Potterton Boiler Problems: Fault Codes and What They Mean

The most common Potterton boiler problems are low pressure (E119), failure to light (E133), overheating (E110), circulation faults (E125) and control board lockouts (E168). Potterton is part of the same group as Baxi, and current Potterton boilers such as the Promax, Titanium and Assure ranges use the same E-code list. If you have looked up a Baxi code, the meaning is usually the same on a Potterton.

How Do You Read a Potterton Fault Code?

On most current Potterton boilers the code appears on a small digital display as E followed by three digits, and it often shows in two halves, for example E1 and then 19. Read it as one code: E119.

Write the full code down before you reset, because it may disappear afterwards. Older Potterton boilers without a digital display, such as some Performa and Suprima models, signal faults with lights instead and use a different code list, so check the manual for those. The model name is on the front panel or on the data badge under the boiler. Our guide to reading E1 codes on Baxi-family boilers explains the split display in more detail, and it applies to Potterton too.

The Common Potterton Codes and What They Mean

These are the codes we are asked about most on current Potterton models. The wording varies slightly between models, so confirm against your manual.

• E110: overheat. The safety thermostat has tripped because the boiler got hotter than it should.
• E118 and E119: low water pressure. System pressure has dropped too far for the boiler to run safely.
• E125: circulation fault. Water is not moving through the boiler properly, often the pump, air or a blockage.
• E128: flame failure. The boiler lit but the flame has been lost repeatedly.
• E133: ignition failure or interrupted gas supply. The boiler tried to light and did not detect a flame.
• E160: fan fault. The fan or its wiring is not working as expected.
• E168: control board lockout. The main board has locked out without a more specific cause, often after a power cut.

Low Pressure: E118 and E119

E119 is the Potterton code you are most likely to fix yourself. It means the pressure in the heating system has dropped below the safe minimum, usually well under 1 bar on the gauge.

Top the system up to about 1 to 1.5 bar through the filling loop, then reset. The E119 low pressure fault page covers the code itself. If the code comes back within days or weeks, water is leaving the system, through a leak, a dripping pressure relief valve or a failed expansion vessel. Finding that is the repair; topping up is not.

Ignition Failure: E133 and E128

E133 means the boiler tried to light and saw no flame. E128 means it lit and then lost the flame several times. Both are lockouts that stop gas being fed to an unlit burner.

Check what you safely can. Make sure the hob or other gas appliances work, a prepayment meter has credit and the gas valve under the boiler is open. In cold weather, check the condensate pipe outside, because a frozen pipe is a very common winter cause of E133 on condensing boilers; thaw it with warm, not boiling, water. If those are fine, the likely causes are the ignition electrode, the flame sensing circuit, the gas valve or the fan, and those are jobs for a Gas Safe registered engineer. The E133 ignition fault page lists the checks in order.

Overheating and Circulation: E110 and E125

E110 and E125 usually share a cause: water is not moving through the boiler fast enough, so it overheats or the boiler detects poor flow and stops.

The common reasons are a sticking or worn pump, sludge in the system, air around the pump after work on the radiators, low pressure, or every radiator valve closed at once. Check the pressure, make sure some radiators are open and bleed any that are cold at the top, then reset once. If the code returns, the pump and flow need checking. Do not keep resetting an overheat, because each restart heats the same trapped water again.

E168 and Other Control Board Lockouts

E168 means the main control board has locked out without identifying a more specific fault. It often follows a power cut, a tripped fuse or work on the electrics.

Switching the boiler off at its fused spur for a minute and back on is sometimes enough after a genuine power interruption. If E168 returns, or appears without any obvious electrical event, the board, its connections or a component it controls needs testing. A failing board can come from water getting into the boiler, so an engineer will look for the source before replacing anything.

When to Call an Engineer, and Is It Worth Repairing?

Reset once after the safe checks. If the same code returns, stop and book a repair. Most Potterton faults are a single part and are worth fixing.

Call straight away, and do not reset, if you smell gas, see soot or scorch marks around the boiler, or hear loud continuous banging. If you smell gas, turn the supply off at the meter if you can, open windows and ring the National Gas Emergency Service on 0800 111 999. On an older Potterton with a failing heat exchanger or several faults at once, ask the engineer plainly whether repair still makes sense. We repair Potterton boilers across London: book a Potterton boiler repair with the model name and full code ready.