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Thread: Overhot water at sink

  1. #1
    Automated Home Lurker
    Join Date
    Apr 2006

    Default Overhot water at sink

    We have a Potterton Kingfisher boiler about 12 years old with motorised valves on CH and Water, no Frost Stat, boiler in kitchen with hot tank above in same cupboard. 9 radiators with rad thermostats on 7 of them (not bathroom or airing cupboard) Water stat on hot tank. No room thermostats.

    The problem is extremely hot water at the sink, the tank is set to 55 deg C but seems to be about 80 deg C. BG changed the tank thermostat today to no effect. System works fine if CH is off, Boiler seems to carry on even though all rad stats are 'satisfied' and have turned 7 rads off. BG man assured me there was only a basic boiler thermostat that simply set the temp of circulating water, could only recommend a room stat to 'overide' boiler. I am sure this problem was not there last winter. Problem came to a head when very high winter quarter gas bill arrived!!
    Do I accept BG advice and fit a room thermostat or tell them to send a better engineer?

  2. #2
    Automated Home Jr Member
    Join Date
    Sep 2005
    Woodside, Nr Hatfield, Herts

    Default Re: Overhot water at sink

    About ten years ago an urban legend was created overnight by some government department claiming that you did not need a room stat if you had TVRís fitted. This is untrue and by fitting one you will save money, otherwise the boiler is keeping the water hot circulating to the radiators without the TVRís.

    Back to the hot water problemÖ. I would say itís the motorised valve which may have got physically stuck in an open position.

    Have a look at the valves and let us know how may you have and if they 2 or 3 way ones.

    An old trick is to tap the valve with the handle end of a screwdriver, but donít blame me if the house fills with water once you knocked the valve onto the floor

  3. #3
    Automated Home Jr Member nickgale's Avatar
    Join Date
    Jun 2005
    Nottingham, UK

    Default Re: Overhot water at sink

    IF BG engineer replaced the 'stat I assume he tested it first and deduced it was faulty, after all it only takes a few minutes to do........ sorry I really should stop making these assumptions!!

    Disconnect the stat, put a continuity tester across the 2 wires and turn it up, assuming the tank is hot, when the stat clicks there should be continuity, when you turn it down again it should click again and continuity will be lost. If this is OK and I'll bet it is (as I'm sure it will be if you put your old stat back on as well) the it's the valve. Turn off the system at the mains, wait 20 secs and the look for the overide lever on the HW motorised valve, move it across - if does so with no resistance then the valve is stuck open (compare it with the CH valve) If the valve is stuck you can free it by removing the motor plate and manually moving it open and closed a few times or get it replaced. BUT be careful you don't loosen any screws that hold the motor head onto the valve - you'll get very wet!

    Then phone BG and ask for your money back!

    Hope this helps?

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