Posted by: @ohdearism

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Hello !

I am having problems with my ASHP

Commisioned in 2016 

When I had a reminder for the annual service, I said that the pressure in my primary circuit was low.

A day after the service the pressure was low again !

It was suspected that the pressure vessel was at fault , In consultation with the company i replaced the schrader valve in the vessel but the next day I was back to zero pressure.

Days later another engineer turned up and repressurised the system and a day later that escaped again.

I have replaced the expansion vessel myself since the company involved said there would be an expensive call out charge for further work on my system. My thinking is that there should be no further call out charges for an ongoing problem not fixed or notified at the time by the service.

I tested the old pressure vessel in water and it was leaking all around the seam. Problem solved  I thought . Photos available of the unit after cutting it open.

After installing the new pressure vessel and priming it and the primary circuit to 1.5 bar the pressure still dropped out of the system.

I have looked at the Samsung unit outside and seen signs of slight fluid weeping under a valve. Photo can be supplied !

I have a inkling that one of my internal heat exchangers or the Samsung unit have sprung a leak for the pressure to keep dropping . How do I find where the problem lies and do I have any redress to the service / installation company if this is found to be the case ? 

Many Thanks for your attention

Alistair

 

 

 

 

 

If your ASHP has both a pressure sensor internally and isolation valves and you also have a pressure sensor one on the expansion vessel then you can isolate your ashp leave for 24-48 hours and see in which half of the system the pressure has been lost.  Otherwise, you may be able to play similar games with any other bits of the system that can be isolated.

I dont see you have a redress against the service company, they appear to have taken reasonable action to fix an evident problem, its not really their fault that there appears to have been more than one problem.

Hello James.

Thank you for your reply.

My AWHP is a Samsung AE090JXYDEH , 2 x SWEP ID2-1414 heat exchangers and a Gledhill ABL250HP thermal store.  5 rads 2 towel rails and 90m2 underfloor heating.

The house is a new build with high spec. insulation and themal efficiency , the heating system was specified as part of the whole design. 

I can not find any valves on the Samsung unit, There are pressure gauges for the primary and heating circuits next to their prospective expansion vessels. Since these cicuits vary in capacity and along with the differances caused by temperature fluctuations it is hard to use these to diagnose the problem.

I suspect I might have to drain the primary circuit disconnect the ASHP and cap off the flow pipes to do a pressure test on the primary circuit and heat exchangers. 

If that fails, I think that I should then remove the heat exchangers and test them individually.

If I drain my system what ratio of glycol to water should I put back in ( I will measure the volume that comes out )

I know I am asking alot, but from experience , the warranty is as useless as the person who causes you to claim off it !

Cheers 

Alistair

If you have heat exchangers between primary and secondary the two circuits are isolated so a leak in one wont affect the other.  So whichever pressure gauge is dropping tells you which circuit to test.  If there are no isolation valves then yes you will need to drain and pressure test, but there isn't much between ashp and heat exchanger so im not sure that, if the leak is in the primary, a pressure test will tell you much that you can't determine buy visual observation.

Have I misunderstood how your system is plumbed?

The primary circuit from the Samsung unit transfers its heat to the secoundry / heating circuit through 2 metal plate heat exchangers.

 Do these fail and would that cause wierd pressure events across both circuits .

I am hoping this because they are cheap to replace compared to the heat pump or digging holes in the plaster to find a leak.

It is the primary that drops its pressure.

 I Will switch system off and top both systems up and pressure vessels and get result overnight ! 

Primary     at 20psi  1.4 bar

Secondary at 15psi  1.0 bar

I am hoping that by doing this i can find the area of fault and then hand it over to an engineer.

PHE s can fail, I'm not sure what the most common failure mode is.  If a plate separating the two circuits failed pressures will presumably equalise, if a plate between one circuit and the air fails presumably only that circuit is affected.

Results overnight may clarify!