Error F7

Safety precautions:

1) If you suspect an electrical supply problem, turn the boiler to off/standby and isolate the fused spur or switch for the boiler if you can do so safely. Do not open the boiler casing or attempt any live electrical work unless you are a qualified electrician. Do not attempt any gas-side repairs, ignition, or component replacement — these require a Gas Safe registered engineer.

2) Before touching anything electrical, switch off the mains at the consumer unit if you need to access a fused spur and you are competent to do so. If unsure, call a professional. Keep children and pets away while you inspect.

Initial homeowner checks (safe, non-invasive):

1) Note the full fault code and when it started. Record boiler model and serial number. Try a simple reset: with the boiler in standby, press and hold the reset button for about 5 seconds (consult your manual for model-specific procedure). Wait and see if the boiler tries to restart or if F7 returns immediately or intermittently.

2) Check other electrical items and lights in the house. Are other appliances dimming or losing power? If multiple appliances are affected, the issue is likely the house supply — contact your electricity supplier or an electrician.

3) Check the consumer unit (fuse box) for any tripped MCBs/RCDs or a blown fuse specific to the boiler circuit. Reset a tripped breaker once. If it trips again immediately, stop and call an electrician.

4) If your boiler is fed from a plug or fused spur, check the plug, lead and fuse (replace the 3A or appropriate fuse only when the device is unplugged). If the boiler is hardwired, do not open the wiring unless qualified.

5) Check meter/prepayment: if you have a prepayment meter or smart meter, ensure credit is available and that supply hasn’t been disconnected.

6) Check basic boiler status items: system pressure (cold reading around 1–1.5 bar), visible leaks, and listen for the fan/pump trying to run when you reset. Low water pressure or no flow can cause other faults; top up pressure only if you know how and the boiler manual directs you to do so.

Specific diagnostic and next-step checks (some require a professional):

1) If the fault returns after reset and only the boiler is affected: call a qualified electrician to measure the supply voltage at the boiler electrical terminal. The electrician will check voltage under load, look for loose or corroded connections at the consumer unit, fused spur, incoming supply and the boiler fused terminal.

2) If mains voltage is low or unstable: the electrician will advise whether the issue is internal wiring, the consumer unit, or the incoming supply. If the incoming supply from the network is at fault, contact your electricity supplier/distribution network operator.

3) If mains voltage is normal but F7 persists: arrange a Gas Safe registered engineer. They will inspect the boiler for internal electrical faults — failing PCB, faulty fan or fan wiring, air pressure switch faults, thermistors, pump seizures, or false flame lockout conditions that can present as low-voltage errors. The engineer can test control voltages at the PCB, inspect wiring harnesses and connectors for loose/oxidised contacts, test the fan motor and pressure switches, and verify gas and flow components.

4) If the engineer finds intermittent faults (e.g. loose connector, failing capacitor or degraded PCB) they will recommend the appropriate repair or replacement. Do not use the boiler if the engineer advises against it until repairs are complete.

When to call a professional:

1) Call an electrician if you find low or unstable house voltage, repeated breaker trips, dimming lights, or if the boiler’s fused supply shows an issue. The electrician will isolate and repair mains wiring faults.

2) Call a Gas Safe registered engineer if the boiler continues to show F7 after supply checks, or if internal boiler components (fan, PCB, air pressure switch, pump, gas valve, thermistor) need testing or replacement. Any work on gas components or the boiler internals must be carried out by a Gas Safe engineer.

Important final notes:

1) Do not attempt live electrical or gas repairs yourself. Incorrect work can cause fire, electric shock or carbon monoxide risks. 2) If the F7 code appeared during a storm or power cut and then cleared after reset, monitor the boiler and call a professional if it returns. 3) Keep records of any checks, resets and engineer visits (model, serial, error frequency) to help diagnosis.