Discuss 1mm or 1.5mm T&E for standard lighting circuit in your average house. in the Lighting Forum area at ElectriciansForums.net
Lee,Out of interest what's most commonly used?
That def sounds like your average house doesn't it! Sorry I took so long to reply but my computer was in the pool house, 50 meters down the corridorLee,
Surely ... or is that 'Shirley' ... there is no 'standard' house and therefore the BS 7671 design rules need to be applied effectively! I am working in a large (?) Georgian property at the moment and the landing lighting circuit is > 50 m in length. Whilst nominal 230 V LED lamps may be fitted, and who would want to replace 8 lamps in each of 2 chandeliers with 100 W incandescents, it is theoretically possible even if the light fittings are not designed for 0.8 kW for someone to do so!
Lee,That def sounds like your average house doesn't it! Sorry I took so long to reply but my computer was in the pool house, 50 meters down the corridor![]()
So you would walk in to your typical, average 3 bed semi to quote for a rewire....you would then apply the design rules as you put it of BS7671 or you would know without a shadow of doubt that a 1mm lighting circuit will be absolutely more than adequate because you are an experienced electrician without putting pen to paper?Lee,
I didn't for one moment imply that the house that I am working on is 'standard' or 'average' ... merely that effective application of BS 7671 design rules are required in every case!
This thread is about "standard lighting circuits in an average house", not about large Georgian properties. We're not talking 8 lamp chandeliers, more single white plastic pendants in the middle of each room, possibly 2 in the lounge.Lee,
I didn't for one moment imply that the house that I am working on is 'standard' or 'average' ... merely that effective application of BS 7671 design rules are required in every case!
... clearly ... as you put it like that ... 1.0 mm2 every time!So you would walk in to your typical, average 3 bed semi to quote for a rewire....you would then apply the design rules as you put it of BS7671 or you would know without a shadow of doubt that a 1mm lighting circuit will be absolutely more than adequate because you are an experienced electrician without putting pen to paper?
Personally I always use 1.5 I hate 1.0mm2 for a few reasons if the attic gets more insulation after I’m away then guaranteed the insulation will be laid over the cable reducing the ccc and if the customer decides in a few years to put up a chandelier in the hall the living room and a bedroom with 6 halogens in it and halogen downlights in the kitchen etc then there is the potential for overloading I also hate terminating 1.0mm it’s easy enough in wagos or ceiling roses but I always end up chopping it in the earth and nuetral bars of a CU even when it’s doubled over because it’s so thin and crappy just my personal preference
I believe there's still an argument for installing sealed unit LEDs, especially if you're planning to use 1mm.
I thought I'd explained that in the previous paragraph - it's so the end user can't change a 7w light bulb for a 100w light bulb, thereby potentially messing up calculations or burning something next to it or whatever. In certain situations the tenants take the light bulbs out and steal them, so there's an argument there as well.What argument is that then? In what application would you select a cable size and then select your light fittings based on the size of the cable?
You never heard of diversity?I thought I'd explained that in the previous paragraph - it's so the end user can't change a 7w light bulb for a 100w light bulb, thereby potentially messing up calculations or burning something next to it or whatever. In certain situations the tenants take the light bulbs out and steal them, so there's an argument there as well.
yeahYou never heard of diversity?
I do agree to an extent but I still just prefer to install 1.5mm2 just makes me feel better?But there's no rhyme or reason for your concerns.
1mm smothered with insulation, #6 with 6A ocpd, will be fine. With a 1.5mm, that could be 10A, what ocpd could you use, that would improve on 1mm?
An RFC could easily be overload, once you step out of the house. Wire RFC in 4mm?
1mm & 1.5mm have the same size cpc.
So that just leaves your nuetral?
I remember years ago getting called out to a building where all the lights weren't working, a day after they'd been re-lamped, some jakey had stolen all of the starters from the sides of the fittingsIn certain situations the tenants take the light bulbs out and steal them, so there's an argument there as well.
Pretty suprised you asked to be honest, surely it depends on what your connecting to the circuit? PS, 1.5mm2, well maybe 1.0mm2, or even 2.5mm2, hmm, where shall I start?Out of interest what's most commonly used?
I'm on about a standard lighting circuit, in your standard house. For example if you was pricing/1st fixing a traditional built newbuild 2 bed semi with standard pendants...what would your usual go to cable be for the lighting circuits? Mine would be 1mm T&E others would choose 1.5mm T&E. I was interested in what is most commonly used, hence the poll.Pretty suprised you asked to be honest, surely it depends on what your connecting to the circuit? PS, 1.5mm2, well maybe 1.0mm2, or even 2.5mm2, hmm, where shall I start?
Go for 1mm2 if your doing a couple of new builds then the cost saving will soon add up (I know its a complete contradiction to what I said earlier but your not me so I assume you don't have the same reservations about 1.0mm that I do)I'm on about a standard lighting circuit, in your standard house. For example if you was pricing/1st fixing a traditional built newbuild 2 bed semi with standard pendants...what would your usual go to cable be for the lighting circuits? Mine would be 1mm T&E others would choose 1.5mm T&E. I was interested in what is most commonly used, hence the poll.
There's a lot of mention of the reduced load of modern LED lighting but no mention of the sometimes appalling power factor and large inrush currents of many of the LED drivers and fittings that at least partially offsets that......
And provide handy auxiliary heating for the gaffTrue, but thinner cable will keep the inrush current down a bit.![]()
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