E20 High

Potterton E20 Fault Code

The Potterton E20 fault code means: your boiler thinks a flame is present even though it hasn't turned the gas on, usually caused by a blocked drain or a faulty sensor.. It appears on 15 Potterton models in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: Flame detected with closed gas valve. Check ionization probe/cable. Check condensate outlet not blocked & vent tube clear

What causes the Potterton E20 fault?

This fault occurs when the boiler's control system senses a flame internal to the unit even though it hasn't signaled the gas valve to open. The most common cause is a surge of water or moisture backing up into the combustion chamber due to a blockage in the condensate drain or a buildup of carbon on the sensing probe. In some cases, a damaged ignition lead or a failing control board can also send a false electrical signal that mimics the presence of a flame.

This fault is more common during the winter months, as freezing temperatures can cause the external condensate pipe to block with ice, forcing water back into the boiler.

Typical repair cost £120-250 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Potterton models that show the E20 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Potterton E20 fault code information on this page is sourced and cross-checked against the official Potterton service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026