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Discuss 20amp DP switch or fcu for 3kw heater? in the Electrical Forum area at ElectrciansForums.co.uk.

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  1. Gavin John Hyde
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    Gavin John Hyde Electrician's Arms

    Location:
    Somerset
    Business Name:
    Sulis Electrical Services Ltd
    Been having a debate with a mate this afternoon about a circuit in his house.
    The circuit is a radial with 16 amp mcb that was previously used to feed his immersion heater that was removed when a boiler was fitted- he doesn't have a radiator in the conservatory and cant afford one to be fitted. he is going to divert the cable from his kitchen where the Cu is out the wall into the conservatory. Then get the electricians at his work to give it the once over.
    He is of the view the way to wire a 3kw electric wall mounted heater in is to use a 13 amp FCU. I am saying no, have to use a DP 20 amp switch fed from breaker. 3kw is just over 13 amp 3000/230 = 13.04 amps and given the circuit is a radial fed with a 16 amp breaker with nothing else on it, the fcu is doing nothing of use and is un-necessary. Also adding 3kw heaters onto a ring will likely overload it.
    This is the bit that then made me chuckle, he has recently been on a job - hes a surveyor for social housing outfit where the electricians have put 2 separate 3kw heaters on 13 amp fcu's joined to the rfc during refurbishments of some social housing units. He seemed oblivious to the issue of having a couple of 3kw heaters plus the other household appliances on the one 32 amp ring!
    It makes you wonder how there haven't been more grenfell fires if the supposed people in charge of quality and standards sign off things like this. Of course given the low power draw of a lot of modern stuff its possible that the circuit might take the 2 heaters in the social housing example, but you don't know if the tenant will plug hoovers, irons and god knows what else in when the heating is on max.
     
  2. westward10
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    westward10 In echoed steps I walk across an empty dream. Electrician's Arms

    Location:
    Northamptonshire
    Dub pole switch, maybe an fcu 30 yrs ago when they could actually cope with 13A but not the tat you get now.
     
    • Agree Agree x 5
  3. Gavin John Hyde
    Offline

    Gavin John Hyde Electrician's Arms

    Location:
    Somerset
    Business Name:
    Sulis Electrical Services Ltd
    I think some of the better quality fcus would hold a good load but i have seen far too many cheap accessories that seem to have ever thinning pieces of metal in them, You also dont know anymore where a lot of the stuff is made as people cash in on the names and make crap stuff.
     
  4. Vortigern
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    Vortigern Electrician's Arms

    Location:
    England
    Business Name:
    F.H. Electrical
    Too often I have come across 13 FCU overheating/melting, serving 3kw heaters/immersion. Double pole switch for me every time.
     
    • Agree Agree x 6
  5. spinlondon
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    spinlondon Trusted Advisor

    Location:
    Harlow Essex
    20A DP switch.
     
    • Agree Agree x 2
  6. Wilko
    Offline

    Wilko Electrician's Arms

    Location:
    Berkshire
    Business Name:
    Wilko Electrics
    If the heater came with a 3 pin plug, I'd use it. If no plug, then I'm not a fan of 3kW loads in FCU either. And just be be a complete Abacus, the 3kW heater will likely be rated that at 240V :) .
     
    • Agree Agree x 1
  7. ashrow
    Offline

    ashrow Active EF Member

    Location:
    Bedfordshire
    I have installed many electric UFH systems where the total load is around 12 amps and had many issues over the months after of the sw/f/spur over heating and welding the fuse in or just failing.... 20 amp dp switch all the time.
     
    • Informative Informative x 2
    • Agree Agree x 1
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