Light switch

[mole81]

Changed a simple light switch earlier, black cable was common and L1 red, previously doing this I'm sure red should be common? Or should I shut up now ha!

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[wine~o]

Convention says that the red (permanent live) goes to com. However the switch itself neither knows nor cares whether red is in com or L1.

It just sits there being a switch.

[Someone-Else]

It really depends on how whoever wired it in the first place chose to wire it, the electricity is not going to complain about the colour of the insulation.
As wine~O suggests, ideally the red should be permanent live and the black should be switched live (With a red marker) But we don't live in an ideal world.

[mole81]

Thanks for the replies, what would happen if the red actually was the permanent live and these were swapped?

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[Someone-Else]

what would happen if the red actually was the permanent live and these were swapped?

As wine~O and I said

However the switch itself neither knows nor cares whether red is in com or L1.

It just sits there being a switch.

the electricity is not going to complain about the colour of the insulation.

The other thing to "wonder about" is:

Is the red permanent live? it may be that the black is permanent live, unless it is tested, or traced back to the other end, no one (apart from whoever installed it) will ever know.
But it's not a case of "well it works so it must be ok" it is a case of, it's wired correctly, it is using the correct size cable, and it works (But it does not have "coloured tags" to identify which is the live)

[mole81]

what would happen if the red actually was the permanent live and these were swapped?

As wine~O and I said

However the switch itself neither knows nor cares whether red is in com or L1.

It just sits there being a switch.

the electricity is not going to complain about the colour of the insulation.

The other thing to "wonder about" is:

Is the red permanent live? it may be that the black is permanent live, unless it is tested, or traced back to the other end, no one (apart from whoever installed it) will ever know

So no risk of electrocution if the permanent live is in the switched live terminal?

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[Someone-Else]

I am curious, why do you think there would be any danger / risk of death?

[mole81]

I am curious, why do you think there would be any danger / risk of death?

Just because they are the wrong way round? I'm not an electrician I'm just capable of changing like for like! Suppose similar thinking if you mix up the terminals on a socket??

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[Someone-Else]

Oh, I see. Thank you.

I shall explain the error in your thinking.

A light switch just sits there (as wine~O said) it is either on or off.

A socket can have anything plugged into it, most devices will "not care" which way round the supply is, but some will, it is these that can be a danger, not to mention that with most sockets the integral switch only turn off the live, so if the item plugged into a reverse-wired socket was still plugged in, but switched off the device and its cable are still live (The switch only turned off the neutral) so if the device was opened (lets say to remove a blockage) it would be possible to get an electric shock as the supply is the wrong way round. That is why before you open any electrical item you must make sure it is isolated from the supply, and the easiest way to do that is to unplug it.

Where as the humble switch, you only press the button, so it matters not which terminal is the live or switched live.

But you also did the right thing, by asking. Better safe than dead.

[mole81]

Oh, I see. Thank you.

I shall explain the error in your thinking.

A light switch just sits there (as wine~O said) it is either on or off.

A socket can have anything plugged into it, most devices will "not care" which way round the supply is, but some will, it is these that can be a danger, not to mention that with most sockets the integral switch only turn off the live, so if the item plugged into a reverse-wired socket was still plugged in, but switched off the device and its cable are still live (The switch only turned off the neutral) so if the device was opened (lets say to remove a blockage) it would be possible to get an electric shock as the supply is the wrong way round. That is why before you open any electrical item you must make sure it is isolated from the supply, and the easiest way to do that is to unplug it.

Where as the humble switch, you only press the button, so it matters not which terminal is the live or switched live.

But you also did the right thing, by asking. Better safe than dead.

Ahhh thank you that makes perfect sense, thanks for the clear explanation!

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[Someone-Else]

[ericmark]

Just because they are the wrong way round? I'm not an electrician I'm just capable of changing like for like! Suppose similar thinking if you mix up the terminals on a socket??

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But they are not wrong way around, although with an on/off switch permanent line is normally com, with a two way switch permanent line is normally L1 or L2, it would be very unusual to use com as permanent line with a two way switch, and with an intermediate switch you don't have a com.

Also both wires are line, one is switched the other permanent, but both are line.

Note:- both the phase conductor and neutral are considered live, so to distinguish the phase conductor is called line and clearly neutral is called neutral, I know we often think of line and live being the same, but if I call line live some one is sure to tell me, as I should know better, no one is worried what you call it however, we all know what you mean.

[wine~o]

Well, between Someone-else and myself I thought we'd pretty much cleared up this thread in layman's terms.

and then...

[Bob225]

lol, To be pedantic the black should have a red sleeve or marker, or a bit of red insulting tape with teeth marks in it (as long as its not harmonised colours)

[mole81]

Thanks for all the replies, simpler wins for me!

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