Error Enn

Safety precautions:

1) If you smell gas, evacuate the property immediately, do not operate electrical switches or the boiler, and call the gas emergency number.

2) If there is visible water leaking from the boiler or pipes, isolate the mains water and the boiler’s electrical supply and call a professional.

3) Always isolate the boiler from the mains supply before removing the case or doing any internal inspection. Do not attempt gas, electrical or sealed-component repairs unless you are Gas Safe registered and trained.

Initial homeowner checks you can safely do:

1) Note or photograph the full display and any other error codes that appear alongside Enn — the secondary code (for example E37, E44 etc.) is the key to the underlying fault. Record the boiler model and serial number.

2) Try a simple reset: follow the manufacturer’s reset procedure in the manual (usually press and hold the reset button as described). If the boiler resets and runs normally, monitor it — if the same fault returns call an engineer. Do not perform repeated resets if there are strong smells, leaks, or hearing unusual noises.

3) Check the boiler pressure gauge. Aim for around 1.0–1.5 bar when cold (1.3 bar is common). If pressure is low (well below 1.0 bar or the gauge shows red), topping up via the external filling loop can be done by a competent homeowner following the manual. If pressure is too high (in the red), isolate the boiler and contact an engineer.

4) Inspect condensate pipe (outside) in freezing weather — if frozen it can cause lockouts. If frozen, thaw with warm (not boiling) water or allow to warm naturally.

5) Check external flue and air intakes for blockages (birds’ nests, leaves, debris) and clear only if easily accessible and safe to do so.

6) Check for obvious signs of water leaks around the boiler, pipework, radiators and the pressure relief valve (PRV) discharge pipe. Recurrent pressure loss suggests a leak or PRV/expansion vessel problem.

7) Check that the boiler has mains electrical supply and the fuse/consumer unit hasn’t tripped. If the display is dead but mains is present, do not open the boiler; call an engineer.

Specific diagnostic steps to gather information (do not attempt internal repairs unless qualified):

1) After safe reset attempts and the simple checks above, if Enn returns, look for the specific E-code shown (E31, E32, E37, E44, E28 etc.). Use your boiler manual or a reputable code list to map that code to likely causes: e.g. E37/E31/E32 relate to thermistor/sensor open or short circuits; E44/E24 relate to low water pressure; E28/E05 relate to fan faults or air pressure switch issues; E02/E01 relate to ignition failures.

2) If the secondary code points to a sensor (thermistor) fault, an engineer will need to check sensor wiring and resistance and replace the sensor if required. Homeowners should not attempt to replace sensors unless competent and qualified.

3) If the code indicates fan/air pressure issues, a Gas Safe engineer should inspect/replace the fan or the air pressure switch; these are gas-safety items.

4) If the underlying code suggests ignition or gas valve problems, do not attempt to fix — contact a Gas Safe engineer.

5) If the underlying issue is repeated low pressure/pressure loss, and you have topped up the system, monitor for a return to low pressure. If it drops again, do not keep topping up — call an engineer to find leaks, check the PRV and expansion vessel.

When to call a professional and what to tell them:

1) Call a Gas Safe registered heating engineer whenever Enn persists after basic resets and pressure checks, or immediately for gas smells, severe leaks, repeated lockouts, ignition/fan/control-board related codes, or if you are unsure.

2) When you call, give the engineer the boiler model (Keston C40 or C55), serial number, the exact display readout (Enn plus any E-code), what you did (reset, topped up, thawed condensate, etc.), and whether there are leaks or gas smells. Taking a photo of the display and of the boiler label saves time.

Final note: Enn is a protective shutdown, not a diagnosis by itself. Some simple homeowner checks (reset, pressure, condensate, flue clearances) may restore operation, but any fault involving gas, ignition, fan, PCB, or internal wiring must be handled by a Gas Safe qualified engineer for safety and to avoid invalidating warranties.