Common problems guide

The most common Potterton Ultra 21 Heat problems

The faults most likely to send a Potterton Ultra 21 Heat into lockout — with plain-English causes, what to check first, estimated repair costs and whether you need a Gas Safe engineer.

12 documented codes
6 most common
0 DIY-safe checks
6 engineer needed

The 6 most common faults

01
1 flash green Engineer

Temperature protection: Maximum flow temperature exceeded, Flow temperature rise rate too high, Excessive difference between flow and return temperature

Full guide for 1 flash green

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
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See the full 12-code list for the Potterton Ultra 21 Heat

Related guides

Boiler losing pressure → No hot water → When to replace → Symptom checker →