys-
a description of the factory configuration codes (codes 1 through tem inputs (temperature reset, demand limit, dual set point,
3) and service configuration codes (codes 4 and 5). etc.) should be connected to the Master chiller. If Lead/Lag
The factory and service configuration codes are found by Balance is disabled, the Master chiller will always be the
lead chiller. If Lead/Lag Balance is enabled, the control will
pressing . These are preset from the factory. They can alternate between the Master and Slave chillers to keep their
be verified by following the description in Table 22. These respective run hours balanced within the value configured
codes MUST be checked and corrected in the field if the for Lead/Lag Balance Delta. The desired leaving fluid set
PSIO-1 module is replaced.
point for the Duplex chiller must be configured in
NOTE: The LOCAL/OFF/REMOTE switch must be in the
OFF position to change configuration codes. the Master chiller. CCN Control of the chillers can be dis-
A label is applied to a control box panel with a list of abled locally through the HSIO by entering and en-
factory and service codes for particular units. Table 23 shows abling the Disable CCN Control value. This value must be
how to configure a new PSIO-1 module for use in a 30HXC- disabled before the chiller will return to Duplex control.
106---501CA water cooled chiller.

30
 Table 19 — Service Function and Subfunction Directory
SUBFUNCTION KEYPAD ENTRY DISPLAY COMMENT
1 Service Configuration Software CESR_500100 Ver
xxx
Unit Type 1 = Air-cooled, 2 = Water-cooled
x 3 = Split system
Number of Cir A Comp
x
Compressor A1 Tonnage
xx
Compressor A2 Tonnage
xx
Oil Switch Configuration
x
Number of Cir B Comp
x
Compressor B1 Tonnage
xx
Compressor B2 Tonnage
xx
Max. Cond. Temp Setpoint 30GX = 154 F (68 C)
xxx.x dF 30HXA = 152 F (67 C)
30HXC = 122 F (50 C)
MOP Set point Default = 52 F (11.1 C)
xx.x dF
Fan Staging Select Displays ‘‘Not Used’’ or a
x number. See Table 5
CPM Board Used?
Yes
Compr. A1 Must Trip Amps Value from CPM module. See Appendix A.
xxx.x
Compr. A2 Must Trip Amps Value from CPM module. See Appendix A.
xxx.x
Compr. B1 Must Trip Amps Value from CPM module. See Appendix A.
xxx.x
Compr. B2 Must Trip Amps CURRENTLY NOT USED
xxx.x
2 Options Configuration 1 Cooler Fluid Select 1 = Water (Default), 2 = Medium Temp Brine
x 3 = Low Temp Brine (HX only)
Min. Load Valve Select Displays Enable/Dsable
x Default: Dsable
Loading Sequence Select 1 = Equal circuit, 2 = Staged circuit
x Default: 2. See page 6
Lead/Lag Sequence Select 1 = Automatic (Default), 2 = Circuit A leads,
x 3 = Circuit B leads
Head Press. Control Type 0 = None (Default, HX), 1 = Air cooled
x (Default, GX), 2 = Water cooled
Motormaster Select 0 = None (Default), 1 = Direct control
x
Water Valve Type 0 = None (Default), 1 = 4-20 mA, 2 = 0-10 V,
x 3 = 20-4 mA, 4 = 10-0 V
Ext. Reset Sensor Select 0 = Space Temp Thermistor (Default)
x 1 = Outside Air Thermistor
Cooler Pump Interlock 0 = No interlock
x 1 = Interlock enabled (Default)
Cooler Pump Control 0 = Not controlled (Default)
x 1 = On/Off Control
Condenser Pump Control 0 = Not controlled (Default)
x 1 = On/Off Control
2 = Off when stages equal 0 (unit off)
Condenser Flow Switch Displays Enable/Dsable
x Default: Dsable
Condenser Water Sensors 0 = Not used (Default), 1 = Used
x
Heat Reclaim Sensors CURRENTLY NOT SUPPORTED
x
3 Options Configuration 2 Cooling Setpoint Select 0 = Single set point (Default), 1 = Dual
x set point (switch controlled), 2 = Dual
set point (clock controlled)
Heating Setpoint Select 0 = Single set point (Default), 1 = Dual
x set point (switch controlled), 2 = Dual
set point (clock controlled)
CURRENTLY NOT SUPPORTED
See Legend on page 34.

