Baxi 105 he condensing

13 Dec 2011
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United Kingdom
Hi All

Problem with the above worked out the prv leaks will replace part but I noticed 1 bar of pressure when heating is on pushes pressure above 2.5 / 3 into the red could there be trapped air in the system bled all rads

Cheers :mad:
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The expansion vessel has probably lost its air pressure, and it should be pumped up to around 10 psi with the water side of the system depressurised. You can use an ordinary foot pump for this, if you can access the schrader valve on the vessel.
Honda that the Blackbird then? :p
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I presume that the heating has to be off and cold before checking the air pressure, how do you depressurise the water side, the shrader valve is at the top I should be able to get to it with pressure guage

Thanks for the assistance
Turn the boiler off and release pressure via a drain cock on the pipework, or by a rad bleed screw. There is possibly a drain cock on the boiler to do this as well.(MI's will show this). Leave the drain cock open and pump the vessel up to approx 10-12 psi. Close all drain points and refill via fill loop and vent air.
Thanks it sounds like I have to drain the full system [all the rads]or do I just open a bleed screw I have easy access to drain cock just need to attach hose, I will switch heating off and allow to cool before proceeding to next level
BEFORE you depressurise the system press the pin in the air valve and let all the air out and see if any water comes out.

THEN proceed with the repressure procedure.

Is it an "instant" model?

yes it is the combi instant 105 HE will this make a differance as the boiler is now cool and I am getting the foot pump and pressure gauge at the ready what does it mean if water comes out?
The EXV often fails on the instant model.

Best fix is to add an external one somewhere.

Hi I would like to say thanks for the advice that you have given,45yearsagasman, Burnerman,Agile
drained system via drain cock below boiler until gauge showed zero and left open was not a lot of air in expansion vessel, I put 12 psi in is that too much or is it okay, when repressurised gauge read 1 bar had heating on for an hour the max gauge whent too was 1.75 bar bled all rads seems to be okay now just switched heating of to see what happens but hopefully all is well and thanks

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