Combi boiler pressure drop

Discussion in 'Plumbing and Central Heating' started by lcleme, 6 Mar 2011.

  1. lcleme

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    Hi there, I wonder if anyone can shed and light on my problem with the dreaded Powermax combi boiler!

    Last week I had my boiler looked at by a gas engineer as I was losing pressure when the system was switched off at night. Pressure was not a problem if I left the boiler and CH on all the time but this was getting costly in gas! The engineer re-pressurised the expansion tank which was low and replaced the PRV which was leaking water but I am still seeing a lose of pressure. This boiler now seems to hold pressure when the CH is on and also when it is off at night. However, as soon as i use any hot water it drops like a stone and then locks out.

    I've checked the expansion vessel valve and when depressed ever so slightly it is releasing air not water. Unfortunately i do not have an air pump to check the air pressure in the expansion vessel. One other thing I have noticed is that when I repressurise the boiler to 1bar the pressure jumps very quickly to just under 3 bar when the boiler switches on. I have been round the house and checked all the radiators but cannot find a leak anywhere. The pipes in my house seem to be some kind of flexible plastic and appear to run through the cavity walls. I cannot see any evidence of a leak anywhere on the ceiling, walls or next to the radiators. I've checked the valves on all the radiators and they seem clean and dry. Downstairs floor is all concrete so I'm guessing pipes are only in the walls.

    Do you think the expansion vessel has given up the ghost, the expansion vessel valve or is it more likely a leak I cannot see?

    Thanks for all your help.

    Lisa
     
  2. gazdaz36

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    If your pressure is climbing when the heating is on then its definitely gonna be a problem either with the expansion vessel or possibly a blockage to the pipe connecting the expansion vessel to the system.If its the powermax he i think the expansion vessel is connected with a flexible hose which might need checking
     
  3. bengasman

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    It does sound like the ev is not working.
    Baffled about the sudden pressure loss when using dhw.

    Best thing to do is stop wasting money on this monstrosity, and replace it with something decent.
     
  4. lcleme

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    Hi folks, thanks for your input. I have however now found a leak coming from my boiler somewhere! There appears to be a brown mark developing on my kitchen ceiling which runs along the joist directly beneath my boiler which is in the upstairs airing cupboard. I have released any pressure in the boiler by running the hot water taps and the boiler now reads 0 bar which i am hoping will minimise any damage. I've switched the boiler off and homeserve are coming on tuesday. I've not looked at the boiler itself to try and figure out where the leak is but from doing a bit of digging ive noticed that some people have had a leaking DHW heat exchanger. Do you think this could be the reason for my loss of pressure when i turn the hot tap on??

    Anyway, thanks guys for all your help with this very frustrating problem!!!

    Lisa
     
  5. bengasman

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    You have my sympathies. Please post the outcome.
     

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