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Discuss System boiler rads on but no hot water in the Central Heating Forum area at

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  1. Bettyboo

    Bettyboo Member

    I have an old system boiler. Tenants are saying rads heating but not hot water. Sorry if this has been asked before but please can you advise what the cause might be?

    Thanks a lot
  2. Harvest Fields

    Harvest Fields Trusted Plumber GSR Top Contributor!!

    Evening Betty. We would need more information really. Like what boiler, what system set up you have I.e diverter valve or zone valves in the airing cupboard?
  3. Bettyboo

    Bettyboo Member

    the boiler is a ELAN 2 RS40
    Not sure if I have diverter only or zone valves -I have various taps next to tank upstairs - my notes say
    • "run pump on first setting if possible with the gage at 6pm to stop a lot of air getting into system"
    • Also have red tap for hot water "which should be turned on and off to stop it ceasing up " - have not been doing this
    • Also other high tap to turn off if a radiator leaks
    • Also there is a lower red tap - advised not to touch
    Any ideas? Thanks a lot
  4. JCplumb

    JCplumb Plumber

    First thought is that a zone valve has stopped working.
    This is a 3 port valve:
    There are also 2 port valves that just have a straight brass part underneath the top box, unlike the brass 'T' shown in this picture.
    There are a few different ways these can be set up, there is C plan, Y plan etc. You probably won't be able to determine what plan you have, but the common factor is zone valves and it sounds like that's your issue to me.
    You can test them, there is a manual override lever on them.
    If you can find a zone valve that has a pipe leading to a low entry point on your hot water cylinder, feel the pipe when your system is set to hot water, then operate the manual lever and see if the pipe gets instantly hotter.
    If so then your valve has gone, usually not a massive job for a plumber to replace the valve.
    There's also a possibility of a blockage in the pipework that goes to and from the cylinder heating coil, but the valve is the first thing I'd check.
  5. jtsplumbing

    jtsplumbing Plumber GSR

    Wow this sounds like a very old system no M/Valves just a pump and a couple of gate valves to shut of heating if not required some photos of controls would help
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