# F2050 slow hz regulation **URL:** \ **Category:** Heatpump\ **Tags:** nibe\ **Created:** [10 October 2026 09:33 UTC](https://community.openenergymonitor.org/t/f2050-slow-hz-regulation/30438 "2026-10-10T09:33:15Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![cjoscar](https://community.openenergymonitor.org/letter_avatar_proxy/v4/letter/c/b3f665/32.png) [@cjoscar](https://community.openenergymonitor.org/u/cjoscar)\ **Post date:** [10 October 2026 09:33 UTC](https://community.openenergymonitor.org/t/f2050-slow-hz-regulation/30438/1 "2026-10-10T09:33:15Z")
Hi Sorry for my bad English, i hope you understand what i am writing. I am the owner of a Nibe f2050-10 with smo 20 a hot water tank and a 100 ltr buffer/ volumizer tank. Heating up a house with both radiators and ufh. I have tried using the buffer with 3-pipe connection and external pump and a lot of different settings for charging pump and external pump. Right now I have removed the external pump and just use the tank as volumizer with 2-pipe connection. I can not get the heat pump to adjust hz up or down slowly to target the wanted temperatur. It usually runs at the minimum 20 hz for a very long time while the dm is just falling and falling and when it is very low the heat pump is going very high in hz and overshooting target temperature or zero DM because it is reaching max temperature between compressor and target temperature which I have tried setting up to 10 degrees. I feel that the heat pump is more a on and off pump rather than inverter controlled. When it goes up in hz it rarely lower the hz again although the target temperature is reached. ---
**Author:** ![dMb](https://community.openenergymonitor.org/user_avatar/community.openenergymonitor.org/dmb/32/22999_2.png) [@dMb](https://community.openenergymonitor.org/u/dMb)\ **Post date:** [11 October 2026 10:58 UTC](https://community.openenergymonitor.org/t/f2050-slow-hz-regulation/30438/2 "2026-10-11T10:58:12Z")
Hi, Welcome to our community; your English is good. There are not too many NIBE owners on here so responses might be limited. I have an older NIBE F1145 GSHP which does not have a variable-speed compressor so I have no personal experience of compressor modulation - although having seen some data from other NIBE systems I would agree that NIBE F-series units tend to operate rather more on-and-off than some other manufacturers’ systems (or than newer NIBE S-series units). A little extra information from you would be helpful: - Which model of NIBE Controller does your F2050 have - is it an SMO20? - How does the compressor frequency behave when running a Hot Water cycle - is that ‘better’ than when running a Heating cycle? - The “Compressor Curve” (as distinct from the Heating Curve) is the main configurable setting to manage compressor frequency - This is under the Service Menu; probably menu entry 5.1.23 if you have an SMO20 - What does that look like - do you have it on the ‘Auto’ setting? Have you tried any manual settings here? It sounds like you already have a good understanding of how the NIBE control algorithm is intended to work, how Degree Minutes influence the behaviour etc. You are probably already aware that the BT25 temperature sensor is an important input to the control logic. David ---
**Author:** ![cjoscar](https://community.openenergymonitor.org/letter_avatar_proxy/v4/letter/c/b3f665/32.png) [@cjoscar](https://community.openenergymonitor.org/u/cjoscar)\ **Post date:** [11 October 2026 14:24 UTC](https://community.openenergymonitor.org/t/f2050-slow-hz-regulation/30438/3 "2026-10-11T14:24:55Z")
Hi David Yes I have smo20 There is no problem during hot water production. I have tried both manually and auto compressor mode, but the behaviour is pretty much the same. Yes I am aware of bt25 and I also think that the bt25 is the problem with the way the heat pump is adjusting hz. Today i am actually trying to run the system without bt25 and for now it seems much better in adjusting hz, but it is a little to early to see, because it is still a little warm here in Denmark so it is running on lowest possible hz (20). I am indeed in contact with Nibe (vølund in Denmark) regarding the way the heat pump is running ---
**Author:** ![dMb](https://community.openenergymonitor.org/user_avatar/community.openenergymonitor.org/dmb/32/22999_2.png) [@dMb](https://community.openenergymonitor.org/u/dMb)\ **Post date:** [12 October 2026 07:51 UTC](https://community.openenergymonitor.org/t/f2050-slow-hz-regulation/30438/4 "2026-10-12T07:51:41Z")
My suspicion is that when variable frequency compressor motors were added to these older F-series systems, NIBE did not attempt to completely avoid cycling and they used a fairly simple control algorithm for the frequency which _reduced_ but did not _eliminate_ on-off cycles. My own F1145 Ground Source unit with a fixed-speed compressor, installed in 2016, uses the same SMO 20 controller hardware (with slightly different software) and that has no option but to cycle the compressor on and off - typically about once an hour when it is cold outside. Their DM ‘accounting’ approach is robust in terms of managing Heating delivery when performing Hot Water or Defrost cycles and is effective at deciding when to Start and Stop a compressor cycle. It seems that NIBE chose to retain most of that control logic for their first generation of variable-speed compressors, with the result that they cycle more than you might expect. David