Honeywell L91B, L91D User Manual 2
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L91A,B,D Proportioning
Pressuretrol® Controllers
FEATURES
• Models available for pressure systems up to 300 psi
(2068 kPa).
• May be used with steam, air, noncombustible gases, or
other fluids noncorrosive to brass or phos-bronze (300
psi model) bellows.
• When used with steam boilers, a steam trap (siphon
loop) is recommended.
• Wiper on controller potentiometer moves in response
to pressure changes.
• L91D has two potentiometers for unison control of two
motors.
• L91B,D models have adjustable proportioning
(throttling) range to allow selection of desired
pressure control range.
• Adjustments made with screws on case top.
• Large, easily-read scaleplates in both U.S. customary
(oz/sq. in., psi, or in. Hg) and metric (kPa, MPa, or mm
Hg) units.
• Steel case with clear plastic cover to observe pressure
settings and potentiometer action.
APPLICATION
L91 Proportioning Pressuretrol® Controllers are Series 90
Modulating Pressure Controllers that provide direct control of
modulating motors or valves used on automatic burners or
steam heating systems.
• Fitting with 1/4 -18 NPT threads allows rapid
installation.
• Surface mount with screws through knockout holes in
case back.
PRODUCT DATA
Contents
Application 1
Features 1
Specifications 2
Installation 5
Wiring 6
Checkout 8
Service Information 9
60-2152—08
L91A,B,D PROPORTIONING PRESSURETROL® CONTROLLERS
SPECIFICATIONS
Table 1. Models available.
Maximum Surge
Pressure
Model
Operating Ranges
a
U. S.
Customary
Units Metric Units
Potentiometer
Proportioning (Throttling) Range at Midscale
U. S.
Customary
Units Metric Units psi kPa
Part No.
b
Adjustable
L91A 0 to 15 psi 0 to 103 kPa 23176CB No 0.5 psi 3.4 kPa 25 172
5 to 150 psi 0.03 to 1.03 MPa 23176CB No 5 psi 0.03 MPa 225 1551
b
10 to 300 psi
0.07 to 2.07 MPa 23176CB No 12 psi 0.08 MPa 350 2413
L91B 0 to 15 psi 0 to 103 kPa 23176CF Yes 1.5 to 12 psi 10 to 83 kPa 25 172
c
5 to 150 psi
10 to 300 psi
0.03 to 1.03 MPa 23176CB Yes 5 to 23 psi 35 to 160 kPa 225 1551
c
0.07 to 2.07 MPa 23176CB Yes 12 to 48 psi 85 to 330 kPa 350 2413
10 to 300 psi 0.07 to 2.07 MPa 23176CF Yes 30 to 110 psi 0.21 to 0.76 MPa 350 2413
L91D 0 to 15 psi 0 to 103 kPa 23176CF Yes 1.5 to 12 psi 10 to 83 kPa 25 172
c
5 to 150 psi
10 to 300 psi
0.03 to 1.03 MPa 23176CF Yes 13 to 52 psi 0.09 to 0.36 MPa 225 1551
c
0.07 to 2.07 MPa 23176CF Yes 30 to 110 psi 0.21 to 0.76 MPa 350 2413
Models (Table 1):
L91A: Single potentiometer; nonadjustable proportioning
range.
Adjustment Means: Screws on controller case top; knurled
knob for main scale setting on 10 to 300 psi (0.07 to 2.07
MPa) models.
L91B: Single potentiometer; adjustable proportioning range.
L91D: Two potentiometers allow unison control of motors;
adjustable proportioning range.
Electrical Rating: 24 Vac.
Setpoint: At low pressure end of proportioning (throttling)
range.
Main Scaleplate: Marked in both U.S. customary (oz/sq. in,
psi, or in. Hg) and metric (kPa, MPa, or mm Hg) units.
Potentiometer Action: Wiper moves toward W on pressure
rise, toward B on pressure fall. Potentiometer is field
replaceable.
Proportioning Range Scaleplate (L91B,D only): Gradu-
ated from A to F with a MIN (minimum) value below A.
(See Table 2 for the value of each division.)
Potentiometer Resistance: 140 ohms (nominal) for L91A, B,
and D models.
Mounting Means: Fitting on bellows has 1/4 - 18 NPT
threads (external on 0 to 16 oz/sq. in., 0 to 4 psi, and 0 to
Pressure Sensing Element: Brass bellows, 10-300 psi
models phos-bronze bellows.
Minimum Ambient Temperature: 32° F (0° C)
Maximum Ambient Temperature: 150° F (66° C)
15 psi models; internal on all other models) for mounting on
a pipe or steam trap (siphon loop).
NOTE: Some models are available with 1/4 - 19 BSP-TR
internal threads; see Table 1.
Also can be surface mounted by screws through two knockout
holes in case back.
ORDERING INFORMATION
When purchasing replacement and modernization products from your TRADELINE® wholesaler or distributor, refer to the
TRADELINE® Catalog or price sheets for complete ordering number.
If you have additional questions, need further information, or would like to comment on our products or services, please write or
phone:
1. Your local Honeywell Automation and Control Products Sales Office (check white pages of your phone directory).
2. Honeywell Customer Care
1885 Douglas Drive North
Minneapolis, Minnesota 55422-4386
In Canada—Honeywell Limited/Honeywell Limitée, 35 Dynamic Drive, Toronto, Ontario M1V 4Z9.
