Betacom 30 pressure issues

boiler pressure whilst on ch demand pressurising pretty high since install (4 yrs ago) now tenant says pressure is 4 bar with prv leaking. I'm going up tommorrow and assuming pv is damaged aim to fix by sticking an external pv.

the question is:-

if I fit a new pv should I fit the same size (8lt/0.5bar) as the internal one and increase the pressure (3 storey house with boiler on bottom floor) or do I need a 12 litre) also do I need to disconnect existing pv (if it's split) or just leave connected?

thanks in advance.

i am gasafe btw

If it requires a new expansion vessel go for the biggest size that fits the available space. An oversized vessel won't matter. For a 3 story building a pre-charge air-side pressure of 1 bar s/be ok (most will be supplied with that anyway). Leave existing one in if not leaking. Ensure a functioning prv is retained boiler-side of any F/R isolators.

ok, been to property the vessel is split, I bought a 12lt Reflex expvessel but when I took it out of box the water inlet has a softish plug inserted. so I took it back thinking it was a mistake in the manufacturing process, but the 8lt version also has the same plug in the end?

so I'm guessing this is normal, yes?

most expansion vessels I fit are 24liter ones for solar and the end is usually open.

confused

anyone fitted a 'reflex' expansion vessel from screw fix? do I remove the seal or leave?

cheers