Combi boiler, increase in preasure when heating is on.

[Spb67]

Hello, I have a Main eco 30 combi 9yrs old.
when the heating is on the pressure rises up to 3.5 or more, then the prv opens, when the heating is off the pressure is way down and the boiler fails to light.
I have refilled it several times and bled the rads, there are no leaks on the pipework that I can see, I have looked under floors etc. The hot water is OK.


Any ideas what it could be?

 

[PrenticeBoyofDerry]

What is the pressure showing when heat off/cold?

It is possible the expansion vessel needs recharging!

 

[Spb67]

Hi, the pressure drops down to .5 , I get a low pressure code flashing,,,, how do I repressure the expansion vessel? Or check it need replacing pressuring

 

[PrenticeBoyofDerry]

You are best getting a gas engineer out to check the expansion vessel.
It can be tested for pressure by using a pressure gauge and recharged by a pump.

 

[Spb67]

Cheers.