Potterton E270 fault codewhat it means and how to fix it
Circulation fault (dry fire) on the Potterton Assure and Promax Ultra: the burner lit with too little water passing the heat exchanger. Not resettable by the owner; engineer.
Take care
Get a Gas Safe registered engineer to look at your Potterton E270
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.
What does the pressure gauge show?
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.
Low or zero
The system has lost water and the exchanger ran dry.
Do not refill and restart repeatedly; an engineer should check the exchanger for damage first.
Normal
Pump, air or a sensor.
Engineer.
What E270 means
"270 — Circulation fault (Dry fire)" is in the Assure and Promax Ultra tables and nowhere in the older Potterton manuals. It is the most serious of the circulation codes because of what it describes: the burner was firing while the heat exchanger had little or no water flowing through it, which is how aluminium heat exchangers get damaged.
The control detects it from the temperature sensors — a flow temperature climbing far faster than the return, or a spread between them that cannot happen with water moving — and shuts the burner down. It is not on either manual's reset list and the Assure user guide shows it without the R, so the boiler decides when it is safe to try again.
The causes are the E125 and 109 causes with less margin: a pump that has stopped, an air pocket at the exchanger, a system that has lost most of its water without the pressure switch having tripped yet, or a flow sensor giving a false reading. Potterton's Assure user guide does not describe 270 to the owner beyond listing it; the installer manual's section J (pump and circulation) is where the engineer goes. Treat it as a stop-and-call code.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| Pump stopped with the burner able to light | The pre-circulation test passed on residual movement and the pump then stalled, or its speed collapsed under load. | Common |
| Air pocket at the heat exchanger | Sensors in air heat fast and unevenly. Follows a top-up or a system drain. | Common |
| Flow or return sensor fault | A sensor reading high (part 7207471, listed as "flow sensor and return sensor") makes the control see a dry fire that is not happening. 154 is the related sensor-test code. | Occasional |
Can you fix it yourself?
Stop — this needs an engineer
What it costs to fix
Typical repair cost
£60–£600
Time on site
1 hour
Pump £180–£300 fitted. Sensor £60–£110. Heat exchanger £450–£600.
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 NTC temperature sensor (flow, return or DHW)
7207471£18–£45Authorised Baxi parts distributor
Price checked 28 September 2026
Baxi / Potterton / Main pump assembly
7684006£120–£240Authorised Baxi parts distributor
Price checked 28 September 2026
Baxi / Potterton / Main automatic air vent
7207776£15–£45Authorised 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
- E110Get it checkedSafety thermostat operated — the primary water overheated — on every Potterton code display. One reset is permitted (5 s knob or 1–3 s button); a second E110 is a circulation fault for an engineer.Related: overheat and circulation
- E125Get it checkedCirculation fault (primary circuit) on every Potterton code display — the water did not warm as expected after lighting, or overshot twice. Pump, air or sludge; an engineer job after one reset.Related: overheat and circulation
- E130Get it checkedFlue NTC operated — the flue gas got too hot — on every Potterton code display. Reset once as the user guide allows; if it returns the heat exchanger or flue needs an engineer.Related: overheat and circulation
- E193Get it checkedThe rotary-switch Pottertons' pre-ignition pump check has failed: the pump ran and the flow never proved. Same causes as E125; no owner reset is offered.Related: overheat and circulation
- E109Get it checkedThe digital-display Pottertons' pre-ignition pump check — Assure Combi, Assure System, Promax Ultra. The flow never proved, so the burner was not lit. Bleed and check pressure; then an engineer.Related: overheat and circulation
- 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
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.