Nibe 44 Fault Code: Causes, Fixes & Repair Costs
What does the Nibe 44 fault code mean?
Fault code 44 on a Nibe heat pump indicates that the soft start card has overheated or that its protective fuses have failed. The soft start card is the electrical component responsible for managing the compressor's start-up sequence, gradually ramping up current rather than allowing a sudden surge. When this card or its fuses fail, the unit detects an unsafe condition and blocks the compressor from running, shutting down heating and hot water output until the fault is resolved.
General guidance only — not a substitute for professional advice, and not certified by an heat pump engineer. Always have your specific appliance assessed by a qualified professional. Any heat pump work must be carried out by an MCS-certified heat pump engineer. If you notice a refrigerant leak, a burning smell or water leaking from the unit, switch it off at the isolator and call an MCS-certified heat pump engineer. Refrigerant work must be carried out by an F-Gas registered engineer.
Common causes
- Blown fuse on the soft start card Common
The most common trigger. The soft start card is protected by one or more dedicated fuses. If an electrical fault or an abnormal current draw causes these fuses to blow, the unit immediately raises alarm 44. Replacing the fuse is the cheapest possible resolution — parts cost very little — but diagnosing which fuse and why it failed still requires a qualified engineer.
- Defective soft start card Common
If the fuses blow repeatedly, or if the card itself has developed an internal fault, the soft start card will need replacing. The card can degrade over time due to heat cycling, voltage spikes from the mains supply, or cumulative electrical stress. This is the mid-range repair outcome for this fault.
- Mechanically seized or blocked compressor Sometimes
If the compressor struggles to start or is partially seized, it draws far more current than normal through the soft start card, causing it to overheat and trip. In this scenario, simply replacing the card or fuse will not solve the problem — the compressor condition must be assessed separately. This is the most serious and expensive outcome.
- Abnormal electrical supply conditions Sometimes
Sustained low voltage, voltage imbalance across phases, or incorrect phase sequencing (related to alarm codes 40–43 on the same range) can all place additional stress on the soft start card, leading to overheating or fuse failure. An engineer should check the incoming supply alongside the card itself.
How to fix it
- Check that the heat pump's power supply is healthy DIY safe
Go to your consumer unit and confirm the MCB or circuit breaker for the heat pump is in the ON position and has not tripped. If it has tripped, reset it once. If it trips again immediately, do not attempt to reset it further — there is an underlying electrical fault that requires an engineer.
- Check around the outdoor unit for any obvious obstructions DIY safe
Ensure the outdoor unit has clear airflow around it. Remove any leaves, debris or built-up ice that might be restricting the unit. While this is unlikely to be the direct cause of fault 44, a restricted unit running under strain can compound electrical stress. Do not attempt to open the casing or touch any internal components.
- Attempt a controller reset DIY safe
On your Nibe controller, navigate to the alarm log, acknowledge the fault and attempt a reset as described in your user manual. If the unit restarts and runs normally, monitor it closely over the following hours. If alarm 44 returns promptly, do not continue resetting — repeated cycling under a live fault can cause further damage.
- Contact a Nibe-approved or MCS-certified heat pump engineer to diagnose the fault heat pump engineer
An engineer will inspect and test the soft start card fuses, the card itself, and assess the compressor's electrical and mechanical condition using specialist diagnostic equipment. They will identify whether the fix is a simple fuse replacement, a soft start card replacement, or whether the compressor requires further investigation. Do not attempt to open the electrical enclosure or touch the soft start card yourself.
- Allow the engineer to replace the defective component and clear the alarm heat pump engineer
Once the root cause is confirmed, the engineer will replace the blown fuse and/or the soft start card, or arrange next steps if the compressor is found to be the underlying issue. On Nibe systems, the alarm will clear automatically once the fault condition is resolved; the engineer will verify normal operation before leaving. Any work involving refrigerant circuits must be carried out by an F-Gas registered engineer.
Parts you may need
- Nibe soft start card (model-specific) · from £180
- Soft start card fuse kit · from £12
- Compressor start capacitor · from £35
The exact spare depends on your boiler's GC number (on the data badge). Check this against the part before buying.
Typical repair cost
Expect to pay roughly £150–£400, depending on the underlying cause.
Frequently asked questions
Can I reset Nibe fault code 44 myself?
You can attempt a single reset from the Nibe controller, and it is worth doing this once after confirming the power supply is healthy. However, fault 44 relates to an internal electrical component — the soft start card — and if the alarm returns after a reset, the underlying fault has not been fixed. Continuing to reset without addressing the root cause risks damaging the compressor. If the fault persists, you will need a qualified engineer.
How much does it cost to fix Nibe fault code 44 in the UK?
For most households, the repair falls in the range of £150–£400, covering an engineer callout, diagnosis, and either a fuse replacement or a soft start card replacement including parts and labour. In a minority of cases where the compressor is found to be mechanically faulty, costs can rise significantly — compressor replacement on a Nibe system typically runs to £1,500–£2,500 or more including labour. That worst-case scenario is much less common than a straightforward card or fuse fix.
What is a soft start card on a Nibe heat pump?
The soft start card is an electrical control board that manages how the compressor starts up. Rather than the full mains current hitting the compressor motor all at once — which would cause mechanical stress and large current spikes — the soft start card gradually ramps up the power. Over time, or under abnormal electrical conditions, the card or its protective fuses can fail, which is what alarm 44 is designed to flag.
Will Nibe fault 44 clear itself once repaired?
Yes. Nibe heat pumps are designed to clear alarms automatically once the fault condition is no longer detected. After an engineer replaces the faulty fuse or soft start card and confirms the compressor is starting correctly, the alarm should clear on the next restart. The engineer will typically verify this before completing the job. If the alarm reappears shortly after repair, it suggests the underlying cause has not been fully resolved — for example, a faulty compressor that is still drawing excessive current.