zoned system, pressure drops when cold (but goes back to normal when i manually open valve)

[Riley]

Which it might with no expansion vessel. I suspect no one wanted to fit it after you’ve begun. Nothing worse than picking up a job halfway through

 

[Paul Cochrane]

Hi @scott_d @Riley just following up this thread again... So do you think the expansion vessel in the combi itself has died, or does the system now need a second EV because I've turned it into a zoned system? I'll have a look and see if there's any pressure in the internal expansion vessel if you think that's a good idea.

Will have time to fix that PRV today too!

Thanks
P

 

[Harvest Fields]

Do not do that if the vessel is inside the boiler casing. You will need a gas safe registered engineer.

 

[Paul Cochrane]

@Harvest Fields cheers! I won't touch it then...

 

[Scott_D]

It’s probably undersized now you have increased the system size

 

[Paul Cochrane]

Thanks @scott_d !

 

[SJB060685]

If system volume has increased then a larger expansion vessel must be calculated for and installed to accommodate the larger volume. If an expansion vessel is too small, lost some charge, lost all charge or charged too much then you should expect PRV discharge and as said above this dripping on any electrics can cause problems.