1mm or 1.5mm T&E for standard lighting circuit in your average house.

[Ian1981]

1mm.
Tho local council jobs insist on 1.5mm for lights and 10mm for cooker circuit.
2.5mm to feed to heating circuit as well for some reason.

 

[GB.Kayak]

Out of interest what's most commonly used?

Lee,

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!

 

[Leesparkykent]

Lee,

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!

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

 

[Aindowsimon]

Generally use 1.5mm but I used 1mm in my own gaff and I think I'm going to revise my standards and generally be 1mm

 

[Adam W]

I'm happy to admit that I prefer to wire sockets in 32A rings because I'd rather terminate 2x 2.5mm cables than 2x 4mm. If the situation called for it I'd be happy to design a lighting circuit so I could use 1mm instead of 1.5mm.

It used to be that the rule of thumb was to allow 100w per point for lighting. We are all aware of improvements in LED technology to the extent that realistically you could allow 12w or even 7w per point without anyone complaining that it's too dark, but there are still a lot of people who remember the first generation of CFL light bulbs which cost a fortune and took half an hour to reach a sickly glow; these people decided that energy saving is not for them and have since gone out of their way to 'play the system' and will know where they can lay their hands on some 100w pearl light tungsten filament bulbs, in fact they probably have a secret stash of them somewhere.

I believe there's still an argument for installing sealed unit LEDs, especially if you're planning to use 1mm.

 

[GB.Kayak]

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

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!

 

[GB.Kayak]

... indeed, I was 'playing' with MS Excel the other day, creating a graph of maximum design current vs circuit length for each size of cable to use as a useful indicator of maximum circuit length for a given design current.

 

[Leesparkykent]

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!

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?

 

[Adam W]

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.

 

[GB.Kayak]

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?

... clearly ... as you put it like that ... 1.0 mm2 every time!

 

[static zap]

Do we have to factor in for global warming !
(how many editions ? ,-oz-weather guys have new stickers)

 

[MFS Electrical]

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

 

[Midwest]

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

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?

 

[davesparks]

I believe there's still an argument for installing sealed unit LEDs, especially if you're planning to use 1mm.

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?

 

[Adam W]

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?

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.