Potterton Suprima Common Problems & Fault Codes (2026 Guide)

The most common Potterton Suprima problems

The faults most likely to send a Potterton Suprima 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

Blocking Engineer

Mains Frequency incorrect or Air Switch Fault > 1 min. or Reset button held in to force a restart

Full guide for Blocking

Earth Fault Engineer

Mains Reversal

Full guide for Earth Fault

Lockout Engineer

Lockout

Full guide for Lockout

Mains ON Only Engineer

Green LED OFF, Red LED ON

Full guide for Mains ON Only

Ext. Call for Heat (Boiler set to STNDBY, Temp. Control set to 'O' Off) Engineer

Green LED FLASHING 2 Per Sec., Red LED ON

Full guide for Ext. Call for Heat (Boiler set to STNDBY, Temp. Control set to 'O' Off)

Ext. Call for Heat (STNDBY switch to ON, Temp. Control set to Max.) Engineer

Green LED FLASHING 2 Per Sec., Red LED OFF

Full guide for Ext. Call for Heat (STNDBY switch to ON, Temp. Control set to Max.)

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 9-code list for the Potterton Suprima