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Main Fuse blows after 15 min when request central heating

Discussion in 'Plumbing and Central Heating' started by Joeathome, 8 Oct 2006.

This topic originated from the How to page called Problems associated with noises from the central heating system.

  1. Joeathome

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    Gents,

    For the first time this year we flicked the timer switch to request central heating. The hot water has been working great all winter. Upon requesting central heating the radiators kicked in and provided heat. However after approx 15 mins the main fuse boxed tripped. After eliminating each fuse it would appear that the electrical problem is down to the central heating request. Turning the fuse box off again leaves me with electric but not heat. To verify this I kicked in the c.h. again 24 hr later and after 15 mins the same problem occurs. Doing this once more straight after the main fuse went straight away, I’m my mind suggesting that something is heating up and creating my issues. Any advice would be greatly appreciated, as the wife is requesting warmth.

    Joe
     
  2. ChrisR

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    Look around the pump and motorised valves for any water leaks. Can be in the boiler too. Doesn't have to be a leak so can be hard to find.

    Boiler is...?
     
  3. Joeathome

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    Chris,

    Thanks for the swift reply. I dont see any leaks or anything around the boiler, all clean and tidy.
    The boider is a Glow-worm, but for loking I dont see a model number.

    One more observation, is that upon kicking in the central heating, the water pump seems to get abnormally warm. Could this be the trouble? I put the heating on, the pump warms up until the point at which is trips the mains? Does this sound realistic or maybe im simply plan stupid..
     
  4. JohnD

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    "Main Fuse?" Is it really a thing with a bit of fuse wire in it, that melted and had to be replaced? Or is it a thing with a reset switch?

    What does the thing that tripped have written on it?

    Does it say B6/B16/B32

    Or 80A/100A?

    Or 30mA?

    Has it got a "Test" button on it?
     
  5. ChrisR

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    We still don't know if it's a Combi, or what. Model , or something, required.

    If it has an external pump,
    a) look for motorised valve(s) and water around there,
    b) disconnect pump and poer it from a plug and socket with the boiler off to see if fuse blows.
     
  6. fitz1

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    sounds like pump problem.
     
  7. Joeathome

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    John,

    (sorry for the plain language) our fuse box is not one that you need to string fuse wire across. It is protected by a RCD and has a reset switch, when it trips it simply flicks a switch. The main switch says 100A, 240V 30mA. I do not have a test button.
    When it electrics trip, I simply reset by switching the main switch off, then past tripped back to on again.

    Thanks for your interest with my issues.
     
  8. Joeathome

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    sorry, it not a combi boiler,
     
  9. Joeathome

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    Fritz, agree and respect your comment. I would never play with gas, Im compitent at DIY but dont mess with gas.
     
  10. Joeathome

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    chris, will try and come back to you, Just waiting for the wife to go shopping before I turn off electric supply. lol...
     
  11. simond

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    Assuming you have a 'fully pumped system' then the pump is going to have been running to supply your hot water during the summer months,before the time you requested the rads to come on.

    It sounds like your RCD is tripping and this could be the pump leaking to earth after it has been on a while, but why did it not trip on hot water provision?

    If the problem has only materialised after turning on CH then it is also possible that a cable's insulation is being compromised by heat in proximity to an underfloor CH pipe.

    These earth leakage faults can be difficult to trace without the right test equipment. If your system is not fully pumped then I would agree that without test equipment the best thing would be to change the pump and see if that cures the problem.

    If the system is fully pumped then the odds on being the pump become less likely and I would advise you to call in a suitably qualified electrician.
     
  12. JohnD

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    OK. the thing that tripped is an RCD which it sounds as if has been installed in place of a main switch. this can be done though it is not ideal as you lose all power in the vent of a fault on a single circuit.

    Electrical appliances with water (like immersion heaters, washing machines and kettles) are common cause of earth leakages that trip RCDs, as are oven elements when old.

    Because of the way your RCD has been installed, it can trip from the accumulation of several small leakages cross all the circuits.

    However it sounds quite likely that it is the boiler or pump in your case.

    An electrician could track down the circuit and appliance causing the trouble, but may not be able to repair it. That could need a heating engineer. I think you need such a person who is equipped to track down electrical earth leakage. It is quite likely related to a water leak.

    BTW:

    I bet you 50p that if you look at your RCD closely you will find that it does have a test button which you are supposed to press quarterly

    What make is your Consumer Unit ("fusebox") and RCD, and about how old? there may be a model or type on it or the MCBs.

    edited: simonds suggestion may be the quickest and cheapest one; if it turns out to be due to a faulty pump, changing it would save the cost if investigating.

    p.s. if the pump get hotter than the pipes connected to it, then it is jammed.
     
  13. Agile

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    """An electrician could track down the circuit and appliance causing the trouble, but may not be able to repair it. That could need a heating engineer. I think you need such a person who is equipped to track down electrical earth leakage. It is quite likely related to a water leak."""

    I would have thought any competent boiler engineer will have an earth leakage clamp meter and be fully competent to trace that kind of fault.

    As said before its most likely to be the pump anyway and just replacing it will almost certainly cure the fault.

    Tony
     
  14. ChrisR

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    Following SimonD's wise line of thought, that the fault appears to be related to the heating specifically, a motorised valve could be the culprit. Many only get power to their motor when CH is called for. Have a look for one, leaks and also smell it, honestly!
    Will look for a pic of one...
    This is the most common , some have a plastic head. You may have one or two valves with only two pipes going in not 3 like this one..??
    [​IMG]
     
  15. pgatsky

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    Had a similar problem recently and it turned out to be the pump which I changed.

    What I would suggest first though is to have a look at your programmer (if you have one) because these things can be delicate little buggers. If you do have one I suggest taking the cover off and looping the live to the HW circuit and then the CH circuit in turn and if the system stays on you can bet your bottom dollor it's actually the programmer tripping out the circuit, which is a lot less grief to replace.

    If its not the programmer it could well be the (3 port) mid position valve as the last thread indicated or the pump.
     

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