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I'm trying to calculate and chose the correct cable to rewire my kitchen. The general vibe for creating final ring circuits is to use 2.5mm Twin & Earth apart from the cooker.

I've been reading up the regs and I have a different answer:

List of appliances in the kitchen:

Kitchen appliances

Total nominal current (forgetting the cooker) = 44.08A

Diversity = 100% x Hungriest appliance + 40% x remaining appliances

= 13.04 + 12.416 = 25.456A

Now consult the table on how the cables are installed:

Regs Table

Mine will be installed in a drywall with insulation = 18.5 amps

..Which is not enough, so am I missing something?

Edit: I'm based in the United Kingdom

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  • I am not sure what your local codes are but on the other side of the pond 2ea 20 amp dedicated circuits are required, usually dishwashers and ovens are on there own circuit. Adding up all the devices will give a maximum possible load that is never used one example is how often are all the burners on a stove / oven (cooker?) on at the same time ? if they are all on they are usually on full for a shorter time so with multiple connected loads derate of the wire size is allowed. If all these devices are cord connected running 2 20 Amp circuits would take care of the problem. 85W for a fridge?
    – Ed Beal
    May 4, 2017 at 13:07
  • Thanks Ed, 85w is what the data badge in the fridge said. You've made me doubt myself, I'll double check.
    – cworner1
    May 4, 2017 at 15:33
  • With a ring circuit you technically have two conductors from the panel to the same circuit. The idea is they self balance. Bleh, ring circuits. Seem like a good way to burn your house down.
    – RomaH
    May 5, 2017 at 14:20

1 Answer 1

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A ring circuit makes a full loop from the distribution panel through all receptacles. What you have is two leads from the panel through all outlets. The total combined load the circuit could support is your 18.5A * 2 = 37A. The idea is that if you are using a device that draws 3A on the left-hand side, the next device you use would balance the load by pulling 3A from the right-hand side of the circuit.

So I do think you have sized the right cable.


Let me try to argue for the radial circuit, if you have room to do it.

Ring circuits can work but your supposed to balance receptacles around the circuit; that is, not all your receptacles should be in the first few metres of the circuit with the remain run just needed to complete the ring. If the distribution of appliances is not balanced that could lead to the load not balanced and one section of the ring with a heavier load than it should be carrying, heating your mains until it started a fire.

A fault in the mains could lead to one of the leads from the panel supporting the entire load of the circuit, suddenly you have the 37A supported on a radial circuit, with a 30A breaker, and a cable rated for only 18.5A. Again, overheating and fire. A fault in a ring circuit may not be all that noticeable.

With a radial circuit, if there is a fault. The most likely result is a blown breaker or the circuit stop working.

There are some arguments about electrical noise induced by full ring. Not sure what the reality of this issue is.

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