Two ovens - how many circuits?

[WiringPeter]

I'm planning to get two single ovens and have been trying to find the best way to do the circuits. People seem to do it every way possible but I have doubts about some of the ways that they are done. The ovens I'm looking at are 16A appliances (max power is approx 14A), so I won't be plugging them into a socket.

My feeling is that two 16A radials would be best. Also, if one of the breakers trip then the other oven can still be used. The circuit(s) will be new so running two cables won't cost much more than one cable.

However, I hear about using a 32A breaker with a dual cooker connection unit and have seen this in people's homes. This seems to be the standard way of doing this but I can't understand how it's safe. There could be something simple that I'm missing though. The ovens (Bosch/NEF/Siemens) come with their own cable cable, and surely this cable would only be rated at 16A? If these cables have a 16A capacity and they go on a 32A breaker then surely that means that they aren't adequately protected? Is this really a safe (and regs compliant) way of doing it?

I think I know what is best but it really bugs me when I don't understand things. Equally, if my ovens were wired with a 32A breaker then I would worry about them unless somebody can explain how the cable won't go if there is a fault.

 

[SparkyChick]

Personally, I would go for two 16A radial circuits.

 

[telectrix]

the ovens are fixed loads, i.e they can't overload the cables, so overcurrent protection is not required. short circuit protection is provided by a 32A breaker, however, so it complies.

 

[Taylortwocities]

Either approach is valid, but I agree with @SparkyChick
Separate circuits is the better bet.

 

[Midwest]

Either or for me, depends if it’s an existing kitchen or it’s being extensively refurbished.

New circuits will require notification to local building control, if your feeling honest, or using a Scheme registered sparks.

This kitchen seems to be taking a long time, thought you would have it done for Xmas.

 

[Wilko]

Hi - Probably a million homes have a single circuit with 32A MCB installed for cooking. But you can have as many circuits as you feel like, of course.
There are some domestic cookers now that have very high power requirements and thinking about those beasts it may give reason to have one of the cables in 10mm. Much more fun .

 

[WiringPeter]

Either or for me, depends if it’s an existing kitchen or it’s being extensively refurbished.

New circuits will require notification to local building control, if your feeling honest, or using a Scheme registered sparks.

This kitchen seems to be taking a long time, thought you would have it done for Xmas.

Big refurb for me, so I think I'm decided on two circuits now as the cost difference is insignificant.

I should have it done for Xmas, just not this Xmas . I've been doing other rooms, and almost ready for the kitchen now.

 

[telectrix]

future proof it. `16mm SWA cleated along the worktop.

 

[WiringPeter]

future proof it. `16mm SWA cleated along the worktop.

I did consider 10mm for future proofing but I suspect it wouldn't go down the wall. 6mm will go down the wall quite easily but 10mm could turn into a much bigger job. I decided that I shouldn't be changing the kitchen for many years so I won't worry about the future too much. Two 16A radials (with the option of 20A breakers) + 32A for the Hob is still better than what most homes have.

 

[Toneyz]

future proof it. `16mm SWA cleated along the worktop.

Why are you trying to sell him your job leftovers?

 

[johnduffell]

is that 14A for each oven after diversity or that is the peak demand? You might find it is fine with both on a 16A supply with 2.5mm or maybe even 1.5mm cable depending on installation method etc.

 

[Toneyz]

Is the hob on another circuit?

 

[WiringPeter]

is that 14A for each oven after diversity or that is the peak demand? You might find it is fine with both on a 16A supply with 2.5mm or maybe even 1.5mm cable depending on installation method etc.

14A is from the spec sheet (max load without diversity). I can't remember the exact numbers, they were 3000-4000W.

 

[WiringPeter]

Is the hob on another circuit?

Yes, on its own.

 

[johnduffell]

14A is from the spec sheet (max load without diversity). I can't remember the exact numbers, they were 3000-4000W.

well I'm no electrician, but in that case the design current could be 14.2A which would be 1.5mm cable in most circumstances and the breaker could be 16A. There's no penalty for using a larger cable though, other than cost, and ease of installation. I would still recommend hard wired on a separate circuit though, as plugging two ovens into the socket circuit would take up a lot of the capacity.

 

[Taylortwocities]

as plugging two ovens into the socket circuit would take up a lot of the capacity.

And is not recommended by BS7671. See appendix 15 for details.

 

[WiringPeter]

well I'm no electrician, but in that case the design current could be 14.2A which would be 1.5mm cable in most circumstances and the breaker could be 16A. There's no penalty for using a larger cable though, other than cost, and ease of installation. I would still recommend hard wired on a separate circuit though, as plugging two ovens into the socket circuit would take up a lot of the capacity.

You may have the wrong idea. None of the cooking appliances will go on the circuit with the socket, partly for the reason you mentioned and partly because of regs. It would be either two 32A circuits (one for the hob and one for two ovens) or a 32A circuit and two 16A circuits. The sockets will be on a completely different (ring) circuit.

I won't go below 2.5mm as I want the potential for at 20A breakers in the future. There is some insulation too (<100mm).

 

[telectrix]

a 32A circuit for hob makes sense. as for the ovens, it's your choice whether to have a 32A circuit for both, or 2 x 16/20A circiuits for the ovens, either way complies. the question is almost as complex as whether I have a beer , cider, or scotch for breakfast. any one will comply with craving, but not necessarily in that order.

 

[johnduffell]

You may have the wrong idea.

I don't think so, as you say in the rest of your post you'd like to oversize the cable and ocpd beyond the design current which is fine, and separation of circuits to minimise inconvenience is a sensible principle. However with the talk of 10mm2 cable i thought it wise to post

 

[telectrix]

always best to have 2 circuits....... Pink Floyd and Black Sabbath, both loud, but not at the same time, accompanied with Roberts thick slice toast and a pint or 2 of Old Peculier. pure Heaven....