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Discuss Cast Iron style rads on 10mm in the Central Heating Forum area at

  1. Bibbs118

    Bibbs118 GSR


    A customer wants cast iron style rads throughout, 9 or 10 in total but currently has 10mm pipe .

    Is there any problems installing this type of rad on mircobore? I'm worried about the water content being much higher and it not circulating?

    Anyone else installed these on mircobore?

  2. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Best go for the alu style

    Cast iron I would do in 15mm
    • Like Like x 1
  3. YorkshireDave

    YorkshireDave Plumber Top Contributor!!

    Typically are they not a high water content beast? If so, I don't know how you'd get sufficient flow...
  4. Harvest Fields

    Harvest Fields Trusted Plumber GSR Top Contributor!!

    Nothing less than 15mm mate. Would take an age to heat up.
    • Agree Agree x 2
    • Winner Winner x 1
  5. Bibbs118

    Bibbs118 GSR

    Yes, this is what worries me, major job replying.

    • Like Like x 1
  6. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Defo not if it's plastic
    • Agree Agree x 1
  7. Matchless.plumb

    Matchless.plumb Trusted Plumber GSR

    • Agree Agree x 2
  8. Bibbs118

    Bibbs118 GSR

    I'll ring the manufacturers tomorrow , try and get something in writing .;););)
    • Funny Funny x 1
  9. Harvest Fields

    Harvest Fields Trusted Plumber GSR Top Contributor!!

    That’s is not funny;);)
    • Like Like x 1
  10. Ric2013

    Ric2013 Plumber Top Contributor!!

    Surely the water flow required is related to OUTPUT, not water content? Agree that a CI rad will contain a lot of water and take a long time to heat up, but a 2kW rad requires a set amount of water, regardless of the water content, otherwise the system won't be balanced properly. So I'd argue that the fact that the radiator is cast iron is largely irrelevant.
    • Agree Agree x 2
  11. Best

    Best Trusted Plumber Top Contributor!!

    Just come to this thread and above ^ was also my first thoughts.
    I think a cast iron rad fed by 10mm will take a very long time to reach full heat because it has large water volume, but will maintain output once reached and then rad will hold heat longer once off.
    Personally I would go with steel cast iron lookalike rads.
  12. Bibbs118

    Bibbs118 GSR

    Cast iron style
  13. YorkshireDave

    YorkshireDave Plumber Top Contributor!!

    Hmm. Output can only be maintained if more energy is input than can be output. The larger the mass of water, the more sensible energy it contains. If the rad dissipates more energy than the volume of water can supply then it simply cannot do its job and complaints ensue - even tho you've told them.

    You would normally slow down flow to improve heat transfer but doing that means you may not move enough mass through in a 10mm system bearing in mind 10mm is the external dia not internal. Other factors mean its usable bore is probably more like 7mm max. This means warm one side cooler the other.

    I'm with Harvest on this one. 12mm copper borderline, 15mm copper to make certain. :eek:
    • Like Like x 1
  14. Bibbs118

    Bibbs118 GSR

    I don't know, all I know is I see loads of microbore and unless it full of magnatight it works, I don't like it but it works.

    And my view on flow is to restrict down as much as possible on the lock shield, so the hot water in rad has time to give off it's heat.

    Not really my area tho.

    Nb . Bungalow, 22mm circuit in the loft with microbore tee offs, not on a manifold.
  15. Best

    Best Trusted Plumber Top Contributor!!

    Cast iron, or that style, will look stupid with 10mm pipes anyhow. I wouldn't do it unless with a total repipe.
    People want luxury look with poor pipework supply.
    Bit like putting a Ferrari body on a Sinclair C5.
    • Like Like x 2
    • Agree Agree x 2
    • Funny Funny x 1
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