Error F.24

Safety first:

- If you smell gas, evacuate the property and contact the gas emergency number immediately. Do not attempt any checks.

- Turn the boiler off and isolate electrical supply before removing any casing or attempting any internal checks. If you are not comfortable working near gas or electrical components, stop and call a Gas Safe engineer.

- Wear gloves/eye protection for any bleeding or water-handling tasks. Have towels and a small container ready for water when bleeding radiators.

Initial checks a homeowner can safely do:

1. Reset the boiler: try a reset from the control panel according to your manual. A reset may clear a transient error but will not fix a persistent circulation problem.

2. Check system pressure: look at the boiler pressure gauge. Normal running pressure is usually around 1.0–1.5 bar. If pressure is very low (<0.8 bar) follow the boiler manual to repressurise using the filling loop, or call an engineer if you are unsure. After repressurising, reset the boiler and see if the F.24 clears.

3. Check isolation valves under the boiler: visually inspect the two small valves on the flow and return pipes beneath the boiler. If they are perpendicular to the pipe they are closed; if they are parallel they are open. If closed, open them carefully (small screwdriver or lever) and then reset the boiler.

4. Bleed radiators: turn the heating off and ensure radiators are cold. Use a radiator key, place a towel and container under the bleed valve, turn the valve a quarter to half turn until you hear a hissing noise (air escaping). When water starts to drip steadily, close the valve. Repeat for radiators showing cold spots or gurgling noises. Re-check boiler pressure and reset.

More specific diagnostics and possible fixes (exercise caution):

5. Listen for pump activity: with the boiler attempting to run, stand nearby and listen for humming or ticking from the pump area. No sound when the boiler is asking for circulation can indicate an electrical or motor failure; a loud hum with no circulation can mean a seized impeller or internal blockage.

6. Look for signs of airlocks: gurgling in pipes, uneven heating where some radiators get hot and others stay cold, or a hissing sound when bleeding indicate trapped air. Bleeding radiators and towel rails is the standard first fix.

7. Gentle tap on the pump (temporary measure): sometimes a seized impeller can free with a very light tap to the pump body (use the back of a screwdriver handle). This is a temporary diagnostic move only — do not remove covers or try to dismantle the pump. If a tap frees it and the boiler runs, arrange for a professional to inspect and replace the pump if needed.

8. Check for sludge or blockages: multiple cold radiators, poor flow even after bleeding, or recurring circulation faults suggest sludge/debris. Homeowners can try bleeding and balancing radiators, but power flushing and removal of internal debris should be done by a qualified engineer.

9. Pump speed and electrical checks: some pumps have adjustable speed settings. Do not attempt internal electrical checks or change wiring; if you suspect incorrect pump speed or an electrical fault between pump and PCB, call a Gas Safe registered engineer.

10. Reset and test: after any action (opening valves, bleeding, repressurising) reset the boiler and observe. If the F.24 clears and the system operates normally, monitor for reoccurrence. If it returns, do not continue trial-and-error repairs.

When to call a professional (must-call situations):

- The F.24 error persists after you have checked pressure, opened isolation valves, bled radiators and reset the boiler.

- The pump appears seized, excessively hot, or emits burning/electrical smells.

- You suspect electrical faults, PCB faults, or need to replace the pump or motor.

- You are not comfortable repressurising the system or accessing the filling loop and isolation valves.

- There are signs of leaks, major blockages, or the heat exchanger may be blocked.

A Gas Safe registered heating engineer can perform safe electrical tests, remove and replace or repair the pump, power-flush the system to remove sludge, inspect/replace the PCB if needed, and fit magnetic filters or limescale devices to reduce recurrence. If you have any doubt about safety or capability, book a qualified engineer rather than attempting invasive repairs yourself.