International Sales and Service Offices in all principal cities of the world. Manufacturing in Australia, Canada, Finland, France,
Germany, Japan, Mexico, Netherlands, Spain, Taiwan, United Kingdom, U.S.A.
60-2152—08 2
L91A,B,D PROPORTIONING PRESSURETROL® CONTROLLERS
Electrical Connections: Internal screw terminals. Hole inside
of case for 1/2 in. conduit.
Dimensions: See Fig. 1; see Fig. 2 for mounting steam trap
(siphon loop).
Weight: 1 lb, 15 oz (0.88 kg).
Finish: Gray.
Replacement Parts:
129178 Thermoplastic Cover.
23176CB Potentiometer: For all L91A models and a few L91B
models (see Table 1); 140 ohms (nominal); length of active
winding is 7/64 in. (2.8 mm).
Table 2. Approximate value of each division (A to B, B to C, etc.) on proportioning
(throttling) range scaleplate (L91B,D,F only)
Operating Range Value of Each Division
U.S. Customary Units Metric Units
0 to 10 oz/sq in. 0 to 7 kPa 6.2 oz/ sq in. 2.7 kPa
0 to 15 psi 0 to 103 kPa 1.8 psi 12.4 kPa
5 to 150 psi (L91B) 0.03 to 1.03 MPa 7.8 psi 0.054 MPa
5 to 150 psi (L91D) 0.03 to 1.03 MPa 6.7 psi 0.046 MPa
10 to 300 psi (L91B with 7/64 in. potentiometer) 0.07 to 2.07 MPa 16.4 psi 0.113 MPa
10 to 300 psi (L91B,D with 1/4 in. potentiometer) 0.07 to 2.07 MPa 13.8 psi 0.095 MPa
23176CF Potentiometer: For all L91D models and most L91B
models (see Table 1); 140 ohms (nominal); length of active
winding is 1/4 in. (6.4 mm).
Accessories:
50024585-001 Steam Trap (siphon loop): 1/4 in. brass pipe
with 1/4 -18 NPT external threads on both ends.
14026 Steam Trap (siphon loop): 1/4 in. steel pipe with 1/4 -18
NPT external threads on both ends.
33312B Knurled Adjustment Knob: With setscrew; fits on main
scale pressure adjusting screw.
4074BWJ Limit Stop Assembly: To limit setpoint ranges;
includes 129564 Range Stop 107194 Range Stop Screw,
and 23466 Wrench.
U.S. Customary
Units Metric Units
3 60-2152—08
L91A,B,D PROPORTIONING PRESSURETROL® CONTROLLERS
M29781
L91A,B,D
ALL OTHER
MODELS
10 TO 300 PSI
0 TO 15 PSI
0 TO 16 OZ/IN
2
1/4-18 NPT
DIM A (SEE TABULATION TABLE)
DIM B (SEE
TABULATION
TABLE)
DIM C (SEE
TABULATION
TABLE)
1
2
2
3
4
1
2
3
4
4-1/2
(114.3) (COVER)
(110.3) (CASE)
(98.8)
3-57/64
3-13/32 (86.5)
(29.4)
(27.8)
(46.0)
(53.5)
(69.9)
(30.2)
1-1/16
1-3/16
(27.0)
(98.4)
(22.2)
4-11/32
(52.8)
(94.5)
(2)
EXTERNAL THREADS ON 0 TO 15 PSI MODELS; INTERNAL THREADS ON ALL OTHER MODELS.
SOME MODELS ARE ALSO AVAILABLE WITH 1/4-19 BSP-TR INTERNAL THREADS; SEE TABLE 1.
PROPORTIONING RANGE ADJUSTING SCREW ON L91B,D MODELS ONLY.
33312B KNURLED ADJUSTMENT SCREW KNOB, 7/8 IN. [22.2 MM] DIAMETER,. KNOB IS INCLUDED WITH 10 TO 300 PSI [0.07 TO .07 MPa] MODELS;
OPTIONAL ACCESSORY FOR OTHER MODELS.
FOR 10 TO 300 PSI [0.07 TO 2.07 MPa] MODELS. DIM C INCLUDES THE KNURLED ADJUSTMENT KNOB.
TABULATION OF DIMENSIONS A, B, AND C
OPERATING RANGE DIM A DIM B
DIM C
CUSTOMARY UNITS METRIC UNITS IN. MM IN. MM IN. MM
0 TO 15 PSI
5 TO 150 PSI
10 TO 300 PSI
0 TO 103 kPa
0.03 TO 1.03 MPa
0.07 to 2.07 MPa
2-7/16
1-5/8
1-1/4
61.9
41.3
31.8
1-7/32
13/16
5/8
31.0
20.6
15.9
6-7/8
5-3/4
6-1/16
174.6
146.1
154.0
1-5/32
1-3/32
1-13/16
2-1/8
3-7/8
2-3/4
7/8
2-5/64
3-23/32
13/16
(20.1)
1-1/16
(27.0)
44
Fig. 1. Mounting dimensions of the L91 Proportional Pressuretrol® Controllers, in in. (mm).
60-2152—08 4
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