new dimmer help with common wire

[just confused]

I bought a dimmer switch and it only has a L1 and L2 terminals which would the common wire go? Only two wires both red but know which is the common new switch has no terminal for it

 

[ericmark]

Should not matter which way around you connect wires.

 

[securespark]

It does say on the switch casing.

 

[sparkwright]

The new dimmer includes a wiring diagram on the back, as seen in your pic.

To comply with the diagram, the permanent live goes to L1.
The switched live goes to L2.

There is no way of telling which wire is which without testing. The fact that a particular wire is in the common terminal is no guarantee that it is the permanent live.

That said, it usually doesn't matter which way round the wires go on a dimmer - though always best to follow manufacturers instructions and diagrams.

 

[Taylortwocities]

TRy ot one way, if it doesnt work then swop the wires. It will not do any harm.

 

[securespark]

 

[ban-all-sheds]

TRy ot one way, if it doesnt work then swop the wires. It will not do any harm.

The potential difference between L1 and L2 will vary from +325V to -325V and back to +325V 50 times per second. How can it matter which conductor goes into which terminal?

 

[Taylortwocities]

I know, you know, all of the "experts" on here know.
I only added it as a bit of reassurance to our newbie DIYer.

 

[ban-all-sheds]

Yeah, but...

If it doesn't work one way that won't be because the wires need swapping...

 

[just confused]

Ok got a multimeter how would I test for live?

 

[Taylortwocities]

Ok got a multimeter how would I test for live?

 

[flameport]

Ok got a multimeter how would I test for live?

By setting it to AC Volts on a range of 250V or above, plugging the two test leads into the correct sockets on the multimeter, connecting one probe to a known earth and the other to the wire you are testing.

However this is not necessary. You have two wires and two terminals. One wire in each terminal. Job done.

 

[just confused]

Ok got a multimeter how would I test for live?

By setting it to AC Volts on a range of 250V or above, plugging the two test leads into the correct sockets on the multimeter, connecting one probe to a known earth and the other to the wire you are testing.

However this is not necessary. You have two wires and two terminals. One wire in each terminal. Job done.

Does it not matter which way they go though they are currently wired like this

 

[eveares]

Does it not matter which way they go though they are currently wired like this

No, because it is AC current and the polarity is constantly changing back and forth at 50Hz. Now what is somewhat important is the the line and switched line wires are properly identified, what can in certain cases be important. (i.e. when you have multiple lights fed from one switch)

In your case, what way round you connect the red (Line) wires to the dimmer is not important.

 

[PBC_1966]

Does it not matter which way they go though they are currently wired like this

No, it doesn't matter. The switch would work just the same if you swapped the two wires over, and the dimmer will work fine whichever way you connect them too.