Questions to NIBE ASHP control settings

Hardware Heatpump
1

Hi all,

I am looking into optimising the settings of my NIBE air source heatpump (VVM S320 indoor unit and S2125 outdoor unit from Sep. 23). However, there is couple of things I cannot find a solution to, so I am now trying my luck with the experts in here :slight_smile:

I have two main questions:

  1. Frequent compressor pre-heating cycles
    Here in Denmark, the temperature has recently increased to a level where space heating is no longer needed. Therefore, the heatpump is off most of the time, but I have noticed that it frequently turns compressor pre-heating on during the day in a fairly regular manner. A good example is today which you can see here: Emoncms - app view
    Most of the day, it turns this compressor pre-heating on (comsumes 170 W of power) for a little less than 10 minutes approximately every 30 minutes. I know the increases in power are caused by compressor pre-heating since this is written in the display of the indoor unit and since I can hear a very faint humming sound from the outdoor unit during these periods. I have checked other NIBE systems on the heatpumpmonitor website, but I have only been able to find one with similar periodic increases, although these only toggle between 12 W and 40 W: Emoncms - app view
    Does anyone know what causes these compressor pre-heating cycles and/or if they can be turned off, unless used prior to hot water production or space heating?

  2. When space heating is not needed, I do not see any reason for the heatpump to quickly complete a hot water production cycle (except if hot water is needed asap). My understanding is that lowering the rate of heat transferred from the heatpump to the hot water tank increases efficiency. Unfortunately, however, I have not found any settings in the NIBE controller which allow me to change anything related to this for hot water production (only for space heating), except for putting the heatpump in silent mode during which I can limit the maximum compressor frequency. This increases efficiency, but I was wondering if anyone knew if other possibilities exists or if there is a good reason for that NIBE only has very limited settings for hot water production.