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I've just spent an hour getting bogged down with the maths trying to work out diversity for 2 cooking appliances on the same circuit (32A MCB) and same isolation switch,

I thought I would give my workings so others can use it as I wonder if some just assume you can still use the 15kW maximum, which you can't.

In fact the the maximum for 1 cooking appliance seems to be 19.3kW (as long as the switch doesn't incorporate a socket), however, on with 2 appliances....

Diversity is 10A plus 30% of the remaining amps (plus 5A if a socket) but this is for each appliance even if on the same circuit.

Therefore for an oven

[10A + ( 0.3 x Q) ] + [10A + (0.3 x Q) ] = 32A

we don't know the maximum size of the cooker and hob (that's what we're trying to find out), so I have just used the letter Q (Q is the current of either the hob or cooker minus the 10A)

Therefore

The above equation is the same as

2 x (10A + 0.3Q) = 32A

20A + 0.6Q = 32A

0.6Q = 12A

Q = 20A

We know that each appliance is allowed to draw a max current of Q +10A, which is 30A. There are 2 of them so 60A.

60A x 230w = 13.8kW (approx)

Therefore maximum combined power for 2 appliances on same circuit with same switch (without a single socket) is

I think you'll all have had enough now, but the maths works out as a maximum combined power of

If you haven't guessed. I have the day off work!

ps.. would you check the maths please @happysteve

I thought I would give my workings so others can use it as I wonder if some just assume you can still use the 15kW maximum, which you can't.

In fact the the maximum for 1 cooking appliance seems to be 19.3kW (as long as the switch doesn't incorporate a socket), however, on with 2 appliances....

Diversity is 10A plus 30% of the remaining amps (plus 5A if a socket) but this is for each appliance even if on the same circuit.

Therefore for an oven

**and**electric hob the maximum current we have is:[10A + ( 0.3 x Q) ] + [10A + (0.3 x Q) ] = 32A

we don't know the maximum size of the cooker and hob (that's what we're trying to find out), so I have just used the letter Q (Q is the current of either the hob or cooker minus the 10A)

Therefore

The above equation is the same as

2 x (10A + 0.3Q) = 32A

20A + 0.6Q = 32A

0.6Q = 12A

Q = 20A

We know that each appliance is allowed to draw a max current of Q +10A, which is 30A. There are 2 of them so 60A.

60A x 230w = 13.8kW (approx)

Therefore maximum combined power for 2 appliances on same circuit with same switch (without a single socket) is

**13.8kW**.I think you'll all have had enough now, but the maths works out as a maximum combined power of

**10.4kW**allowed if the cooker switch incorporates a single socket. (Equation is 25A + 0.6Q = 32A)If you haven't guessed. I have the day off work!

ps.. would you check the maths please @happysteve