Dunkirk boiler troubleshooting

Dunkirk has been manufacturing home heating products since 1928. Currently, its product range includes residential and commercial hot-water boilers, steam boilers, indirect water heaters, and more.

Dunkirk boiler troubleshooting may turn out easier than you expected provided you use a reliable guide. This is exactly what you will find below. Having identified the symptom, check it in the list and try the suggested solutions.

Dunkirk 95M-200 boiler troubleshooting

CodeReason For Soft LockoutCorrective Actions (pressing RESET should restart boiler immediately): 
80.14" Pressure switch contacts open1Check pressure switch for proper operation. Replace pressure switch if moisture has entered switch. Check venting for blockage. Clear if present.
18High Limit Operation: Burner oft until outlet water temperature drops below 180 °F1Happen when heat demand is lower than lowest firing rate of boiler, such as operation of single, small zone. Check system for:
• Verify boiler and system are full of water.
• Verify system does not have trapped air.
• Inspect and verify system piping and components.
• Verify piping agrees with boiler manual recommendations.
2Use contact thermometer to check outlet water temp. Compare to temperature shown with display in "INFO" mode ("1" in first digit). Replace return temperature sensor if results are not close. Replace control module if sensor replacement doesn't solve problem.
19High Limit Operation: Burner offuntil return water temp, drops below 190 °F1Check system for:
• Verify boiler and system are full of water.
• Verify system does not have trapped air.
• Inspect and verify system piping and components.
• Verify water flow is not reversed or pipes crossed.
2Use contact thermometer to check return water temp. Compare to temperature shown with display in "INFO" mode ("2" in first digit). Replace return temperature sensor if results are not close. Replace control module if sensor replacement doesn't solve problem.
High Limit Operation: Return temp, is higher than supply temp.1• Verify boiler and system are full of water.
• Verify system does not have trapped air.
• Inspect and verify system piping and components.
• Verify water flow is not reversed or pipes crossed.
242Use contact thermometer to check return water temp. Compare to temperature shown with display in "INFO" mode ("2" in first digit). Replace return temp, sensor if results are not close. Replace control module if sensor replacement doesn't solve problem.
High limit operation: Outlet water temp, increased too quickly. Non-adjustable default setting 9.8°F/sec1Indicates flow rate too low. Check system for:
• Verify boiler and system are full of water.
• Make sure system does not have trapped air.
• Inspect and verify system piping ana components.
• Verify piping agrees with boiler manual recommendations.
252Verify operation of boiler circulator:
• Check voltage at circulator junction box to ensure 120 vac when boiler operates. If no voltage, check wiring and wiring connections.
• High voltage terminal strip terminals 5 and 6 should show 120 vac for space heating; terminals 3 and 4 should show 120 vac for DHW. Replace circulator if powered but not operating.
• Replace line voltage wire harness if necessary. Replace control module if wire replacement doesn't resolve.
26Aquastat contacts open or LWCO contacts open or 3.5" Switch open1Verify proper setting of control.
Water temp too high, wait for temperature to drop below 180 degrees.
2Check water level in boiler, fill if low.
Press LWCO reset switch on display panel
If problem still exists, check LWCO probe and board according to manufacturer's instructions. Replace if necessary.
3Check pressure switch for proper operation. Replace if moisture has entered switch. Check venting for blockage. Clear if present.
29Blower turning when it should be off.1Check boiler wiring against wiring diagram.
Replace line voltage and low voltage wiring harnesses if necessary. Replace control module if wire replacement doesn't resolve.
30High limit operation: Temperature rise across boiler too high.1Flow rate too low.
Check system for:
Verify boiler and system are full of water.
Inspect and verify system piping and components.
Verify piping agrees with boiler manual recommendations. Make sure system pressure drop is not too high.
2Verify operation of boiler circulator.
Check voltage at circulator junction box to ensure 120 vac when boiler operates. If no voltage, check wiring and wiring connections.
High voltage terminal strip terminals 5 and 6 should show 120 vac for space heating; terminals 3 and 4 should show 120 vac for DHW.
Replace circulator if powered but not operating.
Replace line voltage wire harness if necessary.
Replace control module if wire replacement doesn't resolve.
61Pressure switch contacts closed.1Check pressure switches for proper operation.
Replace pressure switch if moisture has entered switch.
65Blower not operating when turned on.1Turn off power to boiler. Remove line voltage connector at blower. Restart boiler and check voltage across blower plug terminals. If 120 vac is NOT present, inspect wiring and tightness of connections.
Replace line voltage wire harness if necessary.
Replace control module if wire harness replacement doesn't resolve.
2If 120 vac is present on blower wire harness, replace harness and retry. If problem persists, replace blower motor.

Dunkirk Q90-125 boiler troubleshooting

LIGHTSTATUSINDICATES
ONIBC is energized through 24 volt transformer.
POWEROFFIBC is not energized.
BlinkingIBC receives more than 40 VAC.
ONIBC is energizing draft inducer and air flow is proven.
PURGEOFFOff during purge cycle - draft inducer is not powered on or air flow is not proven.
Off during igniter and run cycle - normal operation, purge cycle complete.
BlinkingIBC is locked out. Problem could indicate false positive proof of air flow. Blocked vent, intake air pipe, flue way, or orifice in negative pressure hose.
ONIBC is energizing igniter.
OFFIgniter is not energized.
ONIBC is energizing gas control valve to open.
VALVEOFFGas control valve is closed.
BlinkingIBC is locked out. Problem is flame has not been proven in three (3) ignition attempts. May be due to broken igniter or lack of/low flame signal, or no gas.
On BrightFlame proven.
FLAMEOn DimChecking for flame signal (during trial for ignition)
OFFFlame unproven.

Dunkirk XEB-2 boiler troubleshooting

POSSIBLE CAUSEWHAT TO DO
Thermostat is not set correctlyReset thermostat
Burner is not operating properlyCheck flame. If it is yellow, the burner is not getting enough air. Or, if flame is blue and noisy and seems to lift off the burner, the burner is getting too much air. Contact your service technician.
No electric power to boilerCheck overcurrent protection. Check to be sure electric power supply circuit is “ON”.
Controls out of adjustmentReset according to instructions.
Radiators not heatingOpen radiator vents to excess air. Check flow control valve (if used). It may be in closed position.
Circulating pump not runningCheck overcurrent protection. Check relay operation.
Poor electrical contactCheck all control terminals and wire joints.
Chimney flue is blockedPressure switch will not close and pilot spark will not operate to start pilot. Have your service technician check and correct, if necessary.
Rollout switch blownHave your service technician check heat exchanger for blockage. Replace rollout switch with exact replacement.
Gas input amount is incorrectContact your service technician.
Dirt on seatOpen valve manually. Allow water to run and clear valve seat.
Water logged expansion tankDrain tank, see instructions.