Potterton is one of the UK’s oldest heating brands, founded in 1850. Today, Potterton is part of the BDR Thermea Group alongside Baxi, which means their boilers share the same fault code system — Potterton and Baxi E-codes are identical.
Potterton Boiler Fault Codes
All Potterton Fault Codes 74
| Code | Fault | Severity | Type | View guide |
|---|---|---|---|---|
| E09 | Gas Valve Wiring Fault There is a fault in the wiring to the gas valve — either the connection… | High | Engineer | View Guide |
| E10 | Flow Sensor Fault The flow temperature sensor has failed or has a wiring fault. | Medium | Engineer | View Guide |
| E109 | Poor Circulation / Pre-Circulation Fault The boiler has detected insufficient water circulation during its pre-circulation check. Usually caused by airlocks,… | Medium | Engineer | View Guide |
| E11 | Return Sensor Fault The return temperature sensor has failed or has a wiring fault. | Medium | Engineer | View Guide |
| E110 | Overheat Lockout The boiler has overheated and the safety thermostat has triggered. | High | Engineer | View Guide |
| E116 | High Flow Temperature The boiler flow temperature exceeded its maximum safe level. | High | Engineer | View Guide |
| E117 | Gas Valve Fault The gas valve has a fault — it may not be opening, closing, or responding… | High | Engineer | View Guide |
| E119 | Low Water Pressure System pressure has dropped below the required minimum of 0.5 bar. Shared with Baxi boilers… | Low | DIY Check | View Guide |
| E12 | Differential Water Flow Switch — Remains Open The differential water flow switch is remaining open when it should be closed. Indicates a… | Medium | Engineer | View Guide |
| E125 | Primary Circulation Fault There is insufficient water circulation in the primary heating circuit. | Medium | Engineer | View Guide |
| E128 | Frequent Flame Failure The boiler has lost its flame 12 times in succession and entered a safety lockout. | High | Engineer | View Guide |
| E129 | Frequent Flame Loss — Safety Lockout The boiler has experienced repeated flame loss during operation — a persistent version of the… | High | Engineer | View Guide |
| E13 | Differential Water Flow Switch — Remains Closed The differential water flow switch is stuck in the closed position. Indicates a faulty switch… | Medium | Engineer | View Guide |
| E130 | Flue Thermostat Tripped The flue safety thermostat has triggered due to excessively high flue gas temperatures. | High | Engineer | View Guide |
| E131 | Flue Overheat The flue temperature has reached an unsafe level, triggering the flue thermostat. | High | Engineer | View Guide |
| E133 | Ignition Failure / Frozen Condensate The boiler has failed to ignite. In winter, the most common cause is a frozen… | Medium | DIY Check | View Guide |
| E134 | Gas Valve Open Without Gas The gas valve has been commanded open but no gas has been detected flowing —… | High | Engineer | View Guide |
| E135 | Air Pressure Switch Fault The air pressure switch is not registering correctly — this confirms the fan is running… | High | Engineer | View Guide |
| E14 | Low Gas Pressure The boiler is detecting insufficient gas supply pressure. | High | Engineer | View Guide |
| E15 | Gas Valve Command Fault There is a fault with the gas valve command signal from the PCB to the… | High | Engineer | View Guide |
| E151 | PCB Error (Type 1) The PCB has detected an internal fault of type 1. | High | Engineer | View Guide |
| E152 | PCB Error (Type 2) The PCB has detected an internal fault of type 2. A more serious variant than… | High | Engineer | View Guide |
| E154 | Flow/Return Sensor Temperature Test Failure The boiler has performed an internal temperature sensor cross-check and found the flow or return… | Medium | Engineer | View Guide |
| E16 | Fan Fault The fan is not running at the correct speed. | High | Engineer | View Guide |
| E160 | Fan Fault The boiler fan is not operating at the correct speed or has stopped working altogether. | High | Engineer | View Guide |
| E161 | Fan Fault (Secondary) A secondary fan fault code on Potterton boilers — fan speed or operation is outside… | High | Engineer | View Guide |
| E163 | DHW NTC Sensor Fault The domestic hot water temperature sensor has a fault — short circuit or open circuit.… | Medium | Engineer | View Guide |
| E164 | Pressure Sensor Fault The water pressure sensor is giving an out-of-range signal. May indicate a blocked or failed… | Medium | Engineer | View Guide |
| E168 | PCB Lockout / Unspecified Fault The PCB has detected a fault it cannot specifically identify and has locked out the… | High | Engineer | View Guide |
| E18 | Ignition Electrode Fault The ignition electrode is worn or not sparking. | High | Engineer | View Guide |
| E19 | Gas Valve Fault The gas valve is not responding correctly. | High | Engineer | View Guide |
| E193 | Circulation Fault (Secondary) A secondary circulation fault indicating an issue with water flow that has not yet caused… | Medium | Engineer | View Guide |
| E20 | Flame Failure Lockout The boiler has failed to detect a flame after the ignition sequence. | Medium | DIY Check | View Guide |
| E21 | Flow Sensor Short Circuit The flow NTC sensor has a short circuit. | Medium | Engineer | View Guide |
