A Nibe error code is an alarm number with a short name, such as alarm 220 High pressure alarm, that tells you which part of the heat pump has spotted a problem. When it appears, the red lamp on the front lights up, an alarm symbol shows on the display, and the screen usually suggests a few things to try first.
On systems with a separate outdoor unit, such as the F2040 and F2120, that unit passes its fault to the indoor module or SMO controller, so that is where you will read the number. Exhaust air units like the F750 show alarms on their own display. A green lamp with a service symbol is different: it marks an information message, which is not logged and clears by itself once the cause has gone.
A quick safety word before anything else. Never open the casing or touch wiring inside the unit, as there are live parts and stored energy in the inverter even after the power is off. If an alarm comes back after you acknowledge it, or you are unsure what it means, book a Nibe heat pump repair with us and an engineer will find the cause. For other makes, our heat pump error codes hub covers the main brands.
Is it safe to fix a Nibe heat pump fault yourself?
Only up to a point: you can make basic outside checks, but anything beyond that is engineer work. Look at the display, check the breaker, clear leaves or snow from around the outdoor unit and check the system pressure gauge if you have one. That is about where it stops for most homeowners.
Never remove panels or touch electrics inside the indoor module or outdoor unit. Many Nibe alarms point to the refrigerant circuit, the inverter or the compressor, and work on the refrigerant side is legally restricted to F-Gas certified engineers in the UK.
There is also your warranty to think about. Manufacturer warranties generally expect the unit to be installed and maintained by competent people, so a DIY repair inside the casing could put that cover at risk. Check your paperwork before you do anything beyond the basics.
Please read first: this guide is here to help you understand what your Nibe heat pump is telling you. Every effort has been made to keep the information accurate, but manufacturers update their manuals and codes can differ between models and software versions, so always check the official Nibe manual for changes before acting on anything here. Do not attempt anything that could be dangerous, and avoid any work that could void your warranty. If in doubt, call a qualified heat pump engineer.
If your Nibe heat pump is not showing a code, or you want to rule out the basics first, our guide to air source heat pump stopped working walks through the general checks and matches common faults to error codes across every major brand.
Which Nibe error codes can you check yourself?
A handful of Nibe alarms have simple, safe checks you can do from outside the unit. Everything else in the full list further down needs an engineer.
| Code | What it means | Safe homeowner check | Stop and call an engineer if |
|---|---|---|---|
| 183 | Defrosting in progress | Nothing to do. Wait for the cycle to finish | It shows for hours, or the unit is encased in ice |
| 180 | Anti-freeze active (outdoor below 3 °C) | Information only. Check the house is still warming | Rooms go cold or a numbered fault follows |
| 224 | Fan alarm | Clear leaves, snow or ice from around the fan guard without reaching inside | The fan still will not turn, or the alarm returns |
| 228 / 83 | Defrost failed | Clear snow and ice build-up from around and under the outdoor unit | It comes back after one acknowledgement |
| 223 | Outdoor unit has lost contact | Check the outdoor isolator switch is on and no breaker has tripped | Power is on and the alarm stays |
| 229 | Compressor stopping soon after start | Open radiator valves and turn up room thermostats that are closed down | It repeats once heating demand is normal |
| 220 / 50 | High pressure (heating side) | Check radiator and zone valves are open. If you have a pressure gauge and filling loop and your manual allows it, check the pressure is in range | Pressure keeps dropping, or the alarm repeats |
| 184 | Filter reminder (F750) | Clean the exhaust air filter as your user manual shows, then acknowledge | The filter is damaged or alarms follow the clean |
| 268 | Inverter overcurrent after a power cut | Acknowledge once after the power is back | It shows again without a fresh power cut |
| 998 | Display restarted after a power dip | None needed | It keeps happening |
| 271 / 272 | Outdoor air too cold or too hot to run | Wait for the weather to change | It shows in mild weather, which hints at a sensor fault |
What are the most common Nibe heat pump error codes?
