Wiring a two-way dimmer switch - am I dim?

[nearenuf2me]

Can anyone advise me if it is possible to wire up a two-way circuit with a plate two way light switch and a push on/off, rotary two way dimmer, so that either is able to turn off the light.

At the moment whichever switch turns on the light is the only one that can switch it off.

The dimmer can always dim the light, regardless of how it was switched on.

Is it possible to have either switch able to switch off the light, even if it didn't switch it on?

The dimmer is at the 'remote' end of the circuit at the moment - in other words it only has the red/yellow/blue cable going to it. Does it need to be at the 'feed' end?

what terminals, do I need to put which cables in, on which switch? I have tried various combinations to no avail :-(

Many thanks for any advice.

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[Richard Porter]

I don't see why not. The actual dimmer circuit should be connected to the common pole of the changeover switch. Are you sure the switch linked to the dimmer is two-way, not on/off?

Which means that you've effectively got two on/off switches in parallel.

I can't see immediately how this works but there must be a wiring error.

That's how it should work.

No. If you look at the diagram below you'll see that it doesn't matter which end the supply goes to.

(red) L1 L1 Supply=====O==================================O red ---O===================O--wwww--O--- yellow Load=======O==================================O blue (black) L2 C C L2 Plate switch dimmer push switch

It doesn't matter if L1 and L2 are interchanged. The important thing is that the two common (C) terminals are connected to each other and nothing else.

[Dave Plowman (News)]

Yes. Push on/off dimmers usually have a two way switch and can be treated as one. Provided the dimmer isn't turned down so far the light goes out, of course. But most stop before this. The type that turn off at the end aren't two way - or rather I've not seen one that is.

[John Rumm]

Yup, although at the plate switch end you will be stuck with whatever brightness has been selected at the dimmer end (unless you get some more expensive master slave dimmers)

That's not right.... but I guess you knew that!

This is how it should be...

Yes

Does not matter. If you look at the diagram below, and complete circuit (i.e. light one) will include a path through the dimmer.

Live SW1 SW2

------------*--------------------* L1 / L1 / *--------------* / COM L2 / L2

------------*--------------------* Sw Live

[The Natural Philosopher]

Yes, cos U have half a dozen wired that way.

That is inescapable.

Yes.

Makes no difference.

Your incoming live should probably go to the changeover contact of the simple switch.

Each other contact of the simple switch should go via the three way cable to the same contacts on the dimmer/switch.

The changeover contact on the dimmer switch then goes into one side of the dimmer, and the other is now switched dimmable live.

Whether you take the live feed back to the first switch and feed the lamp(s) from there or have carried the neutral along the third wire to the dimmer, and run the lamp(s) from that, is a matter of personal taste and your wiring layout.

You haven't tried the right one.

Leaving the dimmer aside. you have three terminals on each switch. Incoming live goes into the changeover contact, the two other contacts are connected to the same contacts on the remote switch, and the switched live is taken from ITS changeover contact.

The switched live simply then goes through the dimmer to form a dimmable switched live.

The last bit of the three way cable carries either this switched dimmable live back to the incoming, or the neutral to the remote switch, depending where the lamp feed comes in.

[The Natural Philosopher]

Mine do in fact go all the way down. However when that dim, I forget to turn them off anyway.

So in practice I seldom switch on and find the wretched things on the wrong setting.

[The Natural Philosopher]

Mm. I don't do it that way actually.

I do it this way +------------------+ / \ Live----------+/ \+---------switched live

+------------------+

But yours works equally was well.

Mine always leaves one of connecting the cables iso1ated when on, yours has the interconect always connected to live or switched live. Not sure if that makes any marginal differences really.

[Dave Plowman (News)]

Most will be extending from an existing switch pair in one box. So wiring that switch pair across L1/L2 while using triple and earth to the second switch is the sanitary way - avoiding extra choc blocks.

[John Rumm]

Yup, several ways of doing it.

The one I suggested is what they recommend in the on site guide (fig

7.3.4 in the brown book) for minimising interference with induction loop hearing aid systems.

[nearenuf2me]

Many thanks to all who posted replies.

Fixed it!!!

Problem was due to L1,L2,L3 on each switch pointing to diffrent terminals??? (both UK manufacturers to boot!)

Soo...

When I wired up correctly L1 to L1, etc it was wrong. Solved it with aid of continuity tester.

Is there no standard in this? L1 and L3 were each's common?

Moral, don't take whats written as gospell.

Again, thanks a lot for your advice.

P/s anyone know of someone who could fit a mitred join to a worktop for me in Redhill/Gatwick area? I would buy the tools and have a go myself but it seems a waste for a one off.

Regards, Gerry.

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[Dave Plowman (News)]

If they're written as L 1 2 & 3 I don't think there is a standard.