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TROUBLESHOOTING
Table 8.1: Boiler Troubleshooting Guide
PROBLEM POSSIBLE CAUSES CORRECTIVE ACTIONS
1. No power.
2. Limit (Aquastat) not working.
3. Flame rollout switch open.
4. Blocked vent switch open.
5. Gas off at boiler gas valve.
6. Gas off external to boiler.
7. Plugged orifice spuds.
8. Defective gas valve.
9. Improper wiring.
10. Vent damper malfunctioning.
Burners not functioning.
1. Check line voltage wiring and fuses.
2. Check wiring and contacts, relay, temperature
setting. Clean and adjust as necessary.
3. Replace switch. Locate cause and correct.
4. Reset blocked vent switch. Locate cause and correct.
5. Start boiler using Lighting/Operating
Instructions.
6. Check any gas valves in the line.
7. Check, clean and re-install.
8. Use Figure 8.1 to troubleshoot intermittent
ignition gas valve. Replace if necessary.
9. Check and correct in accordance with wiring
diagrams in Section 6.
10. Refer to vent damper manufacturer’s instructions.
Replace if necessary.
1. Defective gas valve.
2. Short circuit.
Burners will not shut
down.
1. Use Figure 8.1 to troubleshoot intermittent
ignition gas valve. Replace if necessary.
2. Check and correct wiring.
1. Manifold gas pressure too low.
2. Improperly sized/drilled orifice spuds.
3. Leaking gas valve.
4. Burrs on orifice.
5. Low supply gas pressure.
6. Excessive downdraft or draft problems in
boiler room.
Flashback or burning
at orifice spuds.
1. Adjust to proper pressure.
2. Install correct spuds.
3. Replace valve.
4. Remove burrs.
5. Contact gas supplier if natural gas. Adjust
regulator if LP gas.
6. Check air supply, ventilation and venting
system.
1. Insufficient pilot flame.
2. Pilot burner/orifice clogged.
3. Overfiring.
4. Misaligned burners or pilot.
5. Draft problem in boiler room.
Delayed ignition.
1. Increase pilot gas flow.
2. Clean pilot burner and orifice.
3. Reduce rate to input on rating label.
4. Realign burners or pilot.
5. Check air supply, ventilation and venting
system.
1. Underfiring.
2. Limit (Aquastat) set too low.
3. Vent pipe too long.
4. Inadequate chimney or venting system.
Excessive condensation in
vent.
1. Increase rate to input on rating label.
2. Reset aquastat to higher setting.
3. Reposition boiler to reduce length.
4. Check chimney and venting recommendations.
1. Underfiring.
2. Limit set too low.
3. Air in system.
4. Circulator malfunctioning.
5. Circulation system clogged.
6. Incorrect thermostat heat anticipator setting.
Boiler not heating
properly.
1. Increase rate to input on rating label.
2. Reset aquastat to higher setting.
3. Vent air from all points in system.
4. Check circulator, replace if necessary.
5. Shut down and cool boiler, drain and flush
system.
6. Adjust heat anticipator.
1. Leaks in gas piping or fittings.
2. Leaks in gas service line or meter.
3. Obstructed chimney.
4. Obstructed flueways or vent.
5. Undersized chimney or vent, high draft loss
in vent.
6. Draft problem in boiler room.
7. Overfiring.
8. Vent damper malfunctioning.
Fumes or gas odors
1. Locate and repair or replace.
2. Shut down boiler and notify gas provider.
3. Check, repair and/or clean chimney.
4. Clean flueways or vent and remove obstructions.
5. Check National Fuel Gas Code and vent
manufacturer’s recommendations.
6. Check air supply, ventilation and venting system.
7. Reduce rate to input on rating label.
8. Refer to vent damper manufacturer’s instructions.
Replace if necessary.