ML180UHE Series Gas Furnace
Product Information
The ML180UHE Series Gas Furnace is a product of Lennox
Industries Inc. based in Dallas, Texas, USA. The furnace is
equipped with safety devices that protect the user and their
property. It has various parts including the Top Cap, Pressure
Switch, Combustion Air Inducer, Upper Access Panel, Burners, Heat
Exchanger Assembly, Gas Valve and Manifold, Blower Access Panel,
Integrated Control, and Blower Motor (refer to Figure 1). The
product manual warns that improper installation, adjustment,
alteration, service, or maintenance can cause property damage,
personal injury, or loss of life. The product should be installed
and serviced by a licensed professional installer (or equivalent),
a service agency, or the gas supplier.
Product Usage Instructions
Before attempting to perform any service or maintenance on the
furnace, turn off the electrical power to the unit at the
disconnect switch. Keep the furnace area clear and free of
combustible material, gasoline, and other flammable vapors and
liquids. If the furnace is installed in an insulated area, it
should be kept free of insulating material as it may be
combustible. The unit must receive an unobstructed flow of
combustion and ventilating air. Do not block or obstruct air
openings on the furnace or air openings to the area in which the
furnace is installed. Take care to maintain established clearances
surrounding the furnace.
Do not store or use gasoline or other flammable vapors and
liquids in the vicinity of this or any other appliance as this
could result in a fire or explosion hazard. Do not store chlorine
or fluorine products near the unit or introduce these products into
the combustion air as they can cause furnace corrosion.
If you smell gas, do not try to light any appliance, touch any
electrical switch, or use any phone in your building. Leave the
building immediately and call your gas supplier from a neighbor’s
phone. Follow the gas supplier’s instructions. If you cannot reach
your gas supplier, call the fire department.
The blower door must be securely in place when the blower and
burners are operating. Gas fumes, which could contain carbon
monoxide, can be drawn into the living space resulting in personal
injury or death. If your home is left unattended for an extended
period of time, check equipment operation periodically. If this is
not possible, shut off the water supply to the house and drain the
pipes to prevent problems associated with a NO HEAT condition
(frozen pipes, etc.).
Any additions, changes, or conversions required in order for the
furnace to satisfactorily meet the application needs must be made
by a licensed professional installer (or equivalent) using
factory-specified and approved parts.
E 2023 Lennox Industries Inc. Dallas, Texas, USA
506733-02 01/2023 Supersedes 506733-01
ML180UHE SERIES
GAS FURNACE
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), a service agency, or the gas supplier.
Litho U.S.A.
WARNING
FIRE OR EXPLOSION HAZARD.
Failure to follow safety warnings exact ly could result in serious injury, death, or property damage.
Do not store or use gasoline or other flammable vapors and liquids in the vicinity of this or any other ap pliance.
Installation and service must be performed by a qualified installer, service agency or the gas supplier.
WHAT TO DO IF YOU SMELL GAS:
D Do not try to light any appliance.
D Do not touch any electrical switch; do not use any phone in your building.
D Leave the building immediately. D Immediately call your gas supplier from a
neighbor’s phone. Follow the gas supplier’s instructions. D If you cannot reach your gas supplier, call the fire department.
ML180UHE Parts Identification
TOP CAP
PRESSURE SWITCH COMBUSTION AIR
INDUCER
UPPER ACCESS PANEL BURNERS
HEAT EXCHANGER ASSEMBLY
GAS VALVE AND MANIFOLD
BLOWER ACCESS PANEL
INTEGRATED CONTROL
BLOWER MOTOR
FIGURE 1
NOTE – This manual is the property of the homeowner and must be left with the equipment user.
activated, furnace operation will stop. If your home is left unattended for an extended period of time, equipment op
Notice to Homeowner
eration must be checked periodically. If this is not possible, the water supply to the house should be shut off and the
This furnace is equipped with safety devices that protect pipes should be drained. This will prevent problems associ
you and your property. If one or more of these devices is ated with a NO HEAT condition (frozen pipes, etc.)
