1mm or 1.5mm for all internal light runs ?

[LukeD]

Anyone only ever use 1mm T&E for domestic lighting (Average 3 bed etc) Or are you using 1 mm &1.4mm for drops and runs etc ? Now that 90% of stuff is LED bulbs etc . Not thinking for exterior light etc .

 

[telectrix]

Bell wire
?

only for ding-dong lights.

 

[Rockingit]

For domestic, anything other than 1mm is just a waste of money and copper. Even if you de-rate by 50% you're still OK on a 6A CPD.

 

[pc1966]

Our old friend the OSG has the length limits as 68m and 106m for 1mm and 1.5mm on a 6A circuit distributed circuit and the 3% VD limit. Realistically these days you are not counting 100W bulbs so it would be very odd to reach 6A on any light circuit (and with LED lights then 3% is a ridiculous limit to retain) so assuming actual load is 3A = 690W = 2.7kW halogen equivalent then doubling your OSG length limit is reasonable 136m (or 212m for 1.5mm but going to be Zs limited to less).

OSG has 1mm down at 36.2 mOhm/m and 6A MCB Zs limit is 5.87 ohms, so allowing 0.87 for a poor TN-S value of Ze then your length limit for meeting disconnection on Zs becomes 138m (or 165m for 1.5mm/1mm T&E).

Table 7.1(ii) has the CCC of 1mm as above 6A in all methods.

So realistically for any normal home, 1 or 2 stories, there is no electrical case to argue. Yes, for some mansion with a chandelier that would make Liberace jealous you might need some bigger cable, maybe even more MCBs, etc.

So I guess it is more down to physical characteristics and personal preferences.

I like 1mm as many LED lamps have piddling little push-in terminals with little bending radius for the conductors and 1mm is a lot easier then!

 

[littlespark]

only for ding-dong lights.

“Play Ja Ja Ding Dong!”

 

[LastManOnline]

I like 1mm as many LED lamps have piddling little push-in terminals with little bending radius for the conductors and 1mm is a lot easier then!

Correct. For many years I have run the br/bl direct to the switch box as modern homes want a fancy light fitting (not a ceiling rose). Many of these light fittings are incapable of accepting two cables in their inadequate connectors. Plus there is no adequate arrangement for the loop live. So running a single T&E to the lighting point is advantageous.

 

[Dustydazzler]

I guess in the older days of 1 lighting circuit for the entire property with say 15 x 100w bulbs on it then 1.5 for the circuit might have been better

but in 99.9% of modern builds you have at least 2 designated lighting circuits with minimal loading on each so 1.0 is absolutely fine

i honestly don’t know why people waste 1.5 on domestic lighting

 

[123]

I guess in the older days of 1 lighting circuit for the entire property with say 15 x 100w bulbs on it then 1.5 for the circuit might have been better

but in 99.9% of modern builds you have at least 2 designated lighting circuits with minimal loading on each so 1.0 is absolutely fine

i honestly don’t know why people waste 1.5 on domestic lighting

In these parts most (if not all) wholesalers don't stock 1.0mm T&E, 1.5mm is generally used for lighting & heating

 

[LastManOnline]

In these parts most (if not all) wholesalers don't stock 1.0mm T&E, 1.5mm is generally used for lighting & heating

I have never seen a coil of 1.0mm T&E. I am obliged to use 1.5mm here in ROI. However I am surprised that in NI you don't use 1.0mm as you are under UK regs.
I do agree though that 1.0mm is adequate, particularly with the advent of leds,and that the UK is correct in its approach. Gone are the days when a homeowner would have at least two, possibly three 500watt halogen security lights outside his house.

 

[pc1966]

In these parts most (if not all) wholesalers don't stock 1.0mm T&E, 1.5mm is generally used for lighting & heating

That is odd, maybe it is for ease of stock in both UK and ROI rules by the companies.

I can see some sense in stocking 1.5mm for the odd 16A radial circuit and its dual-use for lighting, but for many case I would just opt to use some 2.5mm in those cases as common with the usual RFC used here. Off hand I don't see a lot of 16A radials in use, odd immersion heater, maybe dedicated feed to a boiler or freezer?

However, it also seems odd the ROI does not permit 1mm for lighting like the UK does.

 

[nicebutdim]

In these parts most (if not all) wholesalers don't stock 1.0mm T&E, 1.5mm is generally used for lighting & heating

1.5 is all I've ever seen used for lighting over here, but oddly enough I spotted 1mm as strapper when finally righting the 2 way switch beside me, that was wired upside down. I don't have a great deal of experience in such matters, but it struck me as being unusual.

 

[LastManOnline]

However, it also seems odd the ROI does not permit 1mm for lighting like the UK does.

There are no electrical reasons why it should, nt be permitted. Is it a major issue?... No. But there are times, such as when doing rewires and space in older conduits is very very tight, that a smaller size T&E can make a world of a difference.
That said I have also made good use of a 1.5mm lighting circuit on a 10 amp mcb on occasion whereby small items of electrical equipment could be connected to same circuit (provided they are under 300 watt)