Double Dimmer Switch Question

[Jodo]

I have removed a two gang switch to replace it with a 2 gang dimmer, to find that there are three cables in the switch, each with 2 wires (1 black, 1 red/green). I wired the dimmer up as per the instructions:

L1 to Neutral + link to second L1,
L2 to Live + first light + joined to second L2,
Com joined to Com (no other connection),
Second L2 to second light.

All I get is both lights on constant full, no switch off and no dimmer operation.
I also tried to wire it up as per the original 2 gang switch but I get nothing at all then.
Please help, I started tearing my hair out about 2 hours ago!

Thanks all.....

 

[ban-all-sheds]

I have removed a two gang switch to replace it with a 2 gang dimmer, to find that there are three cables in the switch,

You'd normally only need 2 cables. Is either gang one end of a 2-way switching arrangement?

each with 2 wires (1 black, 1 red/green).

Red/green??? Are you saying that because you have R-G colour-blindness?

I wired the dimmer up as per the instructions:

L1 to Neutral......

Since neutral isn't used with light switches, I doubt that the instructions say that...

How was the switch that you removed wired?

 

[Jodo]

Thanks for the reply ban-all-sheds,

First off, sorry, yes I meant Green/Yellow (it was late )

I don't think either is one end of a 2-way switching arrangement because the switch is in the living room and one switch controls the living room light, the other the dining room light. No other switches control them.

The neutral wire is shown entering L1 on the diagram but it has a circle with a cross in it on the line. I was following the "loop in loop out two way switching" diagram. The other diagrams are "alternative two way switching" which has live on one Com and neutral in the other (but I didn't get anything when I tried that), and "dimmer wiring" which shows just one switch with neutral in L1 and live in Com.

The original switch was wired up with the two com terminals bridged and the live also entering one, and then the other two reds in L1 and L2 on different switches with the neutrals connected to the back box.

Thanks again for the help so far, hope you can sort this out for me!

 

[pdcelec]

Since you demonstrate that you clearly do not understand the very basics of electrical theory, my advice would be to get someone in who does understand

 

[ban-all-sheds]

I'm inclined to agree with pdcelec...

First off, sorry, yes I meant Green/Yellow (it was late )

OK - so you've got 3 normal twin & earth cables, each with red, black & earth.

I don't think either is one end of a 2-way switching arrangement because the switch is in the living room and one switch controls the living room light, the other the dining room light. No other switches control them.

OK - it's not two-way.

The neutral wire is shown entering L1 on the diagram but it has a circle with a cross in it on the line.

The diagram will not be showing neutrals going to the switch. Neutrals do not go to light switches.

I was following the "loop in loop out two way switching" diagram.

Why were you doing that when you don't have 2-way switching?

Also, by the sounds of it, you don't have loop-in wiring.

The other diagrams are "alternative two way switching" which has live on one Com and neutral in the other (but I didn't get anything when I tried that), and "dimmer wiring" which shows just one switch with neutral in L1 and live in Com.

No - that will be the live in COM and the switched live in L1. Does it not make sense to you that for a switch, be it on/off or dimmer, to work it must somehow make and break the circuit connection to the light so that current will flow or not flow? i.e. that it will make or break a connection between the wires connected to the switch terminals? What happens if you connect live directly to neutral?

You were very lucky that you put your wires in L1 & L2, since there is never a connection between them - if you'd used COM and L1 or L2 you'd have blown the fuse and destroyed the dimmer switch...

The original switch was wired up with the two com terminals bridged and the live also entering one, and then the other two reds in L1 and L2 on different switches with the neutrals connected to the back box.

1) Why didn't you copy the arrangement that worked to the new switch?

2) If you have got the neutrals going to the switch location and they are connected to the back box, I sincerely hope it's a plastic one.

Where are the earths connected?

Thanks again for the help so far, hope you can sort this out for me!

I think you should reconsider DIYing...

 

[Qedelec]

I agree with BAS but you should have learnt a valuable lesson from this.... make a note of what was where and copy it to the replacement.

What you have is increasingly common, the live and neutral have been taken to the switch and the two lights supplied by two cables from there.

1. Identify which cable is the live feed (phase and neutral)
2. Connect the RED from this to one terminal of each dimmer (using a strapper)
3. Connect the RED of each of the other cables to the other terminal of each dimmer.
4. Connect all the blacks together in an insulated terminal block (no copper exposed)
5. Connect all the earths together in the back box terminal and connect a piece of 1.5mm from there to the earth terminal of the switch plate.

