Common questions about Potterton codes · Search all brands by code or symptom
What is safe for you to do
Every code here follows the same safety rules. You can:
- press the reset button once, as your user guide shows;
- for low-pressure codes, top up the pressure with the filling loop, as your user guide shows;
- for ignition and flame-loss codes, check the gas is on at the meter and a prepayment meter has credit;
- thaw a frozen plastic condensate pipe outside with warm (not boiling) water;
- check the thermostat, timer and power to the boiler.
Never open the boiler casing. Only a Gas Safe registered engineer may work inside a gas boiler. Codes marked Engineer after one reset have no homeowner fix: reset once, then leave them to an engineer. Codes marked Safe checks first list the one check that relates to that code.
Potterton Assure Combi (25 / 30 / 36)
The Assure Combi flashes an E symbol followed by a two- or three-digit number, e.g. E133.
Source: Potterton Assure Combi Installation and Service Manual, doc. 7717311-01, p. 64, section 10.1 Error codes (Fig. 68). Open the manual (PDF) (Copy hosted by a UK trade site (no manufacturer-hosted copy found))
Ignition / flame
E09 Potterton Assure Combi
Engineer after one resetIgnition / flameWhat it means
Gas valve connection cable fault.
Likely causes
Gas valve lead or connections; the manual says to check board connections and replace the board if it keeps happening.
What you can safely do
There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code comes back after one reset. Ignition and flame faults involve gas, so this is engineer-only.
What does E09 mean on a Potterton Assure Combi boiler?
On a Potterton Assure Combi, E09 is listed in the manufacturer's table as "Gas valve connection cable fault". There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
E15 Potterton Assure Combi
Engineer after one resetIgnition / flameWhat it means
Gas valve fault.
Likely causes
Gas valve or its control from the board.
What you can safely do
There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code comes back after one reset. Ignition and flame faults involve gas, so this is engineer-only.
What does E15 mean on a Potterton Assure Combi boiler?
On a Potterton Assure Combi, E15 is listed in the manufacturer's table as "Gas valve fault". Likely causes include gas valve or its control from the board. There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
E128 Potterton Assure Combi
Safe checks firstIgnition / flameWhat it means
Flame failure during normal operation.
Likely causes
Interrupted gas supply, low gas pressure, a frozen or blocked condensate pipe, or an electrode, flue or gas valve problem.
What you can safely do
Check another gas appliance such as the hob works, the gas meter valve is on and, on a prepayment meter, there is credit. In freezing weather, check the plastic condensate pipe outside: if it is frozen, pour warm (not boiling) water along it. Then press reset once. If the code comes back, stop resetting.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the gas supply is fine and the code returns after one reset. Ignition and flame faults involve gas, so this is engineer-only.
What does E128 mean on a Potterton Assure Combi boiler?
On a Potterton Assure Combi, E128 is listed in the manufacturer's table as "Flame failure during normal operation". Check another gas appliance works, the meter valve is on and any prepay meter has credit, then reset once. If it returns, book a Gas Safe registered engineer.
E133 Potterton Assure Combi
Safe checks firstIgnition / flameWhat it means
Interruption of the gas supply or flame failure: the boiler could not light or prove a flame.
Likely causes
Gas off, an empty prepayment meter, low gas pressure, a frozen condensate pipe, or a spark/sensing electrode, lead or gas valve fault.
What you can safely do
Check another gas appliance such as the hob works, the gas meter valve is on and, on a prepayment meter, there is credit. In freezing weather, check the plastic condensate pipe outside: if it is frozen, pour warm (not boiling) water along it. Then press reset once. If the code comes back, stop resetting.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the gas supply is fine and the code returns after one reset. Ignition and flame faults involve gas, so this is engineer-only.
What does E133 mean on a Potterton Assure Combi boiler?
On a Potterton Assure Combi, E133 is listed in the manufacturer's table as "Interruption of the gas supply or flame failure: the boiler could not light or prove a flame". Check another gas appliance works, the meter valve is on and any prepay meter has credit, then reset once. If it returns, book a Gas Safe registered engineer.
E135 Potterton Assure Combi
Safe checks firstIgnition / flameWhat it means
Interruption of the gas supply, listed in the manual as an internal error.
