Thermal store and mains pressure.

[stiffpilchard]

I have an Albion Thermal Store newly fitted. The pressure control valve is located on the mains inlet after supply to the kitchen and outside tap. The pressure valve is factory set to 3 bar. The guage on the valve indicates that the pressure is going well above the 3 bar, going off the scale (which reaches 4 bar). Any ideas why it is doing this and what risks this is likely to entail. As soon as the hot water tap is turned on at all (even a few drips) the pressure reduces to 3 or below.
I have been advised that a pressure reducing valve installed at the kitchen sink will alleviate this. Any help gratefully received.

 

[ChrisR]

Call the installer back. The precharge in the pressure vessel may be too high. Pressure rises a bit when the water heats.
Suggest a 6-10 bar pressure gauge would be better.

 

[stiffpilchard]

The pressure builds even when the heating has been off for hours. Does that change anything?
I don't think the guage is the problem. My concern is why is the valve not restricting the pressure to 3 bar or thereabouts. Is that not what it is meant to be doing?
Would a pressure restricting valve under the kitchen sink, capping the mains pressure there be any help?
Should I also have a "blow off" valve fitted with a pipe going outside the house for safety?

 

[gas4you]

I will depend on where the guage ius reading the pressure from, before the reducing valve or after. It is before then it is ok to read 4 bar. I don't kmow this make of cylinder so can't comment exactly. You should have a prv set at 8 bar on the incoming mains and a temperature/prv on the cylinder near the top.

 

[Balenza]

gas4you wrote

You should have a prv set at 8 bar on the incoming mains and a temperature/prv on the cylinder near the top.

Its a vented thermal store, not an unvented cylinder, so you dont need these valves.

 

[Balenza]

Chrisr wrote

The precharge in the pressure vessel may be too high

Perhaps their is no pressure vessel fitted at all. ?
Isin't it a small 1.6L potable water shock arrestor that Albion fit to accomodate the expansion. ?

 

[stiffpilchard]

Balenza, I think you are right. It has a small expansion vessel located on the side, probably 1.6l. As previous posts state, it is a vented Albion system, a Thermal Water Store, MFI 30/210. My installer adjusted the pressure reducing valve to 2 bar and now the pressure is building to a max of about 4 when the hot water taps are closed for any length of time. Is this anything to worry about? My installer did not think so but we had so many problems with the last one (installed by a cowboy with no installation guide or users manual left with me), that I am concerned at the slightest thing going wrong. The previous installer did not even have an overflow pipe on the expansion tank on top of the thermal store, hence disaster when it had a fault !

 

[Balenza]

I dont think its anything to worry about. A quick phone call to Albion will confirm one way or another.
Sounds like it is the expansion of water in the coil due to being heated while static which is raising the pressure. The expansion vessel is fitted so this will be taking care of the pressure build up.

Reliance recommend having the cold T ed off to a float operated valve downstream like a WC cistern for example after any nrv,s so in the event of a failure of the expansion vessel or cold water raising slightly in temperature to ambient conditions in a pipe run then the ball valve will act as a low volume expansion relief because of the way it works.