Fitting a new radiator to an oil combi central heating system

Discussion in 'UK DIY' started by chopsaw, Sep 26, 2005.

  1. chopsaw

    chopsaw Guest

    I want to change a radiator on my combi based central heating syste
    WITHOUT having to drain dowm the system. I propose to use a freezin
    mixture on the inlet and outlet pipes and then put the radiator i
    place. (The old radiator has already been removed and the pipe
    temporarily closed off.)
    My problem is will the pressure of the combi system blow the ice plug
    before I can attach the new radiator? Any comments gratefully received
    chopsaw, Sep 26, 2005
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  2. chopsaw

    Andy Guest

    Why not relieve the pressure during the operation. I suppose there are
    various ways to do it, the most obvious being to press the overpressure
    relief valve button and shoot a few litres of CH water out of the overflow
    You can always repressurise it from the filling loop afterwards.

    Andy, Sep 27, 2005
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  3. chopsaw

    John Rumm Guest

    Yup good plan...
    I would not be so keen on that however. It only takes a small bit of
    crud to get lodged in the overpressure valve and you will have a leaking
    system. Better to save the overpressure valve for what it is supposed to

    Draining a litre or two out of a drain point, a radiator tail
    connection, or even a bleeding valve will do the same trick.
    John Rumm, Sep 27, 2005
  4. chopsaw

    John Guest

    NEVER open the relief valve unneccessarily. You have a major chance of it
    failing to reseat correctly with an ensuing slow pressure loss problem. The
    drain valve is the way to go.
    To the OP most oil combis have isolating valves between boiler and heating
    pipework. Shut these and open the air vent on the rad you are working on,
    catching the small amount of water released. this will have effectively
    depressurised the rads without affecting the boiler. If the old valves are
    good and the rad is the same size there may not be a need to do this. Only
    if you wish to change the valves or alter the pipes. Do one at a time or you
    may find the system empties itself around you.
    John, Sep 27, 2005
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