DIY Doctor UK DIY Forums

hi
i have been called out to fix a sime friendly format 80e combi boiler. the problem is the presure gauge is at about 4 bar and there is water comming from the presure relief valve pipe whilst cold. i have narrowed it to the dhw heat exchanger leaking into the primary circuit. the problem is that when i isolate the cold water to the boiler the pressure drops but keeps on dropping to 0 bar. i would have thought that it would stay at 3 bar when the presure relief valve closes. Is this correct of is there a fault with the presure relief valve aswell

any advice would be welcome

cheers
paul

With the cold water turned off is there still water coming from the PRV ? If the pressure relief valve reaches 4 bar, it'll dump enough water to take the gauge to 0.

htg

Hi
yes water still comes out of the PRV when the water is turned off. It keeps on discharging until the gauge reads 0 bar. What I am wondering is if the PRV is stuck open as I think this has been happening for a while judging by the state of the wall where the water hit it
I might just put a new one on whilst the system is drained to be sure
Am I in the right ball park with me thinking it is the DHW heat exchanger. I have checked the filling loop and that is fine

cheers
Paul

Turn off the cold water to the boiler, and run the heating, if the pressure doesn't rise to 4bar, then yes change the plate heat-ex.

And yes, I would also change the PRV.


htg

hi

thanks for the tip but i cant run the heating as the PRV lets water through till the gauge reads 0 bar thus stopping the boiler from firing.
i will change the heat ex and the prv and will let you know how i get on

cheers

paul

hi

managed to do it with replacing the PRV and DHW heat exchanger.

both had rusted

cheers for the advice HTG

paul