Halsted Finest Gold going over pressure ??

[libbynbob]

Hi everyone,
My Halsted Finest Gold combi boiler works fine but i have to top the pressure up every day. I set it at 1 bar but when the system heats up, the pressure soon rises to 3 bar at which point it vents itself to lose this too high pressure. Obviously when it cools down overnight, the pressure is nearly zero and boiler trips out.
I switch it off, boost the pressure back to 1 bar, switch it back on and it works again. I need to know what is causing the pressure to rise like this, as my plumber just said " you need a boiler mate" yeah right, sooner fix it myself.
I am an engineer and have no problems replacing parts or even repairing them, but first i need to know where to look and wondered if anyone in here was familular with this fault and could point me in the right direction.
Thanks, Bob.

 

[EliteHeat]

Problem is (probably) one of the following:-

(1) Connection to the expansion vessel blocked
(2) Expansion vessel has lost its charge
(3) Expansion vessel diaphragm is ruptured
(4) Plate heat exchanger is perforated

 

[libbynbob]

Well thats plenty of options, where to start though, would seem ive got to look at expansion vessel first then
Thanks

 

[gas4you]

Empty the system pressure to zero and test the exp vessel pressure. If water comes out it is completely knackered. Pressure should be around 10 - 16 psi.

If it isn't re-pressurise by searching faq's on here.

 

[Biggles..]

if the vessels shot, to change an ex vessel on these, the boiler has to be removed as it stays on the mounting jig. Save your self the hassle and fit a remote one.

 

[libbynbob]

What kind of prices do the external pressure vessels come in at, i googled them and finished up everywhere except central heating places lol,
Bob.

 

[EliteHeat]

Fifty quid(ish) including wall plate.