Worcester 26CDi losing pressure can not find leak.what next?

[JohnHuson]

Replaced PRV. No sign of leaks. Filling loop not connected. Will refill to 1.7 bar but within a day it has dropped below working pressure with two lights flashing. The guage (replaced) will show nearly zero, when reset it will go back up to half a bar. When refilled it operates as normal on DHW and heating.
Boiler is about ten years old. Replaced fan assembly last week and tried replacing board but of no help.
At what points in the system apart from a leaking pipe connection will water escape please?
If it is a sealed system the areas of leakage must be limited to the PRV, and what other component?
Cheers,
John.

 

[nickso]

radiators, all the pipework to them, heat exchangers (two in your case), all the boiler gubbins.

if it goes down that quickly and theres no puddles n your house it could be the secondary H/E.

 

[kevplumb]

could be main h ex leaking into the condense sump

 

[nickso]

it cant, its a recuperator setup. it could be leaking into the combustion chamber though.

 

[kevplumb]

i was close

 

[nickso]

but no cigar sir.

 

[kevindgas]

sounds more like a diaphragm in the diverter valve failure to me. are you getting hot water as normal or is it cooler than usual?

 

[DazzarGaz]

Is it possible to leave the CH isolated for several hours to see if the system pressure drops?. You really need to identify if it's a boiler leak or a rad/system leak.

 

[JohnHuson]

Yes I have noticed that the DHW is reasonable but then it seems to give an extra burst of pressure and seems to get hotter. I have a spare diverter valve will this stop the pressure dropping? I do not see the reasoning here but my brain hurts and I am to close to the situation to see the real problem.

 

[JohnHuson]

Yes I have noticed that there is quite an amount of warm to hot water going down the condensate....but this is what it should be?
I have to say the technichians from Worcester have not provided anything more than consulting a check list on this problem.
Kevplum made a good point that is it CH or a DHW problem.
I am now sure it is a CW problem......so where can the water go if there is no pipework leak?

 

[JohnHuson]

Which heat exchanger please?

 

[nickso]

loss of system pressure is sod all to do with the diaphragm for a start.

if you are losing vast quantities of water with no signs of a leak anywhere, which you seem to be, then im still guessing with secondary heat exchanger.....its a bitch to get out too. its either that or you have aleak somewhere you dont know about.

if its dropping very fast you can sometimes even hear or see it filling the trap.

as dazzargaz said determining if its a system or boiler leak would be a good step but i would be wary of the isolation valves on these, they are dodgy and thats another cow of a job if you need to replace them.