Page 2
CAUTION
Before attempting to perform any service or mainte nance, turn the electrical power to unit OFF at the disconnect switch.
NOTICE
Any additions, changes, or conversions required in order for the appliance to satisfactorily meet the ap plication needs must be made by a licensed profes sional installer (or equivalent) using factory-speci fied and approved parts.
Safety Instructions
1 – Keep the furnace area clear and free of combustible material, gasoline, and other flammable vapors and liquids. If it is installed in an insulated area, the furnace must be kept free of insulating material. Insulating ma terial may be combustible.
2 – DO NOT obstruct air flow to unit. Unit must receive an unobstructed flow of combustion and ventilating air. DO NOT block or obstruct air openings on the furnace or air openings to the area in which the furnace is installed. Take care to maintain established clear ances surrounding the furnace.
3 – DO NOT store chlorine or fluorine products near unit or introduce these products into the combustion air. These products can cause furnace corrosion.
4 – DO NOT draw return air from a room where this fur nace, or any other gas appliance (ie., a water heat er), is installed. When return air is drawn from a room, a negative pressure is created in the room. If a gas ap pliance is operating in a room with negative pressure, the flue products can be pulled back down the vent pipe and into the room. This reverse flow of the flue gas may result in incomplete combustion and the formation of carbon monoxide gas. This toxic gas might then be distributed throughout the house by the furnace duct system.
WARNING
The blower door must be securely in place when the blower and burners are operating. Gas fumes, which could contain carbon monoxide, can be drawn into the living space resulting in personal injury or death.
Your furnace is a gas appliance. It is critical that the gas supplied to the unit be completely burned to avoid the pro
duction of carbon monoxide gas. Complete combustion of the gas requires, but is not limited to, correct gas pressure and gas flow rate, adequate combustion, air, and proper venting.
WARNING
Asphyxiation Hazard
The exhaust vent for this furnace must be leak-free and must be securely connected to the furnace flue collar at all times.
For your safety and to fulfill the terms of the limited warranty, a licensed professional service technician (or equivalent) must annually inspect this furnace and its vent system.
Exposure to carbon monoxide gas can cause personal injury and even death to all occupants, including pets. Any item that is powered by or gives off heat from a combustion process (including lawn mowers, automobiles, and fire places) has the potential to produce carbon monoxide gas. Because of this, Lennox recommends the use of a car bon monoxide detector in your home, even if you do not own gas appliances. Reliable detectors are available at reasonable retail prices. Contact your Lennox dealer for more details about this investment in your safety.
Your furnace is designed to meet standards set by national agencies, and to operate safely when properly installed and maintained. However, the unit’s performance can be greatly impacted by the individual installation and the op erating environment. It is your responsibility to ensure that this appliance is maintained. Proper maintenance is critical for your safety and the satisfactory operation of the prod uct. Lennox strongly recommends annual inspection and maintenance of this appliance. Contact your Len nox dealer for an inspection by a licensed professional ser vice technician (or equivalent).
DANGER
Danger of explosion.
There are circumstances in which odorant used with LP/propane gas can lose its scent. In case of a leak, LP/propane gas will settle close to the floor and may be difficult to smell. An LP/propane leak detector should be installed in all LP applications. Do not attempt to bleed the gas lines of air. Call your local gas provider.
Page 3
Start-Up & Operation Information
WARNING
If you do not follow these instructions exactly, a fire or explosion may result causing property damage, personal injury or death.
BEFORE PLACING THE UNIT INTO OPERATION, smell all around the appliance area for gas. Be sure to smell next to the floor because some gas is heavier than air and will settle on the floor.
The gas valve on the ML180UHE will be equipped with a gas control switch. Use only your hand to move the switch. Never use tools. If the switch will not move by hand, do not try to repair it. Call a licensed professional service techni cian (or equivalent). Force or attempted repair may result in a fire or explosion.
