Nefit boiler faults: fault codes, causes and parts

All 619 fault codes for Nefit boilers, plus the faults that show no code. Type your code or choose your symptom.

In brief

A fault on a Nefit boiler usually means that the appliance has locked out or is reporting a fault code. Note the code on the display and look it up below: for each code you will find its meaning, checks you can safely do yourself and the parts that are often checked or replaced. Frequently searched: 6A (no ionisation occurs after the ignition phase,…), H13 (the set service interval has elapsed), 6A 227 (the burner does not ignite). No code? Check the water pressure (1.5 to 2 bar when cold), the power supply and the gas tap, and reset once. If the fault comes back, call in a certified gas engineer. If you smell gas, call your national gas emergency number or 112 immediately.

Most searched Nefit faults

These are the codes that visitors to this site search for most often.

6ANo ionisation occurs after the ignition phase,…H13The set service interval has elapsed. Service…6A 227The burner does not ignite No displayThe boiler receives no power.4FThe temperature of the safety sensor is…24Current central heating water temperature 6HThe ionisation (i.e. the flame) is lost…P__Operating phase: The water pressure in the…

See the 25 most searched fault codes of 2026, with the figures behind them →

Nefit boiler faults without a code on the display

Not every fault shows a code. These are the symptoms we come across most often with Nefit appliances, with what you can check yourself before calling someone out.

No hot water, but the heating works

The boiler heats the radiators but not the tap water. Check that the hot water function is switched on in the display (on some appliances it is called DHW mode or summer mode) and that the hot water valve under the boiler is open. If the water stays cold, this usually points to a fouled or leaking DHW heat exchanger, a faulty diverter valve or a DHW sensor giving incorrect readings. View the matching parts → Read the full explanation: no hot water, six causes →

Water pressure keeps dropping

Top up to 1.5–2 bar when cold and bleed the radiators. If the pressure drops again within a few days, the expansion vessel has often lost its pre-charge or there is a small leak in the system. A pressure relief valve that keeps dripping gives the same symptom. View the matching parts → Read the full explanation: water pressure keeps dropping – expansion vessel or leak? →

Boiler shuts down and locks out

The appliance shuts down and only starts again after a reset. Reset once; if the fault comes straight back, leave the reset button alone. Repeatedly resetting a locked-out boiler is not without risk: the safety device trips for a reason. View the matching parts → Read also: is the boiler cutting out because of a sensor or overheating? →

Radiators stay cold

Check that the thermostat is calling for heat, that the radiator valves are open and that the system has enough pressure. If everything stays cold while the boiler is firing, the circulation pump is often not running or the diverter valve is stuck in the hot water position. View the matching parts → Read the full explanation: radiators stay cold →

Ticking, humming or boiling noise

A banging noise at start-up usually points to air or limescale in the heat exchanger. A humming pump may have a worn bearing. A rattling fan is often rubbing or dirty. View the matching parts → Read also: replacing the fan – what to rule out first →

Water under the boiler

Check where it is coming from: the condensate drain (siphon blocked or cracked), the pressure relief valve (pressure too high or faulty expansion vessel) or a fitting. If in doubt, switch the boiler off and close the water supply. View the matching parts → Read the full explanation: water under the boiler – condensate or a leak? →

Nefit boiler fault codes 1 to 150 of 619

The code list is split over 5 pages. Looking for a specific code? Use the search at the top of this page: it searches all 619 codes in one go.