31
 Table 19 — Service Function and Subfunction Directory (cont)
SUBFUNCTION KEYPAD ENTRY DISPLAY COMMENT
3 Options Configuration 2 (cont) Ramp Load Select 0 = Disabled, 1 = Enabled (Default)
x See page 8
Clock Control Select 0 = No clock control (Default)
x 1 = Local clock control
65 = CCN Clock Control
Ice Configuration Select 0 = Disabled (Default)
x 1 = Clock Control
2 = Demand Limit Control
OAT Sensor Select 0 = Disabled, 1 = Enabled
x Default: 0
Remote Alarm Select 0 = Disabled, 1 = Enabled
x Default: 0
Alarm Reset Select 0 = Not selected, 1 = Selected
x (Default, allows use of LOR
switch to reset alarms)
Close Control Select 0 = Disabled, 1 = Enabled
x Default: 0. See page 7
Deadband Multiplier Default: 1.0
x.x
Current Unbalance Alarm Alarm at 10% imbalance; 0 = Disabled, 1 = Enabled
x Default: 1
Voltage Unbalance Alarm Alarm at 3% imbalance; 0 = Disabled, 1 = Enabled
x Default: 1
4 Reset Configuration Table COOLING RESET TYPE See Demand Limit section, page 39
1
Degrees Reset at 20 mA Default: 0
xx.x dF
COOLING RESET TYPE
2
Remote temp=No Reset Default: 20
xx.x dF
Remote temp=Full Reset Default: 125
xx.x dF
Degrees Reset Default: 0
xx.x dF
COOLING RESET TYPE
3
CHW Delta T=No Reset Default: 15
xx.x dF
CHW Delta T=Full Reset Default: 0
xx.x dF
Degrees Reset Default: 0
xx.x dF
COOLING RESET

Select/Enable Reset Type 0 = No Reset (Default) , 1 = 4-20 mA Reset,

x 2 = External Reset, 3 = Return Fluid Reset
HEATING RESET TYPE CURRENTLY NOT SUPPORTED
1
Degrees Reset at 20 mA Default: 0
xx.x dF
HEATING RESET TYPE CURRENTLY NOT SUPPORTED
2
Remote temp=No Reset Default: 125
xx.x dF
Remote temp=Full Reset Default: 20
xx.x dF
Degrees Reset Default: 0
xx.x dF
HEATING RESET TYPE CURRENTLY NOT SUPPORTED
3
HTW Delta T=No Reset Default: 15
xx.x dF
HTW Delta T=Full Reset Default: 0
xx.x dF
Degrees Reset Default: 0
xx.x dF
HEATING RESET

Select/Enable Reset Type 0 = No Reset (Default), 1 = 4-20 mA reset,

x 2 = External reset, 3 = Return Fluid reset
DEMAND LIMIT See Demand Limit section, page 39

Demand Limit at 20 mA Enter 0-100, Default: 0%

xxx.x%

32
 Table 19 — Service Function and Subfunction Directory (cont)
SUBFUNCTION KEYPAD ENTRY DISPLAY COMMENT
4 Reset Configuration Table (cont) Demand Limit Select 0 = None (Default), 1 = Two step switch,
x 2 = 4-20 mA, 3 = CCN Loadshed
Loadshed Group Number 0-99, Default: 0
x
Loadshed Demand Delta 0-60%,Default: 0
xxx%
Maximum Loadshed Time 0-120 min, Default: 60 min
xx min
WATER VALVE PID