Likely causes
Gas supply interruption or a control board fault.
What you can safely do
Check another gas appliance such as the hob works, the gas meter valve is on and, on a prepayment meter, there is credit. In freezing weather, check the plastic condensate pipe outside: if it is frozen, pour warm (not boiling) water along it. Then press reset once. If the code comes back, stop resetting.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the gas supply is fine and the code returns after one reset. Ignition and flame faults involve gas, so this is engineer-only.
What does E135 mean on a Potterton Assure Combi boiler?
On a Potterton Assure Combi, E135 is listed in the manufacturer's table as "Interruption of the gas supply, listed in the manual as an internal error". Check another gas appliance works, the meter valve is on and any prepay meter has credit, then reset once. If it returns, book a Gas Safe registered engineer.
E384 Potterton Assure Combi
Engineer after one resetIgnition / flameWhat it means
False flame: a flame signal is detected when there should be none.
Likely causes
Electrode or wiring fault, moisture, a gas valve not closing, or the board.
What you can safely do
There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code comes back after one reset. Ignition and flame faults involve gas, so this is engineer-only.
What does E384 mean on a Potterton Assure Combi boiler?
On a Potterton Assure Combi, E384 is listed in the manufacturer's table as "False flame: a flame signal is detected when there should be none". There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
Water pressure / circulation
E109 Potterton Assure Combi
Engineer after one resetWater pressure / circulationWhat it means
Pre-circulation fault: the boiler did not see water circulating before lighting.
Likely causes
Low pressure, air in the system, the pump or closed valves.
What you can safely do
There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if you have to top up more than once every few months, the gauge goes above about 2.5 bar when hot, water drips from the outside overflow pipe, or the code returns after topping up.
What does E109 mean on a Potterton Assure Combi boiler?
On a Potterton Assure Combi, E109 is listed in the manufacturer's table as "Pre-circulation fault: the boiler did not see water circulating before lighting". Reset once; if the code comes back, book a Gas Safe registered engineer and quote the full code. Do not open the casing.
E118 Potterton Assure Combi
Safe checks firstWater pressure / circulationWhat it means
Primary system water pressure is too low (the manual says below 0.5 bar).
Likely causes
Water lost from the system through a leak, the pressure relief valve or bleeding radiators, or a flat expansion vessel.
What you can safely do
Look at the pressure gauge while the boiler is cold. If it is below about 1 bar, top it up with the filling loop exactly as your user guide shows, to about 1–1.5 bar or the figure in your guide, then close the loop fully. Check the radiator valves are open, then press reset once.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if you have to top up more than once every few months, the gauge goes above about 2.5 bar when hot, water drips from the outside overflow pipe, or the code returns after topping up.
What does E118 mean on a Potterton Assure Combi boiler?
On a Potterton Assure Combi, E118 means the primary system water pressure is too low (the manual says below 0.5 bar). With the boiler cold, check the pressure gauge; if it is below the level in your user guide, top it up as the guide shows, then reset once. If it returns, book a Gas Safe registered engineer.
E125 Potterton Assure Combi
Engineer after one resetWater pressure / circulationWhat it means
Circulation fault in the primary circuit. The manual says it shows if the water temperature hardly changes 15 to 30 seconds after lighting, or overshoots the set temperature by 30 °C twice within 10 minutes.
Likely causes
Poor primary circulation: a stuck or failed pump, air, low pressure, closed valves or a blocked heat exchanger.
What you can safely do
There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if you have to top up more than once every few months, the gauge goes above about 2.5 bar when hot, water drips from the outside overflow pipe, or the code returns after topping up.
What does E125 mean on a Potterton Assure Combi boiler?
On a Potterton Assure Combi, E125 is listed in the manufacturer's table as "Circulation fault in the primary circuit". Reset once; if the code comes back, book a Gas Safe registered engineer and quote the full code. Do not open the casing.
E270 Potterton Assure Combi
Engineer after one resetWater pressure / circulationWhat it means
Circulation fault (dry fire): the boiler detected it was firing without enough water flow.
Likely causes
Very low pressure, air, a stuck pump or closed valves.
What you can safely do
There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if you have to top up more than once every few months, the gauge goes above about 2.5 bar when hot, water drips from the outside overflow pipe, or the code returns after topping up.
