Mixing Cable Sizes

[m4tty]

Hi,

If a lighting circuit is wired to 1.5 T&E would it be acceptable to add another lighting point and switch onto the circuit in 1.0 T&E as long as it complies with all the calcs.

Wanted to know whether this is seen as ok or rough tbh.

Thanks

 

[ianmacd]

IMO its rough. I do not like 1.0 anyway. Its like fuse wire. Is there any reason you can not use 1.5?

 

[alchemist]

As long as 1mm can take the current for the breaker its on it will be fine (considering installation methods e.g. insulation/grouping decreasing it's capacity.).

It would save money and copper if 1mm was used for all switch drops, as a switch drop in a house would never need 1.5's capacity, which I think is something like 13A - who has a single room with 3KW of lighting? Unless you are feeding the switch and not looping in from the rose.

 

[Sidewinder]

^ as above to both really.

However my dislike of 1.0mm sq would over rule my thinking.

It just seems too flimsy to me, never bought it and don't intend to unless it is customer spec.

Just my take.

 

[Tooold]

Struggled to get 1.5 down exisiting switch drops too often and 1.5 has a 1.0 mm earth, and never thought of it but yes does save on copper. Do use both but not 1.5 on domestic. However would keep cable size the same throughout the circuit just in case of future changes.

 

[Larnacaman]

Maybe a bit rough in a domestic setting, but reducing cable sizes is standard practice in many types of installation.

A good example of such an installation is Street (/Road/Motorway) lighting!! So long as each cable/wire size reduction meets the electrical criteria of the circuit it's supplying, then there is no problem whatsoever....

So, leaving personal preferences and being seen as rough, to one side. There isn't any reason why you can't use 1mm cable on a 1.5mm circuit if the 1mm meets all of that circuits requirements. ...lol!!

 

[Evans Electric]

Nothing wrong with 1.00 mm on the usual small 3 bed semi type job . Again this is a personal preference thing .

 

[ProDave]

I always use 1mm for domestic lighting. Perfectly adequately rated for a 6A circuit.

Apart from anything else, when wiring a chain of downlighters (hate those damn things) most of them struggle to accommodate two 1mm cables in their terminals and most simply will not accept two 1.5mm cables.

I would only use 1.5 if the cable run was unusually long so volt drop might be an issue.

 

[Theorysparky]

would make a comment on the cert about mixed sizes

i always use 1mm with 6amp mcb

its not rocket science to work out the loading and if you provide the certs it dont matter

if it means you get the job over someone else because of say a tenner why worry

if it didnt have applications they wouldnt make it....

 

[Evans Electric]

Come on guys , a little semi with 5 lights on each circuit , why use 1.5 ?

 

[sprocketflup]

But the cost difference between a 100m roll of 1mm or 1.5mm is tiny?

 

[sparkytim]

Nothing wrong with 1mm for domestic lighting ccts, its rated at 11 Amps so even ok on a 10 Amp Mcb in MOST circumstances.

 

[Theorysparky]

[No message]

 

[mikep]

I love bit of 1.0mm, supple and can loop in and out fof down-lighters much easier than 1.5mm, lovely on 3 gang switches etc.

 

[tom1]

i do find 1mm noticeably easier than 1.5

click down lights will comfortably take 1.5

 

[superspark]

i use 1mm on all domestic lighting rewires unless we are talking very long runs etc, 1mm is so much easier to work with in ceiling roses etc. also when rewiring a occupied house and tubes are present for sw drops 1mm pulls down so much easier than 1.5 especially when 2 cables are required at the sw drop it can be the differance between chopping a wall and not having to. and as others have said depending on installation methods etc it carries 11 amps.

 

[green-hornet]

I used to always use 1mm on domestics but more often than not I now use 1.5mm.

 

[muffin]

i use 1.5 so im not limited when they ask for triple lights or a couple of 500 watt floods a few months down the line. its our company view as well, no one here puts in 1.0mm

 

[m4tty]

Ive just done 19 Aurora downlighters with 1.5mm cable and it was tight getting the two cables into each chocblock. Do you guys use them Ashley maintenance free junction boxes for downlighters so only 1 cable into the actual downlight itself.?

Just looking to make it easier next time lol

Cheers

 

[ProDave]

Ive just done 19 Aurora downlighters with 1.5mm cable and it was tight getting the two cables into each chocblock. Do you guys use them Ashley maintenance free junction boxes for downlighters so only 1 cable into the actual downlight itself.? Just looking to make it easier next time lol

Cheers

No I use 1mm t&e so two cables fit into the choc block.

Some of them are still a pita as the design of the cable clamp seems especially designed to work with only 1 cable.

Just one of the reasons I hate downlighters and would never have them in my house. The other being they are a hugely inefficient way of lighting a room.