Nibe 58 Fault Code: Causes, Fixes & Repair Costs
What does the Nibe 58 fault code mean?
Fault code 58 on Nibe heat pumps indicates that a pressure switch has tripped — either on the high-pressure or low-pressure side of the refrigerant circuit. When this alarm triggers, the compressor is immediately blocked and the heat pump stops producing heat or hot water. On most Nibe models the system will not restart automatically; the alarm must be manually cleared via the controller display once the underlying issue has been addressed. Repeatedly resetting without investigating the root cause risks damaging the compressor.
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
- Poor circulation in the heating system (waterside) Common
Restricted or insufficient flow through the heat pump's water-side heat exchanger is the most frequent trigger for a high-pressure alarm. Common culprits include system pressure that has dropped below 1 bar, a partially or fully closed isolation valve, a closed zone valve on a cylinder or underfloor circuit, a blocked Y-strainer or particle filter on the return pipework, or an airlock somewhere in the heating system. All of these starve the heat exchanger of flow, causing pressure on that side to build until the switch cuts out.
- Blocked or restricted collector/brine circuit (ground source models) Common
On ground-source (GSHP) installations, a low-pressure alarm is often caused by reduced flow in the brine loop. The glycol-water mixture in the ground loop should hold around 1 bar; if the level vessel shows a shortfall, or if the loop filter valve is partially blocked or closed, flow drops and the low-pressure switch triggers. Extremely cold ground temperatures can also temporarily lower brine-side pressure.
- Refrigerant-side low pressure or leak Sometimes
If the low-pressure switch has triggered and the waterside and brine circuits appear normal, the fault may lie within the sealed refrigerant circuit itself. A slow refrigerant leak, a partial blockage such as a restriction in the expansion valve, or very low ambient temperatures pushing operating conditions outside normal limits can all cause refrigerant-side low pressure. This must be investigated by an F-Gas registered engineer.
- Faulty or incorrectly wired pressure switch Sometimes
In some cases the pressure switch itself has failed or become intermittent, or its wiring connection has worked loose over time — causing spurious trips that do not reflect a genuine pressure problem in the circuit. This is more likely on older units or after any recent maintenance work on the system.
- Circulation pump fault Rare
If the heating-circuit or brine-circuit pump has failed, seized, or lost prime, flow through the relevant heat exchanger collapses even if all valves are open and pressure is adequate. The resulting lack of flow mimics a pressure fault and will trigger alarm 58.
How to fix it
- Check the heating system pressure at the expansion vessel gauge DIY safe
Look at the pressure gauge on your heat pump or pipework — it should typically sit between 1.0 and 1.5 bar when cold (your installer may have noted the target value on or near the unit). If it reads below 1 bar, top up via the filling loop until you reach the correct level, then close the filling loop valve fully. Consult your system handbook or the label near the filling loop if you are unsure of the procedure.
- Check that all isolation and zone valves are fully open DIY safe
Walk around your system and verify that every isolation valve on the flow and return pipework is fully open (lever handles should be in line with the pipe). Check any zone valves serving underfloor circuits, hot water cylinders, or radiator zones — a valve that has stuck closed or been accidentally shut off will restrict flow enough to trigger the alarm.
- Bleed air from radiators, manifolds, and the heat pump itself DIY safe
Air trapped in the system reduces circulation efficiency significantly. Use a standard radiator key to bleed each radiator starting from the ground floor, working upwards. If your system has an underfloor manifold with bleed points, open these briefly too. Some Nibe units also have a bleed point on the heat pump casing — refer to your user manual for its location. Re-check system pressure after bleeding and top up if it has dropped.
- Inspect and clean the Y-strainer or particle filter on the return pipework DIY safe
Many Nibe installations include a Y-strainer or particle filter on the return pipe, often fitted with lever isolation valves on either side to allow cleaning without draining the whole system. Close the isolation valves either side, remove the filter basket, rinse it under running water to clear any sludge or debris, refit it, and reopen the valves. If you are unsure whether your system has one or where it is located, check with your installer before proceeding.
