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Table 8.
Troubleshooting guide (continued)
Symptoms
N. Power venter will not run.
O. Power venter motor turns on and
off while burners are operating.
P.
Power venter motor will not stop.
Q. Not enough heat.
R. Too much heat.
S. Cold air is delivered on start up.
T.
Cold air is delivered during heater
operation.
GMND-SVX01B-EN
Possible Cause(s)
2.
Pilot adjustment screw turned too
low on combination main gas
valve.
3.
Air in gas line.
4.
Incorrect lighting procedure.
5.
Dirt in pilot orifice.
6.
Extremely high or low gas
pressure.
7.
Drafts around unit.
8.
Pilot valve not opening (faulty
wiring).
9.
No spark (faulty wiring).
10. Defective gas valve.
1.
Loose wiring.
2.
Defective motor overload
protector or defective motor.
3.
Defective power venter relay.
1.
Fan relay heater element
improperly wired.
2.
Defective venter relay switch.
3.
Motor protector cycling on and off.
4.
Motor not properly oiled.
1.
Improperly wired venter relay.
2.
Main burners not lighting while
thermostat calls for heat.
3.
Defective venter relay.
1.
Incorrect gas input.
2.
Heater undersized.
3.
Thermostat malfunction.
4.
Heater cycling on high limit.
5.
Check outside dampers if used.
1.
Thermostat malfunction.
2.
Heater runs continuously.
1.
Fan relay heater element
improperly wired.
1.
Incorrect manifold pressure or
input.
2.
Voltage to unit too high.
3.
Air throughput too high.
Corrective Action
2.
Increase size of pilot flame. Refer to
3.
Purge air from line.
4.
Follow lighting instruction label adjacent to gas valve.
5.
Remove pilot orifice. Clean with compressed air or solvent.
(Do not ream.)
6.
Refer to
"Operation," p.
26.
7.
Eliminate drafts. Refer to
8.
Inspect and correct all wiring.
9.
Inspect and correct ignition system wiring. See symptoms
U, V, and W.
10. Replace gas valve.
1.
Check and tighten all wiring connections per diagrams.
Thermostat wires tagged "W" and "G" must be connected
together (unless special thermostats are used; if so, see
thermostat wiring diagram,
2.
Replace motor.
3.
Check for 24V across terminals on fan relay. If 24V is
present, jumper terminals numbered 2 and 4. If motor runs,
the fan relay is defective and must be replaced. If 24V is not
present, check wiring per diagrams.
1.
Be sure venter relay heater terminals are connected per
diagrams.
2.
Replace venter relay.
3.
Check motor amps against motor name plate rating, check
voltage, replace venter relay motor if defective.
4.
Refer to label on motor.
1.
Check all wiring.
2.
Refer to
H
and
N
symptoms.
3.
Replace venter relay.
1.
Refer to
"Operation," p.
26.
2.
This is especially true when the heated space is enlarged.
Have the heat loss calculated and compare to the heater
output (80 percent of input). Your gas supplier or installer
can furnish this information. If heater is undersized, add
additional heaters.
3.
Replace thermostat.
4.
Check air movement through heat exchanger. Check
voltage to fan motor. Clean power venter motor.
5.
Adjust dampers accordingly.
1.
Replace thermostat.
2.
Check wiring per diagrams; check operation at valve. Look
for short (such as staples piercing thermostat wiring), and
correct; replace gas valve. Refer to
1.
Be sure fan relay heater terminals are connected per
diagrams.
1.
Refer to
"Operation," p.
26.
2.
Check motor voltage with fan running. Should be 115 volts
AC.
3.
Refer to
"Operation," p.
26.
Diagnostics
"Operation," p.
26.
"Installation: Mechanical," p.
12.
"Electrical Connections," p.
24).
"Operation," p.
26.
37
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