| E22 | Flow Sensor Open Circuit The flow NTC sensor has an open circuit. | Medium | Engineer | View Guide |
| E220 | Gas Valve Not Opening The gas valve has received the signal to open but hasn't responded correctly. | High | Engineer | View Guide |
| E23 | Return Sensor Short Circuit The return NTC sensor has a short circuit. | Medium | Engineer | View Guide |
| E24 | Return Sensor Open Circuit The return NTC sensor has an open circuit. | Medium | Engineer | View Guide |
| E25 | DHW Sensor Short Circuit The DHW NTC sensor has a short circuit. | Medium | Engineer | View Guide |
| E26 | DHW Sensor Open Circuit The DHW NTC sensor has an open circuit. | Medium | Engineer | View Guide |
| E27 | Air Pressure Switch Fault The APS is not confirming airflow. | High | Engineer | View Guide |
| E270 | Dry Fire Detected The boiler has fired or attempted to fire without detecting adequate water circulation — a… | High | Engineer | View Guide |
| E28 | Frozen Condensate / Flame Failure (Winter) Flame failure associated with a frozen condensate pipe in cold weather. Identical to Baxi E28… | Medium | DIY Check | View Guide |
| E30 | Diverter Valve Fault The diverter valve is stuck or not switching. | Medium | Engineer | View Guide |
| E31 | PCB Communication Fault Internal PCB communication error. | High | Engineer | View Guide |
| E317 | Wrong Power Supply Frequency The boiler is detecting an incorrect mains power frequency (should be 50Hz in the UK).… | Medium | Engineer | View Guide |
| E32 | Pump Fault The pump is not running or is blocked. | High | Engineer | View Guide |
| E321 | Hot Water Thermistor Fault The hot water temperature thermistor has a fault — applies to store/system boilers with a… | Medium | Engineer | View Guide |
| E33 | Flame Instability The flame signal is fluctuating during operation. | High | Engineer | View Guide |
| E34 | Condensate Blocked The condensate drain is blocked or frozen. | Medium | DIY Check | View Guide |
| E35 | Rapid Temperature Rise Flow temperature is rising too fast, indicating circulation problems. | High | Engineer | View Guide |
| E36 | Pressure Sensor Fault The electronic pressure sensor is reading incorrectly. | Medium | Engineer | View Guide |
| E37 | Safety Thermostat Open The safety thermostat wire or connection is open. | High | Engineer | View Guide |
| E38 | Flue Gas Overheat The flue gas temperature has exceeded safe limits. | High | Engineer | View Guide |
| E384 | False Flame — Gas Valve Off The boiler has detected an ionisation signal (flame) when the gas valve should be completely… | High | Engineer | View Guide |
| E385 | Low Voltage — Under 195V The mains voltage supply to the boiler has dropped below 195V — below the minimum… | Medium | Engineer | View Guide |
| E39 | Frost Protection Active The boiler is running frost protection cycles. | Medium | DIY Check | View Guide |
| E40 | Thermistor / Sensor Short Circuit A temperature sensor has short-circuited, causing the boiler to lock out. | Medium | Engineer | View Guide |
| E41 | Three-Way Valve Timeout The three-way valve did not switch within the expected time. | Medium | Engineer | View Guide |
| E42 | Outdoor Sensor Fault The outdoor temperature sensor is faulty or disconnected. | Low | Engineer | View Guide |
| E43 | eBUS Fault The eBUS communication line has a fault. | Medium | Engineer | View Guide |
| E430 | Water Pressure Test / Test Failed The boiler is performing a water pressure test (normal on commissioning) or the test has… | Medium | Engineer | View Guide |
| E44 | Mains Voltage Fault The mains voltage is outside acceptable range. | Medium | Engineer | View Guide |
| E45 | EEPROM Error PCB memory error. | High | Engineer | View Guide |
| E46 | Coding Plug Fault The boiler coding plug cannot be read. | High | Engineer | View Guide |
| E47 | Pump Kickback Fault The pump failed to restart after a pause. | Medium | Engineer | View Guide |
| E48 | Phase/Neutral Reversed The electrical supply has reversed polarity. | High | Engineer | View Guide |
| E50 | DHW NTC Sensor Fault The domestic hot water temperature sensor has a fault on combi boiler models. | Medium | Engineer | View Guide |
| E53 | Condensate Pipe Blocked The condensate system is blocked, preventing the boiler from operating safely. | Medium | DIY Check | View Guide |
| E55 | Calibration Required The boiler requires calibration — this code appears on auto-calibrating models when the combustion setup… | Medium | Engineer | View Guide |
| E78 | Water Pressure Sensor Fault The water pressure sensor is giving an incorrect reading. May indicate a blocked or failed… | Medium | Engineer | View Guide |
| E83 | Room Controller Communication Fault The boiler cannot communicate with the room controller — may be a wiring fault or… | Medium | Engineer | View Guide |
| E84 | Room Controller Not Recognised The room controller connected to the boiler is not being recognised by the PCB. | Medium | Engineer | View Guide |
| E92 | Combustion Test Alarm During Auto-Setting An alarm has been triggered during the automatic combustion calibration process. The auto-setting procedure detected… | High | Engineer | View Guide |