Mothers boiler giving me a headache

[Riley]

Evening all

the old dears boiler is playing up. Ecotec Plus 837 pressure keeps going up and up. Only goes up when CH on. Was wondering if it was a split PHEX but it's not the old a boiler ???

Filling loop - fine
expansion - fine
did have new pump recently but cannot think what else could be up

losing patience with it and she's moaning so any thoughts appreciated

 

[ShaunCorbs]

turn mains water off and open hot tap does the heating pressure go down? and have you checked expansion vessel at full load??

 

[London Gas]

Have you checked for blockages? Could be a blockage in the lower plate, does that model have the two rubber hoses? Are they blocked?

 

[Riley]

No it's just newer than the rubber hoses.
As I say it only goes up when on CH
I did think phex but everything is working perfectly apart from the pressure rising

 

[AllyBongo]

If you're sure the vessel is charged, I'd guess theres a blockage in the pipe going to the expansion vessel.

 

[Chalked]

I'm with post 5. Blocked pipe between pump and expansion vessel.

 

[Riley]

Great shout