SERVICING
28
Combustion Quality
1. Manifold Gas Pressure must be set for the gas being
used, Natural or L.P., high and low firing rates. If
converted to L.P. gas, check size of all orifices
2. Remove Draft Inducer, Check the integrity of the gasket
between the inducer and the collector box cover, any
air leak here will have a negative effect on combustion.
Check the orifice hole in the collector box, it must be
free of burrs on both sides
3. Make sure burners are clean, not out of position and line
up correctly with exchanger tubes.
4.
Make sure the field installed gas line is not binding and
causing distortion of burner assembly
5. If heat exchanger integrity is uncertain, follow procedures
in Service Bulletin SF-041.
CHECKING VOLTAGE
WARNING
High Voltage!
Disconnect all power before servicing
or installing this unit. Multiple power
sources may be present. Failure to do
so may cause property damage, personal
injury or death.
1. Remove the burner door.
2. Remove cover from the Junction Box and gain access
to incoming power lines.
With Power ON:
WARNING
Line voltage now present
3. Using a voltmeter, measure the voltage across the hot
and neutral connections.
NOTE: To energize the furnace, the Door
Interlock Switch must be engaged at this point.
4. No reading - indicates open wiring, open fuse, no
power, or faulty Door Interlock Switch from unit to fused
disconnect service. Repair as needed.
5. With ample voltage at line voltage connectors, energize
the furnace blower motor by jumpering terminals R to G
on the integrated ignition control.
6. With the blower motor in operation, the voltage should
be 115 volts ± 10 percent.
7. If the reading falls below the minimum voltage, check
the line wire size. Long runs of undersized wire can
cause low voltage. If wire size is adequate, notify the
local power company of the condition.
8. After completing check and/or repair, replace Junction
Box cover and reinstall the service panel doors.
9. Turn on electrical power and verify proper unit operation.
CHECKING WIRING
WARNING
Disconnect ALL power before servicing
1. Check wiring visually for signs of overheating, damaged
insulation and loose connections.
2. Use an ohmmeter to check continuity of any suspected
open wires.
3. If any wires must be replaced, replace with AWM, 105°C.
2/64 thick insulation of the same gauge or its equivalent.
CHECKING THERMOSTAT, WIRING
WARNING
Disconnect ALL power before servicing
1. Remove the blower compartment door to gain access to
the thermostat low voltage wires located at the furnace
integrated control module terminals.
2. Remove the thermostat low voltage wires at the furnace
control panel terminal board.
3. Jumper terminals R to W on the integrated ignition
control.
With Power On (and Door Interlock Switch closed):
WARNING
Line voltage now present
4. Induced Draft Motor must run and pull in pressure switch.
5. If the hot surface ignitor heats and at the end of the ignitor
warm-up period the gas valve opens and the burners
ignite, the trouble is in the thermostat or wiring.
6.
With power off, check the continuity of the thermostat
and wiring. Repair or replace as necessary.
If checking the furnace in the air conditioning mode,
proceed as follows:
7.
With power off, Jumper terminals R to Y to G.
8. Turn on the power.
