Potterton Boiler Fault Codes: Meanings, Causes and Safe Checks

Potterton boilers show fault codes when the appliance detects a problem.

These messages help you understand what may have gone wrong. They can point to low pressure, overheating, ignition failure, poor circulation, sensor trouble, fan faults, or control problems.

Some issues have simple checks. However, many need a Gas Safe registered engineer.

Never remove the casing. Also, do not touch gas parts, flue parts, wiring, the fan, burner, PCB, pump, or internal sensors.

What are Potterton boiler fault codes?

Potterton fault codes are warning messages on the display.

They guide you towards the likely problem area. For example, one message may relate to pressure. Another may suggest ignition, airflow, heat control, or circulation trouble.

Even so, the display does not always give the full diagnosis. It only gives a starting clue.

If the same warning returns after one reset, book professional help.

Common Potterton error codes

E110 – Overheat lockout

E110 means the appliance has reached an unsafe temperature.

This can happen when heat cannot move away from the boiler fast enough. A pump problem, trapped air, blocked pipework, or thermostat issue may be involved.

Possible causes include:

• Poor water movement
• Faulty pump
• Blocked pipework
• Thermostat issue
• Air inside the heating system

If E110 returns after one reset, stop there and call an engineer.

E119 – Low pressure

E119 means the boiler pressure has dropped too low. Some Potterton models use E118 for this issue instead.

Low pressure can stop the heating system from running correctly. It may also cause lockouts.

Possible causes include:

• Small leak
• Recent radiator bleeding
• Natural pressure loss
• Expansion vessel issue
• Pressure relief valve fault

You may top up the system if your manual explains how. However, repeated pressure loss needs proper repair.

E125 – Poor circulation

E125 points to poor water movement through the appliance.

If water cannot move freely, the boiler may overheat or shut down.

Possible causes include:

• Weak pump
• Airlocks
• Sludge build-up
• Blocked pipework
• Closed valves

If radiators heat unevenly, the whole heating circuit may need checking.

E133 – Ignition failure

E133 means the burner has not lit correctly.

This can happen if the boiler cannot start ignition or cannot prove a flame.

Possible causes include:

• Gas supply issue
• Ignition electrode fault
• Frozen condensate pipe
• Flue issue
• Gas valve problem

Check whether other gas appliances work. If they do not, contact your gas supplier or a qualified professional.

E160 – Fan fault

E160 relates to the fan.

The fan helps remove combustion gases. It also supports safe burning.

Possible causes include:

• Failed fan
• Wiring issue
• Obstruction
• Worn part
• PCB signal problem

Do not try internal fan repairs yourself.

E20 – Central heating thermistor issue

E20 points to the central heating thermistor.

This part reads heating water temperature. If the signal becomes wrong, the boiler may struggle to control heat output.

Possible causes include:

• Damaged thermistor
• Loose connection
• Wiring issue
• Sensor failure

If the warning returns, an engineer should test it.

E28 – Flue thermistor issue

E28 relates to the flue thermistor on many Potterton models.

This part monitors flue gas temperature. Because flue safety matters, you should act quickly.

Possible causes include:

• Damaged sensor
• Incorrect temperature reading
• Wiring issue
• Poor connection

Do not remove flue parts or open the boiler.

E40 – Return thermistor issue

E40 points to the return thermistor.

This part reads water temperature as it comes back from the heating circuit.

Possible causes include:

• Failed sensor
• Damaged wiring
• Loose plug
• Poor reading

This small part helps the boiler run efficiently.

E78 – Pressure sensor issue

E78 suggests a pressure sensor problem.

This component sends pressure readings to the controls. If it reports the wrong value, the boiler may show a warning even when the gauge looks normal.

Possible causes include:

• Faulty sensor
• Poor connection
• Wiring issue
• False reading

An engineer can compare the sensor reading with the actual pressure.

E83, E84 and E85 – Communication issue

E83, E84 and E85 point to a communication fault.

This may involve the room controller, receiver, wiring, electronics, controls, or PCB signals.

However, these messages do not always prove PCB failure. A loose connection or external control fault may also be responsible.

Safe troubleshooting checks

You can make a few simple checks before calling an engineer. However, stop if the same message returns.

For E110 and E125

Check whether radiators heat evenly.
Listen for odd pump noises.
Look for obvious external blockages.
Try one reset only, if the manual allows it.

If the warning returns, arrange professional help.

For E119 or E118

Check the pressure gauge.
Top up only if your manual explains the process.
Look for visible leaks around radiators and pipework.
Watch whether the gauge drops again.

Repeated pressure loss usually means another fault exists.

For E133

Check whether the gas supply is on.
See if other gas appliances work.
Look at the condensate pipe during freezing weather.
Try one reset only.

If ignition still fails, call an engineer.

For E160

Listen for the fan starting.
Note any strange noises.
Look for obvious outside obstructions, where safe.

Do not touch internal fan or flue parts.

For E20, E28 and E40

These messages relate to temperature sensors on many models.

A reset may clear a brief signal issue. However, wiring, plugs, and sensor parts need professional testing if the warning returns.

Do not remove the cover.

For E78

Compare the display with the pressure gauge.
Note whether the reading seems wrong.
Arrange inspection if the warning stays active.

A faulty pressure sensor can create misleading pressure warnings.

For E83, E84 and E85

Note the exact message.
Try one reset only.
Check that external controls have power.
Call an engineer if the warning returns.

Communication problems rarely have a simple home fix.

When should you call an engineer?

Call a Gas Safe registered engineer if the same message returns after one reset.

You should also book help if the boiler overheats, fails to ignite, loses pressure often, shows a fan issue, or stops responding.

If you smell gas, turn off the supply if safe. Then open windows, avoid electrical switches, and call the National Gas Emergency Service on 0800 111 999.

For any internal repair, always use a qualified professional.

How to reduce future Potterton faults

Good care can reduce the risk of sudden breakdowns.

Book annual boiler servicing.
Check the pressure gauge often.
Fix visible leaks quickly.
Bleed radiators when needed.
Top up after bleeding, if your manual says to.
Keep the flue terminal clear.
Act early when warnings appear.

During a service, an engineer can test safety parts, check performance, and spot early wear.

Final thoughts

Potterton fault codes help identify the likely area behind a heating problem.

Low pressure may have safe home checks. However, ignition, overheating, fan, flue, sensor, PCB, and communication problems often need expert diagnosis.

If the same warning returns, stop resetting the boiler. Then arrange a professional inspection.

Fast action helps restore safe, steady, and reliable heating.