Proportional PID Gain Default = 1.0

x.x Adjustable from -20.0 to 20.0
Integral PID Gain Default = 0.1
x.x Adjustable from -20.0 to 20.0
Derivative PID Gain Default = 0.0
x.x Adjustable from -20.0 to 20.0
AIR MOTOR MASTER
PID
Proportional PID Gain Default = 1.0
x.x Adjustable from -20.0 to 20.0
Integral PID Gain Default = 0.1
x.x Adjustable from -20.0 to 20.0
Derivative PID Gain Default = 0.0
x.x Adjustable from -20.0 to 20.0
5 Factory Configuration Codes FACTORY CODES

Configuration Code 1 Factory set. See Table 22.

xxxxxxxx
Configuration Code 2 Factory set. See Table 22.
xxxxxxxx
Configuration Code 3 Factory set. See Table 22.
xxxxxxxx
SERVICE CODES

Configuration Code 4 Factory set. See Table 22.

xxxxxxxx
Configuration Code 5 Factory set. See Table 22.
xxxxxxxx
6 NOT USED
7 Transducer Calibration CALIBRATION OFFSET See Pressure Transducer Calibration, page 59

CIRCUIT A PRESSURE

Discharge Pressure
xxx.x PSI
Suction Pressure
xxx.x PSI
A1 Oil Pressure
xxx.x PSI
A2 Oil Pressure
xxx.x PSI
Economizer Pressure
xxx.x PSI
CALIBRATION OFFSET

CIRCUIT B PRESSURE

Discharge Pressure
xxx.x PSI
Suction Pressure
xxx.x PSI
B1 Oil Pressure
xxx.x PSI
B2 Oil Pressure
xxx.x PSI
Economizer Pressure
xxx.x PSI
Calibrate All at 0 PSIG
No
Last Calibration Date
mmm dd - yy
See Legend on page 34.

33
 Table 19 — Service Function and Subfunction Directory (cont)
SUBFUNCTION KEYPAD ENTRY DISPLAY COMMENT
8 Manual Control Table Manual Control Enable LOR switch should be in
Dsable OFF position
Password Protected Will be displayed if not entered
Enter: earlier in current HSIO use
Manual Control Enable
Dsable
Manual Control Enable Switch LOR switch to Local
Enable before proceeding
Circuit A Compressor 1
Off
Circuit A Compressor 1 Provided no alarms exist,
On control will attempt circuit
start within 2 minutes.
Press to stop circuit.
Circuit A Compressor 2 to enable,
Off
to stop
Circuit A Loader 1 to enable,
Off
to stop
Circuit A Loader 2
Off to enable,
to stop
Circuit A Min Load Valve to enable,
Off
to stop
Circuit B Compressor 1
Off to enable,
to stop
Circuit B Compressor 2 to enable,
Off
to stop
Circuit B Loader 1
Off to enable,
to stop
Circuit B Loader 2 to enable,
Off
to stop
Circuit B Min Load Valve
Off to enable,
to stop
9 Dual Chiller Configuration MST SLV

Master/Slave Select 0 = Disabled

0/1/2 1 = Master
2 = Slave
Slave Address Default = 0
0 Adjustable from 0-236
Lead/Lag Balance 0 = Disabled
0/1 1 = Enabled
Lead/Lag Balance Delta Default = 168
xxx hours Adjustable from 40-400
LEGEND
CCN — Carrier Comfort Network
CHW — Chilled Water
CPM — Compressor Protection Module
HSIO — Standard Keypad
HTW — Hot Water
LOR — Local/Off/Remote
MOP — Maximum Operating Pressure
OAT — Outdoor-Air Temperature
PID — Proportional Integral Derivative

34
 Table 20 — Displaying Current Software Version
KEYPAD
FUNCTION ENTRY DISPLAY COMMENT
Carrier Software Part
Software Software CESR_500100 Ver Number, where XXX is
Version XXX the revision number.

