Combi boiler PRV discharging !

[VinceW]

Can anyone let me know what may cause the PRV on a combi boiler to discharge. Thanks.

 

[keego]

Could be a number of things, need more info. Or look at the Radiant Combi exceeding 3 bar posting on here.

 

[VinceW]

Went to call as guy said CH had a leak and Combi losing pressure.....got there he then told me "pressure gauge goes nearly off the scale when CH on and water comes out of overflow"- i PRV outside. I told him he needed a CORGI guy and did not take notice of manufacturer, I am just interested as my first thoughts where faulty pressure vessel.

 

[ChrisR]

Probably the PV is full of water, either due to fault or just no air.
Filling loop left open?
PRvalve probaby leaking permanently, which they can, once opened.

 

[Gas-geezer]

Could be expansion, vessell lost its charge or split check pressure in vessell should be about 0.5 bar, if split press valve at top of vessell if water comes out need new vessell.