 

[Jodo]

Since you demonstrate that you clearly do not understand the very basics of electrical theory, my advice would be to get someone in who does understand

I'm inclined to agree with pdcelec...

OK, i take on board both your comments regarding my (electrics) DIY'ing...

OK - so you've got 3 normal twin & earth cables, each with red, black & earth.

Sorry, I really shouldn't post when it's late. I just re-read my original post and as well as typing red/green instead of yellow/green, I also wrote black instead of red. The source of the misunderstanding is mine, I apologize.
So, I have 3 cables each with 1 red and 1 green/yellow, no blacks at all.

The diagram will not be showing neutrals going to the switch. Neutrals do not go to light switches.

This is a copy of the "One Way Dimmer Wiring" from the leaflet.

make a note of what was where and copy it to the replacement.

Thanks for your input Qedelec. I replaced the original switch with the original wiring configuration which I remembered at the time I removed it. The original switch works perfectly well, but when I transfer the same wiring to the new dimmer I get nothing so I think I may have a dead dimmer switch.

Thanks all for sparing the time to reply, I realise correct information in the first place is always helpful...

 

[Steve]

This is a copy of the "One Way Dimmer Wiring" from the leaflet.

ahhhh, now then. That circle with a cross is your light. The neutral comes after the light, see? the wire between the light and the switch is switched live. That diagram is DREADFUL and it would be very easy for DIYers to mistake this.

Jodo, remember this: if you connect LIVE to L1 and neutral to COM, when happens when you throw the switch? There is a DIRECT connection between LIVE AND NEUTRAL which will DESTROY the switch through heat and arcing and blow the fuse. NEVER connect neutrals to switches.

 

[ban-all-sheds]

Sorry, I really shouldn't post when it's late. I just re-read my original post and as well as typing red/green instead of yellow/green, I also wrote black instead of red. The source of the misunderstanding is mine, I apologize.
So, I have 3 cables each with 1 red and 1 green/yellow, no blacks at all.

OK - it's an unusual cable, but single red & earth does (did?) exist.

One of the reds will be permanently live, the other two will be switched lives going to the two lights.

The only thing that puzzles me is if there are no blacks there, why did you write

The original switch was wired up with the two com terminals bridged and the live also entering one, and then the other two reds in L1 and L2 on different switches with the neutrals connected to the back box.

?

 

[Jodo]

The only thing that puzzles me is if there are no blacks there, why did you write

The original switch was wired up with the two com terminals bridged and the live also entering one, and then the other two reds in L1 and L2 on different switches with the neutrals connected to the back box.

?

I can see why that puzzles you ban. I have changed switches before without a problem but because this was a double dimmer and looked more complicated to wire from the diagrams, I asked my father-in-law for his input. He fitted a shower (with no previous wiring in place) and replaced a fuse box in his own house (both very questionable for most DIY'ers as I have now learned on this forum).

Either he was tired when he looked at my wiring and mistook the green/yellow Earth for Neutral ( ), or he doesn't like me anymore, but I bowed to his higher knowledge and took the Earth to a terminal on the switch!. I should have stuck with my own knowledge at that point, because I would have got through on that. I know Earth is green/yellow just thought they must be sheathed wrong when he told me they were Neutrals as they were loose sheaths.

I will be recommending he have his electrics checked out by a sparky after this and won't be taking a shower there until it happens.

I know I look a complete idiot and will be laughed at, but I have learned a lot here and want to thank you all (again). I take on board all comments about doing my own electrics DIY and will only be changing switches in the future (as believe it or not, I replaced the dimmer with another which is working perfectly well (and is earthed properly )). The pro's will be in for everything else (possibly including 2-way switching) unless I get me some formidable knowledge in the meantime.

Sorry for the long reply but I thought you deserved a thorough explanation to the thoroughly dismal reason for my problems.

OK - it's an unusual cable, but single red & earth does (did?) exist.

ban, the house was built in the early 50's so does it sound like this could be the original wiring? Should I maybe think about getting it rewired? And thanks for all the help....

 

[Memster]

you used to be able to get a 2 core live (red) and earth wre which is now 2 core brown and earth, but tbh ive never used it, much cheaper and easier just to stick on a sleve

u might just fid that when it was orriginally wired it was done wrong, i recently changed a switch for a freidn and found the hole circuit was wrong, earth was set to live, live to neutral and so forth. u might want to invest in a multi meter