- For ground-source systems: check the brine circuit pressure and look for air in the collector loop DIY safe
Locate the level vessel (expansion vessel) for the ground loop and check the glycol level. The brine circuit should hold approximately 1 bar. If the pressure is low or you can see air in the sight glass, this points to a loss of glycol fluid or an airlock in the collector pipework. Bleeding the brine circuit is possible for a competent homeowner but if you are unsure of the procedure, or if you need to add glycol mixture, contact your installer or an MCS-certified engineer.
- Reset the alarm via the Nibe controller display DIY safe
Navigate to the alarm message on the controller screen and select the option to view more information about the alarm, then choose 'Reset alarm and try again.' The display will restart and the heat pump will attempt to resume normal operation. Watch the unit carefully for the first 10–15 minutes — if fault code 58 reappears quickly, do not reset it a second time without calling an engineer, as repeated compressor restarts into a fault condition can cause serious damage.
- If the alarm returns, or if a refrigerant-side fault is suspected, contact an MCS-certified heat pump engineer heat pump engineer
If the fault code comes back after you have carried out the checks above, or if your system pressure and valve positions appear normal, the problem is likely inside the refrigerant circuit, with the circulation pump, or with the pressure switch itself. None of these can be safely investigated by a homeowner. Book a visit from an MCS-certified heat pump engineer; if a refrigerant leak or restriction is suspected, ensure the engineer also holds a current F-Gas qualification, as only F-Gas registered engineers are legally permitted to work on the sealed refrigerant circuit.
Parts you may need
- Y-strainer / particle filter (22mm or 28mm) · from £35
- Heating circuit circulator pump (e.g. Grundfos UPM3 or equivalent) · from £120
- High/low pressure switch (Nibe refrigerant circuit) · from £55
- Brine circuit circulator pump · from £110
- Automatic air vent / bleed valve · from £12
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–£500, depending on the underlying cause.
Frequently asked questions
Can I reset Nibe fault code 58 myself, or do I need an engineer?
You can attempt one reset yourself — but only after carrying out the basic checks described above (system pressure, valve positions, bleeding, strainer cleaning). If the alarm clears and does not return, the issue was likely a temporary circulation problem you have now resolved. However, if fault 58 comes back after a single reset, stop resetting it and call an MCS-certified engineer. Repeatedly forcing the compressor to restart into an unresolved fault condition is one of the most reliable ways to cause expensive compressor damage.
How much does it typically cost to fix a Nibe alarm 58?
For the most common causes — an engineer visit to bleed the system, clean the strainer, or adjust valves — expect to pay roughly £150–£300 including callout. If a circulation pump needs replacing the total is more likely to be in the £300–£500 range. A pressure switch swap usually falls in the same bracket. Refrigerant-side faults such as a leak and recharge sit at the higher end. Compressor replacement is a much rarer and more costly outcome (potentially £1,500–£2,500 all-in); if your engineer suspects the compressor, it is worth getting a second opinion and checking whether your unit is still under manufacturer warranty.
Why does my Nibe keep showing fault 58 in cold weather?
Cold snaps can affect both sides of the system. On ground-source models, very low ground temperatures temporarily reduce brine-circuit pressure, making a borderline-low pressure situation tip into an alarm. On air-source models, extreme cold pushes the refrigerant circuit harder and any marginal issue — a slightly low refrigerant charge, a sluggish circulation pump, or a partially blocked strainer — that goes unnoticed in mild weather can trigger the pressure switch in the depths of winter. If code 58 appears consistently during cold spells, arrange a service visit in autumn before the heating season starts.
Is Nibe fault 58 a refrigerant leak?
It can be, but it is not the most common cause. A refrigerant leak would typically trigger the low-pressure switch rather than the high-pressure switch, and it would be accompanied by a gradual loss of heating performance over weeks or months before the alarm fires. More often, fault 58 is caused by a waterside circulation issue — low system pressure, a closed valve, or a blocked strainer — which is straightforward to resolve. If your engineer checks the waterside and brine circuit and finds nothing wrong, they will then test the refrigerant charge; only an F-Gas registered engineer can legally handle refrigerant.