The Nibe alarms we see most often relate to defrosting, pressure, flow, communication and sensors. Below, causes listed by Nibe come first, and anything marked as general engineering knowledge is our own experience rather than the manual.
Alarm 228 and 83: defrost failed
Alarm 228 means the outdoor unit has failed to defrost ten times in a row (SMO 40 systems), and 83 on the F750 means a defrost did not finish within three hours. Nibe points to low heating flow, too little water in the system or a blocked particle filter. Alarm 183 on its own is just a normal defrost cycle and needs no action.
General engineering knowledge: an iced or blocked evaporator, poor airflow round the unit and a frozen condensate drain often sit behind repeat defrost faults. Clear snow and ice from around the unit, then call us if it returns. Our guide to a frozen outside unit explains what is safe to do.
Alarm 220 and 50: high pressure
These mean the high pressure switch has tripped, 220 on the outdoor unit and 50 on the F750. Nibe lists blocked airflow or a dirty heat exchanger, a closed service valve, low heating flow and a faulty pump or fuse. Switching the unit on and off quickly can also trigger 220.
Installer guidance adds low system pressure, closed isolation or zone valves, an air lock and a blocked strainer. General engineering knowledge: sludge and limescale in the plate heat exchanger choke flow in the same way, and a heat pump powerflush may be part of the fix. Check valves are open, then book an engineer if it repeats.
Alarm 221 and 51: low pressure
This is low pressure in the refrigerant circuit, not the heating water. On the F2040 it trips after three low pressure events within an hour, with a faulty low pressure transmitter or suction sensor among the listed causes. The F750 manual points to exhaust airflow, the pressostat, the refrigerant circuit and the expansion valve.
General engineering knowledge: on an air source unit, a frozen evaporator or clogged fins can cause it. There is no homeowner fix beyond clearing the unit, and refrigerant checks need an F-Gas engineer. If your gauge is dropping instead, see why a heat pump loses pressure.
Alarm 223: communication with the outdoor unit
The indoor and outdoor control boards have lost contact. Nibe lists the outdoor isolator being switched off, wrong cable routing or no 22 V DC at the connector. Check the isolator and breaker, and leave the cabling to an engineer.
Alarms 301 to 308 are the same type of fault on slave heat pumps in a cascade. Installer guidance suggests a tripped fuse, an isolator left off or a damaged cable.
Alarm 224: fan alarm
The outdoor fan speed is not what the controller expects. Nibe lists an obstruction, a faulty fan motor, a dirty circuit board or a blown F2 fuse. Clear anything blocking the guard from outside, and if the fan still sounds rough or will not spin, our article on heat pump noises helps you describe it to the engineer.
Alarm 229: short run times
The compressor has stopped three times in a row shortly after starting. Nibe says to check for closed thermostats, venting, the filter and the pump. General engineering knowledge: low system volume, an oversized unit or an air lock are common causes of short cycling, and it wears the compressor if left.
Alarm 162: high condenser out temperature
Water leaving the condenser is too hot. Nibe lists low heating flow, a high set temperature or an outside heat source, and it clears automatically. General engineering knowledge: closed radiator valves and sludge are frequent culprits, so check valves before calling.
Alarm 230 and 261: hot gas and high heat exchanger temperature
Both point to the refrigerant side running too hot. Nibe lists blocked airflow or heat exchanger, low refrigerant, too much refrigerant (261) and a faulty sensor or board. Keep the unit clear outside; everything else needs an F-Gas engineer.
Alarms 262 to 268: inverter faults
These cover an overheated power transistor, inverter voltage out of range, a lost link to the control board, low refrigerant (266) and a compressor that will not start (267). Alarm 268 is overcurrent after a sudden power failure. Apart from acknowledging 268 once after a power cut, these are engineer jobs, and they do not always mean the compressor has failed.
Sensor alarms: 1, 3, 12 and 277 to 281
A sensor reading is missing, out of range or implausible. Examples are BT1 outdoor (1), BT3 return (3), BT12 supply (12) and the outdoor unit sensors (277 to 281). Nibe says to check the sensor and its connection, then replace the sensor and, if needed, the board. That is engineer work.
