Double fan asst oven and hob on 6mm circuit

[JiM]

I've been given a nice Siemens electric double oven and hob. I currently have a single oven and gas hob.

I'll get the gas hob taken out by an approved pro.

Question is... can I hook up both the hob and the oven to the existing 32A circuit? I'm assuming with a 32A fuse in the CU it's a 6mm cable circuit. The house is 11 years and the CU is in a small kitchen so the cable run is presumably short. It runs up above the ceiling.

HOB - 240V 6.6Kw
OVEN - 230v -240v - 4.3Kw

Both the hob and oven have stranded T&E cables coming from them, not sure if it's 4mm or 6mm (is there a way to tell using a digital callipers?).

By my amateur reckoning the combined appliances equal 27.5A + 18.7A = 46.2A

Do I need a 10mm run and a 40A fuse? If so I guess I will stick with my lowly single oven

Thanks in advance for any help

 

[telectrix]

6mm on a 32A MCB should be fine once you allow for diversity, your corrected current value is 22A ( 27 if you have a socket outlet on the cooker isolator. ) . been several posts about this recently.

 

[fancypantsyeah]

ok if there is only one feed, that is 1 6mm2 t&e cable feeding the 10900 watt or 10.9 kw then the 6mm2 t&e is is no good jim ya gonna need a 10mm2 feed with a 50A MCB to feed the 10.9 KW mate... hope this helps ya out....

 

[telectrix]

ok if there is only one feed, that is 1 6mm2 t&e cable feeding the 10900 watt or 10.9 kw then the 6mm2 t&e is is no good jim ya gonna need a 10mm2 feed with a 50A MCB to feed the 10.9 KW mate... hope this helps ya out....

WRONG!!!!!! not all the elements will be in use/full load at the same time. suggest you look up threads on cooker diversity. this has been in use for up to 15kW rated cookers for 60years and no 6mm has ever fried.

 

[Flyingsparks]

I agree with telectrix here.

When I was at college they connected up a cooker with 2.5mm cable just to see if it would take it. The cable got a bit warm but it worked fine.

 

[brooky25]

Double Oven and electric hob, I have one of these to do tomm. One 32 a6mm feed already there and I am intending on supplying another 32a 6mm feed for hob. I thought double ovens and hob needed 2 6mm feeds ?
Must check book for diversity hmmmm, cheers for this thread may have a bonus tomm

 

[telectrix]

nothing wrong with a separate 32A circuit for the hob, but i'll bet after you install it and switch every element on that you can, then clamp each feed , add them up, and i'll bet you they won't add up to 32A together.

 

[brooky25]

Normally always have 2 separate feeds but this jobs a bit of a pig, so diversity will take over me thinks
Thanks to OP for bringing this up or I would have just been in robot mode, although on the safe side

 

[telectrix]

brooky, just to refresh your memory. from the KW ratings added together, work out the current. then diversity rule says

10A + 30% of remainder = FLC. e.g. 10kW = 45A, so FLC = 10+10.5 = 20.5A

 

[JiM]

Awesome, thanks guys for quick replies, wasn't expecting that

Diversity... hadn't known of this before. This assumes that the appliances will not be on full at the same time?

Cooker - 10A + 30% of remaing rated current + 5% if the CCU has a socket outlet

46.2 - 10 = 36.2

35% of 36.2 = 12.67 + 10 = 22.67

Is this correct or do you add 5% on top of the -10 + 30% sum?

Telectix original reply said 27A with a socket, are my figures incorrect?

I could replace the CCU with a socket-less one for a little extra peace of mind at Christmas time.

One last question...

The CCU feeds a single socket under the worktop which the old single oven is plugged into. Can I put a 30A junction box under there or do I need to run the cables from the oven and hob up through the wall into the CCU directly?

Thanks again for all the help

 

[telectrix]

not 5% for the socket, 5A. and you need to replace the socket under the worktop with a dual outlet connection unit. make sure that the feed from the cooker isolator to the outlet is 6mm and you're good to go.

35% of 36.2 = 12.67 + 10 = 22.67.. ​30% of 36.2, not 35%. so it's 10A+12A+5A=27A

 

[brooky25]

brooky, just to refresh your memory. from the KW ratings added together, work out the current. then diversity rule says

10A + 30% of remainder = FLC. e.g. 10kW = 45A, so FLC = 10+10.5 = 20.5A

Thanks for that, saved me going out to van for green book. Just don't think about it when your stuck in a routine. Bring back commercial installs this house bashing getting on mi nerves now.

 

[JiM]

30% of 36.2, not 35%. so it's 10A+12A+5A=27A Gotcha, I see now, thanks.

One of these and I'm good to go...

http://www.alertelectrical.com/prod/1022/click-45a-easyfit-dual-appliance-outlet-plate#desc

Couldn't find a 32A one.

Woohoo! New oven and hob for me

So is there a way to check that it's 6mm by using a digital calliper to measure the diameter of the cable core? Or is it not that simple?

 

[keniff]

not 5% for the socket, 5A. and you need to replace the socket under the worktop with a dual outlet connection unit. make sure that the feed from the cooker isolator to the outlet is 6mm and you're good to go.

35% of 36.2 = 12.67 + 10 = 22.67.. ​30% of 36.2, not 35%. so it's 10A+12A+5A=27A

My god thank you! Never seen one of these dual outlets this will save me loads of time in future!!

 

[fancypantsyeah]

WRONG!!!!!! not all the elements will be in use/full load at the same time. suggest you look up threads on cooker diversity. this has been in use for up to 15kW rated cookers for 60years and no 6mm has ever fried.

yeah hands up on this occasion made a small wrong calculation,,,lol,,,,i'm an industrial and commercial spark and for commercial premise it's 100% i believe....no excuse should know this one,,,,been very long day yesterday for me....
mind in my defence nothing wrong with over egging cct cables ang cpd's... just expensive and once installed you never have to uprate them,,,,lol... thanks for your imput .......
lol,,,haha and "over eggin " is a technical term ,,,,,lol...haha...