Baxi 105e pressure problem

27 Jan 2009
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Tyne and Wear
United Kingdom

got called to a job last week to a 105e, safety valve dripping-Pressure was at just under 3 bar. released pressure to 1.2bar. disconnected filling loop. heating/hot water ok when I left.The customer claimed to have "fiddled with it" before I got there

A day later pressure back up to 2.8bar, safety valve leaking again heavily.

Went back today, released again to 1.2 bar. When hot water tap is opened, needle on gauge going up to 2 then back to 1, then back up to 2 when heating comes on....

Any ideas-Corgi no 1705


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Not checked that, 8-10 bar sound bout right? I never thought of thet mind-Never ever had one go faulty in 10yrs

Obviously need to drainboiler down first.

Just seems to be getting the pressure from somewhere, was thinking back through diverter valve or heat ex??
Most factory fitted expansion vessels have a Setting of 0.75 bar pre-charge and are rated for the system. usually, thesystem hasn't been cleaned properly and the expansion splits, i say that loosly tho, it kindda moves am allows the water to fill the vessel instead of the bellows. d check your pressure, charge it back up again if needs be and wait for the enevitable call back :evil: which then means new vessel. Top tip unless it's stupidly eas to access just fit a remote expansion(robokit) vessel on system return,as close to boiler as poss. And cap boiler blow off
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Sorry I meant .8 bar-1.0 not 8-10.

i work on cw booster sets and the exp vessel on the booster pump is generally set at 1 bar,

Jst checked the 105 manual there and it says 0.5 cold.

Thanks for the info, appreciated.

When you say cap the blow off, you mean cap off the safety valve on the boiler?
No probs matey. 105 is a swine to swap, it's a full boiler of the wall jobby most of the time.
An the blow off yeh is safety valve. just screw a half inch male iron into the bottom of it where the copper comes out. then the new robo kit usually has another sat on the top of the vessel
The pressure keeps rising and its dripping outside.
You said the filling loop is disconnected.
So where is the system getting all this water for pressure to go up and leak out
If the expansion vessel has gone it would get rid of water but would not be able to replace it.

So it seems more like the plate heat exchanger has gone and allowing mains water to enter the heating side causing the pressure to rise and thus drip out the PRV

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