Table 21 — Compressor Lead/Lag Configuration

SUB-FUNCTION KEYPAD
ENTRY DISPLAY
Options Cooler Fluid Select
Configuration 1 1
Min. Load Valve Select
Dsable
Loading Sequence Select
1
Lead/Lag Sequence Select
1
PASSWD PROTECTED FUNC
Enter Password:
Lead/Lag Sequence Select
0
Lead/Lag Sequence Select
2
NOTE: Configurations may be modified after entering the password. The password is only
required to be entered once. After a period of 10 minutes of no HSIO activity, the user is
automatically logged out and the control requires that the password be entered on the
next use.

35
 Table 22 — Factory and Service Configuration Code Values
UNIT MODEL NUMBER CONF. CODE 1* CONF. CODE 2 CONF. CODE 3 CONF. CODE 4 CONF. CODE 5
30GX080 11460010 13900000 00000170 15400521 12000093
30GX090,105 11560010 13900000 00000180 15400521 12000093
30GX106 11560010 13900000 00000180 15400521 14000095
30GX115 11660010 13900000 00000190 15400521 14000095
30GX125 11660010 14600000 00000161 15400521 14000095
30GX136 11660010 15600000 00000162 15400521 14000095
30GX150 11560010 18000000 00000095 15400521 16000097
30GX151 11800010 15600000 00000176 15400521 07000088
30GX160 11660010 18000000 00000105 15400521 16000097
30GX161 11800010 16600000 00000177 15400521 07000088
30GX175 11800010 18000000 00000119 15400521 07000088
30GX176 11800010 18000000 00000119 15400521 03000084
30GX205 12663910 18000000 00000145 15400521 07000088
30GX206 12803910 16600000 00000217 15400521 09000090
30GX225 12804610 18000000 00000166 15400521 07000088
30GX226 12804610 18000000 00000166 15400521 09000090
30GX250 12806610 18000000 00000186 15400521 09000090
30GX251 12808010 16600000 00000258 15400521 05000086
30GX265 12808010 18000000 00000200 15400521 05000086
30HXA076 31390010 13900000 00000183 15200521 02000063
30HXA086 31460010 13900000 00000190 15200521 02000063
30HXA096 31560010 13900000 00000200 15200521 02000063
30HXA106 31660010 13900000 00000210 15200521 02000063
30HXA116 31660010 14600000 00000181 15200521 02000063
30HXA126 31660010 15600000 00000182 15200521 02000063
30HXA136 31800010 15600000 00000196 15200521 02000063
30HXA146 31800010 16600000 00000197 15200521 02000063
30HXA161 31800010 15600000 00000196 15200521 02000063
30HXA171 31660010 18000000 00000125 15200521 02000063
30HXA186 31800010 18000000 00000139 15200521 02000063
30HXA206 32663910 18000000 00000165 15200521 02000063
30HXA246 32805610 18000000 00000196 15200521 02000063
30HXA261 32806610 18000000 00000206 15200521 02000063
30HXA271 32808010 18000000 00000220 15200521 02000063
30HXC076 21390010 13900000 00000173 12200521 00000058
30HXC086 21460010 13900000 00000180 12200521 00000058
30HXC096 21560010 13900000 00000190 12200521 00000058
30HXC106 21660010 13900000 00000200 12200521 00000058
30HXC116 21660010 14600000 00000171 12200521 00000058
30HXC126 21660010 15600000 00000172 12200521 00000058
30HXC136 21800010 15600000 00000186 12200521 00000058
30HXC146 21800010 16600000 00000187 12200521 00000058
30HXC161 21800010 15600000 00000186 12200521 00000058
30HXC171 21660010 18000000 00000115 12200521 00000058
30HXC186 21800010 18000000 00000129 12200521 00000058
30HXC206 22663910 18000000 00000155 12200521 00000058
30HXC246 22805610 18000000 00000186 12200521 00000058
30HXC261 22806610 18000000 00000196 12200521 00000058
30HXC271 22808010 18000000 00000210 12200521 00000058
*Unit Type will be listed as air cooled, water cooled, or remote split system. Unit type is first digit in
Configuration Code 1 and is 1 for 30GX units, 2 for 30HXC units, and 3 for 30HXA cooling only chillers.
For other options, see Table 19 under the Service subfunction. A label listing configuration codes is
located on the control box door or panel.

