Lennox Merit Series Guide

LENNOX MERIT SERIES™
GAS FURNACE
USER’S INFORMATION MANUAL
FIRE OR EXPLOSION HAZARD.
Failure to follow safety warnings exactly could
result in serious injury, death, or property
damage.
WARNING
!
>Do not store or use gasoline or other
ammable vapours and liquids in the
vicinity of this or any other appliance.
>Installation and service must be performed
by a qualied installer, service agency or
the gas supplier.
WHAT TO DO IF YOU SMELL GAS:
>Do not try to light any appliance.
>Do not touch any electrical switch; do not
use any phone in your building.
>Leave the building immediately.
>Immediately call your gas supplier from
a neighbour’s phone. Follow the gas
supplier’s instructions.
>If you cannot reach your gas supplier, call
the re department.
April 2013

2
LENNOX MERIT SERIES™ PARTS IDENTIFICATION
NOTICE TO HOMEOWNER
Figure 1
NOTE: This manual is the property of the homeowner
and must be left with the equipment user.
This furnace is equipped with safety devices that protect
you and your property. If one or more of these devices is
activated, furnace operation will stop. If your home is left
unattended for an extended period of time, equipment
operation must be checked periodically. If this is not
possible, the water supply to the house should be shut off
and the pipes should be drained. This will prevent problems
associated with a NO HEAT condition (frozen pipes, etc.).

3
Before attempting to perform any service or
maintenance, turn the electrical power to unit
OFF at the disconnect switch.
CAUTION
!
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.
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.
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.
WARNING
!
Do not use this furnace if any part has been
underwater. A ood−damaged furnace
is extremely dangerous. Attempts to use
the furnace can result in re or explosion.
Immediately call a licensed professional
service technician (or equivalent) to inspect
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 necessary.
WARNING
!
Any additions, changes, or conversions
required in order for the appliance to
satisfactorily meet the application needs must
be made by a licensed professional installer
(or equivalent) using factory-specied and
approved parts.
NOTICE
!
SAFETY INSTRUCTIONS
1. Keep the furnace area clear and free of combustible
material, gasoline, and other ammable vapours and
liquids. If it is installed in an insulated area, the furnace
must be kept free of insulating material. Insulating
material may be combustible.
2. After any heavy snow, ice or frozen fog event, the furnace
vent pipes may become restricted. Always check the
vent system and remove any snow or ice that may be
obstructing the plastic intake or exhaust pipes.
3. DO NOT obstruct air ow to unit. Unit must receive an
unobstructed ow 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.
4. DO NOT store chlorine or uorine products near unit or
introduce these products into the combustion air. These
products can cause furnace corrosion.
5. DO NOT draw return air from a room where this
furnace, or any other gas appliance (ie., a water
heater), is installed. When return air is drawn from a
room, a negative pressure is created in the room. If a gas
appliance is operating in a room with negative pressure,
the ue products can be pulled back down the vent
pipe and into the room. This reverse ow of the ue 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.

4
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.
WARNING
!
If you do not follow these instructions exactly,
a re or explosion may result causing property
damage, personal injury or death.
WARNING
!
Carbon monoxide gas is invisible, odourless
and toxic.
WARNING
!
Danger of explosion.
There are circumstances in which odourant
used with LP/propane gas can lose its scent.
In case of a leak, LP/propane gas will settle
close to the oor and may be difcult 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.
DANGER
!
Your furnace is a gas appliance. It is critical that the gas
supplied to the unit be completely burned to avoid the
production of carbon monoxide gas. Complete combustion
of the gas requires, but is not limited to, correct gas
pressure and gas ow rate, adequate combustion, air, and
proper venting.
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
replaces) has the potential to produce carbon monoxide
gas. Because of this, Lennox recommends the use of
a carbon 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 operating
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 product.
Lennox strongly recommends annual inspection and
maintenance of this appliance. Contact your Lennox
dealer for an inspection by a licensed professional service
technician (or equivalent).
START−UP & OPERATION
INFORMATION
BEFORE PLACING THE UNIT INTO OPERATION, smell all
around the appliance area for gas. Be sure to smell next to
the oor because some gas is heavier than air and will settle
on the oor.
The gas valve on the Lennox Merit Series™ 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
technician (or equivalent). Force or attempted repair may
result in a re or explosion.
Placing the Lennox Merit Series™ furnace into
operation:
Lennox Merit Series™ 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 automatically light. The ignitor does not get hot when
there is no call for heat on units with this ignition system.

