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Overloaded fused spur, opinion please

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?
Parents
  • May I suggest that you have increased the likelihood of the ring being overloaded?


    In nominal terms, of the 32 A available, only 13 could supply the two appliances with 19 left over. Now they can draw 26 A with only 6 left over.


    In real world terms, a 13 A BS 1362 fuse will sit there warming up an FCU or plug all day long at 20 A so the "nuisance tripping" would have been around, say 24 A. Similarly, that 32 A MCB will only start thinking about tripping at 37 A. The CCC (27 A for 2.5 mm² T&E in plaster) takes all of this into consideration. So whilst the clothes and dishes are being washed, you decide to have tea and toast. The MCB will cope with the extra 16 A or so for a few minutes. (Or is this where DZ's 500 W energy saving kettle becomes useful?)


    In answer to the question, spurs seem to proliferate as a house gets older. What I really don't like is spurs into the kitchen fed from an adjacent circuit.
Reply
  • May I suggest that you have increased the likelihood of the ring being overloaded?


    In nominal terms, of the 32 A available, only 13 could supply the two appliances with 19 left over. Now they can draw 26 A with only 6 left over.


    In real world terms, a 13 A BS 1362 fuse will sit there warming up an FCU or plug all day long at 20 A so the "nuisance tripping" would have been around, say 24 A. Similarly, that 32 A MCB will only start thinking about tripping at 37 A. The CCC (27 A for 2.5 mm² T&E in plaster) takes all of this into consideration. So whilst the clothes and dishes are being washed, you decide to have tea and toast. The MCB will cope with the extra 16 A or so for a few minutes. (Or is this where DZ's 500 W energy saving kettle becomes useful?)


    In answer to the question, spurs seem to proliferate as a house gets older. What I really don't like is spurs into the kitchen fed from an adjacent circuit.
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