Replacing old rads on 10mm pipes with new slightly smaller rads

Discussion in 'Plumbing and Central Heating' started by Crediblehippo, 6 Sep 2021.

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  1. Crediblehippo

    Crediblehippo

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    Hi all

    All of my TRVs are very old looking and don’t seem to work properly, the temp is either hot or cold despite what number the TRV is set to. My original plan was to replace all of the TRVs but my understanding is that for the hassle of changing them all I might as well replace the rads as they’re all old too!

    The replacement rads I’m looking at are slightly smaller, one is 100mm smaller and the other two are 65mm smaller.

    Do I need some sort of extension piece to bridge the gap? Am I likely to have any issues fitting new rads to 10mm pipe in terms of pressure on the boiler? Also, any general advice as I’ve never changed a rad before?

    Many thanks all.
     
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  3. CBW

    CBW

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    You can get extension pieces, but it would look better with pipework adjusted, eg a small re-pipe.
     
  4. oldbutnotdead

    oldbutnotdead

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    Replacing valves isn't a major job unless the rads are ancient and rusting out from the inside, then it becomes a bit of a pain. You may find that your heat problem is 10mm pipes rather than valves....is the boiler newer than the rads, is the pipework full of sludge etc etc. A bit of investigation might be in order.....
     
  5. Crediblehippo

    Crediblehippo

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    i think boiler is newer than rads, pic attached. The rads get hot no problem but I have no way to regulate the temperature. They are either scolding or cold. That’s why I was going down the new TRV route but thought I might as well replace the rads while I’m there for more modern ones with higher BTU. Only issue is the size equivalents are all slightly smaller.
     

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  6. CBW

    CBW

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    Do you have a room thermostat fitted?
     
  7. leezer3

    leezer3

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    I think the OP is misunderstanding what the TRV numbers actually mean.
    He seems to be expecting them to control the temperature of the radiator :)

    Roughly speaking a number on a TRV represents one 'step' in room temperature (Anything around a degree or two, depending on the TRV)
    Until the room reaches this set temperature, the radiator will be at maximum heat.
    When the temperature is reached, the TRV will close, and the radiator will be cold.
    If the temperature drops below the point set on the TRV, the radiator will be hot again, and so-on.
     
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