Code	Cause
, H	The central heating system does not get hot enough. The cylinder is heated correctly. On the central heating side the appliance fires at low output only.
, H	Central heating does not get warmer than 60 C
, Y	The central heating system gets too hot or not hot enough; the cylinder is not heated. Appliance fires on central heating only. Output set with the domestic hot water setting potentiometer.
-. A	The central heating system gets too hot; the cylinder is not heated. Appliance fires on central heating only and does not modulate down
-. H	The maximum central heating output potentiometer is set too low. The fan runs at low speed only.
-. Y	The central heating system gets too hot or not hot enough; the cylinder is not heated. Appliance fires on central heating only. Output set with the domestic hot water setting potentiometer.
-.H	Central heating does not get warmer than 60˚C
-A 208	The boiler is in service mode
-A 208	The boiler is in chimney sweep mode or service mode.
-H 200	The boiler is firing and is in central heating mode.
-H 200	The boiler is operating for central heating.
-H 200	The boiler is in central heating mode
. A	The central heating system gets too hot; the cylinder is not heated. Appliance fires on central heating only and does not modulate down.
0 of .H	The central heating system is heated correctly, the cylinder (if present) is not
0 of .H	The central heating system gets too hot, the cylinder (if present) is not heated
0 of =.H	The central heating system is heated correctly, the cylinder (if present) is not
0 of =.H	The central heating system is not heated, the cylinder (if present) is
0 of =.H	The central heating system is heated correctly, the cylinder (if present) is not
0 of =.H	The central heating system is not heated, the cylinder (if present) is
0A	Appliance in anti-cycling time
0A 202	Anti-cycling programme operating phase
0A 202	The boiler is waiting.
0A 202	Appliance is in anti-cycling programme
0A 305	The boiler is waiting after the end of hot water mode
0A 305	The boiler is waiting after the end of domestic hot water mode.
0A 305	Central heating operating phase
0A 353	The boiler is waiting. It has never been off for longer than 20 minutes within 24 hours.
0C 283	The boiler is preparing for a burner start. The fan and the pump are activated.
0C 283	Preparation phase
0C 283	The boiler is preparing for a burner start. The fan and the pump are being activated.
0E 265	The boiler is waiting.
0E 265	Standby
0H 203	The boiler is on standby
0H 203	The boiler is on standby
0H 203	Standby
0H 203	The boiler is in standby.
0H of =.H	The central heating system does not get hot enough. The cylinder is heated correctly. On the central heating side the appliance fires at low output only.
0H of =.H	The central heating system gets too hot, the cylinder (if present) is not heated
0H of =.H	Domestic hot water from the cylinder is too cold at high draw-off or the hot water flow rate is too low
0H of =.H	The central heating system gets hot when the cylinder calls for heat
0H of =.H	Domestic hot water from the cylinder is too cold at high draw-off or the flow rate of hot water is too small
0L 284	Ignition phase
0L 284	The gas valve is activated.
0P	Appliance does not start
0U 270	Start-up phase
0U 270	The boiler starts up after the mains supply is switched on or after a reset.
0U 270	The boiler is starting up.
0U 270	The boiler starts up after the mains supply is switched on or after a reset.
0Y	The central heating system and cylinder (if present) are not heated
0Y	The central heating system is not heated sufficiently. Central heating water temperature is higher than set on the flow temperature knob or higher than the heating curve of the weather-compensated controller
0Y	The central heating system is not heated; the cylinder (if present) gets too hot.
0Y	The central heating system gets (too) hot. The appliance restarts continuously. The cylinder (if present) is not heated
0Y 204	The boiler is waiting. The measured flow temperature is higher than the calculated or set heating water temperature.
0Y 204	Operating phase Display test during the start-up phase.
0Y 204	The boiler is waiting. The measured flow temperature is higher than the calculated or set central heating water temperature.
0Y 276	The flow temperature sensor has measured a temperature higher than 95°C.
0Y 276	The flow temperature sensor has measured a temperature higher than 95°C.
0Y 276	The contacts of the flow sensor are open circuit
0Y 277	Water temperature fault
0Y 277	The safety temperature sensor has measured a temperature higher than 95°C.
0Y 277	The safety temperature sensor has measured a temperature higher than 95 °C.
0Y 277	The safety temperature sensor has measured a temperature higher than 95°C.
0Y 285	The return temperature sensor has measured a temperature higher than 95°C.
0Y 285	The return temperature sensor has measured a temperature higher than 95°C.
0Y 285	The return sensor has measured a current central heating return water temperature higher than 95°C.
1013	Maximum burn time reached
1014	The ionisation current is too low
1017	Water pressure too low.
1017	Water pressure too low
1018	Service time elapsed
1021	Domestic hot water temperature sensor defective
1022	The domestic hot water temperature sensor is defective
1023	Maximum operating time including standby time reached.
1065	Pressure sensor defective or not connected.
1068	Outdoor temperature sensor or lambda sensor defective
1073	Short circuit of flow temperature sensor
1074	No signal from flow temperature sensor
1075	Short circuit of heat exchanger temperature limiter
1076	No signal from heat exchanger temperature limiter
1A 316	The flue gas temperature sensor has measured a temperature that is too high.
1C	Connection for flue gas thermostat is open
1C 210	The flue gas sensor has measured too high a temperature and is open.
1L 211	There is no connection across contacts 78 and 50 of the UBA 3 mounting base.
1L 211	UBA fault
1P 346	The temperature of the flue gas temperature sensor rises too quickly.
1U 317	The contacts of the flue gas temperature sensor are short-circuited.
1Y 318	The contacts of the flue gas temperature sensor are open circuit.
2 213	The temperature measured by the flow temperature sensor or the return temperature sensor rises too quickly.
200	The appliance is in central heating mode
200	The boiler is in central heating mode
201	The appliance is in domestic hot water mode
201	The appliance is in domestic hot water mode
202	The appliance is in the switching optimisation programme: the time interval for restarting the burner has not yet elapsed (service function 3-b2).
202	The appliance is in the switching optimisation programme:
202	The boiler is waiting. There has been a heat demand from an on/off or modulating controller more than once per 10 minutes.
203	The boiler is on standby
203	The appliance is on standby, no heat demand present
204	The current flow temperature is higher than the required flow temperature. The burner is switched off.
204	The boiler is waiting. The measured flow temperature is higher than the calculated or set heating water temperature.
2051	Internal fault.
2051	Internal fault
2052	Maximum switch-on time of the ignition transformer exceeded
2052	Maximum switch-on time of the ignition transformer exceeded.
207	The central heating water pressure is too low
207	Operating pressure too low
207	Operating pressure too low.
208	The appliance is in service mode
208	The appliance is in service mode
208	The boiler is in service mode
2085 2908	Internal fault in burner control unit.
2085 2908	Internal fault in burner control unit
210	The flue gas temperature sensor has measured a temperature that is too high and is open
212	The flow or safety temperature sensor measures too rapid a temperature rise
212	Temperature rise of safety or flow temperature sensor too rapid
214	The fan is switched off during the safety time
215	The fan speed is too high
215	Fan too fast
216	The fan speed is too low
217	The fan speed is irregular during start-up
218	The flow temperature sensor has measured a temperature higher than 105 °C
219	The safety temperature sensor has measured a temperature higher than 105 °C
220	The contacts of the safety temperature sensor are short-circuited or the safety temperature sensor has measured a temperature higher than 130 °C
221	The contacts of the safety temperature sensor are open circuit
222	The contacts of the flow temperature sensor are open circuit
222	The contacts of the flow temperature sensor are short-circuited
224	Heat exchanger temperature limiter or flue gas temperature limiter has tripped
224	Flue gas thermostat or heat exchanger temperature limiter tripped
227	Flame is not detected
227	Insufficient ionisation current has been measured after the burner ignited.
227	Insufficient ionisation current measured after the burner ignited
228	An ionisation current was measured before the burner started
228	An ionisation current was measured before the burner started
228	Flame signal despite burner being switched off
229	Flame lost during burner operation
229	Insufficient ionisation current measured during burner operation
231	The mains supply was interrupted during a lockout fault
232	The external switching contact is open
232	Heat source locked out by external switching contact.
233	Coding plug or appliance electronics fault.
233	Coding plug not recognised
233	Coding plug not recognised.
234	The contacts of the gas valve are open circuit.
234	The contacts of the gas valve are open circuit
234	Electrical fault of gas valve.
235	Version conflict between appliance electronics and coding plug.
235	Incorrect coding plug (KIM)
235	Incorrect coding plug (KIM).
237	The burner control unit or the KIM is defective
237	System fault
238	Appliance electronics are defective

