Discuss What size cable do you use for new lighting circuits? in the Electrical Forum area at ElectriciansForums.net

What size cable do you use for lighting circuits?

  • 1mm

  • 1.5mm


Results are only viewable after voting.
Welcome to ElectriciansForums.net - The American Electrical Advice Forum
Head straight to the main forums to chat by click here:   American Electrical Advice Forum

You will get the odd member of the public who buys a new house, finds that some LEDs lamps have failed and replaces them with what they have brought from old homeā€¦. Your nicely calculated maximum load has suddenly trebled!
What if they do it 2 or 3 times, and the supply is only 1mm?
On a 6A MCB then worst case they trip it, or more likely see a bit more dimming/brightening than expected when switching other lights.

Still safe.
 
AFAIK, we're still supposed to design lighting circuits with BC or ES lamps assuming 100W per point, so the above shouldn't arise.
At some point the regs will catch up with LED lighting so the 100W/light and 3% VD will be revised, but until then even if you assume 100W per fitting most flats or building floors are still well within a 1mm / 6A circuit.

I have used 1.5mm and it has the physical strength advantage, but often LED lights with internal connectors are just more of a pain to get the 1.5mm in to place so really now would look to 1mm first and foremost, unless something very unusual applied.
 
1mm FTW, there is a stupid regulation about not using 1mm for 'power' circuits but you can still use it for lights and fans which seems to come from the bigger is better mentality.
I have never understood the rational for that, as the larger T&E still has 1mm CPCs.

The only thing I can guess is it comes down to the risk that DIY folks would start add 13A sockets on to a 1mm circuit for loads assumed to be much lower, etc. But trying to legislate against rubbish workmanship and poor/no design is not really something for those following the regs.
 
Ok here is one, I work both domestic and commercial, I often find commercial with 10A lighting circuits (Also see it in domestic) With more and more people piling more and more insulation into their lofts the derating factor of 0.5 could be achieved that would take it below 10A. Because of this I use 1.5mm when dealing with circuits with 10A lighting just to be safe..

Having said the bullc**p above which 1mm would be fine for most scenarios, here is the two real reasons I only use 1.5mm..

1. I don't have the space to carry around 1mm and 1.5mm T+E as well as 1mm 3core and earth and 1.5mm 3core and earth and then there is singles... so I just carry 1.5mm
2. I find 1.5mm is more resilient in a terminal, have a number of times with 1mm when you do the tug test the copper breaks because of the intents from possibly being over tightened. I don't seem to get this issue with 1.5mm

maybe if copper prices keep going up then I might change my mind but for now mainly really for space and the advantage that I don't have as much stock which is more efficient. The cost difference between 1mm and 1.5mm is not yet enough that I would bother carrying both..

Also although its seems like 68m is a long distance its surprising on a larger house how it can start to get close, 1.5mm you don't have to think about it, its also really difficult to judge how long the run is (Probably me being lazy though)... Would not dis anyone for using 1mm for lighting its just personal preference for the 2 above reasons why I use 1.5mm

Most lighting circuits I work on are 1.5 or occasionally 2.5mm
 
Since I've not seen it mentioned (domestic context), how about 1.5mm2 feed from the consumer unit to one light switch to the next. Then 1.0mm2 from each switch to the light(s). And none of this loop in at the lights nonsense!šŸ˜†
 
Since I've not seen it mentioned (domestic context), how about 1.5mm2 feed from the consumer unit to one light switch to the next. Then 1.0mm2 from each switch to the light(s). And none of this loop in at the lights nonsense!šŸ˜†
You haven't read post 18, then.
It all depends on the calculations. I use 1.5 if it helps meet the regs, but otherwise 1.0,
 
Since I've not seen it mentioned (domestic context), how about 1.5mm2 feed from the consumer unit to one light switch to the next. Then 1.0mm2 from each switch to the light(s). And none of this loop in at the lights nonsense!šŸ˜†

Funnily enough I do see similar in NI - 1.5mm from one point to the next, with switch cables in 1mm. I think this house was done that way, but looped at lights.
 
You haven't read post 18, then.
It all depends on the calculations. I use 1.5 if it helps meet the regs, but otherwise 1.0,

Sorry, I'd missed that post. I've done this on a couple of large domestic new builds (3-storey mansion, CUs in basement plant rooms). I've quite got to like it even for more normal sized houses, and indeed it does mean you always know the feed in/out at a switch, though I'm sure someone will tell me I'm contributing to the rise in copper prices.
 
Feed in and out at switch is the new normal way of wiring lights, if just one or so lights per room on a single switch point. Where things get more complicated, I favour the multi way junction box, fitted somewhere reasonably accessible, with sometimes as many as 20 cables coming to it.
Nothing to do with 1.0 or 1.5 though.
 
When I was at college many years ago one of the other apprentices told us that an electrician he worked with said when he wired lighting the minimum size was 2.5mm and sockets 4mm
Lights in 2.5mm2 - are you sure this electrician wasn't really a builder?
 

Reply to What size cable do you use for new lighting circuits? in the Electrical Forum area at ElectriciansForums.net

OFFICIAL SPONSORS

Electrical Goods - Electrical Tools - Brand Names Electrician Courses Green Electrical Goods PCB Way Electrical Goods - Electrical Tools - Brand Names Pushfit Wire Connectors Electric Underfloor Heating Electrician Courses
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc

Electrical Forum

Welcome to the Electrical Forum at ElectriciansForums.net. The friendliest electrical forum online. General electrical questions and answers can be found in the electrical forum.
This website was designed, optimised and is hosted by Untold Media. Operating under the name Untold Media since 2001.
Back
Top
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock