If your Potterton boiler flashes an unfamiliar error code, don’t worry; it’s more common than you think. Whether it’s a slight temperature dip or a complete system halt, these codes are your boiler’s way of asking for help. Understanding them is often the first step to solving the problem.
In this blog, we break down the most frequent Potterton boiler error codes across the most popular models, including:
- Promax Combi, System & Store
- Promax Ultra, Gold/Titanium Combi & System
- Assure Combi & System models
You’ll find clear explanations of what each code means, what might be causing it, and how to figure out whether it’s a DIY fix or time to call a professional.
At Maintracts Services Ltd, we’ve been handling Potterton boiler issues across London since 1974. Our Gas Safe engineers know the ins and outs of these systems and are ready to respond fast, restore warmth, and keep your home or rental running smoothly.
Call us on 020 8682 2244 to speak to a specialist today.
With Potterton boiler faults, knowing the code is half the battle, let our expert team handle the rest with trusted repairs and peace of mind.
Promax Combi, System & Store Error Codes
| Code | Meaning | What to Check |
| E10 | Outdoor sensor error | A faulty external probe—verify the wiring and reconnect securely |
| E20 | Central heating thermistor fault | Sensor or wiring issue inside the boiler |
| E28 | Flue thermistor fault | The flue temperature sensor may be damaged |
| E50 | Domestic hot water sensor issue | DHW probe could need a replacement |
| E110 | Overheat tripped | Possible water circulation blockage |
| E119 | Low system pressure | Check and repressurise boiler to ~1.2 bar |
| E125 | Primary water circulation fault | Airlock or faulty pump suspected |
| E130/E131 | Flue thermostat fault/lockout | Flammable air passage restriction or lockout |
| E133 | Ignition failure | Gas supply or ignition module fault |
| E151/E152 | PCB error | Circuit board malfunction – likely needs a pro |
| E160/E161 | Fan fault | Fan motor or wiring problem |
| E164 | DHW sensor or flow switch error | Mixed DHW flow sensor/pump connector fault |
| E167/E168 | PCB fault/lockout | Major internal failure |
| E193 | Circulation error | Pump failure or blockage |
Quick Tip: For sensor-related codes (E10, E20, E28, E50), a quick reset and pressurisation sometimes clears the fault.
Promax Ultra, Gold & Titanium Models
These models have a richer feature set—and therefore more codes:
- E09 / E15: Gas valve-related electrical fault
- E53: Flue obstruction ensures nothing is blocking it
- E55: Requires recalibration often a service task
- E78: High water pressure sensor issue
- E83–E87: Room controller not connecting. Check the wireless or wiring link
- E92: Auto-combustion test failed
- Includes all earlier Promax codes (E110, E117, etc.)
Problem-detecting flame (E128, E129) or “dry fire” (E270) usually points to issues with the gas supply, sensors, or the ignition mechanism itself.
Potterton Assure Combi & System Boiler Error Codes
Common codes include:
- E09–E15: Gas valve connections or commands failing
- E20 / E28 / E40 / E50: NTC sensor faults in heating or DHW circuit
- E12/E13: Flow switch stuck open/closed, check valve action
- E83–E87: Communication errors
- E110: Boiler overheat, often due to pump jam or air trap
- E118: Low system water pressure
- E125: Circulation problem in the primary circuit
- E128/E129: Flame fail or repeated flame loss
- E133/E134/E135: Ignition or gas supply issues
- E154: Flow/return temperature mismatch
- E160/163: Fan or DHW sensor faults
- E317/E321/E384/E385: Voltage or frequency issues
- E430 / E430 + flame crossed: Water pressure test failed
Troubleshooting Flow
- Check Pressure
If your gauge reads <1 bar, open the filling loop to repressurise up to 1.2–1.5 bar. - Quick Resets
Turn off power, wait 30 seconds, then restart. Many sensor errors or ignition faults clear themselves on reboot. - Sensors & Wiring
Inspect exposed wiring and sensors, and loose cables can mimic major faults. - Condensate Pipecare
In cold weather, a frozen pipe can cause ignition errors. Thaw it gently with warm water or towels; be cautious! - When to Call the Engineer
Persistent errors like PCB faults (E151/E152/E167/E168), gas valve wiring (E09/E15), or flame-detection fault (E128/E270) need certified Gas-Safe engineers.
Common Real-Life Scenarios
- E119 Low pressure: Just redirect to the filling loop and repressurise.
- E133 Ignition fault: The gas supply may be off. Check cooker or thermostat gas.
- E160 Fan fault: A malfunctioning fan leads to airflow problems; engineer fixes.
- E110/E125 Circulation issues: Could be airlocks, bleeding radiators or resetting pump.
Final Checklist
- Check and adjust pressure first
- Note your model type (Promax vs Assure vs Ultra)
- Reset and retry on minor faults
- Inspect wiring and pipes visually
- Call a Gas-Safe engineer for anything involving gas, flame, PCB, or persistent lockouts
FAQs
What do the most common Potterton boiler error codes mean?
Potterton error codes highlight faults like low pressure (E118/E119), ignition failure (E133), and overheating (E110). Each code identifies a specific issue, helping engineers quickly diagnose and fix the problem.
How do I reset my Potterton boiler after seeing an error code?
Most Potterton models have a reset button on the control panel. Hold it for 3–5 seconds. If the fault persists after resetting, it’s time to call a Gas Safe registered engineer.
Why is my Potterton boiler showing error code E119?
Error code E119 means your boiler’s water pressure is too low. Try topping up the pressure using the filling loop. If the pressure drops again, there may be a leak or system fault.
What should I do if my Potterton boiler keeps locking out?
Frequent lockouts often signal serious issues like overheating, ignition failure, or circulation faults. It’s best to have a qualified heating engineer investigate the cause and restore safe operation.
Can I fix a Potterton boiler error code myself, or do I need an engineer?
Some minor issues, like low pressure, can be fixed at home. But for most error codes—especially repeated faults—it’s safer and smarter to call a certified gas-safe engineer.
Is error code E125 on my Potterton boiler dangerous?
E125 indicates a circulation fault, often due to a pump issue or air blockage. It’s not immediately dangerous but should be inspected promptly to avoid further system damage or failure.
Why does my Potterton boiler lose pressure and show an error?
Pressure loss is typically caused by leaks, bleeding radiators, or faulty components. If your boiler keeps losing pressure, book a service to identify the exact issue and prevent recurring faults.
Are error codes the same for all Potterton boiler models?
No, Potterton error codes vary by model. Promax, Assure, and Gold/Titanium boilers may show different codes for similar faults. Always refer to your manual or consult a heating expert.
How often should I service my Potterton boiler to avoid faults?
Annual servicing is recommended to keep your Potterton boiler in peak condition. It helps detect early signs of wear, ensures efficiency, and prevents most error codes from occurring unexpectedly.
Where can I find a gas-safe engineer to fix my Potterton boiler in London?
Maintracts Services Ltd has been repairing Potterton boilers across London since 1974. Our Gas Safe engineers are ready to provide expert diagnostics, fast repairs, and trusted service when you need it most.
Summary
Potterton boilers communicate effectively via error codes and armed with this guide, you can confidently navigate most issues. While some fixes are simple DIY tasks, serious faults call for professional attention. If your boiler is still locked out or displaying errors after basic troubleshooting, don’t wait. Reach out to a Gas-Safe certified plumber in London who understands these systems inside-out.
Stay warm and stay safe!