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Topic Title: Is 1mm² still a reasonable minimum for domestic lighting circuits
Topic Summary: You get a lot of light for 6 or 10 amps nowadays
Created On: 11 November 2017 04:54 PM
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 12 November 2017 01:25 PM
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geoffsd

Posts: 1760
Joined: 15 June 2010

On rereading the thread title "Is 1mm² still a reasonable minimum for domestic lighting?"

I think only Zoomup has addressed the actual question. I also missed the point.

I suppose it depends on why someone originally decided that a 16A cable should be the minimum for a 6A circuit - or, conversely, why lighting circuits should be protected by 6A OPDs.

Plus, of course, what is a lighting circuit?

As Z said, and the OP implied, why not use smaller flexible cable?
It is allowed by the ridiculous Table 52.3 for - specific appliances, ELV circuits for special applications and, bizarrely, any other application.
 12 November 2017 01:26 PM
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sparkingchip

Posts: 10104
Joined: 18 January 2003

Originally posted by: Blencathra

I carry 1.0, 1.5 twin & 3 core, 2.5, 4.0, 6.0, cat5 indoor & outdoor, hi tuff 1.5, HR flex 1.5, selection of singles, 2 core flex for small appliances plus other odds. My van is decked out split level with Ply and the "ground floor" is full of cable reels



So you are actually operating a mobile shop, pulling up at your customers premises with an selection of materials to be able complete many jobs without incurring additional cost collecting materials from a wholesaler or postponing jobs waiting for a delivery.

Andy B.
 12 November 2017 02:18 PM
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Fm

Posts: 1733
Joined: 24 August 2011

Sounds like the best way to operate Andy
 12 November 2017 02:49 PM
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Blencathra

Posts: 16
Joined: 07 November 2017

Pretty much so, I am primarily an industrial maintenance bod, most of my jobs are breakdowns and minor alterations, I might turn up for one job and get a few while you are here jobs too
 12 November 2017 04:44 PM
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sparkingchip

Posts: 10104
Joined: 18 January 2003

Originally posted by: mikejumper

I'd be reluctant to use cable with a smaller CSA purely on the grounds of mechanical robustness.



Mike Jumper said what needed saying in the first response, however some of us aren't even generally using 1.0 mm.

On the grounds of mechanical strength 1.5 mm has to be used for emergency lighting circuits, so could less than 1.0 mm be justified for general use?

Andy B.
 12 November 2017 06:45 PM
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MHRestorations

Posts: 40
Joined: 22 October 2017

We carry most sizes of T&E even up to 10mm (9.6 and 10.something kw showers are becoming popular these days).

I am with the first answer, mechanical robustness: wouldn't want to go lower than 1.0mm2 except with flex above drop ceilings (where click flow connectors on flexes make slinging the cables about easier.

The note about bellwire is interesting. I DO use a lot of that for 12v LED undercabinet lighting, because it's easy to conceal (it's amazing how many customers don't think about lighting before the kitchen's finished. Bellwire is good for several undercabinet lights running at 12v these days.
 13 November 2017 02:00 PM
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AJJewsbury

Posts: 16007
Joined: 13 August 2003

With the majority of newly installed lighting now being LEDs, is 1mm² still a reasonable minimum for domestic lighting circuits?

The other thing to consider is fault protection - especially if you're using MCBs (or RCBOs) - anything with a mechanical switching system will have a definite minimum switching time - hence energy let-though will increase with PFC. Looking at the official (BS EN) energy let-though levels for MCBs it's tricky enough now to justify 1.0mm2 even at fault levels not exceeding 3kA. Of course if we reverted back to fuses we might be on more solid ground.

The note about bellwire is interesting. I DO use a lot of that for 12v LED undercabinet lighting,

Humm, how does that fit with reg 715.524.201? 1mm2 bell wire (<=3m long)?

- Andy.
 13 November 2017 07:43 PM
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MHRestorations

Posts: 40
Joined: 22 October 2017

Interesting point Andy... I had made the assumption (yes I know) that as the CSA was higher than that supplied as plug in link cables by the manufacturer (Channel Safety Systems) I was on safe ground. As its all plugged in, does it count as fixed wiring or 'part of an appliance' ?
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