Apologies, my first post is a lengthy one, but I wanted to share my experience over the last couple of years with NIBE and their F2050 air source heat pump.

In March 2024, we had an F2050-6 and SMO S40 installed - an ideal match on paper for a heat loss of 4.92kW @ -2.4 °C.

May 2024 saw temperatures rise enough to trigger cooling mode. Shortly after starting, the system would stop with a “Low LP cooling operation” alarm. My installer spoke to NIBE and advised that “we just need to adjust one of the settings in the cooling menu”. Settings changes didn’t work - the same alarm would continue to be raised frequently throughout the summer. I’ll come back to this later on…

Temperatures dropped in December, and the system began to struggle. Below ~3 °C outside it would defrost every 35 minutes, and would barely reach the target supply temperature (40 °C at -2.4 °C) before another defrost was triggered. Eventually, this triggers an emergency mode, which turns on the DHW immersion. This defrosting spiral would continue until the outdoor temperature increased. NIBE Homeowner Care agreed that defrosting this frequently was not normal.

Most of December and January was spent chasing Homeowner Care and my installer for some action. Eventually, it was agreed that NIBE would send an engineer to check the refrigerant charge.

The NIBE engineer visited in February 2025, and found the outdoor unit had 900 g of R32 instead of the 1,300 g specification. A leak must have been ruled out as the engineer recharged the unit to the correct specification. In the following days, the system continued to struggle, so NIBE concluded that the unit may be undersized, and there was nothing more they could do.

After arguing that running for nearly a year with a significant refrigerant deficit may have caused internal damage, NIBE eventually offered a replacement unit. To their credit, they offered an upgrade to the F2050-10, which they promised would ensure the outdoor unit was "both large enough and definitely not faulty".

The F2050-10 was installed in March 2025 and seemed to be working well until December 2025 when firmware version 4.7.5 was released. A few days after applying the update, I noticed repeated pressure/discharge spikes:

Homeowner Care seemed concerned by the high readings and agreed I should downgrade the firmware back to 4.6.4. A later update to 4.7.6 in January caused the same behaviour. Later in the month, I noticed what seemed to be abnormal banding on the evaporator. This photo was taken 9 minutes before a defrost at 3℃ outside:

I asked my installer to escalate to NIBE, who commissioned an independent specialist to investigate. In February 2026, they recovered and weighed the gas from the F2050-10 and found it was undercharged by 290g (1,550g recovered vs 1,840g spec). An overnight nitrogen test confirmed there were no leaks, so the unit was charged to the factory specification. NIBE Customer Care subsequently stated that the unit is “operating as intended”. However, after being correctly charged, the system still appears to be unstable, with frequent high pressure and discharge spikes:

While on site, the engineer asked me if there had been any system alarms - none from the F2050-10, but I mentioned the F2050-6 had triggered “low LP cooling operation” many times. He advised this was a sign of low refrigerant, so the fault with the original unit could have been picked up in May 2024.

I was shocked that a second unit had been confirmed to be undercharged with refrigerant. The nameplate charge level is a fixed engineering specification that is critical to the performance, efficiency, and longevity of the product.

Conscious of my experience with the first unit, I chose to exercise my final right to reject the system with my installer. NIBE quickly offered a third F2050, which I declined due to a total loss of confidence in the product. They subsequently offered a future “F2060” without any further information or timeline for installation. The F2060 doesn’t appear to exist in any UK literature or the MCS database.

It’s over two years since our original installation, and I’m yet to receive the premium heat pump “manufactured in Sweden to the very highest standard” that I paid for. I have two engineers’ reports that document latent defects in both the supplied units.

One faulty unit could be considered bad luck, but two…?