Mains wiring


Postby kilo » Wed Jan 28, 2009 12:00 pm

Hi there,

I recently purchase a ceramic hob cooker with a power rating of 12kw. I have worked out that it will need a 50amp fuse and a 10mm cable. As this is a 1960's house, i'm not sure if the wiring in the house will support the cooker. At present, i have a 100amp main circiut breaker in the consumer unit. Would you suggest i get the house re-wired? Also, what is the standard thickness or ampage of external cables that feed the consumer unit.

Thanks :?
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Postby RFLighting » Wed Jan 28, 2009 6:15 pm

First of all, 12kW works out to over 52A, so a 50A MCB is not suitable.

As for the cable, far more information is required.

How long is the run?

How will it be routed?

What is the ambient temperature of the run?

Will the cable be run through any thermal insulation?

As for the CU, there is no way of knowing with the completely lacking any detail whatsoever information you have provided.

You have not mentioned a local DP isolator in you design, nor an RCD to protect any concealed cables <50mm deep.

There is no standard thinkness of 'external cables'. It would depend entirely on the supply size, length, and age.

Are you aware that as this work is in a kitchen, and is the installation of a new final circuit, it requires notification to your LABC BEFORE you commence the work?
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Postby SparkyPaul » Wed Jan 28, 2009 7:26 pm

Doubt it is a 100A main circuit breaker normally it is only an isolator
What size is the main fuse?
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Postby sparx » Wed Jan 28, 2009 8:30 pm

Hi don't forget regs allow for diversity in cooker supplies, onsite guide says:
first 10A of rated current , plus 30% of remainder plus 5A if socket incorperated in panel so your 50A is actually calculated as :
10+ (30% of 40) = 10+12=22A plus 5A if skt so max of 27A so standard 32A circuit is all required.
Agree all other comments of RFLighting
regards SPARX
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Postby SparkyPaul » Thu Jan 29, 2009 10:05 pm

32A is pushing it a bit
You dont want cold turkey and an upset mrs at xmas do you :lol:
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Postby sparx » Sat Jan 31, 2009 10:40 pm

RFP/SP, Hi guys,
what would you use at cooker end as an isolator?,
would you really run a circuit for 50A? for a cooker!

Our ceramic hob / double oven cooker has been doing dinners for 14 for the last 3 years xmas without a problem on a 32A type b mcb on 6mm2 tw/cpc. thermostats mean only some rings will be on at once.

Using the on-site guide and regs is what sets us aside from the rest!
Sorry but why cost your customers more than necessary by using oversized cables with larger than required MCB which gives a lower level of protection?
IET have always given diversity allowance for domestic cookers, so why ignore best advice available?
see 8.4 page 160 of OSG, and table 1A page 96,
It states "A 30 or 32 A circuit is usually appropriate for a household or similar cookers of rating up to 15kW.
regards SPARX
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Postby SparkyPaul » Sat Jan 31, 2009 11:00 pm

for something as big as that I'd aim for somewhere around 40A-45A
the onsite guide is only guidance it isn't set in stone
looks like youre having cold turkey for xmas :lol:
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Postby sparx » Sun Feb 01, 2009 4:38 pm

Glad you don't work for me! LOL, too expensive.
If IET on site guide to the IET's regs says up to 15 kW on 32A supply & customers cooker is only 12kW that's it! END.
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