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Whining Boiler after changing diverter valve (Worcester 24cdi)

Discussion in 'Plumbing and Central Heating' started by Milk, 14 May 2018.

  1. Milk


    11 Jun 2008
    Thanks Received:
    United Kingdom
    A week ago the diaphragm in the diverter valve of our old Worcester 24cdi boiler finally gave up the ghost. We are planning on replacing the boiler in the not so distant future but we also want to move it to the room above which is nowhere near ready. Long story short, we want another 6 months out of the old Worcester.

    A little research suggested that switching out the diverter valve on the 24cdi is a pain. A few key posts on this forum suggested leaving the plastic flow and bypass pipe in situ. Armed with a set of fresh washers and silicon grease, I followed the advice and everything seemed to go quite well, no leaks, pressure fine, hot water on a dribble. It was only when someone took a celebratory bath that we noticed the whine.

    The whine sounds the same when the boiler is both off and on and is in direct proportion to the flow of water through the hot tap. It becomes audible when the tap is ~ 1/4 open and is very loud when fully open. It is high pitched and has a clean resonance. It originates from the diverter valve / heat exchanger area I've tried to upload a recording but it seems mp3 is not supported.

    We are in a soft water area with high pressure > 3 bar.

    Assuming it something that I have caused here is a list of what I did to replace the diverter valve.
    • Ran heating for 30 minutes.
    • Waited for pump to stop then disconnected power.
    • Drained system (tap on heating return below boiler).
    • Removed the micro switch assembly
    • Wrapped control facia in cellophane.
    • Closed boiler isolators.
    • Closed mains stop tap (isolator was leaking).
    • Drained boiler.
    • Removed filling loop.
    • Removed water to water heat exchanger (Nut was stubborn).
    • Disconnected flow pipe (Nut was really stubborn, moved expansion vessel with the force, nearly hit the DHW sensor).
    • Removed diverter valve bracket and the pull off support plate.
    • Loosened 4 screws of the plastic flow from the manifold.
    • Encouraged the diverter valve out of the manifold and plastic flow.
    • Cleaned up all parts and greased the appropriate bits.
    • Discovered replacement diverter valve uses an improved bracket (which I don't have).
    • Hack sawed existing bracket to fit replacement valve (6mm slot for a lug)
    • Encouraged the replacement diverter valve into its new home.
    • Reversed the process of removal.
    • Opened isolators and stop tap.
    • Added system cleaner via Magnaclean.
    • Repressurised system.
    • Ran heating for 4 hours.
    • Drained system
    • Added inhibitor.
    • Repressurised system.
    EDIT: I forgot to say the replacement valve was reconditioned from HTS.
    Last edited: 14 May 2018
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