Vitocal 300-G : primary circuit

[Quelbazar]

Can anyone confirm that my heat pump is behaving correctly?

Vitocal 300-G: I monitor the supply and return temperatures of my primary circuit.
When the compressor starts up, for example to heat my hot water, I can see that the return temperature is a few degrees lower than the supply temperature.

When the compressor stops, the 2 temperatures rise to room temperature.

BUT: 8 hours after switching off the compressor, the 2 temperatures drop again:

Is my primary circuit circulation pump working again?
Is this standard behavior? Or is there a non-optimal setup in my system?

[Flo_Schneider]

Hello Quelbazar,

I also suspect that the primary pump has been requested. As a rule, this can only have happened due to a heat request.

Many greetings
Flo

[Quelbazar]

Hi Flo,

Thank you for your answer.

However, it seems that my primary circuit switches on after (exactly) 8 hours of inactivity, even if there is no "heat request".
The example below:
- Vitocal 300-G in "hot water only" mode
- Hot water is heated from 2023-08-06 01:05 to 01:40
- At 09:40, the primary circuit seems to switch on again, without the compressor. Supply and return temperatures seem identical.
- A new water heating cycle starts at 2023-08-08 18:45

So I can imagine that the primary circuit circulation pump runs "for nothing" at times.

[Flo_Schneider]

Please tell me the serial number of your equipment.

Greetings 
Flo

[Quelbazar]

7377451301160128 (not a german installation).

[Flo_Schneider · Accepted solution]

Thank you, the behavior described is a protective function of the refrigerant circuit controller. This ensures that the compressor oil is never too cold and thus there are no complications when the heat pump starts.

Many greetings
Flo