36
 Table 23 — Entering Configuration Codes
KEYPAD ENTRY DISPLAY RESPONSE
FACTORY CODES

Configuration Code 1
00000000
Configuration Code 1
21660010
Configuration Code 2
00000000
Configuration Code 2
13900000
Configuration Code 3
00000000
Configuration Code 3
00000200
SERVICE CODES

Configuration Code 4
00000000
Configuration Code 4
12200521
Configuration Code 5
00000000
Configuration Code 5
00000058

SCHEDULE FUNCTION — This function provides a means Dual Set Point Control — This feature can be enabled to
to automatically switch the chiller from an occupied mode allow the use of a second or unoccupied cooling set point.
to an unoccupied mode. Refer to Table 24 for a complete The function can be either switch controlled or clock con-
description of the function. trolled. To enable switch control, set the Cooling Setpoint
The schedules consist of 8 user-configurable occupied time selection under to 1. See page 72 or 73 of Field
periods. The control supports time schedules for local con- Wiring section, depending on unit type, for switch input wir-
trol, remote control and ice building. These time periods can ing to the PSIO-2 module. Configure Cool Setpoint 2 under
be flagged to be in effect or not in effect on each day of the
week. The day begins at 00.00 and ends at 24.00. The ma- to the desired value. The unit will then control leav-
chine is in unoccupied mode unless a scheduled time period ing water temperature to Cool Setpoint 2 when the switch
is in effect. If an occupied period is to extend past midnight, input is closed. To enable clock control, set the Cooling
it must be programmed in the following manner: occupied
period must end at 24:00 hours (midnight); a new occupied Setpoint selection under to 2. Set Cool Setpoint 2 to
period must be programmed to begin at 00:00 hours. the desired unoccupied value. Using , configure lo-
NOTE: This is true only if the occupied period starts at 00:00 cal operating schedules for the desired occupied and unoc-
(midnight). If the occupied period starts at a time other than cupied time periods. The unit will then control leaving water
midnight, then the occupied period must end at 24:00 hours temperature to Cool Setpoint 2 during unoccupied time
(midnight) and new occupied period must be programmed periods.
to start at 00:00 in order for the chiller to stay in the occu-
pied mode past midnight. Each time schedule can be over-
ridden to keep the chiller in an Occupied mode for 1, 2, 3 or
4 hours on a one-time basis.

