new oven v. utility room

[rpas150269]

Hello All,
I have just moved into a house that has a seperate utility room with it's own fuse box (rewirable 5A fuse + 20A fuse) for a strip light and two double sockets, only ever used for a washing machine with a 1.2kw cycle.

This fuse box is wired back to the main consumer unit using 18m of 6mm t+e cable and connected to a 32A mcb cleverly labelled "cooker". All other mcb's on the consumer unit are in use.

The kitchen has an old gas cooker which I want to replace with a Whirlpool electric double oven (the hob will remain gas) rated at a total power consumption of 2kw.

My question is, can I put a junction box halfway along the existing 6mm cable and safely bring a supply from there 2m into the kitchen for the oven (via ccu with no socket)....or....do I need to run 9m of new dedicated 6mm cable for the oven (via ccu) with it's own protection, which will mean installing a new small consumer unit.

And finally, because this is a new appliance in the kitchen, is all of this notifiable before I start, which ever way it gets done?

Many thanks in advance for any advice or suggestions.

 

[ban-all-sheds]

This fuse box is wired back to the main consumer unit using 18m of 6mm t+e cable and connected to a 32A mcb cleverly labelled "cooker".

£ to a p that's because it used to be a cooker circuit, and at some point it was re-purposed as the supply to the utility room. 6mm² is a PITA to use for sockets, FCUs etc (in fact I'm not sure if all makes of accessories will even accept 2 x 6mm²...), hence the small CU.

My question is, can I put a junction box halfway along the existing 6mm cable and safely bring a supply from there 2m into the kitchen for the oven (via ccu with no socket)

As long as the JB is accessible, you could (have fun getting 3 x 6mm² cables into it), but not to a CCU, as that is unfused - read the installation instructions for your cooker....

....or....do I need to run 9m of new dedicated 6mm cable for the oven (via ccu) with it's own protection, which will mean installing a new small consumer unit.

Why do you think you need 6mm² cable for a 2kW load?

And finally, because this is a new appliance in the kitchen, is all of this notifiable before I start, which ever way it gets done?

Replacing the cooker is not notifiable if it doesn't include the provision of any new fixed cabling a consumer unit - see Schedule 2B here.

Is there nowhere you can just plug the cooker in?

 

[rpas150269]

Thanks for the very speedy reply ban-all-sheds.

Yes, the JB is accessible and yes 3 x 6mm² into it = much fun, but you say not then into the unfused ccu. I am probably being a bit simple but wouldn’t the existing 32A mcb protect the new spur too?

Sorry I forgot to mention in my original post that the installation instructions are very limited and simply say “appliance must be connected to the power supply by means of an all pole disconnect switch with a min gap of 3mm”

The oven wire has no plug on the end so I assumed that a ccu and cable outlet would be required.

I also thought 6mm² would be needed to avoid mixing cable sizes on that circuit and not because the load necessarily required it (which it doesn’t).

I was unsure if the general rule of thumb for electric ovens was to have a dedicated radial with its own mcb, even with the load of only 2kw (hence my original question).

Having read up some more and discovering that 2.5mm² cable would be sufficient for the load, can I spur off the existing kitchen ring to a ccu in that size or do I still need to go back to the consumer unit with a dedicated 2.5mm² cable and an appropriate mcb?

If I put a 13A plug on the oven wire how do I to comply with the install instructions?

Oh dear!! Another load of questions……many thanks for your help with this.

 

[ban-all-sheds]

I am probably being a bit simple but wouldn’t the existing 32A mcb protect the new spur too?

Yes, but it won't protect the cable from the CCU to the oven, or the oven itself if that's relying on a 13A fuse..

Sorry I forgot to mention in my original post that the installation instructions are very limited and simply say “appliance must be connected to the power supply by means of an all pole disconnect switch with a min gap of 3mm”

The oven wire has no plug on the end so I assumed that a ccu and cable outlet would be required.

You can put a plug on, or connect it to a fused connection unit.

I also thought 6mm² would be needed to avoid mixing cable sizes on that circuit and not because the load necessarily required it (which it doesn’t).

It would, but then what do you do about the external cable to the oven? Use 6mm² for that as well?

Having read up some more and discovering that 2.5mm² cable would be sufficient for the load, can I spur off the existing kitchen ring to a ccu in that size or do I still need to go back to the consumer unit with a dedicated 2.5mm² cable and an appropriate mcb?

Actually, 1mm² would be OK for the load, but you'd have other compliance issues if you spurred off the kitchen ring with that.

If you want to spur off the ring, then go to an FCU with a 10/13A fuse, not a CCU, or to a socket. Either is notifiable, of course.