Placing the ML180UHE furnace into operation:
ML180UHE units are equipped with an ignition system. Do not attempt to manually light burners on this furnace. Each time the thermostat calls for heat, the burners will automati cally light. The ignitor does not get hot when there is no call for heat on units with this ignition system.
Operating the Gas Valve (Figure 2 and Figure 3)
1 – STOP! Read the safety information at the beginning of this section.
2 – Set the thermostat to the lowest setting.
3 – Turn off all electrical power to the unit.
4 – This furnace is equipped with an ignition device which automatically lights the burners. Do not try to light the burners by hand.
5 – Remove the upper access panel.
6 – Move switch on gas valve to OFF. See figure 2 and fig ure 3.
7 – Wait five minutes to clear out any gas. If you then smell gas, STOP! Immediately call your gas supplier from a neighbor’s phone. Follow the gas supplier’s instruc tions. If you do not smell gas go to next step.
8 – Move switch on gas valve to ON. See figure 2 and fig ure 3.
MANIFOLD PRESSURE ADJUSTMENT
SCREW
MANIFOLD PRESSURE
OUTLET PORT
INLET PRESSURE
PORT GAS VALVE SHOWN IN ON POSITION
FIGURE 2
Inlet Pressure Tap
Outlet Pressure Tap
GAS VALVE SHOWN IN ON POSITION
FIGURE 3 9 – Replace the upper access panel. 10 – Turn on all electrical power to to the unit. 11 – Set the thermostat to desired setting. NOTE – When unit is initially started, steps 1 through 11 may need to be repeated to purge air from gas line. 12 – If the appliance will not operate, follow the section
“Turning Off Gas to the Unit” and call your licensed pro fessional service technician (or equivalent). Turning Off Gas to the Unit
WARNING
If overheating occurs or if gas supply fails to shut off, shut off the manual gas valve to the furnace before shutting off electrical supply.
1 – Set the thermostat to the lowest setting. 2 – Turn off all electrical power to the unit if service is to be
performed. 3 – Remove the upper access panel. 4 – Move switch on gas valve OFF. 5 – Replace the upper access panel.
WARNING
Do not set thermostat below 60°F (16°C) in heating mode. Setting thermostat below 60°F (16°C) reduces the number of heating cycles. Damage to the unit may occur that is not covered by the warranty.
Filters
All ML180UHE filters are installed external to the unit. Fil ters should be inspected monthly. Clean or replace the fil ters when necessary to ensure proper furnace operation. Replacement filters must be rated for high velocity airflow. Table 1 lists recommended filter sizes. A filter must be in place when the unit is operating.
TABLE 1
Furnace Cabinet Width
Filter Size
Side Return
Bottom Return
14-1/2″ 17-1/2″
21″ 24-1/2″
16 X 25 X 1 (1) 16 X 25 X 1 (1) 16 X 25 X 1 (1) 16 X 25 X 1 (2)
14 X 25 X 1 (1) 16 X 25 X 1 (1) 20 X 25 X 1 (1) 24 X 25 X 1 (1)
Page 4
Maintenance
A licensed professional service technician (or equivalent) should inspect the complete system each season (heating and cooling). The following maintenance procedures should only be conducted by a licensed professional ser vice technician (or equivalent). Do not attempt to service the unit in any way.
WARNING
ELECTRICAL SHOCK, FIRE, OR EXPLOSION HAZARD. Failure to follow safety warnings exactly could result in dangerous operation, serious injury, death or property damage. Improper servicing could result in dangerous opera tion, serious injury, death, or property damage. Before servicing, disconnect all electrical power to furnace. When servicing controls, label all wires prior to dis connecting. Take care to reconnect wires correctly. Verify proper operation after servicing.
WARNING
Asphyxiation Hazard The exhaust vent for this furnace must be leak-free and must be securely connected to the furnace flue collar at all times. For your safety and to fulfill the terms of the limited warranty, a licensed professional service technician (or equivalent) must annually inspect this furnace and its vent system.