Order parts for your Nefit boiler

Nefit parts are available from Instalpunt; shipping to EU countries from €12.95 (€16.95 for more distant countries), usually 3–5 working days.

Parts per Nefit-series: ProLine (NxT) · TrendLine (II) · EcomLine · TopLine.

View Nefit parts →

Frequently asked questions about Nefit faults

What does a fault on a Nefit boiler mean?

The appliance is reporting that it has shut itself down or cannot continue. The code on the display points to the group of causes: ignition, water pressure, a sensor, the fan or communication with the thermostat. The table above shows, for each code, what Nefit means by it.

How do I reset my Nefit boiler?

The reset button is on the control panel of your Nefit boiler; on most appliances you hold it down for two to five seconds until the display responds. Reset once. If the same fault comes straight back, resetting will not solve it and a part or a setting needs attention. Always consult the manual for your model: the position of the button and how long to press it differ per series.

Can I fix a Nefit fault myself?

You can top up the water pressure, bleed the system, replace filters and clean a siphon yourself. Anything behind the sealed section of a gas appliance is a different matter: work on the gas valve, burner, heat exchanger and flue must be carried out by a certified gas engineer.

How much does it cost to fix a fault?

That depends on the cause and whether a part is needed. With us you can see the part straight away with its price and delivery time, so you know where you stand in advance. If you call in an engineer, always ask about the call-out charge and hourly rate before they come.

Where can I find the right part for my Nefit?

Check the rating plate for the exact type and use it to search our catalogue, or search directly by the manufacturer number of the faulty part. Each part lists the appliances it fits.