What does E270 mean on a Potterton Assure Combi boiler?
On a Potterton Assure Combi, E270 is listed in the manufacturer's table as "Circulation fault (dry fire): the boiler detected it was firing without enough water flow". Reset once; if the code comes back, book a Gas Safe registered engineer and quote the full code. Do not open the casing.
Temperature / overheat
E110 Potterton Assure Combi
Engineer after one resetTemperature / overheatWhat it means
The safety (overheat) thermostat has operated: the primary water overheated.
Likely causes
Poor circulation, low pressure, air, a stuck pump, or the thermostat or board.
What you can safely do
Let the boiler cool for 20 to 30 minutes, then press reset once. If the code comes back, leave the boiler off.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code comes back after one reset. Overheat shut-downs are safety devices doing their job, so this is engineer-only.
What does E110 mean on a Potterton Assure Combi boiler?
On a Potterton Assure Combi, E110 means the safety (overheat) thermostat has operated: the primary water overheated. There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
Flue / fan / air
E130 Potterton Assure Combi
Engineer after one resetFlue / fan / airWhat it means
The flue NTC has operated (flue overheat).
Likely causes
Overheating flue gases, often linked to poor circulation or a blocked heat exchanger, or a sensor fault.
What you can safely do
There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the terminal looks clear and the code returns. Flue and fan faults can affect how combustion gases leave your home, so this is engineer-only.
What does E130 mean on a Potterton Assure Combi boiler?
On a Potterton Assure Combi, E130 means the flue NTC has operated (flue overheat). There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
E160 Potterton Assure Combi
Engineer after one resetFlue / fan / airWhat it means
Fan or fan wiring fault.
Likely causes
A failed fan, fan wiring or the control board.
What you can safely do
There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the terminal looks clear and the code returns. Flue and fan faults can affect how combustion gases leave your home, so this is engineer-only.
What does E160 mean on a Potterton Assure Combi boiler?
On a Potterton Assure Combi, E160 is listed in the manufacturer's table as "Fan or fan wiring fault". Likely causes include a failed fan, fan wiring or the control board. There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
Sensors / thermistors
E20 Potterton Assure Combi
Engineer after one resetSensors / thermistorsWhat it means
Central heating (flow) NTC sensor fault.
Likely causes
Failed sensor or wiring.
What you can safely do
Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code returns. Testing and replacing sensors means opening the casing, so this is engineer-only.
What does E20 mean on a Potterton Assure Combi boiler?
On a Potterton Assure Combi, E20 is listed in the manufacturer's table as "Central heating (flow) NTC sensor fault". Likely causes include failed sensor or wiring. There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
E28 Potterton Assure Combi
Engineer after one resetSensors / thermistorsWhat it means
Flue NTC sensor fault.
Likely causes
Failed flue sensor or wiring.
What you can safely do
Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code returns. Testing and replacing sensors means opening the casing, so this is engineer-only.
What does E28 mean on a Potterton Assure Combi boiler?
On a Potterton Assure Combi, E28 is listed in the manufacturer's table as "Flue NTC sensor fault". Likely causes include failed flue sensor or wiring. There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
E40 Potterton Assure Combi
Engineer after one resetSensors / thermistorsWhat it means
Central heating return NTC sensor fault.
Likely causes
Failed sensor or wiring.
What you can safely do
Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code returns. Testing and replacing sensors means opening the casing, so this is engineer-only.
What does E40 mean on a Potterton Assure Combi boiler?
On a Potterton Assure Combi, E40 is listed in the manufacturer's table as "Central heating return NTC sensor fault". Likely causes include failed sensor or wiring. There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
E154 Potterton Assure Combi
Engineer after one resetSensors / thermistorsWhat it means
Flow/return sensor temperature test fault.
Likely causes
Flow and return sensors giving implausible readings, poor circulation or a sensor fault.
What you can safely do
Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code returns. Testing and replacing sensors means opening the casing, so this is engineer-only.
What does E154 mean on a Potterton Assure Combi boiler?
On a Potterton Assure Combi, E154 is listed in the manufacturer's table as "Flow/return sensor temperature test fault". There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
E321 Potterton Assure Combi
Engineer after one resetSensors / thermistorsWhat it means
Hot water NTC sensor fault.
