Help with cooker cable(s)

[bananaman]

Any help with the following situation would be greatly appreciated. I'll be as brief as I can:

I'm having a new kitchen installed, including two new ovens. These are specified as:

Oven1: 3.68KW "total connected load". Conventional oven
Oven2: 3.60KW"total connected load". Combination uwave and oven

Prior to planning this, I had an electrician renew the consumer unit and provide a single cooker MCB slot, ready and waiting for the new cable runs from thre consumer unit to the kitchen ovens. This is a 50A MCB.

The kitchen fitter has surveyed the job and is now maintaining the following. I'd appreciate your opinions on the following statements:

1. I cannot supply two ovens in the kitchen from a single cable from the consumer unit - whether it is 6mm2 or 10mm2 cable. I will need two breakers at the CU and two cables running to the kitchen. One for each oven.

2. Run a 6mm2 cable from the CU for the conventional oven and run a separate 2.5mm2 cable from the CU to the uwave combination oven.

3. As I cannot supply both appliances from a single cable, however big, I will need to have the 50A breaker swapped for a smaller rating and of course, have an extra one fitted too.

Can any of this possibly be right?

Thanks in anticipation.

 

[sparkybird]

Each oven is around 16A. so the idea way would be to have 2 x 16 or 20A circuits and isolators for each one.

However, I can't see why you cant I have 1 x 10mm (50A) circuit suppliying the isolators and then each appliance. Except that the supply to each oven would need to be run in 10mm - this might be a problem if the connections aren't roomy. Plus terminating 2 x 10mm into a 1 gang back box is a right giggle.
Each isolator and outlet would need to be rated at 50A. Also check the manufacturers info as it might state 'must be supplied by a 16A circuit'.


A better solution (if there's space) might be to use the 50A circuit to supply a mini CU, then feed each oven in 2.5mm and a 16/20A breaker.

Hope this helps

SB

Oops, just re-read your post and realised that the 10mm cable/50A circuit isn't in place as yet! SO your best bet is to run 2 separate circuits 2.5mm would be fine for both, but if you want to future proof then use 6mm for one. Both would require a different sized breaker in the board. Not sure why doing this is a problem? Is there not a spare way in the board?

Either way, you'll need a sparks, not a kitchen fitter (unless he/she is a sparks of course!)

 

[ban-all-sheds]

Plus terminating 2 x 10mm into a 1 gang back box is a right giggle.

 

[sparkybird]

Ban - yes that's a good solution for the outlet, but not for the isolators!

Unless you'd have both ovens on 1 isolator? Even then with 1 less 10mm cable, it's still a PITA

Hey that pics looks like the 2 cables out the bottom are smaller than the one in the top! Can't be right? How are they (fuse) protected?

 

[ban-all-sheds]

Unless you'd have both ovens on 1 isolator?

Why not?

Hey that pics looks like the 2 cables out the bottom are smaller than the one in the top! Can't be right? How are they (fuse) protected?

Maybe the ones coming out are in free air, and therefore have a higher CCC?

Or maybe since neither individual appliance can overload them they are OK on the breaker for the large cable from the POV of fault protection? (but FGS don't tell holmslaw that or he'll get all tedious and w*nky again).

 

[bananaman]

Guys,

Thanks for all the replies. I'm still a bit confused, for the following reasons:

1. The original spark that fitted the 50A breaker was clearly aware that it would feed two ovens - he is qualified, so I'm not sure whether he was just wrong or optimistic about feeding two ovens from a single cable into the kitchen.

2. I DO have a single spare way at the CU - but I was hoping to hang onto this for unforeseen future use - I don't want to get caught with no spare ways at the CU at some point in the future.

3. This is nothing to do with the technical aspects of this, but the fitter (nominated by the kitchen supplier) immediately struck me as a purveyor of fine manure. This immediately led me to think that his reasoning for the two cable solution was to avoid a slightly more difficult job in handling 10mm2 cable. I'm a reasonable guy and I will accept a compromise where necessary. But I suspect I am being asked to run two circuits just to save the fitter/electrician the bother of handling the admittedly difficult 10mm2 cable. As the picture from Ban-all-sheds indicates that a single feed should be possible, I'd rather the fitter and his electrician made a bit of an effort to meet the needs of the (high) paying customer!

 

[sparkybird]

Well it might end up being cheaper to run two smaller circuits than large one....

Personally, I would always isolate each appliance separately, but BAS seems to be inferring that these has been a long discussion about this on this forum recently... might be worth a look. My reasoning is that if you need to isolate one oven, then at least you can use the other if isolated separately.

If you want to keep 1 spare way, there's always the mini CU option I suggested.

Can you not go back to the original electrician and ask him to put the fitter right??

SB

 

[ban-all-sheds]

Personally, I would always isolate each appliance separately,

Better, but nobody seems to get excited about a double oven, or even an entire cooker, being on one isolator, so if needs must...

but BAS seems to be inferring that these has been a long discussion about this on this forum recently...

Not that I recall.

If you want to keep 1 spare way, there's always the mini CU option I suggested.

And another instance appears where a switch-like MCB module for a grid system would be ideal...

 

[sparkybird]

oooh, you're on fire today, BAS!

So many options.... which to chose?

 

[ban-all-sheds]

Dunno.

Do you wear a nightie?

 

[EFLImpudence]

Even if you install 10mm² cable (a good idea) why are you using a 50A MCB and creating problems?

Edit - This was intended for Sparkybird.

 

[EFLImpudence]

Oven1: 3.68KW "total connected load". Conventional oven
Oven2: 3.60KW"total connected load". Combination uwave and oven

Not much these days.

Prior to planning this, I had an electrician renew the consumer unit and provide a single cooker MCB slot, ready and waiting for the new cable runs from thre consumer unit to the kitchen ovens. This is a 50A MCB.

You only need 32A for your ovens.

The kitchen fitter has surveyed the job and is now maintaining the following. I'd appreciate your opinions on the following statements:

Get an electrician

1. I cannot supply two ovens in the kitchen from a single cable from the consumer unit - whether it is 6mm2 or 10mm2 cable.

Rubbish. 10mm² would be better in case you want bigger ovens in the future.

I will need two breakers at the CU and two cables running to the kitchen. One for each oven.

He would but doesn't need two.

2. Run a 6mm2 cable from the CU for the conventional oven and run a separate 2.5mm2 cable from the CU to the uwave combination oven.

Even a 6mm² would be big enough for both. In fact, 4mm² would if ideal conditions.

3. As I cannot supply both appliances from a single cable, however big,

Yes you can. The whole house is supplied from a single cable.

I will need to have the 50A breaker swapped for a smaller rating and of course, have an extra one fitted too.

A 32A will suffice for your ovens and then you can use smaller cable to each oven, i.e. 4mm²

Can any of this possibly be right?

The bits I wrote are.

Get an electrician.

 

[EFLImpudence]

Untitled

• EFLImpudence
• 22 Jul 2011
• 1

As a note - One cooker switch is sufficient, in my opinion.
It is for isolation for maintenance and in emergencies.

Should an oven explode (they don't often) it is likely you would panic and not remember which was which if there were two.

 

[RF Lighting]

Yep that looks ideal to me.

Sounds like this new bloke is a prime example of someone having a go at electrics that doesn't really understand what they are doing.

Can you get your original electrician back to wire your ovens for you?

 

[ban-all-sheds]

someone having a go at electrics that doesn't really understand what they are doing.

Isn't that part of the job description for kitchen fitters?