37
 Table 24 — Schedule Function and Subfunction Directory
SUBFUNCTION KEYPAD ENTRY DISPLAY COMMENT
1 Ice Build Schedule* SCHEDULES: OCCPC01S Extended Occupied Time
Timed Override: 00
SCHEDULES: OCCPC01S Two hour override entered
Timed Override: 02
MTWTFSSH OCC UNOCC Displays current stored schedule
01- 00000000 00:00 00:00 (First 2 numbers are schedule, 01-08)
MTWTFSSH OCC UNOCC Monday-Friday now occupied
01- 11111000 00:00 00:00
MTWTFSSH OCC UNOCC Occupied time now set
01- 11111000 21:00 00:00
MTWTFSSH OCC UNOCC Unoccupied time now set
01- 11111000 21:00 06:30 Ice Build schedule completed
MTWTFSSH OCC UNOCC Can enter up to 7
02- 00000000 00:00 00:00 additional ice build schedules
2 Local Schedule† SCHEDULES: OCCPC02S Extended Occupied Time
Timed Override: 00
MTWTFSSH OCC UNOCC Displays current stored schedule
01- 00000000 00:00 00:00 (First 2 numbers are schedule, 01-08)
MTWTFSSH OCC UNOCC Monday-Friday now occupied
01- 11111000 00:00 00:00
MTWTFSSH OCC UNOCC Occupied time now set
01- 11111000 06:30 00:00
MTWTFSSH OCC UNOCC Unoccupied time now set
01- 11111000 06:30 21:00 Local schedule completed
MTWTFSSH OCC UNOCC Can enter up to 7
02- 00000000 00:00 00:00 additional local schedules
3 Remote Schedule SCHEDULES: OCCPC65S Extended Occupied Time
(Currently Not Timed Override: 00
Used) MTWTFSSH OCC UNOCC Displays current stored schedule
01- 00000000 00:00 00:00 (First 2 numbers are schedule, 01-08)
MTWTFSSH OCC UNOCC Monday-Friday now occupied
01- 11111000 00:00 00:00
MTWTFSSH OCC UNOCC Occupied time now set
01- 11111000 06:30 00:00
MTWTFSSH OCC UNOCC Unoccupied time now set
01- 11111000 06:30 21:00 Remote schedule completed
MTWTFSSH OCC UNOCC Can enter up to 7
02- 00000000 00:00 00:00 additional remote schedules
4 Holiday Configuration** HOLIDAYS : HOLDY_01 Can configure holiday start day
Starts on 00/00 00 days and duration
HOLIDAYS : HOLDY_01 Start of holiday set
Starts on 12/23 00 days
HOLIDAYS : HOLDY_01 Holiday duration set
Starts on 12/23 10 days
5-33 Holiday Configuration through HOLIDAYS : HOLDY_02 Allows configuration of 29
Starts on 00/00 00 days additional holiday periods

*Ice configuration select must be set to 1 for clock control. The ice configuration can be accessed by pressing and scrolling down.
†Clock control select must be set to 1 for clock control. The clock control can be accessed by pressing and scrolling down.
**The BROADCAST function (BRODEFS table) must be activated (change to YES and download) when using the LID-2B controller, Building
Supervisor or ComfortWorks™ software for the control to recognize holidays.

