Honeywell L91A User Manual

PRODUCT DATA
Put UPC Code Here
60-2152—08
L91A,B,D Proportioning
Pressuretrol
®
Controllers
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.
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.
• Fitting with 1/4 -18 NPT threads allows rapid
installation.
• Surface mount with screws through knockout holes in
case back.
Contents
Application 1
Features 1
Specifications 2
Installation 5
Wiring 6
Checkout 8
Service Information 9

Honeywell L91A Specifications

General

Brand	Honeywell
Model	L91A
Category	Control Unit
Language	English

Summary

Installation

Location and Mounting

Details on where and how to mount the controller, including siphon loop connections.

Wiring

Setting

Instructions on adjusting the main scale setpoint and proportioning range for optimal performance.

Proportioning Range (L91B,D Only)

How to adjust the proportioning (throttling) range on specific L91 models.

Typical Operation

Explains how pressure variations affect the controller's operation and firing rate.

Checkout

Controller Operation Troubleshooting

Troubleshooting steps for diagnosing and resolving controller operational issues.

Service Information

Calibration

Factory calibration process and how to adjust the main scaleplate for accuracy.

Maintenance and Cleaning

Guidelines for upkeep, including cleaning potentiometer components.

Replacing the Controller Potentiometer

Detailed steps for safely removing and installing a new controller potentiometer.