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Topic Title: Oven question
Topic Summary: Ring main or separate circuit
Created On: 08 November 2017 11:10 AM
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 08 November 2017 11:10 AM
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Gil123

Posts: 2
Joined: 08 November 2017

We have just had our kitchen refitted, and changed from a freestanding cooker (oven and hob) to separate integrated hob (6.5kw) and oven (4.3kw).

I gather only one can go into the 32amp cooker switch, and it makes sense, to me at least, if that's the hob. We've had conflicting opinions on what to do with the oven. Some have said to put a 20amp fused spur off the 32amp ring main (relatively painless decor wise). Others have said it needs to have a new laid from the fuse box, and its own circuit (a much bigger job).

Bearing in mind that the ring main also has dishwasher, washer/dryer, toaster etc.

What is the best thing to do? Is it safe to take it off the ring main? Is it legal?

Thank you for any advice.
 08 November 2017 12:01 PM
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ArduinoXR

Posts: 48
Joined: 16 August 2017

Is there a separate ring main for sockets in the kitchen? Or is this 32A ring main covering everything?
 08 November 2017 12:09 PM
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Gil123

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Joined: 08 November 2017

No, just one for the whole house.
 08 November 2017 12:13 PM
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ArduinoXR

Posts: 48
Joined: 16 August 2017

oh right....You need to put it on it's own circuit then.

As a matter of interest is it common in the UK to have the whole house on a ring?
 08 November 2017 12:20 PM
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dustydazzler

Posts: 1451
Joined: 19 January 2016

Originally posted by: ArduinoXR

oh right....You need to put it on it's own circuit then.



As a matter of interest is it common in the UK to have the whole house on a ring?


Was very common
Pretty much every house I have ever worked on that was built / wired pre 1990s had one 30/32a rfc for all its general socket outlets
 08 November 2017 12:23 PM
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AJJewsbury

Posts: 16014
Joined: 13 August 2003

No such thing as a 20A fused connection unit (they're 13A max) - in theory you could put a 20A fuse or MCB in a small consumer unit fed off the ring, but that's well outside accepted good practice (not to say it's necessarily a problem, but you'd need some very careful calculation to back up the decision).

Presuming the manufacturer(s) are happy with 32A protective devices I don't see a problem in connecting both the hob and the oven to the exiting cooker circuit - you can even get get twin outlet connection plates for the very purpose. (e.g. http://www.tlc-direct.co.uk/Products/AA45DCOP.html )

As a matter of interest is it common in the UK to have the whole house on a ring?

Pretty common, especially in pre-1980s houses. The original ring circuit design was specifically intended to cover the whole of a 1,000 ft2 house - i.e. what was typically being built after WWII.

- Andy.
 08 November 2017 12:24 PM
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ArduinoXR

Posts: 48
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In Ireland we always had downstairs on a 20A ring and upstairs on 1 or 2 radials depending on size. Nowadays there's only ever a ring for the kitchen, 1 radial for the rest of downstairs and no change for upstairs. Is it similar for new domestic builds in the UK now?
 08 November 2017 12:30 PM
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broadgage

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Originally posted by: ArduinoXR

oh right....You need to put it on it's own circuit then.



As a matter of interest is it common in the UK to have the whole house on a ring?


It was common, and is still IMO acceptable for a small home.
In most more modern homes, two ring circuits would be common one for upstairs and one for downstairs is the usual arrangement.

For a large or well equipped home, I would normally recommend three ring circuits, one for the kitchen and utility room, one for the rest of the lower floor, and one for the upper floor.
 08 November 2017 12:32 PM
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dustydazzler

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Joined: 19 January 2016

New builds are pretty much wired however the fitter chooses.
I have worked in new flats where one flat is wired totally different from next door as they were wired by 2 different fitters.
Chucking in 4 radials instead of 2 rings is perfectly acceptable

I recently worked with an American sparks who told me their new build code is that each room is on a designated circuit (lights and sockets share the same circuit)
 08 November 2017 04:46 PM
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mapj1

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Joined: 22 July 2004

In a house that has been extended or re-furbished, you will find lights up, light down, normally separate, sometimes together, sometimes a bit confused around the light switches for hall stairs/landing. Beware the shared neutral.

For sockets, often one long meandering ring that does one socket per room that is the original, then maybe a new ring for the kitchen or possibly a 'lasso' circuit where the old cooker 30A line was used as the origin for a short ring above the work top, and a new cooker point has gone in at 45A elsewhere. Then any extension of any size will have its own 6A radial for new lights, even if its only 2 lamp-holders, and a new ring or radial.

Of course the loading is such that all the sockets probably could be under one 32A breaker, but there is a convenience of isolation by zones.

One side effect of part P needing new circuit notification is that it discourages the proliferation of new circuits by auxilliary trades like alarm installers, conservatory and kitchen fitters, so (round here at least )we are now moving back to seeing circuits extended rather than a new one along side for small stuff.
This makes the diversity/load demand type sums based on breaker sizes even less useful than they never really were.

For the OP, I;d suggest that oven and hob can share a circuit breaker if the cable is adequate.

Most things are legal, some are unwise.

-------------------------
regards Mike
 08 November 2017 09:52 PM
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MHRestorations

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mapj1... 'lasso' circuit. I like that one. I've always called it a 'ring on a stalk' before!
 08 November 2017 10:26 PM
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AJJewsbury

Posts: 16014
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mapj1... 'lasso' circuit. I like that one. I've always called it a 'ring on a stalk' before!

I thought the 'Forum Standard' name was "lollipop circuit"
- Andy.
 09 November 2017 04:23 PM
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kellyselectric

Posts: 186
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If it was me ide put the hob and oven on one 45 amp circuit just because if ever theres a big meal being cooked ie xmas time or similar then there should be enough power available
 09 November 2017 04:26 PM
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kellyselectric

Posts: 186
Joined: 22 July 2016

Just did the calls 10800 watts into 240 volts is 45 amps so right on the limit but ok as long as you dont plug the kettle in Lol
 09 November 2017 05:09 PM
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geoffsd

Posts: 1762
Joined: 15 June 2010

The usual 32A circuit will be fine - applying diversity for 45A cooking appliances, it's 20.5A, so 32A is ample.

32A is good for 15kW even with an integral socket on the cooker switch.

The Christmas reference is a myth.
 09 November 2017 05:21 PM
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mapj1

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I'd put it all on one as well, but I'd consider there to be a large enough safety margin for the kettle without risking a trip or cable damage.

It will be a very black meal if all rings and the oven are all on full blast together for much more than a minute or two at a time.
In any real case, even Christmas dinner, the rings will be pinging on and off asynchronously once "up to heat"
The breaker curves, which are very deliberately made like that because wires heating up also take time to do so, show that we may well have a few minutes even at 90A on a 45A circuit before things start to feel warm, let alone at more like 60A - how big is the kettle ? There is enough time to boil a kettle at least once every 10 mins.
Problem may arise if cooker switch is hanging off and a thick wire trails out of the back door to supply a welder in the back yard of course (Or worse if it is two pieces of 3 core flex with all 3 cores strapped to make singles.)
But that is likely to be a single bloke's sort of household, and realistically he can't be cooking and welding and making tea at once, and so in that case again we see that load diversity sorts it out. Though shutting the kitchen door may be difficult, there is a precedent for not worrying about this, even on a space station.



-------------------------
regards Mike
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