Service - Lennox G40UH Series Installation Instructions Manual

Thermostat Heat Anticipation
Set the heat anticipator setting (if adjustable) according to
the amp draw listed on the wiring diagram that is attached
to the unit.
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__________
NOTE − Do not secure the electrical conduit directly to the
air ducts or structure.
Blower Speeds
NOTE − CFM readings are taken external to unit with a dry
evaporator coil and without accessories.
1 − Turn off electrical power to furnace.
2 − Remove blower access panel.
3 − Disconnect existing speed tap at control board speed
terminal.
NOTE − Termination of any unused motor leads must be insu-
lated.
4 − Refer to blower speed selection chart on unit wiring dia-
gram for desired heating or cooling speed.
5 − Connect selected speed tap at control board speed
terminal.
6 − Resecure blower access panel.
7 − Turn on electrical power to furnace.
Electronic Ignition
The integrated ignition control has an added feature of an
internal Watchguard control. The feature serves as an auto-
matic reset device for ignition control lockout because the
burner has failed to ignite. This type of lockout is usually due
to low gas line pressure. After one hour of continuous ther-
mostat demand for heat, the Watchguard will break and re-
make thermostat demand to the furnace and automatically
reset the control to begin the ignition sequence.
Flue And Chimney
1 − Check flue pipe, chimney and all connections for tight-
ness and to make sure there is no blockage.
2 − Check unit for proper draft.
3 − Is pressure switch closed? Obstructed flue will cause
unit to shut off at pressure switch. Check flue and outlet
for blockages.
4 − Reset manual flame rollout switches on burner box
cover.
Failure To Operate
If the unit fails to operate, check the following:
1 − Is the thermostat calling for heat?
2 − Are access panels securely in place?
3 − Is the main disconnect switch closed?
4 − Is there a blown fuse?
5 − Is the filter dirty or plugged? Dirty or plugged filters will
cause the limit control to shut the unit off.
6 − Is gas turned on at the meter?
7 − Is the manual main shut-off valve open?
8 − Is the internal manual shut-off valve open?
9 − Is the unit ignition system in lock out? If the unit locks out
again, call the service technician to inspect the unit for
blockages.

Service

Disconnect power before servicing unit.
Label all wires prior to disconnection when servicing
controls. Wiring errors can cause improper and dan-
gerous operation. Verify proper operation after ser-
vicing.
At the beginning of each heating season, a qualified techni-
cian should check the system as follows:
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.
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.
Filters
All G40UH(X) 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.
Flue And Chimney
Check the flue pipe, chimney and all connections for tight-
ness and to make sure there is no blockage.
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__________
Cleaning the Heat Exchanger and Burners
NOTE − Use papers or protective covering in front of the fur-
nace while you clean furnace.
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WARNING
CAUTION
WARNING