Problem with dimmer on 3 way light circuit

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mattwnz

20149 posts

Uber Geek

#248153 12-Mar-2019 15:59

My parents have had a bedroom wired on a new build so LED downlights are on a 3 way circuit. So there is a switch next to each of the two doors leading into the room, and the third switch beside the bed has the dimmer on it so they can reduce the brightness at night . This was on the plans prior to wiring. However the dimmer only sometimes works, and depends on which of the other switches are on an off. It isn't a problem with the lights themselves. Apparently the electrician has said that the dimmer would need to go on a light switch by the door, as apparently that would be the main line into it, even though the plans show it should go on the one beside the bed. Does anyone know why this would be and whether anything could be changed to fix this. There is no roof space, so wouldn' t be easy to rewire.

TechSol

299 posts

Ultimate Geek

Technical Solutions Aust

#2196608 12-Mar-2019 16:21

It's to do with which switch has the feed going through to the light fitting itself. The dimmer really needs to be there.

The other option would be to use the Legrand Excel life dimmers, which allow a slave pushbutton at another switch to slave the dimming.

mattwnz

20149 posts

Uber Geek

#2196617 12-Mar-2019 16:36

Thanks that is what I suspected. Currently they are PDL 600 series rotary dimmers, and apparently the lights allow phase cut dimming . Are the Legrand ones similar to these push button PDL ones, like this one to allow slave dimming http://www.pdl.co.nz/Trade/Products/ProductDetail?catNo=PDL654PBM&cat=1&sc=1&r=63599&nt=63599-510575&nt2=510575-323597 As they are stuck with PDL fittings.

TechSol

299 posts

Ultimate Geek

Technical Solutions Aust

#2196619 12-Mar-2019 16:39

mattwnz:

Thanks that is what I suspected. Currently they are PDL 600 series rotary dimmers, and apparently the lights allow phase cut dimming . Are the Legrand ones similar to these push button PDL ones, like this one to allow slave dimming http://www.pdl.co.nz/Trade/Products/ProductDetail?catNo=PDL654PBM&cat=1&sc=1&r=63599&nt=63599-510575&nt2=510575-323597 As they are stuck with PDL fittings.

No personal experience with the PDL ones, but I would be surprised if they didn't have a slave dim option. The legrand ones look similar.

mattwnz

20149 posts

Uber Geek

#2196621 12-Mar-2019 16:39

TechSol:

mattwnz:

Thanks that is what I suspected. Currently they are PDL 600 series rotary dimmers, and apparently the lights allow phase cut dimming . Are the Legrand ones similar to these push button PDL ones, like this one to allow slave dimming http://www.pdl.co.nz/Trade/Products/ProductDetail?catNo=PDL654PBM&cat=1&sc=1&r=63599&nt=63599-510575&nt2=510575-323597 As they are stuck with PDL fittings.

No personal experience with the PDL ones, but I would be surprised if they didn't have a slave dim option. The legrand ones look similar.

Thanks for your help. I will suggest the electrician looks into that as a way to fix the issue.

mattwnz

20149 posts

Uber Geek

#2202676 21-Mar-2019 00:14

Despite the electrician previously saying the dimmer would need to be moved to a different switch, they have managed to get it working on this one, which is good. However we did noticed that the dimmer dial dims the light in the wrong direction from the indicator on it as shown by the photo below.If we turn it anticlockwise it dims, but the indicator show it should brighten/ We contacted PDL, and apparently they only make a dial that is printed in one direction, and aren't aware of any issues with the indicator direction being wrong. Reversing the dimmer wires apparently makes no difference. Does anyone know what is normally done to get a dimmer to go in the opposite direction, or is it related to it being on a three way circuit. The electrician has apparently said that that is just how it is made.

TechSol

299 posts

Ultimate Geek

Technical Solutions Aust

#2202687 21-Mar-2019 06:51

The dial in your picture is actually correct..... it’s a matter of perspective - picture putting a static white line indicator on the plate behind the dial and it will make more sense.

It’s impossible to wire the dimmer backwards in this instance

Ge0rge

2052 posts

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#2202688 21-Mar-2019 06:52

I'm not sure why you think there is something wrong with the dimmer to be honest.

Imagine a mark drawn at 12 o'clock on the face plate of the switch. As you turn the dimmer clockwise, the indicator line will move past this mark, steadily getting thicker as the light gets brighter. Turn it anti-clockwise, and the line gets thinner relative to the mark, with a corresponding dimming of the light.

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trig42

5810 posts

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#2202712 21-Mar-2019 08:39

I would expect the light would get dimmer as you turn it anticlockwise. Makes sense.

The picture also backs this up.

mattwnz

20149 posts

Uber Geek

#2202905 21-Mar-2019 16:20

TechSol: The dial in your picture is actually correct..... it’s a matter of perspective - picture putting a static white line indicator on the plate behind the dial and it will make more sense.

It’s impossible to wire the dimmer backwards in this instance

Thanks. yes that does make more sense if a white reference dot is put on the top, as that gives the dial a different meaning. I do wonder why they didn't think of adding something to the module. Also clockwise rotation to increase brightness, like a volume dial makes sense. The picture is actually upside down, but I guess the module can be rotated so the indicator on the dial can be at the top and then reference a mark at the top. At the moment it would need a mark to be on the side to make sense. One reason I was also confused is becuase PDLs own website shows the dimmer dial in two different directions depending on the dimmer module as shown below. They have said it is likely an error, as they only produce one print for all the dials.