W Bosch Greenstar 28i _pressure build, then dump

[borntohula]

Hi all,

I have a 4yr old worcester bosch greenstar 28i combi boiler. The prv keeps kicking in and discharging water. When I first noticed this, I repressurised and bled the system to 2 bar, fired up the heating again and left if to heat up. Within an hour or so the water was dumped and pressure reduced.

Since repeating repressurising the system and firing up again, i have watched the pressure dial increase until it hits 3 or so bar then it dumps....i'm guessing this is the pressure to which the prv is set.

I've been led to believe this problem could be caused by the expansion vessel. If so, is this a common fault? And can it be remedied by increasing the pressure of the vessel? Hoping it won't need replacing :s

I have to confess, i noticed this in March, and have left it as one of those things to get sorted. . . dunno if it could have been caused by the cold winter as my boiler is in my cellar.

Any advice on how to remedy this would be much appreciated. I am an nvq level 2 plumber so feel i could fix myself if not too complex a problem.

Thanks for reading!

 

[Destroyer2813]

Two bars a bit high should be mor 1.5 as the water will expand when hot and may be whats causing it to get near to three bar. Regardless of the fact your are nvq qualified your are not GSR so you shouldnt be touching the boiler

 

[anz]

Yes it is likely to be the expansion vessel, could be blocked, could just need repressurising. Best get an experienced Gas Safe registered engineer on the case.

Whereabouts in West Yorkshire are you?

 

[Kev the gas]

Poss the expansion vessel isnt big enough for the volume of water in the system.

As above get someone qualified to check it out, you may need an additional expansion vessel.

 

[borntohula]

Fair enough destroyer, just wondered if it was anything straight forward and simple . . and I'm in Halifax anz.

 

[PHILPLUMB]

Release presure from system and check pressure in vessel using a tyre gauge.Also check prv is seating and not passing when upto 1.5 bar.

 

[thunderboxtech]

Check that the expansion vessel hose is connected to the boiler! I seem to remember that on this boiler you had to remove a plug and connect the vessel on initial comissioning. Have been to one that was'nt connected and was over pressurising.