Which error code might you see in common situations?
The situation you are in often narrows down the alarm. This table matches everyday problems to the Nibe codes most likely to appear.
| Scenario | Nibe codes you may see | First check |
|---|---|---|
| Cold snap and iced outdoor unit | 183, 180, 228, 83, 221, 271 | Clear snow and ice from around the unit and let a defrost finish |
| Losing pressure or low pressure | 220, 50, 55 | Look at the pressure gauge, if fitted, and for drips at valves |
| Radiators lukewarm | 162, 229, 182 | Make sure radiator valves and room thermostats are open |
| No hot water | 6, 340, 64 | Check the display for a hot water block and note the alarm number |
| After a power cut | 268, 998, 223 | Check the breaker and isolator, then acknowledge once |
| Unit noisy or fan not spinning | 224, 222 | Clear the fan guard from outside and listen for scraping |
| After a service or filter clean | 184, 223, 220 | Acknowledge the filter reminder and confirm the isolator is back on |
If the house is also cold, our guide to a heat pump not heating covers causes that do not always show a code.
How do you reset a Nibe heat pump?
You reset most Nibe alarms by acknowledging them on the display, using the option shown on the alarm screen. Nibe splits alarms into three types:
- Automatic: clears by itself once the cause has gone.
- Manual: needs you to acknowledge it on the display.
- Neither: some alarms cannot be cleared by the user at all, and need an engineer.
Nibe says you can safely acknowledge any alarm, but it will come back if the fault is still there. Green-lamp information messages need no reset. The exact menu steps vary by model, so follow your user manual rather than guessing.
Avoid switching the power off and on repeatedly to clear a code. On the F2040, quick power cycling can itself trigger alarm 220, and resetting over and over hides the real cause while the unit keeps straining. If an alarm returns after one acknowledgement, that is your cue to book an engineer.
Nibe error code list
This list covers the F2040, F750 and SMO 40 families, plus Nibe's general alarm overview. Some numbers mean different things on different models (3, 12 and 254, for example), and F2120 and S2125 outdoor units share the 220 to 281 range with the F2040, so check your own manual too.
| Code | Meaning | Who should fix |
|---|---|---|
| 1, 3, 6, 12, 14, 15, 16 | Sensor faults: outdoor, return, hot water, supply, hot gas, fluid pipe, evaporator | Engineer |
| 40 to 42 | Compressor phase missing (F750) | Engineer |
| 43 | Phase sequence wrong (F750) | Engineer |
| 44 | Soft-start fuse fault (F750) | Engineer |
| 50, 150 | High pressure alarm, and temporary high pressure (F750) | Homeowner check, then engineer |
| 51 | Low pressure alarm (F750) | F-Gas engineer |
| 52 | Temperature limiter tripped (F750) | Engineer |
| 54 | Compressor motor protection (F750) | F-Gas engineer |
| 55, 155 | Hot gas alarm, high hot gas temperature | Engineer |
| 56, 57 | Wrong serial number or software | Engineer |
| 64, 327 | Low exhaust air temperature (F750) | Homeowner check, then engineer |
| 70 to 72 | Communication with internal cards | Engineer |
| 73 to 99 | Accessory and room unit communication | Engineer |
| 83 | Defrost unsuccessful (F750) | Homeowner check, then engineer |
| 100 | Inverter communication fault | Engineer |
| 162, 163 | High condenser out or in temperature | Homeowner check, then engineer |
| 180 | Anti-freeze active | Information only |
| 182, 274, 275 | Load monitor limiting power; main fuse may be too small | Engineer or electrician |
| 183 | Defrosting in progress | No action |
| 184 | Filter reminder (F750) | Homeowner check |
| 203 to 205 | Inverter alarm types I to III | Engineer |
| 220 | High pressure, outdoor unit | Homeowner check, then engineer |
| 221 | Low pressure, outdoor unit | F-Gas engineer |
| 222, 231 | Motor protection or phase fault, outdoor unit | Engineer |
| 223 | Lost contact with outdoor unit | Homeowner check, then engineer |
| 224 | Fan alarm | Homeowner check, then engineer |
| 225 | Flow and return pipes swapped | Engineer |
