Common problems guide

The most common Potterton Sirius WH problems

The faults most likely to send a Potterton Sirius WH into lockout — with plain-English causes, what to check first, estimated repair costs and whether you need a Gas Safe engineer.

This model is discontinued. Parts can be harder to source and expensive. If repair costs are mounting, a new A-rated boiler may be the smarter choice.

The 6 most common faults

01

E20 High Engineer

Your boiler has stopped working because a sensor that measures the water temperature is not sending a signal, causing the system to shut down as a precaution.

Est. cost: £150-250
Parts: NTC Temperature Sensor, Wiring harness

Full guide for E20

02

E50 High Engineer

Your boiler is currently unable to accurately measure the temperature of the water it is heating, so it has stopped working as a safety precaution.

Est. cost: £120-200
Parts: Domestic Hot Water NTC Sensor

Full guide for E50

03

E128 High Engineer

Your boiler has detected that the flame inside has gone out unexpectedly while it was trying to heat your water or home.

Est. cost: £120-250
Parts: Ignition electrode, Flame sensor, Gas valve

Full guide for E128

04

E129 High Engineer

Your boiler has detected that the internal fan is moving too slowly to safely clear exhaust gases, so it has stopped working as a safety precaution.

Est. cost: £180-350
Parts: Fan assembly, Printed Circuit Board (PCB), Flue sensor

Full guide for E129

05

E132 High Engineer

Your boiler is failing to light because it is either not receiving enough gas or your room thermostat is preventing it from turning on.

Est. cost: £120-250
Parts: Gas valve, External thermostat, PCB

Full guide for E132

06

E133 High Engineer

Your boiler is failing to ignite because it is not receiving a reliable supply of gas.

Est. cost: £120-250
Parts: Gas valve, Ignition electrode, Condensate trap

Full guide for E133

Parts most often replaced

on the Potterton Sirius WH

NTC Temperature SensorWiring harnessDomestic Hot Water NTC SensorIgnition electrodeFlame sensorGas valve

Based on parts cited in our fault code database. Your engineer will confirm what's actually needed after diagnosis.

Call a Gas Safe engineer if…

You can smell gas or see signs of a leak
The Potterton shows an Emergency or High severity code
The boiler keeps locking out after repeated resets
You've tried the DIY checks and the fault hasn't cleared
There's visible water leaking from the boiler
The flame is yellow or orange instead of blue

See the full 13-code list for the Potterton Sirius WH