Honeywell

l Wiper on the controller potentiometer moves in response to

pressure changes.
l L91 D has 2 potentiometers for unison control of 2 motors.

L91 PROPORTIONING
l L91F has a fixed resistor and a manually-adjusted trim
potentiometer in series with the controller potentiometer; for

PRESSURETROLCONTROLLERS special applications in electronic bridge circuits.

l LSlB,D, and F models have an adjustable proportioning
L91 PROPORTIONING PRESSURETROL CONTROLLERS ARE (throttling) range to allow selection of desired pressure control
SERIES 90 MODULATING PRESSURE CONTROLLERS THAT range.
PROVIDE DIRECT CONTROL OF MODULATING MOTORS OR l Adjustments are made by screws on top of case.
VALVES USED ON AUTOMATIC BURNERS OR STEAM HEAT-
ING SYSTEMS. l Large, easily-read scaleplates are marked in both customary
(or/in.*, psi, or in. Hg) and metric (kPa, MPa, or mm Hg) units.
0 L91A 0 L91B 0 L91D 0 L91F
l Steel case has clear plastic cover so that pressure settings
l Models available for pressure systems up to 300 psi [2066 and potentiometer action can be observed.
kPa].
l Fitting with l/4-16 NPT threads provides rapid installation.
l These controllers may be used with steam, air, noncombust-
ible gases, or other fluids noncorrosive to the brass or phos- l Controller can also be surface mounted by screws through
bronze (300 psi models) bellows. holes (knockouts) in back of case.

I SPECIFICATIONS 1
TABLE I-MODELS AVAILABLE

0.03 to 1.03 MPa 0.09 to 0.36 MPa

IO to 300 ps.0 0.07 to 2.07 MPa 23176CF Yes 30 to 110 psi 0.21 to 0.76 MPa 350 2413
L91 Fa 0 to 15 psi 0 to 103 kPa 9 Yes 1.5 to 12 psi 10 to 63 kPa 25 172
5 to 150 psi 0.03 to 1.03 MPa 9 Yes 13 to 52 psi 0.09 to 0.36 MPa 225 1551

aScaleplates are marked in both customary (ozlin?, psi, or in. Hg) and Metric (kPa, MPa. or mm Hg) units.
bModels available with or without steam trap (siphon loop).
‘Includes steam trap (siphon loop).
dModel available with l/4 in. BSP-TR internal threads (British Standard Pipe Threads) for mounting.
eL91F models have onefixed resistor and one manually-adjustable trim potentiometer in series with thecontroller potentiometer. Varidus combinations of resistance
values and locations of the fixed resistor and trim potentiometer are available. See Table II.
fLength of active winding is 7/64 in. [2.8 mm] for Part No. 23176CB, and l/4 in. [6.4 mm] for Part No. 23176CF.
gSee Table II for potentiometer part number.

D.A. Form Number 65-0059

12-66* @Honeywell Inc. 1966
 FINISH: Gray.
MAIN SCALEPLATE: Marked in both customary (oz/in.*, psi, or in.
Hg) and Metric (kPa. MPa. or mm Hg) units.
PROPcJRTlONlNG RANGE PROPORTIONING RANGE SCALEPlATE (L919, D, and F only):
ADJUSTING SCREW graduated from A to F with a MIN (minimum) value below A. (See
(L91B.D.F.ONLY) CONTROLLER
POTENTIOMETER(S) Table Ill for the value of each division.)
MAIN SCALE
IM P O T E N T I O M E T E R
MOUNTING MEANS: Fitting on bellows has l/4-18 NPT threads
ADJUSTING
JUSTING SCREW (external on 0 to 16 oz/in2, 0 to 4 psi, and 0 to 15 psi models;
internal on all other models) for mounting on a pipe or steam trap
(siphon loop).
POTENTIOMETER NOTE: Some models are available with l/4-19 BSP-TR internal
threads: see Table I.
WIPER ARM(S)
Also can be surface mounted by screws through 2 holes
PROPORTIONING (knockouts) in back of case.
SCALEPLATE
(L91B,D,F ONLY)

PROPORTIONING

INDICATOR TABLE II-L91 F RESISTANCE VALUES AVAILABLE

(L91B.D.F ONLY)

-BELLOWS HOUSING

In Blega 11.2 23367F 3/16 4.8 470 518 t2ohms, R-B

In B lega 17.6 233676 3/16 4.8 870 942+2ohms,R-B
ln w legb 380.0 23176- l/4 6.4 2080 2515 f lOohms,
IMAIN SCALE
SETTING
INDICATOR
aAvailable for Oto 15 psi [Ot 103
o kPa] models only.
n1 KNURLED ADJUSTMENT KNOB ON IO TO 300 PSI
[0.07 TO 2.07 MPa, MODELS.
bAvailable for Oto 15 psi IOto 103 kPa] and 5to 150 psi [0.03 to 1.03 MPa]
models.
El275
'Nominal resistancevalues.

eManually adjustable trim potentiometer is 100 ohms (nominal) in all L91F

FIG. l- SETTING AN L91 PROPORTIONING PRESSURETROI models. With zero pressure on the bellows, adjust the trim potentiometer to
obtain the resistance values listed between terminals R and 8, or between
CONTROLLER. terminals R and W, as indicated.

TABLE III-APPROXIMATE VALUE OF EACH DIVISION

MODELS: (A TO 9, B TO C. etc.) ON PROPORTIONING (Throttling)
LSlA-single potentiometer; nonadjustable proportioning RANGE SCALEPLATE (L919,D.F only)
range.
L91 B-single potentiometer; adjustable proportioning range. OPERATING VALUE OF EACH
L91D-2 potentiometers allow unison control of 2 motors; RANGE I DIVISION
adjustable proportioning range. CUSTOMARY UNITS METRIC UNITS CUSTOMARY UNITS METRIC UNITS
L91 F-single potentiometer; adjustable proportioning range;
fixed resistor and manually-adjustable trim potentiometer in
series with controller potentiometer. ~
ELECTRICAL RATING: 24 Vat.
POTENTIOMETER ACTION: Wiper moves toward “w” on pressure
rise; toward “6” on pressure fall. Potentiometer is field 2 to 50 psi 14 to 345 kPa 4.7 psi 32.4 kPa
replaceable.
5 to 156 psi 10.03 to 1.03 MPal 7.8 psi 1 0.054 MPa
POTENTIOMETER RESISTANCE: 140 ohms (nominal) for LSlA,B,
(L91B)
and D models; see Table II for L91 F models.
PRESSURE SENSING ELEMENT: Phos-bronze bellows. 5to 150 osi 10.03to 1.03 MPal 6.7 psi 1 0.046 MPa
MAXIMUM AMBIENT TEMPERATURE: 150 F [66 C]. (LSlD,i)
MINIMUM AMBIENT TEMPERATURE: 32 F [0 C]. 10 to 300 psi 0.07 to 2.07 MPa 16.4 psi 0.113 MPa
ADJUSTMENT MEANS: Screws on top of controller case; knurled (L918 with 7/64 in.
knob for main scale setting on 10 to 300 psi [0.07 to 2.07 MPa] pot.)
models.
SET POINT: At low pressure end of proportioning 10 to 300 psi 0.07 to 2.07 MPa 13.8 psi 0.095 MPa
(throttling) range. (LSlB,D with l/4
WEIGHT: 116.15 oz. [0.88 kg]. in. pot.)

PRINTED IN U.S.A.