Odd pressure drop issue

[JNGAS]

Hi all

I will try to keep this a simple as possible.
Customer is continullay losing system pressure daily, when heating hot water.
This happens after hot water demand is achieved.
The very strange thing......... the pressure loss on the F/R sealed primary circuit, is being caused by the 6 bar expansion relief valve activating
(Cold feed - RWC combination valve).

After much head scratching, the only thing I can think of is that the cylinder coil has gone!?
Already tried turning off cylinder hot water draw off, and then opening the filling link, but no water flowing from hot tap.
Possibly a very small hole in cylinder coil?

Any ideas would be much appreciated

thanks in advance

 

[Madrab]

Erm, that sounds very like you are working on an unvented cylinder (UV)? If that's the case then unless you're qualified then it's not something that should be worked on. If you're not then please ask the client to contact someone who is. If you are then you should know what to be ruling out first. The fact that it seems the sealed system is losing it's pressure via the Expansion PRV may be a red herring but it needs to be looked into by a qualified UV specialist

 

[picasso]

If the coil had a pinhole it would pressurise the feed and return not drop the pressure, valve opening probably caused by flat expansion vessel and if there is no sign of a leak try isolating the boiler to see if the main heat exchanger is leaking down the condensate (assuming its a steamer)

 

[JNGAS]

If the coil had a pinhole it would pressurise the feed and return not drop the pressure, valve opening probably caused by flat expansion vessel and if there is no sign of a leak try isolating the boiler to see if the main heat exchanger is leaking down the condensate (assuming its a steamer)

Expansion vessel is precharged at 1.5bar and 3 bar PRV is not releasing water.
5 / 6 yr old Heat only Worcester bosch - will check condensate running boiler in isolation from cylinder
thanks