Potterton E55 fault codewhat it means and how to fix it
Calibration required on the Potterton Promax Ultra — shown after the gas valve or board is replaced until the engineer runs the calibration routine. Not a fault an owner will meet unprompted.
Before you start
Get a Gas Safe registered engineer to look at your Potterton E55
We do not pass enquiries to a repair firm, so there is no form here. Find a Gas Safe registered engineer through the Gas Safe Register, and ask to see their registration card when they arrive — it is the register, not the van, that tells you they are qualified.
Has an engineer just worked on the boiler?
The right answer depends on what you can see. Pick the one that matches.
Choose the option on the left that matches what your appliance is doing, and the answer for that case appears here.
Yes, today or recently
The calibration step was missed.
Call the same engineer back; it is part of the job they did.
No
Unusual; the board has lost its setting.
Engineer with an analyser.
What E55 means
Only the Promax Ultra table has this row: "55 — Calibration Required". The installation manual explains when it appears — "followed by 55 (after replacing R.D.S.) indicates calibration required (Section 14.2)" — where R.D.S. is the electronically controlled gas valve and section 14.2 is the calibration procedure the engineer performs with a combustion analyser after fitting one. It is a status code more than a fault: the board knows a component has changed and will not run at full rate until the combustion has been set. It carries the spanner in the user guide table and is not on the reset list.
An owner should only ever see 55 in the minutes after an engineer has changed the gas valve or the PCB, and if it is still on the display after the engineer has gone, the calibration was not completed and the same engineer should come back. There is nothing to do from the panel. The Assure, Promax, Titanium and Gold have no calibration code.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| Gas valve replaced and calibration not run | The expected reason. Section 14.2 of the Ultra manual must be completed with an analyser. | Common |
| PCB replaced | A new board has no record of the valve setting and asks for the routine. | Occasional |
| Calibration lost | Rarely, the stored setting is corrupted and the board requests it again without a part change. | Rare |
Can you fix it yourself?
Stop — this needs an engineer
What it costs to fix
Typical repair cost
£60–£120
Time on site
30 minutes
Calibration visit £60–£120; free if the engineer who changed the part comes back.
Typical UK prices including parts and labour, updated September 2026. Your quote may differ.
Parts you may need
We may earn a commission if you buy a part through one of these links. It does not change what you pay, and it does not affect which parts we list.
Baxi / Potterton / Main gas valve
7683968£120–£240Authorised Baxi parts distributor
Price checked 28 September 2026
Own this appliance and had this code? . Nothing is published until a person has read it.
Related Potterton fault codes
- E83Usually simple to fixCommunication error on the Potterton Assure and Promax Ultra: the board has lost contact with a connected control such as an OpenTherm room unit. Check the control and its wiring first.Related: electronics and power
- E103Get it checkedCodes 103, 104, 107 and the word "Bat" on the Potterton Assure: the user guide names them only to say contact your installer or Baxi Customer Support. They concern the safety board's battery.Related: electronics and power
- E131Usually simple to fixInterruption of power supply while in fault mode — the Potterton Promax Store only. The power went off while another code was showing. Restore power, read the code that follows.Related: electronics and power
- E119Get it checkedThe sealed system on a rotary-switch Potterton — Promax, Titanium, Gold, Heatmax — has dropped below half a bar. The window shows E1 and then 19. Fill to 1–1.5 bar and it clears itself.Related: same brand
- E133Get it checkedGas supply interrupted, ignition failed or no flame detected — every Potterton generation. Confirm the gas supply, one reset (5 s on the knob, 1–3 s on the button), and call if it returns.Related: same brand
- E118Get it checkedThe digital-display Pottertons — Assure Combi, Assure System, Promax Ultra — have dropped below half a bar on the heating circuit. Repressurise to 1–1.5 bar and the boiler restarts on its own.Related: same brand
Own a Potterton boiler? Save it and its codes come first next time.
Related guides
Technical review
Not reviewed by an engineer
No engineer has read this page. Severity follows what the manufacturer publishes, and we would rather tell you that than let a byline imply a sign-off.
Sources and how we verified this
We establish the facts from the sources below and then write the explanation ourselves. We do not copy manufacturer wording and we do not host their manuals.
- Manufacturer technical and service documentation
This page has not been reviewed by an engineer, and we would rather tell you that than imply otherwise. The severity rating follows what the manufacturer publishes: where they say isolate the appliance and call someone, so do we.