Dimmer switch wiring *peace of mind question*

[morphe]

Can someone me at peace of mind please. In my sons bedroom I have installed a dimmer, this is how I connected it.

L1......RED

L2.....EMPTY

C.......BLACK

I have a red and black wire.


Earth wire is wired into the casing and not to the switch, so Ijust left that there.

Can they cause fires, I have a 60w bulb, and dimmed to the lowest light.

 

[Scoby_Beasley]

Technically, the red should go to 'com' (thats if wired correctly originally), the black, which should have a red tag, is the switched live, in fact, when the light is on, they are both live, no neutral, no earth. The L2 is for when you have 2 switches controlling 1 light, another story.
And if you have an earth connection on your switch plate (i.e. metal) this should have a short tag wire (earth) to the back box to link it into your earth system.
Hope that helps.

 

[sparky (sfd)]

Technically, the red should go to 'com' (thats if wired correctly originally), the black, which should have a red tag, is the switched live

doesnt really matter which way round youve put them but this is how its mostly done

 

[morphe]

Technically, the red should go to 'com' (thats if wired correctly originally), the black, which should have a red tag, is the switched live, in fact, when the light is on, they are both live, no neutral, no earth. The L2 is for when you have 2 switches controlling 1 light, another story.
And if you have an earth connection on your switch plate (i.e. metal) this should have a short tag wire (earth) to the back box to link it into your earth system.
Hope that helps.

I will change them round tommorow, how does the switch work if it's wired wrong, or will it work even if it's the wrong way round, is it dangerous the way it is?

The back plate and front are both plastic.

 

[breezer]

don't worry you can leave it as it is

 

[sparky (sfd)]

is it dangerous the way it is?

nothings dangerous about it it will still work excatly the same

 

[ban-all-sheds]

nothings dangerous about it it will still work excatly the same

Is that always true for dimmer switches? I'd be concerned that there might be some electronics which are expecting 240V to be applied to the input of a circuit and a load to be applied to the output.

I know a switch will work whichever way you wire it, but will a dimmer? I've never wired one up the wrong way to find out.

 

[securespark]

With dimmers it is possible to use L2 as switched output on one way circuit to no ill effect... try it!!

With a rocker switch it matters to the extent that if you wire the switch live to L2 the light will be on in the up position, but with a rotary or push dimmer it matters not a jot.

 

[sterose]

Technically, the red should go to 'com' (thats if wired correctly originally), the black, which should have a red tag, is the switched live, in fact, when the light is on, they are both live, no neutral, no earth. The L2 is for when you have 2 switches controlling 1 light, another story.
And if you have an earth connection on your switch plate (i.e. metal) this should have a short tag wire (earth) to the back box to link it into your earth system.
Hope that helps.

I will change them round tommorow, how does the switch work if it's wired wrong, or will it work even if it's the wrong way round, is it dangerous the way it is?

The back plate and front are both plastic.

Because of the nature of AC (i.e. alternating current), it does not matter which way around you wire components into the mains.

In alternating current, the current actually reverses 50 times a second. This means the neutral is actually the 'live' side for a split second every second.
This is why those 'Figure of 8' (the ones with an 'infinity' sign shape, you normally get them on Sky Digiboxes for example) plugs go in either way round.

So dont worry about the wiring arrangement.

 

[securespark]

Of course, it goes without saying that when it comes to single pole (light) switches and edison screw light fittings it is imperative that correct polarity is observed:

Single pole switches always operate on the live conductor.

ES Light fittings always have the centre pin wired to live.

This is very important!!

 

[ban-all-sheds]

Sterose - that isn't actually how it works at all.

The voltage of the phase conductor relative to neutral alternates from +340V to -340V 50 times a second. At no point is the neutral at anything other than 0V.

Also there is no neutral in a light switch, be it a dimmer or a simple on-off.

And whilst a simple rheostat will work whichever way round you connect it, I remain unconvinced that the generic case of an electronic circuit would be the same, but if everybody is sure that you can connect the supply to the output of a dimmer and the load to the input and that it will work, then I will have to revise that opinion.

 

[yankey-sparky]

The question here is whether the dimmer would work properly and safely whether it was hooked up "backwards" or "forwards", since there is a question of which side it is expecting to see the load applied. For some DC components, this is a concern, but not for AC. Since the current switches direction twice every cycle, the dimmer can actually be considered to be on both sides of the load. During the first half of the AC cycle it is in front of the load, and when the current switches direction it is then behind the load.

So as far as operation is concerned, it will work fine whether you hook up Com on the breaker side or on the light side. However, I would recommend wiring it up with Com on the breaker side so you don't confuse someone else who would expect it to be hooked up "forwards".

Also, please disregard the comment made by Sterose, it is not only technically incorrect but also confusing the issue.

 

[securespark]

yankeysparky

Agree wholeheartedly with what you say.

Although, technically speaking, a switchwire effectively becomes a neutral

when the light is off (with lamp in situ). This is how neon locators work - one side of neon goes to permanent live and the other to the switchwire. When the light is off the switchwire is a "neutral" and when the light is on, the switchwire becomes alive, and the neon goes off.

 

[breezer]

to follow on fom that:

it is true but a neon is actualy gas (pure neon lights up red) which is "exited" by the voltage difference, so if you take the lamp out the neon will not work, but as there is no physical conductor that is why the lamp never even glows

 

[yankey-sparky]

Although, technically speaking, a switchwire effectively becomes a neutral when the light is off (with lamp in situ).

I fear we're getting too far off topic here, but I cannot agree with this statement. The switchwire is at zero volts with respect to earth, true, but I will not call it a neutral because it is not a grounded conductor. (Earthed conductor? What's the UK term?)

This isn't just semantics, this lies at the very heart of what it means to be a neutral wire. It's not even "effectively" a neutral wire because of the fact that it is possible to raise it significantly above earth ground, which cannot be done with a true neutral conductor.