Ceramic Hob

jimmo

My ceramic hob made some dramatic noises the other day and the upshot is that whilst 3 of the cooking rings work normally the fourth ring heats up when it is switched off (i.e. cooker power is on at the wall isolator switch but the control knob for the individual cooker ring is in the off position). However if I turn the offending control knob on, the offending cooker ring switches off.
My initial thoughts were to look for an "off the shelf" replacement and fit it myself the same day.
My thinking was that as a like for like replacement I could do it myself (without offending Part P) by disconnecting the 10mm twin and earth cable from the existing hob and connecting it to the new hob.
First stop, Comet and, low and behold, every hob on display comes complete with a fitted 4 core and earth (2*L and 2*N). The round cable is approx 15mm diameter.
My understanding is that there are 2 separate circuits within hobs, each serving 2 cooker rings and so I feel quite confident that I understand why the new round cable is fitted.
I also know that the existing 10mm twin and earth feeding the hob is contained within oval (or flat) conduit within the kitchen wall and there is no way that a 15mm dia round cable will fit in there.
My thoughts are that I need to chase out the existing wiring from the isolator switch to the hob, put in new round conduit and the new round cable and connect the 2 Ls to the L on the isolator and the 2 Ns to the N on the isolator.
It makes sense to me but I would be grateful for any criticisms or approvals.

fluffpot

It's more usual to have a cooker outlet behind the hob/oven and wire the flex into there rather than straight to the isolator. This means the hob can be changed easily.
http://www.tlc-direct.co.uk/Products/MKK5045.html

You also need to check that the cables are the correct size for the hob - what is it's total kW rating and the size of the circuit breaker in the consumer unit?
The fact that your hob works when the isolator is off, suggests there may be a problem with the wiring in here too.

jimmo

Thanks for taking the trouble to reply.
Actually, as no-one had replied by the time I was ready to start work this morning I just got on with it, as planned, and used the new hob to cook this evening.