Vaillant Ecomax 824- pressure rise/drop

14 Dec 2011
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United Kingdom

I wonder if anyone can offer some advice before i start fiddling with my boiler. I moved into my property 2 months ago and noticed the boiler had absolutely no pressure. Despite this the heating still worked and the pressure would rise to c.1.2 bar. As i didn't know the boiler i called a plumber out to service it. He said the boiler was fine but the expansion vessel needed re-charged (he did this but i did not see him do it). THis seemed to calm the boiler down but i noticed the pressure slowly dropping in the boiler (0.5 bar over 2 weeks). I topped the boiler up but this seemed to make the boiler work at a higher pressure. Again the pressure slowly dropped and i have topped up again, now the boiler is running at around 3 bar so i have had to reduce the thermostat to reduce the pressure (not good in the winter).
To me it still sounds like the expansion vessel causing the problems rather than a leak leading to pressure loss. It makes sense to me that the vessel is slowly retaining more and more water leading to more top ups and more pressure although i dont quite understand how these things work. On most forums i have read it suggests the PRV triggers with this problem but i havent experienced that. Perhaps this is because ive identified the problem before the water quantity gets that high. I have pressed the valve and only air comes out. Do you think the plumber might have re-charged wrong (maybe not emptying boiler/not leaving drain valve open)? My next task is to empty the boiler and check the EV pressure myself so any advice prior to this would be appreciated because i'm not that confident at doing it. If the pressure is wrong i need to top up to 0.7-0.9 bar. Will this get all the excess water out of the vessel or do you need to overpressurise to force it all out and then reduce the pressure again?


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Have a look at WIKI - FAQ 7
that will tell you how to repressurise your EV

However on the Ecomax you have to access the Combustion Door which is out of scope for DIY as you will have to carry out gas safety checks afterwards so it is a job for a Registered gas Engineer ;)

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