58
SERVICING
VENTING
The venting system should be planned and installed with
the following in mind:
•
Should not be longer than necessary.
•
Use 45° elbows rather than 90° elbows when pos-
sible.
•
Must not sag or otherwise trap condensate.
•
Use longest radius fittings possible.
•
If using 3" venting, make the transition from 2" to 3"
as close as practically possible.
•
Ensure there is no flue gas recirculation into the com-
bustion air pipe.
CONDENSATE DRAINAGE
Furnace combustion can be affected if a furnace is holding
condensate. Check for proper connections of drain hoses,
make sure furnace condensate trap is clean. Make sure
furnace is not is not improperly sloped. Make sure air condi-
tioning coil drain is not interfering with furnace drain.
OTHER CAUSES
1. Manifold Gas Pressure must be set 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 heat exchanger tubes, including the
heat exchanger orifice plate – this is the plate which
mounts to the front panel of the heat exchanger between
the burners and the heat exchanger tubes, make sure it
is not loose, missing a screw or hanging down between
the burners and heat exchanger causing flame impinge-
ment.
4. Make sure the field installed gas line is not binding and
causing distortion of burner assembly.
5. If the furnace is installed as a one pipe system; make
sure the surrounding area and structure are adequate to
provide combustion air.
6. Make sure there are no cabinet air leaks allowing supply
air to affect combustion.
7. If heat exchanger integrity is uncertain, follow procedures
in Service Bulletin SF-041.
S-1 CHECKING VOLTAGE
WARNING
HIGH
VOLTAGE
D
ISCONNECT
ALL
POWER BEFORE SERVICING OR
CHANGING ANY ELECTRICAL WIRING.
M
ULTIPLE POWER
SOURCES MAY BE PRESENT.
F
AILURE TO DO SO MAY CAUSE
PROPERTY DAMAGE, PERSONAL INJURY OR DEATH.
1. Remove cover from the Junction Box and gain access to
incoming power lines.
With Power ON:
L
INE VOLTAGE NOW PRESENT
WARNING
2. 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.
3.
No reading - indicates open wiring, open fuse, no
power, or faulty Door Interlock Switch from unit to
fused disconnect service. Repair as needed.
4.
With ample voltage at line voltage connectors, ener-
gize the furnace blower motor by jumpering terminals
R to G on the integrated ignition control.
5.
With the blower motor in operation, the voltage should
be 115 volts ± 10 percent.
6.
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.
7.
After completing check and/or repair, replace Junction
Box cover and reinstall the service panel doors.
8.
Turn on electrical power and verify proper unit opera-
tion.
S-2 CHECKING WIRING
D
ISCONNECT
ALL
POWER BEFORE SERVICING.
WARNING
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.