If I put a 13A plug on the oven wire how do I to comply with the install instructions?

A plug and socket are perfectly acceptable, and in compliance with the wiring regulations.

 

[Steve]

Your oven has an energy use of 2kw PER HOUR. The elements will actually be more like 5kw maximum (they cycle on and off on stats). This is the value you need. I wish Argos and the like would stop confusing folk by telling them stuff like this.

 

[ban-all-sheds]

 

[rpas150269]

Thanks again ban-all-sheds...

So, without wanting to labour the point...stick a 13A plug on the oven flex (which is 4mm² btw...does that make any difference in this case?) and plug it into a convenient socket on the ring main.

This sounds nice and easy so obviously I will now try and complicate it for myself a bit more!!

This is a double oven to go in a tower housing...for neatness I don't want the flex coming up through worktop or through the side of the cabinet to reach the nearest socket.

Does a socket under the worktop at the back of an adjacent cabinet satisfy accessibilty rules for easy isolation? If so, can I extend the ring main to incorporate it?

Many thanks once again.

 

[ban-all-sheds]

So, without wanting to labour the point...stick a 13A plug on the oven flex (which is 4mm² btw...does that make any difference in this case?)

Other than the fact that you won't be able to fit 4mm² cable into a plug and even if you could the fuse would probably blow the first time you turned the oven on because it isn't a 2kW load as you said, no, it makes no difference at all.....

 

[GaryMo]

Your oven has an energy use of 2kw PER HOUR. The elements will actually be more like 5kw maximum (they cycle on and off on stats). This is the value you need. I wish Argos and the like would stop confusing folk by telling them stuff like this.

Steve, a 2kW oven is just that - 2kW.
Now stop confusing folk by telling them stuff like this!

 

[rpas150269]

OK..very sorry to you ban-all-sheds for the timewasting and thanks Steve for pointing out my error....

I suppose I might have got away with blaming Ikea/Whirlpool....but when I opened the packaging fully and checked the rating plate it clearly states 4.3KW....doh!!

So, going back to my original question, I cannot tap into the existing 6mm² supply to the utility room, therefore, unless there are any other suggestions...

I will need a new (small) consumer unit, a conveniently located ccu, a cable outlet behind the cooker all hooked together in at least 2.5mm² cable, but perhaps better in 6mm² for future proofing and a new mcb...but what size mcb?

And of course all of this should be done by a trained professional who will give me a shiny new certificate afterwards.

 

[Steve]

Your oven has an energy use of 2kw PER HOUR. The elements will actually be more like 5kw maximum (they cycle on and off on stats). This is the value you need. I wish Argos and the like would stop confusing folk by telling them stuff like this.

Steve, a 2kW oven is just that - 2kW.
Now stop confusing folk by telling them stuff like this!

From the start, the OP told us it was a double oven. How many double ovens do you see with a rating of 2kw? Even a single oven has a rating of at least 2.5kw.

Its now commonplace, thanks to the energy efficiency people at big companies, for retailers and manufacturers to advertise the energy consumption of their appliances PER HOUR, but not the actual rating. The actual rating may sometimes only be found on the rating plate (and by ringing their helpline before purchase)! They further confuse matters for DIYers by telling them the rules in the instructions for European installations, which are totally different to ours. Its a minefield.

How is a DIYer meant to do a non-notifiable straight swap without knowing all this?

 

[GaryMo]

Steve, I just stated that a 2kW oven is a 2kW oven, not a 2kW PER HOUR oven.
I've yet to see an oven rated in kWh.

 

[ban-all-sheds]

From the start, the OP told us it was a double oven. How many double ovens do you see with a rating of 2kw? Even a single oven has a rating of at least 2.5kw.

Yup - I'll hold my hand up for that one - didn't spot that he'd said it was a double oven.

 

[ban-all-sheds]

I've yet to see an oven rated in kWh.

Energy class: A.
Energy consumption with a standard load, top and bottom heating: 0.79 kWh.
Energy consumption with a standard load, pastry function: 0.92 kWh.


Energy consumption main oven convection / forced air - / 0.79kWh
Energy consumption second oven convection / forced air 0.79kWh / -


TOP OVEN TECHNICAL SPECIFICATION:
Energy class 'A'.
Energy consumption 0.77kWh.
Net cavity volume 38 litres.
Medium size.
BOTTOM OVEN TECHNICAL SPECIFICATION:
Energy class 'B'.
Energy consumption 0.98kWh.
Net cavity volume 53 litres.
Medium size.

 

[GaryMo]

Are kWh ratings displayed on the rating plates or in the technical specification booklets?