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Diagnostics
Table 8.
Troubleshooting guide (continued)
Symptoms
F.
Gas Odor.
G. Delayed ignition.
H. Failure to ignite.
I.
Condensation of water vapor.
J.
Burner won't turn off.
K. Rapid burner cycling.
L.
Noisy power venter.
M. Pilot will not light or will not stay
lit.
36
Possible Cause(s)
1. Shut off gas immediately!
2.
Blocked heat exchanger/venting.
3.
Drafts around heater.
4.
Negative pressure in building.
5.
Blocked draft hood.
1.
Excessive primary air.
2.
Main burner ports clogged near
pilot.
3.
Pressure regulator set too low.
4.
Pilot decreases in size when main
burners come on.
5.
Pilot flame too small.
6.
Drafts around venter.
7.
Improper venting.
1.
Main gas valve off.
2.
Lack of power at unit.
3.
Thermostat not calling for heat.
4.
Defective limit switch.
5.
Improper thermostat or
transformer wiring.
6.
Defective gas valve.
7.
Defective thermostat.
8.
Defective transformer.
9.
Loose wiring.
10. Defective ignition control.
1.
Condensation of water vapor.
1.
Poor thermostat location.
2.
Defective thermostat.
3.
Improper thermostat or
transformer wiring at gas valve.
4.
Short circuit.
5.
Defective or sticking gas valve.
6.
Excessive gas supply pressure.
1.
Loose wiring connections at gas
valve or thermostat.
2.
Excessive thermostat heat
anticipator.
3.
Unit cycling on high limit.
4.
Poor thermostat location.
5.
Draft on pilot.
6.
Defective ignitor control.
7.
Defective high limit.
1.
Power venter wheel loose.
2.
Power venter wheel dirty.
3.
Power venter wheel rubbing
housing.
4.
Bearings are dry.
1.
Main gas valve off.
Corrective Action
1. Inspect all gas piping and repair.
2.
Clean heat exchanger/flue.
3.
Eliminate drafts. Refer to
4.
See
"Installation: Piping," p.
5.
Clean draft hood.
1.
Close air shutter. Refer to
2.
Clean main burner ports.
3.
Reset manifold pressure. Refer to
4.
Supply piping is inadequately sized. Refer to
Piping," p.
16.
5.
Clean pilot orifice. Refer to
6.
Eliminate drafts. Refer to
7.
Refer to
"Installation: Piping," p.
1.
Open all manual gas valves.
2.
Replace fuse or turn on power supply.
3.
Turn up thermostat.
4.
Check limit switch with continuity tester. If open, replace
high limit switch.
5.
Check wiring per diagrams.
6.
Replace gas valve.
7.
Check thermostat and replace if defective.
8.
Be sure 115 volts is supplied to the transformer primary,
then check for 24 volts at secondary terminal before
replacing.
9.
Check and tighten all wiring connections per diagrams.
10. Replace, if necessary. Also see U, V, and
1.
Refer to
"Installation: Venting," p.
1.
Relocate thermostat away from drafts.
2.
Replace thermostat.
3.
Check wiring per diagrams.
4.
Check operation at valve. Check for short (such as staples
piercing thermostat wiring), and correct.
5.
Replace gas valve.
6.
Refer to
"Installation: Piping," p.
1.
Tighten all connections.
2.
Adjust thermostat for longer cycles. Refer to
Electrical," p.
24.
3.
Check for proper air supply across heat exchanger.
4.
Relocate thermostat. (Do not mount thermostat on unit).
5.
Eliminate drafts. Refer to
6.
Replace ignitor.
7.
Jumper limit switch terminals 1 and 2. If burner operates
normally, replace switch.
1.
Replace or tighten.
2.
Clean power venter wheel.
3.
Realign power venter wheel.
4.
Oil bearings on power venter motor. (Refer to label on
motor.)
1.
Open all manual gas valves.
"Installation: Mechanical," p.
12.
16.
"Operation," p.
26.
"Operation," p.
26.
"Installation:
"Operation," p.
26.
"Installation: Mechanical," p.
12.
16.
W
symptoms.
18.
16.
"Installation:
"Installation: Mechanical," p.
12.
GMND-SVX01B-EN
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