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Discuss What type of system do I have? in the Central Heating Forum area at

  1. Jdbecks

    Jdbecks New Member

    I replaced a radiator from a single to a double and now the radiator lock shield is leaking from the spindle. The lock shield is quite old with a 3/4 union. I looked to see if I can pack the spindle but the spindle is threaded inside a threaded nut, which when I undo, also unscrews the lock shield spindle.

    I have a condensing boiler with a vented hot water tank, in my loft I have an overflow/expansion tank which supplies the cold fill loop for the boiler. I was under the impression the cold water tank in the loft was an expansion tank for the central heating, but then why does the boiler require a cold fill loop and pressurised to run?

    Its so I can drain the system and replace the lock shield, but I might pay a plumber to do it and also replace another radiator just in case I encounter any issues.

    In my previous house my central heating had a cold expansion tank in my loft and a second tank too. So this house only having one throws me.

  2. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Sounds like the tank in the loft is for your hot water eg cylinder (should be a big ish tank around 30-50 gallons)

    The heating sounds sealed eg filled via the filling loop
    • Agree Agree x 1
  3. Jdbecks

    Jdbecks New Member

    Thanks, it’s late and and I just read my op! it’s a little mumble jumble so apologises for that.

    If my system is sealed, that means I can just drain my central heating and I won’t have to isolate anything else as the only feed is via the fill loop for the boiler?
  4. DuncanM

    DuncanM Plumber GSR

    Correct. If there is a pressure gauge and a filling loop just open drain point/s and open bleed valves on rads. Then close them and fill and then bleed again, top up to 1 bar when cold. Add enough inhibitor
    • Like Like x 1
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