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 19 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

[Dreadnaught]

11 hours ago, Dan F said:

Mine works fine with cooling and anti-freeze valves.

 

Same here - as another data point.

[JohnMo]

21 minutes ago, Dillsue said:

added some insulation but there's still plenty exposed

Wouldn't you just be better fixing the half arsed job left by others. 

 

22 minutes ago, Dillsue said:

still plenty exposed so hopefully the trace heating will keep any freezing at bay

Been involved in lots of poorly installed heat tracing in my past.  Heat tracing that isn't extremely well insulated, may as well not be there. Even with insulation you need to have suitable Watts per metre rating for it to be effective. Was this all calculated or was a stab in the dark? What powers it in a power cut, so does it actually afford any protection?  Or is a sticky plaster that isn't really needed and isn't very effective?

[Dan F]

59 minutes ago, Dillsue said:

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

 

Does your trace heating still work in power cut?  You'd want it off all the time, but only on if power cut of ASHP failure. How do you trigger the trace heating when power/ashp fails, and what powers the trace heating when you have no mains?

[Dillsue]

2 hours ago, JohnMo said:

Wouldn't you just be better fixing the half arsed job left by others. 

 

Been involved in lots of poorly installed heat tracing in my past.  Heat tracing that isn't extremely well insulated, may as well not be there. Even with insulation you need to have suitable Watts per metre rating for it to be effective. Was this all calculated or was a stab in the dark? What powers it in a power cut, so does it actually afford any protection?  Or is a sticky plaster that isn't really needed and isn't very effective?

The missing insulation is on the pipes within the HP omitted by LG, presumably because they expect the HP to run continuously, even though they have a feature to enable a backup boiler in cold weather. With all the bends, strainers, sensors and other pipework it would be difficult to get it all effectively insulated

 

The trace heating manufacturer gave a table of insulation thicknesses needed for a particular size of pipe giving 25mm of insulation for 28mm pipe so that's what we've got.

 

A genny powers it in anything but a short power cut. Having the trace heating is more for if we shut the HP down in very cold weather to run on the WBS rather than flog the HP. It will also protect it if it fails in cold weather and can't get fixed quickly. At £48 it's probably cheaper than antifreeze valves or glycol??

Edited 6 hours ago by Dillsue

[JohnMo]

56 minutes ago, Dillsue said:

even though they have a feature to enable a backup boiler in cold weather

That is for under sizing the heat pump. So in extreme weather if after a given time not reaching flow setpoint it will fire the immersion.

 

1 hour ago, Dillsue said:

trace heating is more for if we shut the HP down in very cold weather to run on the WBS rather than flog the HP

The heat pump will manages itself in those circumstances, it just starts the circulation pump on a continuous or intermittent basis based on outside temperature. So your heat tracing isn't really doing anything.

[Dillsue]

1 hour ago, JohnMo said:

That is for under sizing the heat pump. So in extreme weather if after a given time not reaching flow setpoint it will fire the immersion.

 

The heat pump will manages itself in those circumstances, it just starts the circulation pump on a continuous or intermittent basis based on outside temperature. So your heat tracing isn't really doing anything.

According to the Therma V manual, 3rd party boiler, immersion and inline backup heater are all separate features with separate wiring and settings. The settings for the 3rd party boiler only offer an OAT trip point and a hyteresis value so the HP doesnt restart until its warmed up a bit. Won't be testing til the winter so will see how accurate the manual is then!!