ELECTRIC COOKER/HOB


Postby denboy09 » Sun Jun 27, 2010 10:58 am

I want to replace my electric cooker/hob with new ones (hob is both propane & electric) both are being feed by a 45a MCB and 6mm cable. The new appliance ratings are "oven = 2.2Kw + hob = 7.6Kw". Had a elecrtician give me a awful quote . he says i need to have the 6mm cable replaced with a 10mm one. Does any one have a idea how to get round changing the cable. Consumer is around 11m away so it ripping up brand new carpets and floorboards. I could ask comet to change the hob for a 6Kw one. Wife wont be happy with that idea :idea:
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Postby ericmark » Mon Jun 28, 2010 3:39 pm

The cable size has to match the overload device not the cooker. So taking it to a ridiculous point you could feed a cooker with 2.5mm cable and a 16A overload even though with all rings in use it would trip. This would not be of much as you could only use one ring.

However a 32A supply on a 6mm cable would allow 7360 watt which likely would run 3 rings flat out as long as you want.
However near every ring will not run flat out but will switch on and off so we call this diversity and the 7360W will likely run all you have without any problem.

However induction hobs are different as they have cooling fans and if they trip they may over heat and same with some built in ovens.

The main thing is how do you have a 45A MCB and 6mm cable? If clipped direct i.e you can see the cable it is not buried in the wall you may have 45A with 6mm and also if the cable is rated at 90 degs C and not the normal 70 degs C you may still be within the allowance 58A x 0.78 = 45A when buried in a wall.

So although unlikely the 6mm cable may be OK with 45A MCB. And if not then using a 32A MCB would still likely run all you have and unless there is a problem with cooling fans if it trips can't see a problem. And even then I would think there must be a safety margin in case the whole power fails anyway.

If it were me and the 45A MCB is too big and as I have said it may be OK. But if it was I would change to 32A MCB and warn you it may trip at Christmas which is about only time you are likely to use all rings and oven together.
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Postby ericmark » Mon Jun 28, 2010 3:40 pm

Repeat post deleted.
Last edited by ericmark on Tue Jun 29, 2010 11:18 am, edited 1 time in total.
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Postby denboy09 » Mon Jun 28, 2010 6:35 pm

Thanks am begining to understand the concept. Checked consumer unit again and i got it wrong first time the 45amp mcb is for 10mm cable to the electric shower. So you are saying i am ok with 32amp mcb feeding the 6mm which in turn feeds 7.6k ceramic hob & a 2.2 electric fan oven. Did notice the cooker switch also has a 13amp socket so with diversity the 6mm cable and 32mcb would be ok?
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Postby ericmark » Tue Jun 29, 2010 5:23 pm

Yes I would think unless a induction hob it will be OK 9.8Kw = 42.6A which is of course well above the 32A available but the MCB will not trip the second it exceeds 32A there is a curve time against current and looking at curve it will take over an hour to get to tripping point and by that time the simmerstats will be clicking off and on so you will not be drawing 42.6A anyway.

If you had an induction hob because of the boost function there may be more of a problem but unlikely even then you would have a real problem.

How many times do you use all four hobs and switch them all on together will cold pots on them all and also switch on oven at the same time?

Problem with many houses is they don't have RCD's and not only would it need a new cable you may also need new consumer unit to house RCD so in the main not a good route.
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