Potterton
Promax System 24kW
System Boiler
24kW
2012-2020
ErP A
74 fault codes
<p>The Promax System 24kW is a system boiler from Potterton, available at 24kW output. Produced 2012-2020.</p>
Promax System 24kW Fault Codes 74
Code
Description
Severity
Type
E09
Gas Valve Wiring Fault
There is a fault in the wiring to the gas valve — either the connection cable…
High
Engineer
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E10
Flow Sensor Fault
The flow temperature sensor has failed or has a wiring fault.
Medium
Engineer
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E109
Poor Circulation / Pre-Circulation Fault
The boiler has detected insufficient water circulation during its pre-circulation check. Usually caused by airlocks, closed…
Medium
Engineer
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E11
Return Sensor Fault
The return temperature sensor has failed or has a wiring fault.
Medium
Engineer
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E110
Overheat Lockout
The boiler has overheated and the safety thermostat has triggered.
High
Engineer
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E116
High Flow Temperature
The boiler flow temperature exceeded its maximum safe level.
High
Engineer
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E117
Gas Valve Fault
The gas valve has a fault — it may not be opening, closing, or responding to…
High
Engineer
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E119
Low Water Pressure
System pressure has dropped below the required minimum of 0.5 bar. Shared with Baxi boilers —…
Low
DIY
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E12
Differential Water Flow Switch — Remains Open
The differential water flow switch is remaining open when it should be closed. Indicates a circulation…
Medium
Engineer
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E125
Primary Circulation Fault
There is insufficient water circulation in the primary heating circuit.
Medium
Engineer
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E128
Frequent Flame Failure
The boiler has lost its flame 12 times in succession and entered a safety lockout.
High
Engineer
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E129
Frequent Flame Loss — Safety Lockout
The boiler has experienced repeated flame loss during operation — a persistent version of the flame…
High
Engineer
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E13
Differential Water Flow Switch — Remains Closed
The differential water flow switch is stuck in the closed position. Indicates a faulty switch or…
Medium
Engineer
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E130
Flue Thermostat Tripped
The flue safety thermostat has triggered due to excessively high flue gas temperatures.
High
Engineer
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E131
Flue Overheat
The flue temperature has reached an unsafe level, triggering the flue thermostat.
High
Engineer
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E133
Ignition Failure / Frozen Condensate
The boiler has failed to ignite. In winter, the most common cause is a frozen condensate…
Medium
DIY
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E134
Gas Valve Open Without Gas
The gas valve has been commanded open but no gas has been detected flowing — the…
High
Engineer
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E135
Air Pressure Switch Fault
The air pressure switch is not registering correctly — this confirms the fan is running before…
High
Engineer
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E14
Low Gas Pressure
The boiler is detecting insufficient gas supply pressure.
High
Engineer
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E15
Gas Valve Command Fault
There is a fault with the gas valve command signal from the PCB to the valve.…
High
Engineer
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E152
PCB Error (Type 2)
The PCB has detected an internal fault of type 2. A more serious variant than E151.
High
Engineer
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E154
Flow/Return Sensor Temperature Test Failure
The boiler has performed an internal temperature sensor cross-check and found the flow or return sensor…
Medium
Engineer
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E160
Fan Fault
The boiler fan is not operating at the correct speed or has stopped working altogether.
High
Engineer
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E161
Fan Fault (Secondary)
A secondary fan fault code on Potterton boilers — fan speed or operation is outside expected…
High
Engineer
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E163
DHW NTC Sensor Fault
The domestic hot water temperature sensor has a fault — short circuit or open circuit. On…
Medium
Engineer
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E164
Pressure Sensor Fault
The water pressure sensor is giving an out-of-range signal. May indicate a blocked or failed sensor.
Medium
Engineer
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E168
PCB Lockout / Unspecified Fault
The PCB has detected a fault it cannot specifically identify and has locked out the boiler.
High
Engineer
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E18
Ignition Electrode Fault
The ignition electrode is worn or not sparking.
High
Engineer
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E193
Circulation Fault (Secondary)
A secondary circulation fault indicating an issue with water flow that has not yet caused full…
Medium
Engineer
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E20
Flame Failure Lockout
The boiler has failed to detect a flame after the ignition sequence.
Medium
DIY
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E220
Gas Valve Not Opening
The gas valve has received the signal to open but hasn't responded correctly.
High
Engineer
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E23
Return Sensor Short Circuit
The return NTC sensor has a short circuit.
Medium
Engineer
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E24
Return Sensor Open Circuit
The return NTC sensor has an open circuit.
Medium
Engineer
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E270
Dry Fire Detected
The boiler has fired or attempted to fire without detecting adequate water circulation — a 'dry…
High
Engineer
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E28
Frozen Condensate / Flame Failure (Winter)
Flame failure associated with a frozen condensate pipe in cold weather. Identical to Baxi E28 —…
Medium
DIY
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E317
Wrong Power Supply Frequency
The boiler is detecting an incorrect mains power frequency (should be 50Hz in the UK). This…
Medium
Engineer
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E321
Hot Water Thermistor Fault
The hot water temperature thermistor has a fault — applies to store/system boilers with a hot…
Medium
Engineer
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E35
Rapid Temperature Rise
Flow temperature is rising too fast, indicating circulation problems.
High
Engineer
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E36
Pressure Sensor Fault
The electronic pressure sensor is reading incorrectly.
Medium
Engineer
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E37
Safety Thermostat Open
The safety thermostat wire or connection is open.
High
Engineer
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E384
False Flame — Gas Valve Off
The boiler has detected an ionisation signal (flame) when the gas valve should be completely closed.…
High
Engineer
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E385
Low Voltage — Under 195V
The mains voltage supply to the boiler has dropped below 195V — below the minimum operating…
Medium
Engineer
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E40
Thermistor / Sensor Short Circuit
A temperature sensor has short-circuited, causing the boiler to lock out.
Medium
Engineer
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E41
Three-Way Valve Timeout
The three-way valve did not switch within the expected time.
Medium
Engineer
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E42
Outdoor Sensor Fault
The outdoor temperature sensor is faulty or disconnected.
Low
Engineer
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E430
Water Pressure Test / Test Failed
The boiler is performing a water pressure test (normal on commissioning) or the test has failed,…
Medium
Engineer
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E50
DHW NTC Sensor Fault
The domestic hot water temperature sensor has a fault on combi boiler models.
Medium
Engineer
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E53
Condensate Pipe Blocked
The condensate system is blocked, preventing the boiler from operating safely.
Medium
DIY
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E55
Calibration Required
The boiler requires calibration — this code appears on auto-calibrating models when the combustion setup needs…
Medium
Engineer
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E78
Water Pressure Sensor Fault
The water pressure sensor is giving an incorrect reading. May indicate a blocked or failed sensor.
Medium
Engineer
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E83
Room Controller Communication Fault
The boiler cannot communicate with the room controller — may be a wiring fault or controller…
Medium
Engineer
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E84
Room Controller Not Recognised
The room controller connected to the boiler is not being recognised by the PCB.
Medium
Engineer
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E92
Combustion Test Alarm During Auto-Setting
An alarm has been triggered during the automatic combustion calibration process. The auto-setting procedure detected a…
High
Engineer
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