Ideal Mini c28 boiler pressure loss

[Charles Oldroyd]

Hi

My Ideal Mini C28 has recently started losing pressure. Cold pressure is set to 1 bar, when running this increases to just over 2 bars. It is discharging water from the overflow and within a day the cold pressure drops to 0.5 bar.

Also, it has a tendency when running to cut out, then start up again after a couple of seconds. I'm not sure whether these 2 problems are related or not. There is no issue with radiator temperature or hot water unless the pressure falls too low. Then it wont fire up but just cycles round starting up and cutting out.

I'm wondering if this is a pressure vessel fault.

Informed assistance would be appreciated.

Thanks,

Charles

 

[terryplumb]

Overflow ? Are you referring to the pressure relief pipework ? Water shouldn't come out of that until your system pressure reaches close to 3 bar ,not 2.
Does pressure ever reach 3 bar ?

 

[Charles Oldroyd]

Hi 2.5 bar as far as I can tell, then drops to 0.5 bar when boiler cools down after discharging water from the pressure relief pipe. I've ordered a replacement expansion tank.

 

[Rodders53]

Just thinking out loud:
Most likely is surely the PRV (pressure relief valve) not reseating properly? Then it will pass water - faster as pressure rises.

Likely caused by the expansion vessel (EV) having lost pressure since last service check? Failed EVs usually present water at the Schrader tyre valve, I believe?

A new vessel may well not fix the badly reseating PRV and even require a new PRV fitted?

 

[terryplumb]

As above ,the PRV will very likely need replacing,and the EV may just need recharging. Water coming out the EV's valve doesn't necessarily mean it's failed.

 

[Rodders53]

Water coming out the EV's valve doesn't necessarily mean it's failed.

Every day's a school day... how can water get into the air side of a EV membrane?

I am genuinely curious (from condensation of vapour in the recharge air ?).