Switch wire protocol

[jackruss]

Disclaimer: I am NOT using this information to perform any illegal electrical work!

Hi All,

I am trying to find out what is the correct protocol for running switch wire.

Players;

1.5 sq twin and earth feed
1.0 sq switch wire ( white and red)

Junctioned at or about the light fitting, the feed active is switched down the WHITE switch wire, to the common of the light switch.

The RED of the switch wire is then returned via the number 1 of the switch to the light fitting.

Is this the correct protocol?

thanks.

[Sutty]

Pretty close.
Swap the red & white for no other reason than to maintain a common standard.
Red being an unswitched active....white is switched active.

[jackruss]

thanks

Not that I am actually doing anything with them.


JR

[Pulse]

Sutty is on the money, as you mentioned the junction usually occurs at the light fitting or in a junction box nearby, the other option is to do all this at the light switch by soldering earths together and using a "loop" terminal for your neutrals.

Cheers
Pulse

[Ivan in Oz]

Disclaimer: I am NOT
Players;

1.5 sq twin and earth feed
1.0 sq switch wire ( white and red)

thanks.

Change of Gauge [Guage]...........................:confused:
Change of size of Wire,
Not going there:eek: :( :(

[Mazza]

I agree with the above advise but would also like to add that the switched cables should also be 1.5mm2.

This is because the circuit breaker in the board has been rated to handle the 1.5 supply and not the 1mm you plan to use.

This could potentially be a fire risk.

[Barry_White]

Just one other point is that you shouldn't mix 1mm2 with 1.5mm2 cable. Either use one or the other but don't mix them.

Other wise the other information is correct.

[Mazza]

lol, I went through all that registration stuff cos nobody else seemed to have noticed that and then within seconds of posting others do to.........lol.

Soz, I just dont want to see people burn there houses down.

[Barry_White]

I agree with the above advise but would also like to add that the switched cables should also be 1.5mm2.

This is because the circuit breaker in the board has been rated to handle the 1.5 supply and not the 1mm you plan to use.

This could potentially be a fire risk.

Mazza

He doesn't say what size breaker he is using so he can use either cable depending on what size breaker the circuit has, he just can't mix them but most leckys today use 1.5mm2 multi strand cable for light circuits.

[Mazza]

Mazza

He doesn't say what size breaker he is using so he can use either cable depending on what size breaker the circuit has, he just can't mix them but most leckys today use 1.5mm2 multi strand cable for light circuits.

He stated that the supply was in 1.5mm.

[Mazza]

Mazza

He doesn't say what size breaker he is using so he can use either cable depending on what size breaker the circuit has, he just can't mix them but most leckys today use 1.5mm2 multi strand cable for light circuits.

He stated that the supply was in 1.5mm.

[Woodhouse Elect]

While you are :eek: NOT doing any electrical work;) , the advice given in the previous posts is sound; Keep colours standard, keep cable size same and probably the most important for a handyman keep the cable size and the rated fixtures at the correct rating for the breaker(or vice versa).

[jackruss]

Thanks Guys

As mentioned, I am not wiring!!

Just broading my understanding.

This is exisiting wiring I'm checking. (which is inconsistent anyway- older switch wire is solid core red and black, so in that situation the black is the switched active!!)

(I have a little knowledge, and therefore a little dangerous when double checking work done.!)

No one panic about the house burning down, or insurance or any other concerns.


Now that said.

The lighting circuit, domestic, 10A breaker

Light fitting switch , lets say 100w batten.

All multi strand wire,

why would 1.0mm2 be an issue? Is this just good housekeeping or is there a sound reasoning behind it,as it only carries the switched active to the fitting and terminates there.

It draws at a maximum .416A, well within what 1.0 sq can carry, additional feed only carries on through the 1.5 sq.

JR

[Mazza]

The reason is because in a situation whereby there is a short circuit, that 1mm cable will draw far more than what it does when simply activating the light and hence will heat up heaps more than the 1.5mm.

Yes it is probable that the fuse/CB would still protect it considering its only 10A, it is still a no no.

Depending on the circumstances it is possible for a 1,5mm supply to be provided with a 16A breaker, however this would quite possibly be to much for the 1mm cable........again depending on the circumstances.

[Pulse]

Mazza, the short circuit current capacity is the reason why we have an MEN system with low fault loop impedance so that fault currents are easily carried to ground and trip the circuit breakers. This will not cause the wires to overheat since that is the purpose the circuit breaker after all.

The real problem is that if someone comes along in the future and thinks, great, 1.5mm2 and installs a 12 or 16A breaker and then installs devices that draw this current through the switch wire then the 1mm2 switch wire is not protected and could catch on fire in normal everyday use.

These are a lot of "ifs" and you won't have troubles as long as the breaker is sized to protect the smallest wire on the circuit, switching or feed, it doen't matter.

Cheers Pulse

[jackruss]

again.

1mm2 cable has a protective device rating of 10A, but can can carry much higher than than before failure.

The way I read the standard, up to 4 times (?? though I take this with a grain of salt).

Anyway as said, the maximum rating for 1.5mm2 is 16amps, and even that thru 1mm2 is not going to melt it. Copper melts at over 1080 deg C

Now all that said, I apologise for causing this direction in the thread, because on closer examination, it appears to be 1.5mm2 switch wire any way! :eek: . ( whats the difference between 0.69116mm radius and 0.56433 mm radius!)

But I appreciate everyone's concern, without the overly preachy tones!

JR

[Mazza]

Mazza, the short circuit current capacity is the reason why we have an MEN system with low fault loop impedance so that fault currents are easily carried to ground and trip the circuit breakers. This will not cause the wires to overheat since that is the purpose the circuit breaker after all.

The real problem is that if someone comes along in the future and thinks, great, 1.5mm2 and installs a 12 or 16A breaker and then installs devices that draw this current through the switch wire then the 1mm2 switch wire is not protected and could catch on fire in normal everyday use.

These are a lot of "ifs" and you won't have troubles as long as the breaker is sized to protect the smallest wire on the circuit, switching or feed, it doen't matter.

Cheers Pulse

No argument here brother, I was trying to keep it simple for him. As you have said the CB is there to protect the smallest cable, however there should not be any cable in the circuit that is smaller than what it starts out as from the CB.

[Mazza]

again.

1mm2 cable has a protective device rating of 10A, but can can carry much higher than than before failure.

The way I read the standard, up to 4 times (?? though I take this with a grain of salt).

Anyway as said, the maximum rating for 1.5mm2 is 16amps, and even that thru 1mm2 is not going to melt it.

Now all that said, I apologise for causing this direction in the thread, because on closer examination, it appears to be 1.5mm2 switch wire any way! :eek: . ( whats the difference between 0.69116mm radius and 0.56433 mm radius!)

But I appreciate everyone's concern, without the overly preachy tones!

JR


JR there is no absolute rating for a cable as it just depends on how it is used and in what environment etc.

For example it is possible for a 1mm2 copper cable to carry up to 20a legally in some circumstances and only 5A in others..............it all depends.