CAUTION
To ensure proper operation, a licensed professional service technician (or equivalent) should check the burner flame and conduct a combustion analysis annually.
Annually (before heating season) inspect furnace venting system, vent cap, heat exchanger, and burners for corro sion, deterioration, or deposits of debris. Remove any ob structions.
Inspect the furnace for obvious signs of deterioration.
Inspect the furnace venting system to make sure it is in place, physically sound, and without holes, corrosion, or blockage.
Vent pipe must be clear and free of obstructions and must slope upward away from the furnace.
Inspect the furnace return air duct connection to ensure duct is sealed to the furnace and terminates outside the space containing the furnace.
Inspect the physical support of the furnace to guarantee that it is sound without sagging, cracks or gaps around base and it maintains seal between base and support.
During a seasonal check the service technician will con duct a combustion analysis. The technician will also in spect the indoor blower, burner flames, electrical connec tions and the venting system.
Blower
Check the blower wheel for debris and clean if necessary. The blower motors are prelubricated for extended bearing life. No further lubrication is needed.
WARNING
The blower access panel must be securely in place when the blower and burners are operating. Gas fumes, which could contain carbon monoxide, can be drawn into living space resulting in personal inju ry or death.
Electrical
1 – Check all wiring for loose connections. 2 – Check for the correct voltage at the furnace (furnace
operating).
3 – Check amp-draw on the blower motor with blower ac cess panel in place. Motor Nameplate__________Actual__________
Service Reminder
Call your Lennox service technician if the unit will not oper ate. Before calling, always check the following to be sure service is required:
1 – Check that electrical disconnect switches are ON. 2 – Check room thermostat for proper setting. 3 – Replace any blown fuses or reset circuit breakers. 4 – Gas valve should be ON. 5 – Air filter should not be plugged, which will limit air flow. 6 – Is gas turned on at meter? 7 – Is manual main shut-off valve open? Record the model and serial number of the furnace. These numbers are on the unit nameplate, which is located on the blower deck below the combustion air inducer.
Serial Number __________________
Model Number __________________
Page 5
Safety Precautions
If you discover any of the following, shut down your unit, and contact a Lennox dealer for an inspection by a licensed professional service technician (or equiva lent).
D If you repeatedly hear any new or unfamiliar sounds while your unit is operating, there may be a problem. For example, poorly performing burners can produce unfa miliar noises.
D If you smell any unusual odors, your unit may be operat ing improperly. For example, units can give off unfamil iar odors if components are required to operate in ab normal conditions.
D Look for visible signs of a malfunctioning unit. Examples include unusual amounts of condensate on windows in side your house, visibly burnt components or unusual dirt or rust accumulations on the vent pipe or in the unit.
D If you experience headache, nausea, fatigue, or dizzi ness, the cause could be exposure to carbon monoxide gas. This is often misdiagnosed as the flu because symptoms are similar. If you suffer from flu-like symp toms that are exaggerated at home, but seem to sub side while you are away from the house, exposure to carbon monoxide could be the cause.
WARNING
Do not use this furnace if any part has been under water. A flood-damaged furnace is extremely dan gerous. Attempts to use the furnace can result in fire or explosion. Immediately call a licensed pro fessional service technician (or equivalent) to in spect the furnace and to replace all gas controls, control system parts, and electrical parts that have been wet or to replace the furnace, if deemed neces sary.
Your vigilance may pay off in early detection of a problem before either personal injury or property damage occurs. Do not hesitate to contact a qualified service technician as an investment in your well being.
Planned Service
Pay attention to your furnace. Situations can arise be tween annual furnace inspections that may result in unsafe operation. For instance, items innocently stored next to the furnace may obstruct the combustion air supply. This could cause incomplete combustion and the production of car bon monoxide gas.
