Overview
E152 on Potterton Promax (Combi, System and Store) boilers is an error that commonly appears in two different contexts in publicly available references. Potterton error lists for Promax models sometimes show E152 as a printed circuit board (PCB) error — meaning the boiler’s control electronics have detected an internal fault. Other guides and service reports associate E152 with a domestic hot water NTC (temperature) sensor fault or related wiring/communication problems. Because different Potterton models and firmware revisions use codes differently, E152 should be treated as an electronic/sensor control fault rather than a simple mechanical problem. Severity is moderate to high: the fault will often result in loss of domestic hot water or a boiler lockout and can stop normal operation. It is not normally an immediate safety danger in itself, but it affects core control systems (PCB, sensors, wiring) and connects to gas and electrical circuits. Simple checks and a reset can occasionally clear transient faults, but diagnosis and any internal electronic or gas-related repairs should be performed by a qualified Gas Safe engineer. DIY steps are limited to safe visual checks, pressure checks and basic resets; anything that involves gas components, mains wiring, replacing sensors or replacing the PCB must be left to a professional.
Possible Cause: PCB error
Troubleshooting Steps
Safety first:
- If you smell gas, evacuate the property, do not operate electrical switches or the boiler, and call the gas emergency number immediately. Do not attempt any repairs.
- Isolate electrical power to the boiler at the external isolator or fuse spur before touching any internal components or wiring. If you are not comfortable isolating the unit, stop and call a Gas Safe engineer.
- Do not attempt to replace the PCB, gas valve, or gas-carrying components yourself. These are gas/qualified-electric tasks and require a Gas Safe registered engineer.
Initial homeowner checks (safe, non-invasive):
1. Note the exact error code and any additional messages or LED patterns. Record the boiler model and serial number to give to the engineer.
2. Try a simple reset: use the boiler reset button (hold for 3–5 seconds) or switch the electrical supply off at the isolator for 30 seconds, then restore power and see if E152 returns. Some transient electronic faults clear with a reset.
3. Check the system pressure on the pressure gauge. If pressure is low (typically below 1.0–1.2 bar), follow the boiler manual to repressurise to the recommended level (commonly 1.0–1.5 bar). Low pressure can cause sensor/circulation faults.
4. Check whether central heating radiators and hot water behave differently: does CH still work while DHW is lost? That info helps identify whether the fault is DHW-sensor related or a broader PCB issue.
5. Inspect externally visible pipework and the condensate trap/pipe for blockages or freezing in cold weather. A blocked condensate can cause faults that affect boiler operation.
Specific diagnostic checks you can perform if comfortable and safe (observe isolation rule above):
6. Visual inspection of the boiler PCB area: after isolating power and only if you are confident, remove the outer case to look for obvious signs of damage—burn marks, swollen components, loose multi-pin connectors, or water/condensate ingress on the circuit board. Do not probe or touch the board while it is live.
7. Check plug-in connector security: many PCB/sensor faults are caused by a loose connector. With power isolated, gently press down on identifiable multi-pin connectors (that are externally accessible when the casing is removed) to ensure they are fully engaged. Note: some connectors are hard to reach or require partial disassembly—if unsure, stop and call an engineer.
8. Sensor wiring check: trace the domestic hot water NTC sensor wiring where visible; look for obvious breaks, corrosion or disconnected plugs. If the wiring is intact but obvious damage exists, do not attempt complex repairs—photograph the damage for the engineer.
9. Flow switch/pump observation: if you hear the pump running on demand and radiators get hot but there is no hot water, the diverter valve/flow-switch/DHW sensor could be implicated. These components generally require an engineer for testing and replacement.
When to call a professional and what to tell them:
- Call a Gas Safe registered engineer if the code returns after reset, if you found loose or burnt connectors, any signs of water damage or burnt PCB components, or if there is no hot water or boiler lockout. Also call a pro if you are uncomfortable performing any of the steps above. Persistent E152 on multiple resets usually indicates a sensor failure, wiring fault to the PCB, or a PCB fault that requires specialist diagnostics and replacement.
- Provide the engineer with: boiler model and serial, the exact error code (E152), what you have already checked (pressure, reset, visible wiring, condensate), and whether central heating still operates. Photographs of any visible damage or connectors are useful.
Final notes and cautions:
- Because E152 is reported both as a PCB error and as a DHW NTC/sensor related fault depending on model and documentation, do not assume a single fix. The engineer will use diagnostic tools to read live voltages/thermistor resistances and test the PCB.
- Replacing the PCB or sensor is not a DIY job. Work on gas and mains electrical parts must be carried out by a Gas Safe registered engineer to be safe and to maintain warranty and compliance.
- If the boiler is under warranty or a service contract, contact the manufacturer or your service provider before commissioning independent repairs to avoid voiding cover.
Helpful Resources
Boiler Manual
Download the official PDF manual for the Potterton Promax Combi, System, and Store.