Relocating an electric oven...

[barki]

Hello all

I'm DIY replacing our entire kitchen - This will be the 4th time I've done a kitchen on my own so I'm confident with most of it.

However, this time is the first time that I'm actually moving the location of the oven. Until now I've just used the existing electrical infrastructure and switched the oven for a new one in the same or nearly the same place.

I just wanted to ask how to do this really. I'll write out my plan cowboy style, and see if anyone shouts at me...



Ok;

Existing Infrastructure:

Consumer unit is only a couple of meters away, in the next room.

There is a separate MCB for the oven/hob. The whole unit is on 100A but I can't see the specific rating of the Oven MCB - It's just labelled "61/B32" (is this 32A?).

The Oven/hob MCB is not on the RCB protected part of the unit - Google tells me this is no problem.

In the kitchen, the oven and hob are both fed from a single intermediate switch on the wall. With a nice chunky cable running to it - I find it difficult to tell the sizes of cable. Including the grey sheath it looks about 20mm across.


The Room:

Hob - The new hob will be in the same location as the existing hob.

Oven - The replacement oven will be a double unit housed in a tall cupboard and situated in the position where that brown handbag is in the photo.

Both walls are solid walls.

Picture below;

My cowboy plan & Appliance loads;

I was planning on taking a spur from the existing intermediate switch and running a channel along the wall and around the corner to the new location where I'd install a second intermediate switch and a short run to a socket which would be hidden behind the oven / tall cabinet. In both locations I'd be putting in 45A switches. One for hob, around the corner for oven.

I've bought some nice deeper socket back boxes to help with this - but not the cable yet.

Obviously, since I can't identify the rating of the MCB or the gauge of the existing cable, I'm a little worried about melting wires......especially since the load will be going up a little.....

The existing hob has a rating of 5.9kW , new hob has a rating of 6.2kW

The existing oven has a rating of 4.12kW ; new oven has a rating of "4.4 - 4.8 kW"








A couple of questions that jump to mind;


Do I need to have an electrician sign off my additional spur?

How can I work out he gauge of the existing cable, and therefore if the new load is too great? Can measuring the grey sheath be a decent indicator? (its black/red stuff by the way...house is 2001 build).

Am I missing anything that may make this unsafe?






Cheers very much in advance to anyone who can offer help

Tom

 

[omega015]

Yeah it appears your oven is currently on a 32amp mcb. 20mm could be 16mm but that sounds like a beefy cable to me, I would get this verified by someone else. Maybe get an offcut of various sizes so you can gauge this better, or isolate the mains and have a look behind the switch. If its not much trouble running a fresh appropriately rated cable from the CU would be best (given the age of your cable) and avoids spurs etc.. (which have their own current limits) but that almost certainly would require signing off/notifiable work. In which case, maybe getting a sparky in to do those would be the best thing to do.

In order to know if the oven/hob is not going to melt the cable we really need to know the thickness of it (and if its in good condition which would require testing with an appropriate tester).

 

[EFLImpudence]

I was planning on taking a spur from the existing intermediate switch and running a channel along the wall and around the corner to the new location where I'd install a second intermediate switch and a short run to a socket which would be hidden behind the oven

There should be an outlet plate under the hob.

If not, fit a dual outlet plate and run one cable to new position and there fit a single outlet plate.
https://www.tlc-direct.co.uk/Products/AA45DCOP.html
If you bury it, it should be RCD protected so just run it clipped to the wall or clipped in an unfilled channel under the worktop.

No need for another switch.

Do I need to have an electrician sign off my additional spur?

No, but you should test it.

How can I work out he gauge of the existing cable, and therefore if the new load is too great? Can measuring the grey sheath be a decent indicator? (its black/red stuff by the way...house is 2001 build).

//www.diynot.com/wiki/Electrics:flatpvccables

Buy the same size - likely 6mm².
It will be Brown and Blue. It matters not; it is the copper coloured bit that matters.

 

[JohnD]

It might be 6mm, which, depending on how it is run, is probably ample for 32A.

And 32A is enough for your hob and oven.

See "Diversity"
https://www.tlc-direct.co.uk/Book/6.5.2.htm

p.s.
too slow!

A good aid to sizing cables is to buy a few cable clips in common sizes.
https://www.tlc-direct.co.uk/Main_Index/Cable_Accessories_Index/Cable_Clips_1/index.html
In your house you will probably mostly find 1.5mm, 2.5mm and 6mm. You might have 16mm if there is an electric shower.

You may not often see 1mm, 4mm or 10mm, but you will find they are not quite right for the more common clips, and you will see the difference if you compare them.

Buy boxes of clips if you have much to do, but hardware stores often sell small quantities in plastic bags at exorbitant prices.

 

[JohnW2]

It might be 6mm, which, depending on how it is run, is probably ample for 32A.

Indeed, but if it really is anything approaching 20mm wide, it's going to be bigger than 6mm² (10mm², or even 16mm² - which would seem pretty unlikely) hence far meatier than needed.

Kind Regards, John

 

[omega015]

His hob and oven could potentially be 11 kw (about 45a?) although he's been running potentially about 10 kw (40a) with the existing appliances. Although assuming he hasn't tripped the 32a breaker, then he hasn't had it all on full at the same time (or my maths is off tonight)

 

[JohnW2]

His hob and oven could potentially be 11 kw (about 45a?) although he's been running potentially about 10 kw (40a) with the existing appliances. Although assuming he hasn't tripped the 32a breaker, then he hasn't had it all on full at the same time (or my maths is off tonight)

Even a 45A (max) cooker only counts as a 20.5A load after diversity, so there would definitely not be expected to be any problem on a 32A circuit.

In fact, when diversity is taken into account, a 32A circuit can support cooking appliance load(s) up to a total of about 19kW.

Kind Regards, John

 

[omega015]

10a + 30% for cooking appliances? I never liked the idea of diversity on certain circuits.

 

[JohnD]

I agree the cooker Diversity rules seem rather optimistic, but 32A does seem to work, even on Christmas day.

If it turns out to be necessary, and the OP's cable and method are up to it, the MCB could be upgraded to 40A, but that should be professionally done.

Please have a look at the diversity link I posted.

BTW if the OP's cable really is oversize, it may be quite difficult to get it into the terminals and squash it neatly into the backbox.

 

[EFLImpudence]

Or, he could use 4mm² cable

 

[JohnW2]

10a + 30% for cooking appliances? I never liked the idea of diversity on certain circuits.

Well, it's obviously not appropriate for some types of circuit, but for domestic cooking appliance circuits it seems to work fine. In commercial kitchens, diversity is not so generous, which makes sense.

A year or three ago, a friend of mine who was very sceptical about diversity decided to do the experiment. He put pans full of water on all the hob plates, then turned them all on "full", together with whatever oven(s)/grills he could also simultaneously turn of "full". He measured the energy consumption (from 'everything cold - hence the worst-case scenario) using a clamp-on probe and had to take on a rather sheepish demeanour when, contrary to what he was expecting/hoping to 'prove', the average consumption over a period (I think 30 mins, maybe an hour) proved to actually appreciably less than would be anticipated by the standard diversity calculation!

Kind Regards, John

 

[JohnW2]

Or, he could use 4mm² cable

He probably could - but he would presumably prefer to use what has already been installed - which sounds as if it is (perhaps far) more than adequate.

Kind Regards, John

 

[barki]

Cheers guys loads of useful help there

I love this site!!