Vaillant arotherm plus - losing water pressure in cooling

[ndl]

I'd a 7kw arotherm plus installed beginning of the year. It has the cooling chip which had been working for about 2 months in the summer.

 

However, for the last month or so, when cooling is run for a while (approx 0.5-1 hour), I lose all water pressure.  See that anti freeze valves are releasing all the water. 

When cooling turned off, water pressure has been fine and hot water cycle can run without issue.

Installer changed both valves but still the same.  Vaillant tech/engineer said it's not designed to have the anti freeze for this usecase. They can only recommend I remove the valves and use Glycol for anti freeze instead. My installer has not other suggestions.

Has anyone had similar issue or any other suggestions? TIA

[Dan F]

Mine works fine with cooling and anti-freeze valves.  What anti-freeze valves are they? Have they been switched out? 

 

They should only open at 3C +/- 1C. What temperature does your flow temp drop to during cooling?

[Nickfromwales]

How cold are you running the cooling?

[Dan F]

31 minutes ago, Nickfromwales said:

How cold are you running the cooling?

Mine for reference, same model, hits 4C minimum.    I don't have it set that low, but because it cycles the flow temp drops beyond target temp before compressor turns off. My install has the Caleffi valves.

Edited 10 hours ago by Dan F

[JohnMo]

Run my system without glycol and without anti freeze valves.

 

Why do you need either? Both are there to protect the heat exchanger in the ASHP casing from freezing. It's a big chunk of metal that will not freeze easily, it's also insulated by the manufacturer and in a casing. It isn't freezing any time soon irrespective of temperature outside.

 

Are antifreeze valve or glycol used in external oil boilers - no.

 

Other disadvantage of anti freeze valves. Is they are directly exposed to air, so will activate way before any damage would occur if heating is off. Once activated you have drained out part of the water from your heating system, how do you fix if you are not hands on and your plumber isn't available?

[Dan F]

1 hour ago, JohnMo said:

Run my system without glycol and without anti freeze valves.

 

Why do you need either? Both are there to protect the heat exchanger in the ASHP casing from freezing. It's a big chunk of metal that will not freeze easily, it's also insulated by the manufacturer and in a casing. It isn't freezing any time soon irrespective of temperature outside.

 

Are antifreeze valve or glycol used in external oil boilers - no.

 

Other disadvantage of anti freeze valves. Is they are directly exposed to air, so will activate way before any damage would occur if heating is off. Once activated you have drained out part of the water from your heating system, how do you fix if you are not hands on and your plumber isn't available?

 

The risk is only in the case of power-cuts in below freezing. With power the ASHP itself keeps things from freezing.  I don't disagree with you, but manufacturers clearly can't recommend that instalations don't either either anti-freeze valves or glycol.

 

 

[JohnMo]

4 minutes ago, Dan F said:

The risk is only in the case of power-cuts in below freezing

But how many hours do you need and how low below freezing

 

Nice simple to read article here

https://renewableheatinghub.co.uk/do-air-source-heat-pumps-really-need-glycol/

[Dillsue]

An alternative to glycol or antifreeze valves is trace heating. A £50/4metre length runs through our insulation around the outdoor pipes with a loop coiled up in the bottom of the HP under the water pipework. Our HP isn't particularly well insulated and most of the water pipework wasnt insulated at all. Ive added some insulation but there's still plenty exposed so hopefully the trace heating will keep any freezing at bay