5
Operating the Gas Valve (Figure 2)
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 lever on gas valve to OFF. See gure 2.
7. Wait ve minutes to clear out any gas. If you then smell
gas, STOP! Immediately call your gas supplier from a
neighbour’s phone. Follow the gas supplier’s instructions.
If you do not smell gas go to next step.
8. Move lever on gas valve to ON. See gure 2.
Figure 2
GAS VALVE SHOWN IN OFF POSITION
MANIFOLD
PRESSURE
OUTLET
PORT
INLET
PRESSURE
PORT
MANIFOLD
PRESSURE
ADJUSTMENT
SCREW
White Rodgers 3600 Gas Valve
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
professional service technician (or equivalent).
Turning Off Gas to the Unit
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 lever on gas valve OFF.
5. Replace the upper access panel.
FILTERS
MAINTENANCE
All ML180A lters are installed external to the unit. Filters
should be inspected monthly. Clean or replace the lters
when necessary to ensure proper furnace operation.
Replacement lters must be rated for high velocity airow.
Table 1 lists recommended lter sizes.
A lter must be in place when the unit is operating.
Table 1
Furnace
Cabinet Width
Filter Size mm (in) and Quantity
Side Return Bottom Return
A − 338
(14−1/2”)
406 X 635 X 25 1
(16 X 25 X 1)
356 X 635 X 25 1
(14 X 25 X 1)
B− 446
(17−1/2”)
406 X 635 X 25 1
(16 X 25 X 1)
406 X 635 X 25 1
(16 X 25 X 1)
C − 533
( 21”)
405 X 635 X 25 1
(16 X 25 X 1)
508 X 635 X 25 1
(20 X 25 X 1)
D − 622
(24−1/2”)
405 X 635 X 25 2
(16 X 25 X 1)
610 X 635 X 25 1
(24 X 25 X 1)
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 service
technician (or equivalent). Do not attempt to service the
unit in any way.
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
operation, serious injury, death, or property
damage.
Before servicing, disconnect all electrical
power to furnace.
When servicing controls, label all wires prior
to disconnecting.
Take care to reconnect wires correctly.
Verify proper operation after servicing.
WARNING
!

6
Annually (before heating season) inspect furnace venting
system, vent cap, heat exchanger, and burners for
corrosion, deterioration, or deposits of debris. Remove any
obstructions.
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.
Inspect the condensate drain and trap for leaks and cracks.
The drain and trap must also be cleaned and the trap must
be lled with water.
During a seasonal check the service technician will conduct
a combustion analysis. The technician will also inspect the
indoor blower, burner ames, electrical connections 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.
BURNER FLAME
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.
Motor Nameplate__________Actual__________
VENTING SYSTEM
Asphyxiation Hazard
The exhaust vent for this furnace must be
leak-free and must be securely connected to
the furnace ue collar at all times.
For your safety and to fulll the terms of the
limited warranty, a licensed professional
service technician (or equivalent) must
annually inspect this furnace and its vent
system.
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 injury or death.
WARNING
!
To ensure proper operation, a licensed
professional service technician (or equivalent)
should check the burner ame and conduct a
combustion analysis annually.
CAUTION
!
SERVICE REMINDER
Call your Lennox service technician if the unit will not
operate.
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 lter should not be plugged, which will limit air ow.
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 __________________

7
SAFETY PRECAUTIONS PLANNED SERVICE
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
equivalent).
> 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
unfamiliar noises.
> If you smell any unusual odors, your unit may be
operating improperly. For example, units can give off
unfamiliar odours if components are required to operate
in abnormal conditions.
> Look for visible signs of a malfunctioning unit. Examples
include unusual amounts of condensate on windows
inside your house, visibly burnt components or unusual
dirt or rust accumulations on the vent pipe or in the unit.
> If you experience headache, nausea, fatigue, or dizziness,
the cause could be exposure to carbon monoxide gas.
This is often misdiagnosed as the u because symptoms
are similar. If you suffer from u-like symptoms that are
exaggerated at home, but seem to subside while you
are away from the house, exposure to carbon monoxide
could be the cause.
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 qualied service technician as
an investment in your well being.
You should expect a service technician to check the
following items during an annual inspection. Power to the
unit must be shut off for the service technician’s safety.
Fresh air grilles and louvers (on the unit and in the
room where the furnace is installed) − Must be open and
unobstructed to provide combustion air.
Burners − Must be inspected for rust, dirt, or signs of
water.
Vent pipe − Must be inspected for signs of water, damaged
or sagging pipe, or disconnected joints.
Unit appearance − Must be inspected for rust, dirt, signs
of water, burnt or damaged wires, or components.
Blower access door − Must be properly in place and
provide a seal between the return air and the room where
the furnace is installed.
Return air duct − Must be properly attached and provide
an air seal to the unit.
Operating performance − Unit must be observed during
operation to monitor proper performance of the unit and the
vent system.
Combustion gases − Flue products must be analyzed and
compared to the unit specications.
Problems detected during the inspection may make it
necessary to temporarily shut down the furnace until the
items can be repaired or replaced.
Pay attention to your furnace. Situations can arise
between 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
carbon monoxide gas.

8
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: ML18007036A - E or EC. All service must be done by a
licensed professional installer (or equivalent), a service agency, or the gas supplier.
Cabinet Parts
> Upper access panel
> Blower panel
> Top cap
Control Panel Parts
> Transformer
> Integrated control
> Door interlock switch
Blower Parts
> Blower wheel
> Blower housing
> Motor
> Motor mounting frame
> Motor capacitor
> Blower housing cutoff plate
Heating Parts
> Flame sensor
> Heat exchanger assembly
> Gas manifold
> Combustion air inducer
> Gas valve
> Main burner cluster
> Main burner orices
> Pressure switch
> Ignitor
> Primary limit control
> Flame rollout switches
Product contains breglass wool.
Disturbing the insulation in this product
during installation, maintenance, or repair will
expose you to breglass wool. Breathing this
may cause lung cancer. Fibreglass wool may
also cause respiratory, skin, and eye irritation.
To reduce exposure to this substance or for
further information, consult material safety
data sheets available from address shown
below, or contact your supervisor.
WARNING
!

9
START-UP & PERFORMANCE CHECKLIST

10
Australia 13 23 50 New Zealand 0800 653 330
Web www.lennoxaus.com.au
UNIT OPERATION