Discuss What size cable do you use for new lighting circuits? in the Electrical Forum area at ElectriciansForums.net
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.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?
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.AFAIK, we're still supposed to design lighting circuits with BC or ES lamps assuming 100W per point, so the above shouldn't arise.
I have never understood the rational for that, as the larger T&E still has 1mm CPCs.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.
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
2.5mm, often the correct choice for a warehouse with rows of 300 to 800w lights.Most lighting circuits I work on are 1.5 or occasionally 2.5mm
Good point! The assumption that I (and probable most) made was the poll was about domestic lights.2.5mm, often the correct choice for a warehouse with rows of 300 to 800w lights.
I consider that to be a reasonable assumption. If we're including commercial, then does that include floodlit stadia with towers of several kW each, or the lights around the circuit at yesterday's GP?Good point! The assumption that I (and probable most) made was the poll was about domestic lights.
I'd guessed it did relate to domestic, but added that comment as a response to points raised in the quoted post.Good point! The assumption that I (and probable most) made was the poll was about domestic lights.
You haven't read post 18, then.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!
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!
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,
Most lighting circuits I work on are 1.5 or occasionally 2.5mm
Lights in 2.5mm2 - are you sure this electrician wasn't really a builder?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
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