baxi 105e

[glassman8]

hi my baxi 100e combi boiler is giving me some problems, started out with diafram leaking ,so replaced with complete unit ,starts up ok hot water everything ok, but pressure builds up on its own i have replaced top up valve just in case it was sticking but still builds up, i have drained off pressure whilst it was running but it just builds up again until safety valve opens? any ideas
thanks denis

 

[Mark Br]

How quickly does the pressure increase and does it only happen when you are using the boiler

 

[glassman8]

hi pressure builds up soon as you turn mains water on?
thanks denis

 

[corgiman]

sounds like the DHW Hex

try posting this in the plumbing forum you may get more responses

 

[45yearsagasman]

Plate heat exchanger has failed internally and is allowing mains water to pass directly to the primary side. No repair is possible other than a new plate heat exchanger. If you have replaced other water carrying parts then you should be able to tackle this. Use 4 new seals.

 

[bengasman]

Take off the silver hose after topping up, and see what happens then.

 

[glassman8]

hi boiler now working fine no leaks, changed heat exchanger and all ok thanks for all your advice denis