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System boiler stopping firing

Discussion in 'Plumbing and Central Heating' started by kreyszig, 27 Jan 2021.

  1. kreyszig


    4 Jun 2013
    Thanks Received:
    West Glamorgan
    United Kingdom
    We have an old (Glow-worm Hideaway) gas system boiler, with drayton valves on both CH and HW. Something is up with the CH microswitch I think, as it will keep the pump running when the CH is switched off at the controller. A lever on those valves makes it clear that the valve is shut but the pump carries on running.

    However, if the whole system is switched off for a while (i.e. no power to the controller, pump, valves) - and time does make a difference - then the pump will not activate when it is switched back on (as expected - valves are shut).

    That's one thing, for now we get round it by just turning the whole system off. Clearly I need to change the valve as the microswitch is busted (not a removable head one so I've been putting it off). Unless it's something else as well..

    What has started happening lately is after running OK for a while, the CH is on at the controller, the valve is open and the pump is running, but the boiler isn't firing and the rads go cold.
    Again if I switch the system off, wait a while and turn it back on, whey presto the boiler fires up and the rads heat up.

    I'm curious as to why the boiler might decide not to fire if the valve says go and the pump is active.

    There is a single room thermostat, set to max (old and painted stuck) and there's no way the room is at that temp.

    The CH doesn't look at the tank thermostat does it? I've turned that down a bit recently.

    Also I should mention the controller is an old british gas one (quick google and it looks just like a Drayton LP522) which I've already replaced once just in case. I'm kind of suspicious of a wiring fault leading to the controller, wondering if something is temperature sensitive..
    Last edited: 27 Jan 2021
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  3. sxturbo


    12 Jan 2014
    Thanks Received:
    United Kingdom
    Change the valve and check the wiring and see what happens.

    Sounds like the faulty microswitchnis causing issues
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