Error E151

Safety precautions:

1. If the boiler shows a PCB error, do not attempt to bypass lockouts or safety interlocks. Never interfere with gas connections or the ignition system unless you are a Gas Safe registered engineer.

2. Before doing any visual checks, switch the boiler off at the room thermostat and then switch off the mains electrical isolation to the boiler. If you are checking inside the casing, isolate the gas supply as well and only remove covers if you are competent and confident it is safe to do so.

3. If you smell gas or suspect a leak, evacuate the property and contact your gas emergency service immediately.

Initial homeowner checks (safe, simple steps):

1. Note the exact error code and any other codes displayed and take a photo of the display for the engineer.

2. Try a basic reset: use the boiler reset/button or switch the electrical supply off for 30 seconds and then back on. If the fault clears and the boiler runs normally for a period, still arrange a service because intermittent PCB faults can recur.

3. Check boiler pressure on the gauge. If pressure is very low (<1.0 bar) repressurise the system to around 1.0–1.5 bar following the manual instructions. Low pressure can produce unrelated faults that mask other issues.

4. Do a quick visual inspection around the outside of the boiler for obvious signs of water leaks, corrosion or condensation. Check the condensate pipe (in cold weather) for freezing or blockage.

5. Check the electrical supply: ensure the boiler is receiving mains power (fuse not blown, isolation switch on). If you have recent mains instability or brownouts, note that for the engineer.

Specific diagnostic and fix steps (for competent DIY persons only; otherwise skip to the professional section):

1. After isolating mains and gas, remove the boiler cover only if you are competent. Visually inspect the PCB for burn marks, discoloured components, loose connectors, corrosion or signs of water ingress.

2. Check that all plug-in connectors on the PCB are firmly seated. Re-seat connectors gently if they appear loose. Do not pull on wires; press on the plastic housings.

3. Look for any obvious damaged components, bulging capacitors or cracked solder joints. If you see significant damage, do not attempt solder repairs unless you are trained — replacement is usually required.

4. If you have electrical testing skills and the appropriate tools, with the boiler isolated, you can continuity-check fuses and inspect wiring to sensors, pump and fan. Do not power the PCB to live-test unless you are trained to diagnose boiler electronics safely.

5. If a reset temporarily clears the fault but it reappears, note when it fails (immediately on power-up, after firing, during warm-up) as that helps the engineer identify whether the PCB itself or a peripheral component is causing the error.

When to call a professional and what they will do:

1. Persistent E151, E152, E167, E168 or any PCB-related lockout requires a Gas Safe registered engineer. PCB replacement or repair is an electrical and gas appliance task and should not be performed by an unqualified person.

2. The engineer will isolate and test the boiler, carry out live diagnostics with multimeter and specialist tools, check voltages and signals, and inspect/replace failing peripheral components (fans, pumps, thermistors, flow switches, gas valve) which can cause secondary PCB faults.

3. They will also check for water leaks and corrosion that may have damaged the PCB, repair the root cause (for example seals, pipework or pump leaks) before fitting a new board. After replacement they will commission the boiler, run safety checks and verify stable operation.

Final notes:

1. Do not attempt to bypass safety controls or run the boiler if you suspect the PCB or any safety component is faulty. That could create an unsafe condition.

2. Record model and serial numbers, the exact error code(s), and when the fault occurred, and provide these to the engineer. That speeds diagnosis and ensures correct replacement parts.

3. If in doubt, stop and call a Gas Safe registered engineer to diagnose and repair the fault.