Likely causes
Failed hot water sensor or wiring.
What you can safely do
Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code returns. Testing and replacing sensors means opening the casing, so this is engineer-only.
What does E321 mean on a Potterton Assure Combi boiler?
On a Potterton Assure Combi, E321 is listed in the manufacturer's table as "Hot water NTC sensor fault". Likely causes include failed hot water sensor or wiring. There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
Other / controls
E83 Potterton Assure Combi
Engineer after one resetOther / controlsWhat it means
Communication error.
Likely causes
Lost communication between the boiler's electronics and its controls.
What you can safely do
There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code stays after you have checked the controls, or keeps coming back.
What does E83 mean on a Potterton Assure Combi boiler?
On a Potterton Assure Combi, E83 is listed in the manufacturer's table as "Communication error". Likely causes include lost communication between the boiler's electronics and its controls. Reset once; if the code comes back, book a Gas Safe registered engineer and quote the full code. Do not open the casing.
Common questions
About Potterton fault codes
2 questions
Which Potterton fault codes can I usually deal with myself?
On the Potterton ranges in our guide, only these codes have a safe homeowner check first: E128, E133, E135 for gas supply or flame loss (check the meter and credit); E118 for low pressure (top up). Reset once afterwards. Every other code needs a Gas Safe registered engineer; never open the casing.
Where can I find the official fault code list for my Potterton Assure Combi?
Potterton publishes the fault table in the installation and servicing manual for the Assure Combi (7717311-01, p. 64). CombiCert's fault code guide explains 19 codes from it. Check your data badge matches this model first, because codes differ between ranges. Write down the exact code before resetting, so the engineer can diagnose it faster.
Codes by type: Potterton Assure Combi (25 / 30 / 36)
6 questions
Which Potterton Assure Combi fault codes relate to the flue, fan or air supply?
On the Potterton Assure Combi, the manufacturer's table has 2 flue, fan or air supply codes: E130, E160. None of these has a homeowner fix beyond one reset. Do not open the casing; book a Gas Safe registered engineer and quote the full code.
Which Potterton Assure Combi fault codes mean the boiler will not light or loses its flame?
On the Potterton Assure Combi, the manufacturer's table has 6 ignition or flame codes: E09, E128, E133, E135, E15, E384. For E128, E133, E135, first check the gas meter, prepay credit and another gas appliance, then reset once. The others need a Gas Safe registered engineer.
Which Potterton Assure Combi fault code relates to controls or other faults?
On the Potterton Assure Combi, the manufacturer's table has one controls or other code, E83. E83 is listed in the manufacturer's table as "Communication error". This code has no homeowner fix beyond one reset. Do not open the casing; book a Gas Safe registered engineer and quote the full code.
Which Potterton Assure Combi fault codes point to a temperature sensor fault?
On the Potterton Assure Combi, the manufacturer's table has 5 temperature sensor codes: E154, E20, E28, E321, E40. None of these has a homeowner fix beyond one reset. Do not open the casing; book a Gas Safe registered engineer and quote the full code.
Which Potterton Assure Combi fault code means the boiler is overheating?
On the Potterton Assure Combi, the manufacturer's table has one overheat code, E110. E110 means the safety (overheat) thermostat has operated: the primary water overheated. This code has no homeowner fix beyond one reset. Do not open the casing; book a Gas Safe registered engineer and quote the full code.
Which Potterton Assure Combi fault codes relate to water pressure or circulation?
On the Potterton Assure Combi, the manufacturer's table has 4 water pressure or circulation codes: E109, E118, E125, E270. For E118, first check the pressure gauge when cold and top up if low, as your user guide shows, then reset once. The others need a Gas Safe registered engineer.
Code still showing? Book a repair
CombiCert Ltd is a Gas Safe registered business (621146) in Telford, Shropshire. Our team of 2 to 5 engineers is led by director and Gas Safe engineer Peter Jefferson. Boiler repair from £90 + VAT, parts quoted separately.
Send us the make, model and the exact code on WhatsApp and we will tell you what we need to check.
Explanations are written by CombiCert from the manufacturer manuals listed, which you should check for your exact model. This page is general information, not a diagnosis. If you smell gas, call 0800 111 999.