Single Oven Install - Existing Wiring!

[jmwhooper]

I have a new oven, it's a 2.35kw single oven. The manual says it must be hard wired on an all poles isolating switch. This seems a bit over kill for a 2.35kw oven and the old one was wired on a 13amp plug. I could get a 45a switch with 13amp socket for trhe microwave like http://www.screwfix.com/p/45a-sw-13a-skt/17157

The double plug powered the old oven and a microwave, plus had a spur to power the extractor fan. It seems from a quick look at the consumer unit, that the oven plugs are on the same ring as the rest of the downstairs sockets.

Also, on taking out the existing oven the wiring looks a bit suspect. It has been there for a while but I'm wondering if we should get it tidied up. A new double gand plug was fitted above the oven compartment and this was wired from an old double gang box behind the oven using terminal blocks wrapped in electrical tape. You can see in the pic below the top part is the upper shelf where the microwave sat with the new double socket and below the shelf is the oven compartment with the old back box and wiring to the new plug.

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• jmwhooper
• 6 Sep 2011
• 1

Should the terminal blocks be replaced with a J box or something else or it is ok to leave it?

 

[ban-all-sheds]

1) Guidance in the current Wiring Regulations is that an oven over 2kW should be on a dedicated radial circuit.

2) The ring has not been extended to supply that socket, it's a spur, which means you must not have another spur from it.

3) The cable supplying it looks too small.

4) The work needed to rectify it is notifiable, so it would be a lot easier and cheaper to get an electrician.

 

[jmwhooper]

Thanks, you confirmed my fears.

I think a new oven radial is possible so longs we can hide the first couple of metres of the new mains wiring behind the kitchen cabinets, before we reach the floorboards and can then run it under the floor and up to the CU.

If this is allowed I can get an electrician in to do it and it shouldn't involve any chasing of walls or destructive changes.

 

[ericmark]

What is required will depend on what you already have and how much the electrician you find wants to stick to the rule book.

Since over 2kW it should be on a dedicated circuit and if buried in the wall either Ali-tube cable or a RCD is required. Since dedicated it does not need to be RCD protected at the plug but it would need marking oven only.

Many electricians shy away from using Ali-tube cable as it is hard to buy short lengths and often one has to buy it by the role and it's expensive.

Depends on how the manufacturers instructions are worded you may get away with just plug and socket or you may need an isolator switch as well. Likely an electrician would use a FCU (fused connection unit).

Under floor one has to consider rodent attack. May even need SWA cable but the electrician will advise on which method is best and which is cheapest.

 

[jmwhooper]

Had another look at the wiring last night. Half of the kithen is an extension and I'm pretty sure that until our new CU was fitted the sockets in the extension were on their own circuit with a separate fuse on the old fuse box.

Now it seems that the RCD in the new CU for the downstairs sockets isolates all sockets in the kitchen at the same time with no separate circuit. Is it possible that the electrician could have combined them onto a single RCD when installing the new CU?

If so we now have a single 32A RCD for the kitchen and all other downstairs sockets. In the kitchen we have the usual; tumble dryer, washing machine, dishwasher, oven, gas hob, extractor fan, microwave. Seems like a lot of load for one circuit.

Would it be wise to ask the electrician who does the oven radial to separate these 2 circuits again, at least then all the main appliances in the kitchen are plugged into the extension end and won't share the circuit with the other downstairs sockets any more.