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Vaillant arotherm plus heat pump frost protection

Kentuk · 2025-02-03T22:15:58Z

Hi Our heat pump frost protection mode is kicking in 8oC or below, not 4oC as per vaillant manual. In addition rather than elevating the flow temperature from 6oC to 12oC it is elevating 14oC to 30oC. Vaillant have been unable to resolve this and now saying this is normal. Needless to say this is causing unnecessary energy consumption and wear and tear. Appreciate anyone with similar experiences. Thank you Kevin

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Air Source Heat Pumps (ASHPs)

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Kentuk

(@kentuk)

Active Member Member

Joined: 11 months ago

Posts: 8

Topic starter 04/02/2025 2:02 pm

@jamespa

At those times on the 6/7th Frost protection kicked in. The two flow temperatures are the starting and ending for the frost protection period. The duration was around 15minutes. Yes showing frost protection on the controller.

I was expecting it to only kick in when the outside temperature reached 4oC and then elevate the flow from 6 to 12oC.

258-DHW; apologies 258 is the heat pump cycle number and DHW for heating the hot water.

When i moved the outdoor sensor indoors , the number of frost protection cycles reduced. The heating came on as per the programme.

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JamesPa

(@jamespa)

Illustrious Member Moderator

Joined: 3 years ago

Posts: 3756

04/02/2025 2:25 pm

Im sorry but I really don't understand from what you have said how you are running your heat pump (for example how can WC work when the outdoor sensor is indoors, and that being the case how did the heating 'come on' as per the programme'? ). Its also going to be difficult to work out things based on what happened over 2 months ago and with the outdoor sensor indoors.

Can I suggest you

1. relocate your outdoor sensor outdoors

2. take screenshots of the settings governing the heating schedule, room influence mode and weather compensation

3. when the problem next occurs record:

what the heat pump should have been doing according to the program you had set up and why you think this

the indoor and outdoor and flow temperatures on the sensocomfort

the time of day and date.

With a fresh example and more data on how you are running your heat pump maybe it will make sense, currently I am sorry but it doesn't, at least not to me.

I apologise I cant be more helpful at present however its difficult to tell what is going on with the various changes to configuration and the moving of the outdoor sensor, particularly as the latter is so absolutely fundamental to the control of the unit all of the time not just for frost protection.

This post was modified 11 months ago 3 times by JamesPa

4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.

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Kentuk

(@kentuk)

Active Member Member

Joined: 11 months ago

Posts: 8

Topic starter 04/02/2025 5:42 pm

Much appreciated for your help and thoughts. I will keep a diary. Thank you again

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JamesPa

(@jamespa)

Illustrious Member Moderator

Joined: 3 years ago

Posts: 3756

04/02/2025 6:32 pm

@kentuk

It occurs to me, have you got a timed heating schedule and if so what is it. Can you tell me why the indoor temperature was so low in the records in the diary. Something isn't making sense about the whole setup.

Just to emphasize, the outdoor sensor isn't primarily for frost protection, it's part of the basic weather compensation control loop of the system. It really has to be outside.

4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.

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