Induction Hob Isolator Rating

I am having a Siemens induction hob fitted to my new kitchen which has a maximum load rating of 7400Kw. From my calculations at a nominal 240v this is approx 30.8 amp.
A 6.0mm T&E has been installed for this hob supplied by a 32 amp RCD.
My question is whether a 32A DP isolator is sufficient or if I should spec a 45A isolator?
The only reason for asking is that MK don't appear to do a 1 gang 45 amp isolator only 2 gang and all the rest of the isolators are 1 gang 20amp switches. I know I could get another make but I prefer to use MK

There is obviously a diversity factor to apply in that its unlikely all heating elements will be on simultaneously but that is possible. The crazy thing is that I am told by the kitchen fitters that these hobs come with a 4mm?? flex fitted and not a direct supply cable connection so it leaves a 4mm flex protected by a 32 amp RCD!!
Am I OK with a 32Amp isolator or should I fit an alternative 1 gang 45 amp DP switch?
Many thanks
Fozzie

FozzieBear said:

My question is whether a 32A DP isolator is sufficient or if I should spec a 45A isolator?

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As you have a 32A MCB, then anything 32A or above will do. 45A is usual.

I know I could get another make but I prefer to use MK

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If that is to match other accessories, then fair enough.
If that is not the reason, then it is not a valid reason.

There is obviously a diversity factor to apply in that its unlikely all heating elements will be on simultaneously but that is possible. The crazy thing is that I am told by the kitchen fitters that these hobs come with a 4mm?? flex fitted and not a direct supply cable connection so it leaves a 4mm flex protected by a 32 amp RCD!!

Click to expand...

4mm² is adequate.
6mm² cable is used because it is used and that is what people use. It is a legacy of when it was necessary with rewireable fuses.

EFLImpudence said:

As you have a 32A MCB, then anything 32A or above will do. 45A is usual.


If that is to match other accessories, then fair enough.
If that is not the reason, then it is not a valid reason.


4mm² is adequate.
6mm² cable is used because it is used and that is what people use. It is a legacy of when it was necessary with rewireable fuses.

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Many thanks for quick reply,
The oven and hob isolators are to be located in the backs of the cupboards using 47mm plasterboard boxes. Single boxes have cable entry top and bottom but as the MK 45 amp isolators are two gang it means the boxes need to be rotated 90 degrees meaning cable entry is then in the side which is not practical in the circumstance. I will have to use another make of 45 amp isolator that fits in a single box. Thank You Again
Fozzie

As you don't need isolators at all you could get rid of them. Or use one isolator for both.

winston1 said:

As you don't need isolators at all you could get rid of them. Or use one isolator for both.

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Thanks Winston. I appreciate the response but don't want to get into the debate about whether an isolator is required for an oven/hob as that discussion has raged on these forums numerous times. As I understand it it is best practice and the kitchen company fitting the kitchen and the appliances require and isolator in order to do their final connections.
For clarification there are 4 separate ovens each with their own 4.0mm radial on a 16A RCD and an induction hob in the island with a 6.0mm feed from a 32A RCD
If I didn't have an isolator(s) I would still have to have cooker outlet/appliance connection unit in order to join the supply cables to the flexes on the appliances so for a few more £ why not fit an isolator rather than a connection unit?
Many thanks
Fozzie

FozzieBear said:

As I understand it it is best practice and the kitchen company fitting the kitchen and the appliances require and isolator in order to do their final connections.

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That is rubbish. They can isolate at the CU. And that is what I would do even if there a separate local isolator. After you have to remove the local isolator to make the connections and the input will still be live near where you are working.

FozzieBear said:

For clarification there are 4 separate ovens each with their own 4.0mm radial on a 16A RCD and an induction hob in the island with a 6.0mm feed from a 32A RCD

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I assume you mean MCBs not RCD's. Why are you using 4mm cable on a 16A circuit? 2.5mm is more than enough. 1.5mm is also OK.

"I will have to use another make of 45 amp isolator that fits in a single box. "

https://www.toolstation.com/click-mode-45a-dp-switch/p10475