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 .

 

[littlespark]

Typo on the post? 1.4??

1.5 normally, but will use 1.00mm if just doing links between downlights on the same switch. That sort of thing.

 

[Dave OCD]

Realistically 1mm is more than enough , 1.5mm in domestic lighting is just a waste of money and copper. Although I do like 1.5mm for surface clipped cables in garages or outbuildings, just nicer and easier to get looking spot on.

 

[Pete999]

Typo on the post? 1.4??

1.5 normally, but will use 1.00mm if just doing links between downlights on the same switch. That sort of thing.

Why the mix of cable sizes LS? Seems counter productive and unnecessary.

 

[littlespark]

1.00 would be fine, if it wasn’t for 2 feet of insulation sitting on top of it, and it’s the main feed cable from the CU.

Why I use two sizes? I bought 1.00 in error, used it for some downlights etc, but next visit to wholesalers, I got 1.5.
Using both drums up now.

 

[Pete999]

1.00 would be fine, if it wasn’t for 2 feet of insulation sitting on top of it, and it’s the main feed cable from the CU.

Why I use two sizes? I bought 1.00 in error, used it for some downlights etc, but next visit to wholesalers, I got 1.5.
Using both drums up now.

So your mistake then? can't see how you can try and convert people due to a mistake on your part.

 

[littlespark]

Not trying to convert anybody… just saying what I do.

the original question was “anyone ONLY ever use 1mm?”
I was saying no, I use both.

 

[SJD]

For a small property (e.g. 3-bed semi-sized) then I normally use only 1mm2.

For a larger property (e.g. 3 storey mansion with longer cable runs) I typically use 1.5mm2 for the feed, which is nowadays going from CU to switch to switch. Then 1mm2 from the switches to lighting points, which will often be a string of downlights.

Not a problem to have reels of both, in fact I make sure I've got supplies of both.

 

[e-spark]

longer runs on 3 or 4 storey houses use 1.5 the rest 1mm twin n earth; 1mm 3core for all switch wires to leave earth and neutral in each back box.

 

[7029 dave]

I used to like using 1mm for the simple reason of pulling through conduit on switch drops etc on rewires.

 

[e-spark]

I used to like using 1mm for the simple reason of pulling through conduit on switch drops etc on rewires.

with needing neutral in back boxes now im finding got dig the 16mm b/boxes out and put 25mm ones in especially 2 way switching and 2 or 3 gang switches.

 

[catdog1121]

I think the norm used to be 1mm for downstairs lights and 1.5mm for upstairs to account for possible insulation which sometimes people put masses of it...

Personally I just use 1.5mm, for the simple reason that I only have to carry 2 reals, 1.5mm T+E and 1.5mm 3core and Earth rather than 4 reals.. I agree its a bit of a waste of copper but also prefer working with 1.5mm as when it goes into a screw terminal its less likely to break off... But thats just personal preference, I might change if copper prices keep going the way they are though..

 

[Dustydazzler]

I started off using 1mm , then moved over to 1.5mm as the price wasn’t much different back then

now I almost exclusively use 1mm for domestic lighting , I do have some 1.5 part rolls to use up if I feel it’s necessary

 

[telectrix]

I use cat5, it's even cheape r.esp the cca crap.

 

[Dustydazzler]

Bell wire
?

 

[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.