Bosch Worcester 28i Junior Combi Pressure problem

[atshuttle169]

Hi guys, this is my first post to this forum, so please accept my apologies in advance if this subject has been answered previously.

I have a BW28i junior combi which is about 4 years old. Everything has worked fine until the past two weeks.

The water pressure level has just recently started to drop and needs topping up by the filling-loop. I fill it up to 1 or 1.5 bar and it will remain at that pressure until the C/H stat calls for heat.

As the radiators heat up, the pressure guage will steadily rise up to between 3.5 and 3.9 (too high as I think the pressure should be no more than 2.5 bar?) and the pressure relief valve will discharge externally, (which I think is correct due to the excess pressure). The system then needs filling up again.
No obvious leaks at either the radiators, pipework or in the boiler casing, just evidence of water coming out of the external discharge pipe when the system is up to heat and reaching about 3.5 bar.

Any ideas as to what the problem may be? Could it be a faulty expansion vessel, the pressure relief valve or .... ? Thanks in advance for any help or ideas.

Tom

 

[plumbnuts]

See FAQ about re-pressurising expansion vessels and testing if it is knackered.

 

[atshuttle169]

Thanks for the link on 'sealed heating systems'. Very interesting article.


If it's the expansion vessel that's knackered, what sort of price would it cost to replace and have fitted?

It looks as if the whole boiler would have to be dismantled to fit as it's right at the back!

 

[kitch0978]

it might just need re-charging but if it needs replacing a remote one can be added somewhere else on the system if need be...........