Very small diameter wiring behind light switch

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mdf

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#236445 2-Jun-2018 10:56

I've loosened some switch faceplates to paint. The wires behind the lightswitch are much smaller than I expected:

They also seem to be red and orange.

The bulb these control is an LED so not huge power demands. But hoping for a quick steer as to whether this is okay or requires professional attention?

richms

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#2027423 2-Jun-2018 10:59

That is normal for the old days. Tiny little wall box so they just bring a twin switch wire down. Means you cant put any smart switch in or fancy dimmers because of no neutral there.

Richard rich.ms

mdf

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#2027426 2-Jun-2018 11:06

Phew. Thanks for that. I'll still see about getting it replaced eventually but just had images of imminent fire hazards (it's a kids room).

sparkz25

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#2027506 2-Jun-2018 14:18

richms:

That is normal for the old days. Tiny little wall box so they just bring a twin switch wire down. Means you cant put any smart switch in or fancy dimmers because of no neutral there.

you can still install a dimmer, providing its not a 1000w dimmer

Bung

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#2027510 2-Jun-2018 14:49

richms:
That is normal for the old days. Tiny little wall box so they just bring a twin switch wire down. Means you cant put any smart switch in or fancy dimmers because of no neutral there.

Not just the old days. The light fitting will have a live terminal regardless of switch position so you must isolate at board.

Edit. Switching the CB or pulling the fuse is the way to isolate all circuits but some will just flick the switch. This is one time when that short cut could backfire.

sbiddle

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#2027515 2-Jun-2018 15:21

Wiring lights this was the norm in NZ up until the '90s. Some installs are better than others - I've seen plenty of lights over the years that have regular red and black TPS that hasn't even had the black wire sleeved.

The serious downside of this as pointed out above is that the light socket is always live even if you turn the switch off. It also means you can't install a smart switch of any sort as their is no neutral wire at the switch.

Aredwood

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#2027573 2-Jun-2018 18:25

Lights can be wired in either system, both old houses and brand new. My 1969 house has the power fed to the switches first. While a friend who is a sparky, uses the top fed system on new work. (power fed to the light first)

He does it that way, because it uses less cable. And it avoids having to derate the capacity of the cables due to having multiple cables next to eachover. Depending on the job, the shorter runs might also allow smaller cable to be used while still complying. Another cost saving. Although he uses 3 core for the drops to the switches. Meaning there is often a spare core that could be connected to neutral, or used to add a second switch.

DarthKermit

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#2027582 2-Jun-2018 18:35

That old wiring will still have the same cross-sectional area as the new stuff does: 1 mm squared.

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k1w1k1d

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#2027773 3-Jun-2018 11:47

I would have thought that the rules stated that power had to go to the switch first, not to the lamp?

I assume that he is wiring houses to a set price, so any savings(shortcuts) go in his back pocket.

Would not be happy with this in my house!

richms

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#2027783 3-Jun-2018 12:33

k1w1k1d:

I would have thought that the rules stated that power had to go to the switch first, not to the lamp?

I assume that he is wiring houses to a set price, so any savings(shortcuts) go in his back pocket.

Would not be happy with this in my house!

Why would you be unhappy? It meets all requirements and works fine. Only issue with looping at the light is when inexperianced people come along to change the fitting over and find 4 or 5 terminals in use instead of the 3 they were expecting.

Richard rich.ms

Aredwood

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#2027796 3-Jun-2018 13:49

k1w1k1d:
I would have thought that the rules stated that power had to go to the switch first, not to the lamp?

I assume that he is wiring houses to a set price, so any savings(shortcuts) go in his back pocket.

Would not be happy with this in my house!

It still does go via the switch first. From a purely electrical point of view. The circuit is exactly the same. Only difference is the physical routing of the conductors. The terminals in the light fittings are still dead when the switch is off.

As for price savings, the builder would have asked for quotes. And if someone figures out a cheaper way of doing the job while still complying. They can submit a cheaper quote while still making the same profit margin for themselves. And they will get the job.

As above, the only extra safety risks are to DIYers who don't understand different wiring systems. And they are the people who should be getting an electrician to do the work instead.

mclean

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#2029627 5-Jun-2018 09:40

Aredwood: It still does go via the switch first. From a purely electrical point of view. The circuit is exactly the same. Only difference is the physical routing of the conductors. The terminals in the light fittings are still dead when the switch is off.

When the switch is off there's no power to the lamp terminals, but the loop terminal is still live.

Coil

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#2029629 5-Jun-2018 09:43

I really hope that your wiring is not the kind where it switches the phase at the switch and has a junction in the ceiling to the light fittings. I'd always run a feed into the switch then loops to each light from there.

Aredwood

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#2029934 5-Jun-2018 17:49

mclean:
Aredwood: It still does go via the switch first. From a purely electrical point of view. The circuit is exactly the same. Only difference is the physical routing of the conductors. The terminals in the light fittings are still dead when the switch is off.

When the switch is off there's no power to the lamp terminals, but the loop terminal is still live.

But that loop terminal is not user accessible. In that replacing a failed light bulb has no extra risk. You have to remove the light fitting to access that terminal.

Aredwood

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#2029940 5-Jun-2018 17:56

Coil:
I really hope that your wiring is not the kind where it switches the phase at the switch and has a junction in the ceiling to the light fittings. I'd always run a feed into the switch then loops to each light from there.

You would love the light that is just inside the front door of my house. The cable goes first to the switch, then to the light, then another cable goes to some more light switches and lights in different rooms.

So there is an always live loop terminal behind that light fitting, despite the cable going to the switch first.