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Overloaded fused spur, opinion please

Foffer
I was an industrial electrician and have now come across a domestic wiring issue where nothing appeared wrong with the installation.  Those with more experience will have probably have come across this many times.


The kitchen is supplied by a 2.5mm T&E ring fed from a B32 circuit breaker.  On this ring there is a 13A fused switched spur above the worktop feeding a double socket underneath via 2.5 T&E.  There is a washing machine and a dishwasher plugged into this double socket.  Every so often, I assume when both appliances are heating at the same time, the 13A fuse in the spur blows.  The cable supplying this double socket is in the wall so the current-carrying capacity appears to be 18.5A so this was probably being overloaded as well.


I understand that in the regs diversity covers some aspects of this situation, but this specific situation must occur often surely?  The switched spur gives the ability to switch off the appliance easily without having to pull it out in order to reach the switch, so is surely desirable?


In this case I have installed a second switched fused spur feeding a single socket and converted the other to a single.


Is this a common problem in kitchens?
  • 0
    I`ve always had a preference for a 20A DP switch on a ring (or a radial) for sockets feeding appliances from behind unless easily access, simply for a quick means of urgent disconnection from mains. OK the Regs do not require it but I feel it could, exceptionally, make a difference. I feel certain that the terminals are designed or tested for 32A but visibly they appear the same or similar to socket terminals in the brands I use so I feel happy to do that. I suspect that I could be gtaken to task for using them on a ring.


    As for Bod and his 20A JB, if it were say 25A JB I might be happy but I`m not aware of the existence of readily available ones.


    Just a note about the 3 x 2.5 conductors - a 4.0 radial strictly does not facilitate a 2.5 spur adding by the standard but it is encouraged in the guidance
  • 0
    perspicacious:
     if the 20 A DP switch supplies only a single socket-outlet, surely overload current protection is not necessary as per 433.3.1 (ii).


    Simply, are the INPUT/loop in terminals of a 20 A DP switch suitable for connection to a 32 A RFC irrespective of whatever is on the OUT terminals?


    Regards


    BOD


    This is the same question re Wago's ? Provided the terminals are sized for either 2x2.5 sq mm or 2x4 sq mm, surely there's not an issue here?


    And ...


    Does the 20 A DP switch need to be protected by a B20, C20 or D20 ... can it be protected by a B25? or B32 provided the load determines overload protection is not necessary? Imagine I have a machine with B20 breakers on the input, and I supply it from C25 or B32, is this OK to go through a 20 A DP switch or would I need a 25 A or 32 A DP switch ?


    Let's not get fault protection ("adiabatic"), and ADS (meet a disconnection time for safety), confused with protection against overload current.


  • 0
    ebee:

    Just a note about the 3 x 2.5 conductors - a 4.0 radial strictly does not facilitate a 2.5 spur adding by the standard but it is encouraged in the guidance


    It's also fair to say that the terminal performance in BS 1363 is a minimum requirement, a manufacturer may make their terminals suitable for other configurations that exceed BS 1363 requirements.


  • Former Community Member
    0 Former Community Member
    This is the same question re Wago's ? Provided the terminals are sized for either 2x2.5 sq mm or 2x4 sq mm, surely there's not an issue here?


    Until that is answered, there's no point in adding further asides unless a career in politics is looming?


    Again, simply, are the INPUT/loop in terminals of a 20 A DP switch suitable for connection to a 32 A RFC irrespective of whatever is on the OUT terminals?


    Regards


    BOD

  • 0
    perspicacious:
    This is the same question re Wago's ? Provided the terminals are sized for either 2x2.5 sq mm or 2x4 sq mm, surely there's not an issue here?


    Until that is answered, there's no point in adding further asides unless a career in politics is looming?


    Again, simply, are the INPUT/loop in terminals of a 20 A DP switch suitable for connection to a 32 A RFC irrespective of whatever is on the OUT terminals?


    Regards


    BOD

     


    Provided the manufacturer's information shows that the conductor sizes for the terminals are suitable for 2 x 2.5 or 2x 4 sq mm, I don't believe there's a problem. Many of them are suitable for the same conductor configurations as BS 1363 accessories.


    Is there any reason to conclude otherwise?


    So, I checked - BS EN 60669-1 is being used for switches now, not the general standard BS 5733.


    20 A switches are tested for temperature rise with a current of 25 A, which is broadly in line with the tests for BS 1363 accessories.


  • 0
    well Bod, they look to be.

    I imagine that manufacturers prefer to make higher production runs of less types of terminals  . say 6, 32 & 45 amps might be a start


    I mean terminals connecting adjacent cables and their ratings not the thru rating
  • Former Community Member
    0 Former Community Member
    Provided the manufacturer's information shows that the conductor sizes for the terminals are suitable for 2 x 2.5 or 2x 4 sq mm, I don't believe there's a problem. Many of them are suitable for the same conductor configurations as BS 1363 accessories.


    Is there any reason to conclude otherwise?


    Conclude as opposed to assume? When I contacted several manufacturers years ago asking if their 20 A DP switch input terminals were suitable for connection to a 32 A RFC, of the few that re[plied, their only comment was that the switch was made to BS 5733.


    Regards


    BOD
  • Former Community Member
    0 Former Community Member
    Wago 773-104

    Max 2,5 cable

    Terminal current rating 24 A


    However, Table 4D5 Method C for 2.5 cable gives 27 A


    27 A > 24 A


    Regards


    BOD
  • 0
    perspicacious:

    Wago 773-104

    Max 2,5 cable

    Terminal current rating 24 A


    However, Table 4D5 Method C for 2.5 cable gives 27 A


    27 A > 24 A


    Regards


    BOD


    Your point, I'm guessing, is that 773's are not always suitable for all circuits with 2.5 sq mm cables ... but that still doesn't answer RFC's.


    For 2.5/1.5 cable, Reference Methods 100, 102, A and C are permitted for 32 A mcb/RCBO, or 32 A BS 88-2 or 88-3 fuses.


    From 4D5 for 2.5, Reference Methods 100 and 102 are only 21 A, and Reference Method A is only 20 A !


    So is the 773 suitable for RFC's?


  • 0
    perspicacious:
    Provided the manufacturer's information shows that the conductor sizes for the terminals are suitable for 2 x 2.5 or 2x 4 sq mm, I don't believe there's a problem. Many of them are suitable for the same conductor configurations as BS 1363 accessories.


    Is there any reason to conclude otherwise?


    Conclude as opposed to assume? When I contacted several manufacturers years ago asking if their 20 A DP switch input terminals were suitable for connection to a 32 A RFC, of the few that re[plied, their only comment was that the switch was made to BS 5733.


    Regards


    BOD


    Hopefully, then BS EN 60669-1 will sort that out then, per earlier post?


    I agree, it's not made easy. The response you received was far from helpful.


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