Lennox LF25-075A

Page 1
INSTALLATION
INSTRUCTIONS
UNIT HEATERS
507930-01
3/2019
LF25-030/105 Compact Unit Dimensions.......................2
Compact Unit Parts Arrangement ...................................3
LF25-125/200 Standard Unit Dimensions ......................4
LF25-250/400 Standard Unit Dimensions ......................5
Standard Unit Parts Arrangement...................................6
Shipping..........................................................................7
Optional Accessory .........................................................7
Requirements in USA .....................................................7
Requirements in Canada ................................................7
Additional Requirements ................................................8
Unit Heater Installation ...................................................8
Combustion and Ventilation Air.......................................8
Rotation of Combustion Air Inducer - 125/150................9
Venting............................................................................9
Electrical Connections .................................................. 14
Gas Connection ...........................................................18
Leak Check ..................................................................18
Unit Start-Up ................................................................18
To Turn O󰀨 Gas to Unit ................................................19
Heating Sequence of Operations ................................19
Ignition Control LED ....................................................20
High Altitude Adjustments ............................................20
Gas Flow .....................................................................20
Gas Pressure Adjustments .......................................... 20
Limit Control Switch ......................................................21
Louver Vane Adjustment ..............................................21
Combustion Air Pressure Switch .................................21
Flame Rollout Switch ...................................................21
Service..........................................................................21
Start-Up and Performance Checklist ........................... 22
LF25
30,000 to 400,000 Btuh Series
Table Of Contents
RETAIN THESE INSTRUCTIONS
FOR FUTURE REFERENCE
WHAT TO DO IF YOU SMELL GAS:
Do not store or use gasoline or other
cinity of this or any other appliance.
formed by a qualified installer, service
agency or the gas supplier.
Do not try to light any appliance.
Leave the building immediately.
Do not touch any electrical switch; do not use
any phone in your building.
Immediately call your gas supplier from a
neighbor's
structions.
If you cannot reach your gas supplier, call the
fire department.
FIRE OR EXPLOSION HAZARD.
Failure to
ly could result in serious injury, death,
or property damage.
WARNING
Be sure to read and understand the
structions in this manual.
ation, service or maintenance can cause
serious injury, death or property damage.
WARNING
Improper installation, adjustment, alteration, service or
maintenance can cause property damage, personal injury
or loss of life. Installation and service must be performed
by a licensed professional installer (or equivalent), service
agency or the gas supplier.
CAUTION
As with any mechanical equipment, personal injury can
result from contact with sharp sheet metal edges. Be
careful when you handle this equipment.

Lennox LF25-075A Specifications

General

Heating Capacity	75, 000 BTU/h
Phase	1
Min Circuit Ampacity	15 Amps
Width	17.5 inches
Fuel Type	Gas

Summary

General Safety Warnings

Fire or Explosion Hazard Warning

Warning about fire or explosion hazard due to improper installation or operation.

What to do if you smell gas

Instructions on immediate actions to take if gas smell is detected.

USA Installation Requirements

Aircraft Hanger and Garage Installations

Residential Installation

Canada Installation Requirements

Combustion Air Hazards

Hazards of Insufficient Combustion Air

Risks associated with inadequate combustion air supply.

Substances Affecting Heat Exchanger

List of substances detrimental to the heat exchanger.

Venting General Recommendations

Venting Compliance Codes

Compliance with NFPA 54/ANSI Z223.1 and CSA-B149 codes.

Vertical Vents - Metal Vent Pipe

Vertical Venting Specifics

Horizontal Venting Guidelines

Venting Requirements for Category III Appliances

Horizontal Vent Termination Clearances

Venting Using a Masonry Chimney

Prohibition of Common Venting

Masonry Chimney Requirements

Removal from Common Vent

Electrical Connections

Direct Spark Ignition System

Explanation of the direct spark ignition system.

Wiring Diagram and Grounding

Instructions for wiring, grounding, and thermostat connections.

High Voltage Wiring Diagram (030105)

High Voltage Wiring Diagram (125 K-200 K)

High Voltage Wiring Diagram (250 K-400 K)

High Voltage Power Connections

Diagram for high voltage power connections for 250K-400K models.

Low Voltage Thermostat Connections

Diagram for low voltage thermostat connections.

Gas Connection and Supply

Gas Supply Piping Sizing

Considerations for determining correct gas pipe size.

Drip Leg and Shut-off Valve

Requirements for drip leg and manual shut-off valve installation.

Gas Piping Leak Check

Safety Warning for Leak Check

Warning against using open flames for leak detection.

Pressure Testing Isolation

Procedure for isolating the unit during pressure testing.

Unit Start-Up Procedures

Safety Warnings Before Lighting

Critical safety warnings before initiating the start-up process.

Gas Smell Detection

Instructions for smelling for gas and handling potential leaks.

Gas Valve Operation

Appliance Start-Up Sequence

Step-by-step procedure for starting up the appliance.

Turning Off Gas to the Unit

Procedure for safely turning off the gas supply to the unit.

Heating Sequence of Operation

Ignition and Flame Proving

Describes ignition process, flame sensing, and lockout.

Ignition Control LED Indicators

LED Status and Unit Operation

High Altitude Adjustments

Canada Altitude Derating

Recommendations for Canada altitude derating.

USA Altitude Derating

Requirements for USA altitude derating and manifold pressures.

Gas Flow Check

Gas Pressure Adjustment

Line Pressure Check

Checking gas line pressure at maximum firing.

Manifold Pressure Adjustment

Adjusting manifold pressure based on rating plate and altitude.

Service and Maintenance

Safety Precautions for Service

Essential safety precautions before performing service.

Annual Inspection

Requirement for annual inspection by a licensed technician.

Burner Cleaning and Inspection

Flue Passage and Flue Box Cleaning

Combustion Air Inducer Cleaning

Electrical Checks

Flue and Chimney Check

Failure to Operate Troubleshooting

Steps to check if the unit fails to operate.

Safety Shut-off Valve Test

Start-Up and Performance Checklist

Checklist Items

List of items to check during start-up and performance verification.