Diversity for a double oven

[Gringoking88]

Hi all,

Can I please check my understanding of diversity for cooker circuits and the installations of cookers.

My understanding is for cooker circuits (cooking appliances) is you take the first 10A then 30% of the remainder plus 5 A if you have a socket on the circuit. To me this means if I have a cooker rated at 3800W e.g. 16.5A (3800/230) I would be using 10A + (6.5A * .3 = 1.95A) so total demand for the cooker = (10A + 1.95A) 11.95A.

The first question is, is this correct and assuming it is, if I also have an hob rated at say 6000W or (6000W/230v) 26A do I class this as another 30% e.g. my cooker at 11.95A + (26A * .3 = 7.8A) giving a total circuit demand of (11.95A + 7.8A) 19.75A as its on the same circuit or is it again worked out the first 10A + 30% (10A + (16A * .3) = 14.8A which would give a total demand of (14.8A + 11.95A) 26.75A?

The last question is in terms of the cable used from the appliance to the connection (cooker connection unit or plug) do you use diversity for that too? For example, if my cooker is rated as above regardless of what else is on the circuit could I in effect use a 13amp plug to connect it as its apparent demand after diversity is 11.95A?

Many thanks in advance,

M

 

[Midwest]

The diversity formulae is correct, and quickly looking at your calculations, they look correct as well.

As regards your question on calculating the total load for the one appliance, but two separate parts, might bring some debate here.

Personally I would calculate the total load, as you have done. Both the oven and hob can operate, separately or independently, as opposed a single oven, which has a selector switch, which can only turn on main oven or grill for example.

If this is a hypothetical question, then we cannot refer to the manufacturers instructions, which can sometimes give some guidance.

If the manufacture states an appliance can be connected via a 13amp plug, it will say so. However, in this example I doubt that will be suggested. Appendix 15 recommends loads of cooking appliances etc, above 2kW should be connected via their own radial circuit, and not connected to an RFC.

Edit; reading your question as one appliance, like a range cooker e.g.

 

[Wilko]

Hi M - most UK appliances seem to have ratings done at 240V, so perhaps check. But you are playing safe at 230V anyway
1. Agree
2. I treat a 2nd appliance as needing another 10A up front, to get the bigger number overall. Again on the safe side.
3. I'd take note of manufacturer's instructions as @Midwest says. If they put a plug on it ok, but I would not fit one myself. If there is no plug and they ask for 13A fuse, I do the DP FCU as there's one less moving part.

 

[Octopus]

Unless there is a plug fitted you should always use a fused or fixed output imho.

 

[ruston]

3. I'd take note of manufacturer's instructions as @Midwest says. If they put a plug on it ok, but I would not fit one myself. I do the DP FCU as there's one less moving part.

As an aside . Howdens have a label fitted to the oven flex now not to fit a plug and state in the instructions to fit a double pole ....
I fitted a replacement one the other week were the oven connections were burnt to a crisp ,so I am assuming that they have had proplems with this.

 

[lurch]

Bs7671 states fixed appliances 2kw or more should have dedicated circuit. 32 amp circuit has stood the test of time and future proofs any upgrade from 2.4kw fan ovens.

Sorry off at a tangent to your original query....... but worth noting I feel.