38
Temperature Reset — The control system is capable RETURN FLUID TEMPERATURE RESET — In this ex-
of providing leaving fluid temperature reset based on return ample, the unit set point is reset from full load based on the
fluid temperature. Because the temperature difference be- chilled fluid return temperature. The example uses a reset
tween leaving and return temperature is a measure of the value of 10 degrees at full reset. Full reset is at a 2-degree
building load, return fluid temperature reset is essentially an temperature difference across the cooler and no reset would
average building load reset method. be at a 10° F difference across the cooler. See Fig. 10 and
Under normal operation, the chiller maintains a constant Table 28.
leaving fluid temperature approximately equal to the chilled Demand Limit — Demand Limit is a feature that allows
fluid set point. As building load drops from 100% down to the unit capacity to be limited during periods of peak energy
0%, entering cooler fluid temperature drops in proportion to usage. There are 3 types of demand limiting which can be
load. Thus, the temperature drop across the cooler drops from configured. The first type is through 2 switch inputs, which
a typical 10° F (5.5° C) at full load to a theoretical 0° F will reduce the maximum capacity to 2 user-configurable per-
(0° C) at no load. See Fig. 8. centages. The second type is by a 4 to 20 mA signal input
At partial load, leaving chilled fluid temperature may be which will reduce the maximum capacity linearly between
lower than required. If this is allowed to increase (reset), the 100% at a 4 mA input signal (no reduction) down to the user-
efficiency of the chiller increases. Amount of reset can be configurable level at a 20 mA input signal. The third type
defined as a function of cooler temperature drop. This is a uses the CCN Loadshed module and has the ability to limit
simple linear function that requires 3 pieces of input data for the current operating capacity to maximum and further re-
the set function that will vary depending on measurement duce the capacity if required.
method used. See the following sections and Table 25. To use Demand Limit, select the type of demand limiting
NOTE: Reset set points are not accessible unless the reset to use. Then configure the Demand Limit set points based on
function is enabled first. The Control Point will be recalcu- the type selected.
lated taking into account the set point plus the amount of
reset. This is done as a field configuration. Select one of the DEMAND LIMIT (Switch Controlled, 30GX only) — In this
3 choices for type of reset: Return Fluid Reset, External Tem- example, demand limit by switch control will be configured
perature Reset, or 4 to 20 mA Signal Reset. See Table 25. and the switch set points will be set at 75% and 40%. Ca-
pacity steps are controlled by 2 relay switch inputs field wired
If dual set point control is enabled, the amount of reset is to PSIO-2, terminal 28 for switch 1 and terminal 25 for switch
applied to whichever set point is in effect at the time. 2. See Table 29.
Tables 26-28 demonstrate how to activate reset. For Demand Limit by switch control, closing the first stage
EXTERNAL TEMPERATURE RESET — In this example, demand limit contact will put the unit on the first demand
the unit set point is reset from full load at 90 F (32 C) to a limit level. The unit will not exceed the percentage of ca-
maximum reset value of 10° F (5.5° C) at 25 F (−6.7 C) pacity entered as Demand Switch 1 set point. Closing con-
outdoor ambient. This means that if the chilled fluid set point tacts on the second demand limit switch prevents the unit
is 44 F (6.7 C), there is no reset if the temperature is 90 F from exceeding the capacity entered as Demand Switch 2
(32 C). At a temperature of 25 F (−6.7 C), the chilled fluid set point. The demand limit stage that is set to the lowest
set point would be reset to 54 F (12.2 C). See Fig. 8 and demand takes priority if both demand limit inputs are closed.
Table 26. A field-supplied outdoor air thermistor must be con- If the demand limit percentage does not match unit staging,
nected to PSIO-2 as shown in Fig. 37. the unit will limit capacity to the closest capacity stage.
To activate this function for space temperature reset leave To Disable Demand Limit: Enter as shown
both the External Reset Sensor Select and the OAT Sensor in Table 29. Scroll down to Demand Limit Select and press
Select at 0, and change the Select/Enable Reset Type to 2,
following the procedure in Table 26. to select no Demand Limit control.
EXTERNALLY POWERED RESET (4 to 20 mA) — In this
example, the unit set point is reset from full load at 4 mA to
a maximum reset value of 10° F (5.5° C) at 20 mA. See
Fig. 9 and Table 27.

Table 25 — Temperature Reset Set Point Limits

MEASUREMENT METHOD
Type 1 — 4-20 mA Type 2 — OAT/Occupied Space
INPUT DATA DESCRIPTION (With 500-Ohm Resistor) (External Sensor) Type 3 — Return Fluid
Variable Limits Variable Limits Variable Limits
Maximum Reset Amount — Degrees Reset (−30 to 30 F) Degrees Reset (−30 to 30 F) Degrees Reset (−30 to 30 F)
Allowable range for maximum at 20 mA −34 to −1 C −34 to −1 C −34 to −1 C
amount which LWT set point
is reset.
Maximum Reset Reference — — — Remote temp = (20 to 125 F) CHW Delta T = (0 to 15 degrees F)
Temperature at which Full Reset −7 to 52 C Full Reset 0 to 8° C
maximum reset occurs. cooler temperature rise
Minimum Reset Reference — — — Remote temp = (20 to 125 F) CHW Delta T = (0 to 15 degrees F)
Temperature at which No Reset −7 to 52 C No Reset 0 to 8° C
no reset occurs. cooler temperature rise
LEGEND
CHW — Chilled Water
OAT — Outdoor-Air Temperature
LWT — Leaving Fluid Temperature

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 Fig. 8 — Cooling External Temperature Reset

Fig. 9 — 4 to 20 mA Cooling Temperature Reset

Fig. 10 — Cooling Return Water Reset

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