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Cable required to install new induction hob on existing oven cable
Hi. We are looking to get a new induction hob replacing the old gas one.
The new hob is rated at 7.2kW. Rather than get a new wire to support the hob we were thinking of maybe using the existing oven wire to power both the new hob and oven.
The existing oven is rated as 5.2kW.
The existing gas hob runs to a separate box with a 3amp fuse in it so obviously can't be used for the new hob.
The cooker is on a separate wire from the RCD box which has a 32A type B RCD switch on it. There is a separate 45A cooker switch in the kitchen to isolate the feed to the cooker.
What we are unsure of though is the rating of the existing cable for the oven and we are going to get a professional to have a look.
In the meantime is there an easy way to find out what the rating is ? It’s a very thick grey cable (approx.. 15mm wide) and the wires inside it are made up of about 6 twisted copper wires. Total thickness of the combined copper is about 3-4mm. There’s no obvious markings on the outside casing of the wire.
Additionally, what rating of cable would I need to support both the oven and new hob ? I tried to work it out but then got confused with ‘diversity (?)’
I know I said we have a guy coming to look at it but this is so I sort of know what he is talking about !!
Update 22 Mar
Thanks for all the replies. The electrician has looked and recommended either a upgrade of the existing cable and fuse or a new separate cable from the fuse box to its own junction box behind the cupboards which does seem the easiest option as it can be routed outside rather than under floorboards.
3 Answers from MyBuilder Electricians
Best Answer
Sounds like you have a 6mm cable that should be able to handle 40amps without an issue.
Normally you would add the two items together so that's 12.4kw (12400 watts/230volts = 53amps). Ideally a 10mm cable from the fuseboard would be the best option, but when taking diversity into account you would normally allow for 10amps constant use, so that reduces the current to 43amps and then you would allow for around 30% of this (i.e. 30% of 43 amps = approx. 15amps) so a 6mm cable with a 32amp MXCB should be fine, but speak to your electrician and see what he says.
Answered 17th Mar 2014
Standard circuit for an oven and hob up to 15kw is a 6mm twin and earth with a 32A type B MCB, this allows for diversity (because your cooking appliance is not always using its full load all the time, due to it being thermostatically controlled)
Answered 13th Oct 2015
Using diversity a 6mm T+E cable run appropriately will be suitable to operate an oven and hob of rating up to 15KW as per on site guide guide appendix H4 as long as these are not over ruled by manufacturers fitting instructions.
Answered 17th Mar 2014
