Potterton Promax Ultra Combi fault codes

Built 2015–2019

Digital display with the fullest Potterton table: adds 55 (calibration), 117 (pressure too high) and 134 (gas valve open without gas) to the Assure list.

Codes on the Promax Ultra Combi follow the same Potterton scheme as the rest of the range. Where a code behaves differently on this generation, the code page says so.

Potterton fault codes

Every published Potterton code. Open a code to see which models and years it applies to.

E119The sealed system on a rotary-switch Potterton — Promax, Titanium, Gold, Heatmax — has dropped below half a bar. The window shows E1 and then 19. Fill to 1–1.5 bar and it clears itself.Get it checked
E133Gas supply interrupted, ignition failed or no flame detected — every Potterton generation. Confirm the gas supply, one reset (5 s on the knob, 1–3 s on the button), and call if it returns.Get it checked
E118The digital-display Pottertons — Assure Combi, Assure System, Promax Ultra — have dropped below half a bar on the heating circuit. Repressurise to 1–1.5 bar and the boiler restarts on its own.Get it checked
E110Safety thermostat operated — the primary water overheated — on every Potterton code display. One reset is permitted (5 s knob or 1–3 s button); a second E110 is a circulation fault for an engineer.Get it checked
E125Circulation fault (primary circuit) on every Potterton code display — the water did not warm as expected after lighting, or overshot twice. Pump, air or sludge; an engineer job after one reset.Get it checked
E128Flame failure during normal operation on the Potterton Assure and Promax Ultra: the burner was lit and went out. Resettable; recurring E128 wants an engineer.Get it checked
E28Three meanings on Potterton: incorrect PCB fitted (Gold Combi HE 2007), flue NTC fault (2008–2014 and all digital displays), or flue NTC, air pressure switch, blocked flue or condensate (2015–2019 combis).Get it checked
E130Flue NTC operated — the flue gas got too hot — on every Potterton code display. Reset once as the user guide allows; if it returns the heat exchanger or flue needs an engineer.Get it checked
E160Fan or fan wiring fault on every Potterton code display: the fan did not start or reach speed. A component fault in the user guide's words — note it and call; no reset is offered.Get it checked
E20Central heating NTC fault on every Potterton code display — the flow temperature sensor is open or short circuit. The user guide says note the code and call; no reset is offered.Get it checked
E193The rotary-switch Pottertons' pre-ignition pump check has failed: the pump ran and the flow never proved. Same causes as E125; no owner reset is offered.Get it checked
E135The Assure and Promax Ultra's internal-error ignition code: the control blames its own side of the gas valve rather than the supply for the flame that never came. One reset; then an engineer.Get it checked
E109The digital-display Pottertons' pre-ignition pump check — Assure Combi, Assure System, Promax Ultra. The flow never proved, so the burner was not lit. Bleed and check pressure; then an engineer.Get it checked
E117Primary water pressure above 2.7 bar on the Potterton Promax Ultra. Usually an over-filled system or a failed expansion vessel; an engineer should let it down and find out which.Get it checked
E50Hot water NTC fault on rotary-switch Potterton combis — Promax Combi, Titanium, Gold Combi, Store, Heatmax. The domestic hot water sensor is open or short. Note the code and call.Get it checked
E09The Assure and Promax Ultra's gas valve connection cable fault: the board has lost its wiring link to the valve. Resettable once; recurring 09 is a wiring or PCB job.Get it checked
Red light flashingPotterton Assure Heat, Titanium Heat and Ultra Heat have no display: the illuminated button flashes red a number of times when the boiler has locked out. The count is the code.Get it checked
E15The Assure and Promax Ultra's own-valve code: the board has detected a fault in the gas valve itself, not its cable. One reset allowed; then an engineer with a meter.Get it checked
E384The Assure and Promax Ultra report a flame signal while the gas valve is shut. An electrode or PCB fault, and the Assure manual's answer is to go over the board.Get it checked
E270Circulation fault (dry fire) on the Potterton Assure and Promax Ultra: the burner lit with too little water passing the heat exchanger. Not resettable by the owner; engineer.Get it checked
E134The Promax Ultra's timed-out ignition: the gas valve was held open for the whole ignition period and nothing arrived to light. Check the supply, reset once, then call.Get it checked
E154Flow/return sensor temperature test on the Potterton Assure and Promax Ultra: the two heating sensors disagree with each other or with physics. Usually circulation; sometimes a sensor.Get it checked
E321Hot water NTC fault on the Potterton Assure Combi and Promax Ultra — the digital-display successor to E50. Shown with a spanner; hot water stops, engineer needed.Get it checked
E83Communication error on the Potterton Assure and Promax Ultra: the board has lost contact with a connected control such as an OpenTherm room unit. Check the control and its wiring first.Usually simple to fix
E40Central heating return NTC fault on the Potterton Assure and Promax Ultra. The return sensor is open or short. Shown with a spanner; engineer.Get it checked
E103Codes 103, 104, 107 and the word "Bat" on the Potterton Assure: the user guide names them only to say contact your installer or Baxi Customer Support. They concern the safety board's battery.Get it checked
E55Calibration required on the Potterton Promax Ultra — shown after the gas valve or board is replaced until the engineer runs the calibration routine. Not a fault an owner will meet unprompted.Usually simple to fix
E131Interruption of power supply while in fault mode — the Potterton Promax Store only. The power went off while another code was showing. Restore power, read the code that follows.Usually simple to fix

Potterton fault codes

Other Potterton models