Oven cable size

[garryb]

I've been doing some work on my father's park home, and the next job, now that I've changed the CU, is to run a dedicated circuit for a new shoulder-high built-in oven. He describes it as a '20 amp oven'. It hasn't arrived yet, but It's something like so...

'm sure most people will say 'use 6mm T&E', which I will most likely use, but if 4mm T&E is rated at 32 amp and the oven is 20amp, and the run is about 12m from oven to CU, is there anything in the regulations that would not permit the use of 4mm T&E for this circuit, with a 32 amp DP switch and a 32amp mcb?

Reason: just a tad easiuer to work with in the crawl space of the park home.

Thanks in advance for any input. Garry

[Andy Wade]

3950 W divided by 230 V gives you a design current for your circuit of just over 17 A. If it's on its own dedicated circuit a 20 A Type B MCB should be used.

No, and it's quite possible you could use 2.5mm^2 T&E, subject to checking the grouping and ambient temperature factors. Consulting Table

7.1 in the OSG establishes the max circuit length as 27 metres (limited by voltage drop). For 4mm^2 cable the max length is 43 m.

[Andrew McKay]

I'm not qualified to give advice on this so the following might not be suitable.

If routing a cable might be an issue then you might find that you could use a flexible butyl cable with multi-strand inners. Regular domestic ovens are invariably wired with this stuff from the local cooker outlet point. Examples shown on the following web page:

don't know the installation you are working with obviously, but I wouldn't personally choose to run the whole 12m from oven to CU. I'd run say 10m (ish) from the CU to a cooker outlet point as fixed wiring, then perhaps use butyl to run to the oven.

Andrew

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[Dave Plowman (News)]

Permanently connected cookers are usually wired in 6mm TW&E. I've never seen 6mm three core butyl. The outside of a cooker shouldn't get hot enough to require butyl. The only common use for it in a house is for the final connection to an immersion heater, or storage rad.

[garryb]

to be difficult to route. I was just asking myself why It *has* to be

6mm, and if the regs actually stipulated this, that was all.

Indeed, just to clarify things, this is what I was intending doing. It's about 12m in total, from the CU to the oven, including the DB switch and the outlet point.

And Andy, I did mean to write '20amp mcb' as apposed to 32 [honestly!], particularly if I use 4mm T&E.

cheers Garry

[Miketew]

Indeed, just to clarify things, this is what I was intending doing.

It's about 12m in total, from the CU to the oven, including the DB switch and the outlet point.

And Andy, I did mean to write '20amp mcb' as apposed to 32 [honestly!], particularly if I use 4mm T&E.

cheers Garry

The reason that cooker supplies are run in 6mm, is beacause even now lot of free standing or built in cookers have a four ring hob as well a an oven and some of the double ovens draw a fair current too. wiring i done to cope with the normal variations in appliances rather than on specific appliance and so have to cope with the expected maximum load For a 12 mtr run I would use 4mmsqd rahter than 2.4 to minimise vol drop under load and in case he decides to buy a bigger oven at som time and use a 20 or 24 amp breaker for it the final connection usually around a metre to your cooker connection unit can be in 2.5m heat proof cable which is still protected by a 20/24A breaker

-- Miketew