Annual Furnace Maintenance At the beginning of each heating season, and to comply with the Lennox Limited Warranty, your system should be checked as follows by a licensed professional service technician (or equivalent).
WARNING
ELECTRICAL SHOCK, FIRE, OR EXPLOSION HAZARD. Failure to follow safety warnings exactly could result in dangerous operation, serious injury, death or property damage. Improper servicing could result in dangerous opera tion, serious injury, death, or property damage. Before servicing, disconnect all electrical power to furnace. When servicing controls, label all wires prior to dis connecting. Take care to reconnect wires correctly. Verify proper operation after servicing.
1- Check wiring for loose connections, voltage at indoor unit and amperage of indoor motor.
2- Check the condition of the belt and shaft bearings if ap plicable.
3- Inspect all gas pipe and connections for leaks.
4- Check the cleanliness of filters and change if necessary (monthly).
5- Check the condition and cleanliness of burners and heat exchanger and clean if necessary.
6- Check the cleanliness of blower assembly and clean the housing, blower wheel and blower motor if neces sary.
7- Inspect the combustion air inducer and clean if neces sary.
8- Evaluate the heat exchanger integrity by inspecting the heat exchanger per the AHRI heat exchanger inspec tion procedure. This procedure can be viewed at www.ahrinet.org
9- Ensure sufficient combustion air is available to the fur nace. Fresh air grilles and louvers (on the unit and in the room where the furnace is installed) must be properly sized, open and unobstructed to provide combustion air.
10 Inspect the furnace venting system to make sure it is in place, structurally sound, and without holes, corrosion, or blockage. Vent system must be free and clear of ob structions and must slope upward away from the fur nace. Check flue pipe, chimney and all connections for tightness and to make sure there is no blockage. Vent system should be installed per the National Fuel Gas Code
11 Inspect the furnace return air duct connection to ensure the duct is sealed to the furnace. Check for air leaks on supply and return ducts and seal where necessary.
Page 6
12 Check the condition of the furnace cabinet insulation and repair if necessary.
13 Perform a complete combustion analysis during the fur nace inspection to ensure proper combustion and oper ation. Consult Service Literature for proper combustion values.
14 Verify operation of CO detectors and replace batteries as required.
Perform a general system test. Turn on the furnace to check operating functions such as the start-up and shut-off operation. 1 – Check the operation of the ignition system, inspect
and clean flame sensor. Check microamps before and
after. Check controls and safety devices (gas valve, flame sensor, temperature limits). Consult Service Manual for proper operating range. Thermal Limits should be checked by restricting airflow and not dis connecting the indoor blower. For additional details, please see Service and Application Note H049.
2 – Verify that system total static pressure and airflow set tings are within specific operating parameters.
3 – Clock gas meter to ensure that the unit is operating at the specified firing rate. Check the supply pressure and the manifold pressure. On two-stage gas furnaces check the manifold pressure on high fire and low fire. If manifold pressure adjustment is necessary, consult the Service Literature for unit specific information on adjusting gas pressure. Not all gas valves are ad justable. Verify correct temperature rise.
Repair Parts List
The following repair parts are available through Lennox dealers. When ordering parts, include the complete furnace model number listed on the CSA International nameplate — Example: ML180UHE045P36A. All service must be done by a li censed professional installer (or equivalent), a service agency, or the gas supplier.
Cabinet Parts Heating access panel Blower access panel Top Cap
Control Panel Parts Transformer Integrated control Door interlock switch
Blower Parts Blower wheel Motor Motor mounting frame Motor power choke (3/4 and 1 hp) Blower housing cutoff plate
Heating Parts
Flame Sensor Heat exchanger assembly Gas manifold Combustion air inducer Gas valve Main burner cluster Main burner orifices Pressure switch Ignitor Primary limit control Flame rollout switches
WARNING
This product contains a chemical known to the State of California to cause cancer, birth defects, or other reproductive harm.
Page 7
Air-Conditioning, Heating, and Refrigeration Institute | AHRI
