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Thread: radiators cold

  1. #1
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    Default radiators cold

    hi,

    I have a valilant combi boiler VCW GB 242EH i believe. the boiler has no problem supplying water on demand to the shower and taps, but the radiators only get mildly warm when heating is turned fully up. Also 3 radiators in the house stay stone cold! I have bled all radiators in the house and its made only a very minor difference to the working rads but still have 3 cold rads. the pressure is fine and stays consant, however on the boiler the temperature gauge is not working, could this indicate that the thermostat is faulty. Could i have a blockage somewhere or is the pump faulty, the boiler is 10+ yrs old.

    any help gratefully recieved.

    paul.

  2. #2
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    Default Re: radiators cold

    hi,

    on the cold rads check the pipes are heating, if they are, indicates sludge or obstruction in the rad itself.

    if the pipes are cold, i'd open up all the rads so the flow is 100% on all rads.
    this will ensure the water is 100% flowing around the system. you may find depending how its plumbed, by turning off the flow on 1 rad may effect the flow to the next rad etc etc, thus been restricted so much, the last 3 rads are flat cold.

    this may put your rads off balance but at laest you'll be able to tell.

    have u tried drainning the whole system and refilling? using a rad key to let the air out as you fill up. if u do drain the system, get a glass and gather some of the water for inspection, does it have bits in it? is it black?
    remember to add corresion inhibitor back into the system, but obviously at 20 a tube, do this once your happy the system is fine.
    i ended up flushing my system 8 times before my problems were fixed.
    all i did was shut off a rad at the top of the house, undo the key and let out the water that is under pressure, and pump the stuff in as i had a double rad, as i pumped stuff in there, the water was displaced from the other side - once done, open up the rad again and switch on the central heating for an hour or so to ensure its fully mixed round the system. it will take a week or so to be fully mixed.

    hope this helps.

  3. #3
    Moderator toscal's Avatar
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    Default Re: radiators cold

    You might just need to bleed the radiators again, sometime they take a couple of goes to get all the air out. Also they may need rebalancing. Try following the advice given on this site http://www.diyfaq.org.uk/plumbing/rad-balance.html It takes quite a while to do properly but seems to work. Spent 2 days last year doing mine.
    Also do you have a room thermostat, and what is the setting and where is it located. If this is faulty then it could be switching off to early. Mind you if the boiler is over 10 years old it could be the pump. My pump has just packed up on my Combi boiler which is around the 10 years old mark.

  4. #4
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    Boilers have a series of control mechanisms designed to distribute heat and hot water at peak times. As combination boilers do not require hot water storage, heat loss is greatly reduced. I think your radiators may need bleeding or the thermistat may need moving to a different temp.

  5. #5
    tomkent45
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    I had the same problem and I tried to bleed the radiator and the problem ends. Thanks!

  6. #6
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    What is your boiler thermostat for ch set at? Your room stat doesn't have any influence on the radiator temperature; it's either on or off.

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