| 228 | Ten failed defrosts in a row (SMO 40) | Homeowner check, then engineer |
| 229 | Short compressor run times | Homeowner check, then engineer |
| 230, 261 | Hot gas, high heat exchanger temperature | F-Gas engineer |
| 232 | Low evaporation temperature (SMO 40) | F-Gas engineer |
| 250, 251, 254 | Accessory communication (SMS, MODBUS, SCA); 254 on F2040 is the accessory card | Engineer |
| 262 to 265, 267 | Inverter and compressor start faults | Engineer |
| 266 | Insufficient refrigerant | F-Gas engineer |
| 268 | Inverter overcurrent after a power cut | Homeowner check, then engineer |
| 271, 272 | Outdoor air too cold or too hot | Homeowner check |
| 277 to 281 | Outdoor unit sensor faults | Engineer |
| 294 | Incompatible outdoor unit | Engineer |
| 301 to 308 | Communication with slave heat pumps | Engineer |
| 340 | Low supply air temperature, hot water blocked (F750) | Information only |
| 404 | Pressure sensor BP4 fault (F2040) | Engineer |
| 421 to 481 | Inverter alarms (odd numbers permanent, even temporary) | Engineer |
| 900 | Country not set | Engineer |
| 995 to 997 | External alarm, extra heat or compressor blocked via AUX input | Engineer |
| 998 | Display restarted after a power dip | No action |
Where can you find the official Nibe manual?
Nibe publishes its service manuals and alarm lists as PDFs on its own document store, and these are the documents this guide is based on. Pick the one that matches your model.
- NIBE F2040 service manual (SEM GB 1503-1)
- NIBE F750 service manual (part no. 431508)
- NIBE SMO 40 alarm list (TIF EN 2042-1)
Need help with a Nibe heat pump fault?
We repair Nibe heat pumps across the UK, from F2040 and F2120 air source units to F750 exhaust air units. Our engineers are F-Gas certified, we are MCS accredited, and every repair comes with a 12-month guarantee.
We start with proper fault diagnosis, reading the alarm log and testing sensors, flow and the refrigerant circuit, so you pay for a fix rather than guesswork. Where possible we offer same-day visits, and our emergency heat pump repair service covers homes left without heating or hot water.
Many of the alarms above, especially flow, defrost and high pressure faults, are far less likely on a unit that is looked after. Annual heat pump servicing keeps filters, strainers and airflow in good order, and our heat pump cover plans spread the cost of servicing and repairs. You can read more on our Nibe heat pump page.
To book, call 0333 041 5130 or contact our team online.
Frequently asked questions
Does a Nibe alarm void my warranty?
No, an alarm on its own does not affect your warranty, because it is the unit protecting itself. Problems tend to arise when a fault is ignored for a long time or someone without the right qualifications opens the unit. Check your warranty terms and keep a record of each service.
Are Nibe alarms stored after they clear?
Yes, Nibe logs its alarms, so an engineer can see what happened even after you acknowledge one. Green-lamp information messages are not logged and simply disappear once the condition has passed. Write down any alarm number and the time it appeared, as that speeds up diagnosis.
Can I see Nibe alarms on my phone?
If your heat pump is connected to the internet through Nibe's online service, alarms can show in the app as well as on the display. Not every installation is connected, so ask your installer if you are unsure. The app tells you a fault exists but does not replace a visit when the alarm keeps coming back.
Does a Nibe alarm mean the compressor has failed?
Usually not. Many Nibe alarms, including several sensor and phase faults, lock the compressor on purpose to protect it until the cause is found. A locked compressor is a safety state, and the root cause is often a sensor, a fuse or poor flow.
How long does a Nibe heat pump repair take?
Many repairs, such as a sensor, fan or flow problem, can be finished in a single visit once the fault is found. Inverter boards and refrigerant work can take longer if parts need ordering. We will tell you what to expect after diagnosis.
