On 18/02/2014 12:15, wrote:
Boiler is in daughter's house. System has 7 single panel radiators.

With the cold pressure on 1.2 bar, it rises pretty quickly to about
2.5 bar when hot.

I found my neighbour has exactly the same boiler and that barely
moves - a couple of tenths of a bar.

Is the pressure rise anything to be concerned about, and is there a
logical reason why they would they be so different?


Well 2.5 bar is not too high and is within the allowable range. However
its quite a large rise for a system that does not sound like it has a
huge water content. Hence as others have suggested, it may indicate a
lack of charge in the pressure vessel.

Assuming it has not actually ruptured, it may just need a top up. To do
this you need to turn off the boiler and let the system cool, then bleed
a couple of litres of water out of the system somewhere (from a rad
connection say) to relieve the pressure in the system.

Then (if you can get to it) there should be a shrader valve (like on a
car tyre) on the expansion vessel. Test that with a pressure gauge, and
if its low (i.e. less than say 2 bar) pump it up with a normal tyre
pump, to whatever is recommended in the manual (probably over 2 bar)

If when you test the valve pressure, waster comes out, then you know the
vessel is knackered.



--
Cheers,

John.

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