Error F.23

Safety precautions:

1. Before doing anything, ensure the boiler is powered down when accessing internal panels or components. Turn off the electricity to the boiler at the isolator switch. Do not open the boiler cover unless you are Gas Safe qualified. Be aware pipes can be very hot — avoid burns. Never tamper with the gas supply or any sealed components.

2. Do not continually press reset: repeated resets can hide the problem and allow further damage. If the fault returns after one reset, arrange professional help.

Initial checks a homeowner can do (safe, low-risk):

1. Note the exact fault code, any other messages, and whether the boiler is in lockout. Take photos of the display if you call an engineer.

2. Try a single reset following the manufacturer’s instructions. If the fault clears and stays cleared, monitor closely; intermittent faults still need investigation.

3. Check system water pressure on the boiler gauge. If pressure is very low (typically below ~1.0 bar cold) top up to the recommended level following the boiler handbook. Low pressure can affect circulation.

4. Feel the flow and return pipes at the boiler inlet/outlet carefully and briefly (use a glove or a thermometer if available). Do not hold on if very hot. A very large difference in temperature supports the F.23 condition but be cautious of burns.

5. Bleed radiators to remove possible airlocks: ensure heating is off and radiators are cold, use a radiator key to open bleed valve until water flows, then close. After bleeding, re-check system pressure and top up if needed.

6. Check that thermostatic radiator valves and lockshield valves are open on several radiators, and that any zone valves or room thermostats are calling for heat as expected.

7. Listen at the boiler for pump noise or vibrations when the boiler attempts to run (if you feel competent to turn power back on to observe). No pump noise or silent pump suggests pump failure or electrical fault.

Further diagnostic steps (record findings, then call if not resolved):

1. If bleeding radiators and topping up pressure do not help and the boiler still locks out with F.23, do not attempt to remove the boiler front cover or touch internal components. Collect symptoms: which radiators are hot/cold, whether hot water is affected, whether you can hear the pump running, and whether any valves feel warm/cold.

2. Check for closed isolation valves on the pipework to the pump or bypass pipework (these are sometimes behind the front cover or external service valves). Do not force valves inside the boiler; only accessible external isolations can be checked safely.

3. If you have an external magnetic filter or inline filter, check the visible indicator/pressure drop (if manufacturer guidance allows) but do not dismantle sealed parts.

What a Gas Safe engineer will do (why you should call a professional):

1. Isolate and safely open the boiler to inspect the pump, motor, and wiring. They will check pump rotation, shaft condition, and correct speed setting; replace the pump if seized or electrically faulty.

2. Measure flow and return temperatures with proper instruments and check thermistor/NTC sensors for correct resistance and operation; replace faulty sensors or wiring as needed.

3. Inspect valves (motorized zone valves, bypass) and controls for correct operation; repair or replace faulty valves or controls.

4. Diagnose and clear blockages: chemical flushing or a professional powerflush may be required to remove sludge and limescale. They may fit or clean a magnetic filter and advise ongoing inhibitor use.

5. Check the heat exchanger for scale build-up or damage and the system for airlocks and circulation problems that require more than simple radiator bleeding.

6. Carry out leakage, gas, and safety checks after any repair, then reset and run the system to confirm the fault is cleared.

Important final points:

1. If the F.23 code returns after your basic checks, contact a Gas Safe registered heating engineer. Provide them with the observations you made (radiator behaviour, pump noise, pipe temperatures, pressure readings, whether a reset temporarily cleared the fault).

2. Do not attempt boiler internal repairs, gas valve/service, or part replacements unless you are a qualified Gas Safe engineer. Incorrect repairs risk injury, carbon monoxide, or further damage.

3. Keep the boiler isolated and turned off if you suspect a major circulation or pump failure until a professional can inspect it.