2 Way Light Switching Problem

chrisreduk · Post by **chrisreduk** » Wed Oct 24, 2007 1:01 pm

I have viewed the diagram on the site of how to wire both ends of a 2way switching circuit. Unfortunately my wiring is 1.5 twin and earth and comprises of RED (live) Black (neutral) and a bare Earth wire. The cable shown in the diagram without going into colour coding has FOUR wires including a Yellow.

I know it can be difficult to explain, but any help with this would be greatly appreciated. I just need to know where the black and reds go as the earth obviously grounds the backplates.

Thanks in advance

Chris

PS If I can figure out how to post photos of both ends of my problem I will do that as soon as possible.

Tryanything · Post by **Tryanything** » Wed Oct 24, 2007 1:44 pm

Hi and welcome
you need 3 core and earth cable for two way switching you only have 2 core and earth so your going to have to pull a new cable in

Stoday · Post by **Stoday** » Wed Oct 24, 2007 3:16 pm

Tryanything wrote:
you need 3 core and earth cable for two way switching you only have 2 core and earth so your going to have to pull a new cable in

Oh no you don't need 3-core. You can do it in 2-core.

2-core for the strappers, connected to L1 and L2. Then Live to the C of one switch and the switch wire to the C of the other switch.

Hoovie · Post by **Hoovie** » Wed Oct 24, 2007 3:24 pm

If you wire like that, would it mean that one of the switches has to always be on for the light to come on (i.e. if it was off, the position of the other switch would not matter and thr light would not come on?)

Post by **ultimatehandyman** » Wed Oct 24, 2007 3:48 pm

I'll move this to the sparks forum

Post by **ultimatehandyman** » Wed Oct 24, 2007 6:30 pm

A picture would probably help Chris please

Stoday · Post by **Stoday** » Wed Oct 24, 2007 8:11 pm

Hoovie wrote:If you wire like that, would it mean that one of the switches has to always be on for the light to come on (i.e. if it was off, the position of the other switch would not matter and thr light would not come on?)

No.

Either switch can switch on or off, just like any normally wired 2-way switch circuit. There are two strappers, let's call them A and B. Switch 1 switches live to either strapper A or B. Switch 2 connects the lamp to strap A or B. So if A is live, switch 2 can switch the lamp on & off.

If you leave the lamp off, and it's connected to strapper B, switch 1 can switch the lamp on by switching the live to strapper B instead of A.

And so on.

Hoovie · Post by **Hoovie** » Wed Oct 24, 2007 8:37 pm

OK, I'll take your word for it

(makes me wonder why 3-Core cable is normally used for 2-way switches though)

sparkydude · Post by **sparkydude** » Thu Oct 25, 2007 6:50 pm

3 core cable is normally used to save having to wire more than one cable to the second switch as you would have to feed the switch at one end, and then have 2 cores betwwen then another s/live from the second switch so makes it confusing for DIYers LoL

Nick

Stoday · Post by **Stoday** » Thu Oct 25, 2007 7:39 pm

The advantage of the 3-wire method is that provided you feed and take the switch wire from one end, the net current over the cable is nil.

In the 2 strapper case, there is no return current over the strappers. This leads to some magnetic field leakage that can be heard in induction loops, for example. It's just not good practice to wire in a way that allows magnetic fields to leak around.

chrisreduk · Post by **chrisreduk** » Mon Oct 29, 2007 11:01 am

Thanks to everyone who responded to my request for help.

I already knew that 1.5 twin and earth would work in a two way switching circuit, because it has worked for the past 15 years with that wiring in place. My problem arose when the switch at one end failed and needed to be replaced. My son removed the old switch thiking it would be an easy job to replace.

I persevered and tried many wiring combinations (without blowing any fuses) and finally have it working again. My son has learned a valuable lesson and so have I.

Once again, thanks for all the help.

Chris

Wood Magnet · Post by **Wood Magnet** » Mon Oct 29, 2007 5:19 pm

Thanks for the update Chris, glad you got it sorted.

2 Way Light Switching Problem

2 Way Light Switching Problem

Thanks everyone!!