Old wiring makes electrics confusing

[ngodley]

hi guys/girls, (posted this in the incorrect forum earlier!)

I removed a 1 gang/1 way light switch from the living room of my victorian house and the wires there are red, black and a bare earth....

I want to fit a metal faced 1 gang/1 way dimmer which has, ~ (with an arrow which i think is "common".... and L1 and L2.

I have tested both the red and black with a current tester (when live) and theyre both live.....

From other posts ive read, i would think the red goes to common and the black goes to L1 with the earth obviously going to the box but as theyre BOTH LIVE when switched on, im a bit confused and dont really want to fry the new dimmer.

HELP WOULD BE GREATLY APPRECIATED!

*** One other thing... they all VERY short.... is it common practice to extend short wires when required?? the other option does not please me!!

Thanks in advance.

Read more: //www.diynot.com/diy/threads/old-wiring-makes-electrics-confusing.428300/#ixzz3T37Fv7Np

 

[sparkwright]

Usually the red is the permanent live
and
the black (with a red sleeve over it hopefully) is the switched live - ie the live that goes to the lamp.

Your dimmer should contain a wiring diagram to show which terminals should be used. I've noticed different manufacturers do show different wiring arrangements, surprisingly, so best go with the diagram if there is one.

You're going to tell me there's no diagram, aren't you/

You must connect the earth wire to the earth terminal on the metal faceplate. It would also be desirable to connect a new piece of earth wire from the metal faceplate to the metal back box (if it is metal).

 

[ngodley]

Yeah when i took the plate off originally, BOTH the red and black had crappy little bits of red tape on them.

The whole house was a botch job from what i can tell...... So i would like to do it properly (but do it myself of course).

The dimmer is from Varilight...
http://www.diy.com/departments/vari...otary-dimming-400w-dimmer-switch/54100_BQ.prd

I just wasnt sure wether both red and black would be constantly LIVE when free from their terminals/free from the switch and touched with a tester.

 

[Chri5]

What is this tester you post about?

 

[ngodley]

Voltage tester

 

[PrenticeBoyofDerry]

Voltage tester

Two pole/probe or non-contact or screwdriver tester?

To Identify perm live, test using a two pole indicator between live and earth.

 

[ngodley]

Ok..... that sounds great but it comes down to this....

say i went out and bought a two pole indicator.... i wouldnt know which wires to put it onto, nor what the read out would mean!

Unfortunately im learning.

I would be ok with paying someone to come and sort it for me but thats not DIY and i really want to learn this