Honeywell L91B 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 L91B Specifications

General

Brand	Honeywell
Model	L91B
Category	Control Unit
Language	English

Summary

Features of L91A,B,D Controllers

Application of L91 Pressuretrol Controllers

L91 Controller Specifications

Ordering Information

Installation Guide

Location and Mounting

Instructions on where to install the controller and how to physically mount it on boilers or at remote locations, including siphon loop connections.

Wiring the L91 Controller

Setting Up the L91 Controller

Main Scale Set Point Adjustment

Guidance on adjusting the primary operating pressure setpoint using the scaleplate and adjustment screw for desired control pressure.

Integration with Limit Controllers

Explains how to properly set the L91 controller when used with other limit controllers for precise system control and pressure limits.

Proportioning Range Adjustment

Details on how to adjust the throttling range on L91B and L91D models for desired pressure control.

Typical Operation Explained

Checkout and Testing Procedures

Troubleshooting Improper Operation

Steps to diagnose and identify potential issues if the controller is not operating as expected, including checking potentiometer resistance.

Service and Maintenance

Calibration Procedures

Guidance on calibrating the controller to match actual system pressure with the setpoint for accurate readings.

Routine Maintenance Tips

Advice on keeping the controller protected from dirt and dust, and performing basic upkeep for optimal performance.

Potentiometer Cleaning and Replacement

Detailed instructions for cleaning the potentiometer or replacing the entire controller potentiometer unit.