Boiler pressure too high.

[Mark G]

Morning,

I've got an Alpha HE CB33 combi boiler. The pressure needs topping up occasionally but last night the pressure went up to 3 bar. I bled about a pint out of a radiator and the pressure dropped to about 2.5 bar. The heating was n't on and after about 10 mins the pressure had gone back up to about 2.75 bar.

I tried the heating later on and the pressure went back up to about 3 bar, after switching it off the pressure gauge stayed at 3 bar. This morning it was still the same.

Any advice would be greatly appreciated.

Thanks, Mark

 

[kay-jay]

check the filling loop is isolated and not passing


KJ

 

[SimonG]

If the heating is on I would say expansion vessel, heating off could be the filling loop passing or a split in the plate heat exchanger.

 

[Mark G]

I've tried that and it's definitely closed off. I'm wondering if it could be a fault with the actual pressure gauge/needle itself?

Thanks though.

 

[Alpha man]

Is your mains water pressure strong? If the loop is turned off fully, either expansion vessel is empty or the DHW plate heat exchanger is faulty causing water creepage through the plate!!

 

[Gray0689]

Check to see if your prv is passing when heat on if itis I'd say its your expansion vessel bust