Boiler Fault Codes

Boiler attempted to ignite but did not detect a flame within the trial-for-ignition period.

Flame was established but was lost during normal operation.

Boiler outlet water temperature exceeded the high-limit setting (typically 210°F). Manual reset required.

Optional manual-reset low or high gas pressure switch has tripped. Manual reset required after correcting condition.

Optional flow switch or low water cutoff device is open. Manual reset required after correcting condition.

Blocked drain switch detected excessive condensate buildup inside the unit. Manual reset required.

Flue gas temperature exceeded maximum allowable limit. Indicates abnormal combustion or blocked heat exchanger.

Combustion air proving switch or blocked flue switch did not make within the expected time frame.

Combustion blower (fan) did not reach commanded speed within the expected time, or lost speed during operation.

Gas valve circuit fault, modulating valve cannot reach commanded position, or a wiring fault exists.

Outlet water temperature sensor is reading out of range (open or short circuit).

Return (inlet) water temperature sensor is reading out of range.

Flue temperature sensor is open or reading out of range.

Outdoor reset sensor is open or out of range. Boiler will operate without outdoor reset until corrected.

Communication lost between cascaded boilers or between the boiler and a Building Management System (BMS).

Space heating demand blocked by the control (WWSD active or BMS command).

24VAC control voltage is below minimum threshold; boiler blocked from starting.

Manual reset high limit switch is open. Boiler will not fire until switch is manually reset.

Temperature differential between boiler outlet and inlet exceeds maximum allowed value. Firing rate is being limited.

Flue temperature is elevated; controller is limiting maximum firing rate.

DHW tank demand blocked because combustion fan has reported a problem.

Boiler outlet water temperature has reached the set limit; firing rate is reduced or blocked.

Temperature rise from inlet to outlet is exceeding allowable rate. Firing rate is being capped.

Outlet water temperature exceeds software high-limit setpoint, preventing firing.

Boiler is in anti-cycling delay period and will not restart until the delay has elapsed.

System water pressure is below minimum threshold or the low-water cutoff device has opened.

Thermal fuse or over-temperature switch on the heat exchanger body has opened, indicating extreme localized temperature.

Stack (flue gas) temperature has exceeded the high-limit setting on the Power-Fin boiler.

Inlet water temperature to the boiler exceeds maximum allowed value, preventing firing to avoid thermal shock.

Header or system sensor (cascade/modular systems) is open or out of range.

FTXL fire tube boiler detected low system water pressure below minimum operating pressure.

Annual service reminder has triggered. Boiler continues to operate but service is needed.

Gas pressure dropped below minimum during firing

Stack gas temperature exceeded maximum allowable limit

Third ignition trial failure, manual reset lockout

DHW outlet temperature sensor open or short circuit

DHW inlet temperature sensor open or short circuit

Fan speed dropped below minimum during firing

Condensate system fault detected, blocked drain or backup

Low water cutoff device has activated

Header temperature sensor open or short circuit

External high limit circuit is open

Auxiliary sensor 1 open or short circuit

Outdoor air temperature sensor open or short circuit

Boiler sequencing communication fault

Modbus communication fault

Boiler outlet water temperature exceeded the high-limit value; boiler has locked out.

Boiler inlet water temperature exceeded the high-inlet limit, indicating return water is too hot.

Boiler failed to establish a flame on 3 consecutive ignition attempts.

Flame lost during normal operation (not during ignition trial).