Utica Dunkirk E28 Error Code
Flue NTC Fault E40 Central Heating Return NTC Fault Hot Water NTC Fault (tank ve
Source: dcc-115__utdu-dcc-115-dcc-205-dcb-75-dcb-165-iom.pdf
What does Utica Dunkirk E28 mean?
E28 on Utica-Dunkirk DCC/DCB condensing boilers indicates a fault with the flue NTC heat exchanger temperature sensor. The control board cannot read a valid temperature from this sensor, which monitors flue gas or exhaust-side heat exchanger temperature. The boiler shuts down because the sensor is essential to detecting flue over-temperature and triggering the high-limit function.
Symptoms
- Boiler display shows E28 and enters lockout
- No heating or domestic hot water output
- Fault appears immediately on startup or mid-cycle
- Boiler does not reset automatically
Common causes
- Failed or open-circuit flue NTC sensor
- Loose or disconnected wiring connector at the sensor or PCB
- Damaged sensor lead wire (chafed, kinked, or burned by flue heat)
- PCB input failure on the flue sensor channel
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Diagnostic steps
Inspect sensor wiring and connectors
Locate the flue NTC sensor on the exhaust section of the heat exchanger. Reseat the wiring connector firmly and check for heat damage to the cable insulation.
Measure sensor resistance
Disconnect the sensor and measure resistance at ambient temperature. Verify the reading against the NTC resistance chart in the IOM; an open reading confirms sensor failure.
Replace the flue NTC sensor
Install an OEM replacement sensor, ensuring the sensor body seats fully into the flue sensor pocket. Reconnect the wiring harness and inspect for heat damage to nearby components.
Reset the boiler
Press and hold the RESET button for at least 2 seconds, then run the boiler through a complete heating cycle to confirm E28 does not return.
Contact technical service if fault persists
If E28 recurs after sensor replacement, the PCB flue sensor input circuit may be defective. Contact Utica-Dunkirk at 1-800-325-5479.
When to call a professional
Call a licensed technician if you are not able to safely access the flue side of the heat exchanger or if the fault persists after sensor replacement. The flue NTC position requires working near hot exhaust components, and PCB replacement requires full recommissioning including combustion calibration — both tasks that require a qualified technician.
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Other Utica Dunkirk Error Codes
,E28,E40,E50,E160,E321,and E431 -Indicate possible faulty components. 53 - Indic
, 78 and 92 - Indicates possible wrong calibration, a new calibration is needed.
,E135 - Indicate the gas supply has been interrupted, ignition has failed or fla
,E 133, E 134,E 135, E 09,E 15,E 128 and E 384 - are displayed it is possible to
Gas Valve Connection Cable 日 10 External Probe Fault 12 Water Flow Switch Open 1
Water Refill Enabled E 19 Max Time Of Water Refill 20 Central Heating Flow NTC F
PCB to be set by the "Calibration Function" E 171 Fan parameter Out of range in
87 Communication error E92 Combustion test alarm during auto-setting E 1 109 Pre
E11 between the supply and return temperatures too Sensor not/poorly connected N
Temperature of heat exchanger is above the normal range (high- limit thermostat
5 burner start-up failures that the air inlet and exhaust flue are not blocked C
False flame signal Ignition transformer defective Gas valve defective valve and
Sources: dunkirk.com, uticaboilers.com