Pressure Drop on Unvented System

[eddie twadds]

I am having on-going issues with loss of pressure in our unvented system in our new build house and am after some advice so I can have a sensible conversation with the heating engineer.

Set-up as follows:
Potterton Promax HE
Twin zones CH (Zone 1 = bottom floor and Zone = top two floors) via Siemens controls
Range HE cylinder and two expansion vessels in the airing cupboard.

Pressure has been dropping on CH and I have had to bleed rads and refill the system on at least four occasions in as many months. No visible leaks in system.

Heating engineer suggested placing tissue in tundish to see if water escaping from the CH expansion vessel which has been confirmed. New CH expansion vessel fitted; system repressurised and all working. Well, it is but there is still water dripping onto the tissue and the pressure is falling again. Takes about three days to go from cold 1.5 bar to almost 0.

Any suggestions why this is still occurring?

 

[JPC]

it could be that the prv is not sitting properly now and letting water by.

does the pressure on the central heating swing up to 3 bar...hope not as new ev fitted

 

[gas4you]

Either it hasn't been fitted properly, or maybe it was never the EV leaking in the first place?

Don't know these boilers, but is the AAV anywhere near the EV?

 

[eddie twadds]

Jamie

I'll check to see if there is a pressure increase with CH switched-on.

Dave

AAV's are beyond my scope of knowledge. I wouldn't know what one looked like if it landed on me (or what it does). If you tell me what it could look like then I'll have a butchers.

The boiler is in the utility room on the ground floor and the EVs and tank in the airing cupboard on first floor.

Thanks
Martin

 

[gas4you]

Sorry, mis-understood, thought this was a system boiler

What does the chap who replaced the EV say about it?

 

[eddie twadds]

Soz - don't know yet - the company (who did the install for David Wilson Homes) is due back out next week.

The last guy seemed knowledgeable so have been happy with their efforts to date - I just like to try and learn a little bit about what they're doing.

Just read the WIKI - oops!

 

[baxpoti]

Sorry, mis-understood, thought this was a system boiler

I think, it is the system version, in this case!

 

[eddie twadds]

Not sure of the definition of system boiler. My setup as follows:
Potterton Promax HE in utility room.
Unvented Kingspan cylinder and two separate expansion vessels in airing cupboard (red for CH with filling loop and pressure guage and white for DHW) plus actuators and other interesting looking Honeywell control stuff.