Home>Discussions>ELECTRICAL & LIGHTING>3 way dimmers. I'm feeling pretty dim.
22 posts / 0 new
Last post
brettmarl
3 way dimmers. I'm feeling pretty dim.

I have new a circuit that I put in during a basement remodel that has a pair of fixtures on a 3-way switch. there is a normal 3-way switch at one end and a 3-way dimmer at the other end.

Installed, everything works fine. Several weeks later, and the solid 3-way only works if the dimmer 3-way is in the ON position. the position of the dimmer slider does not impact things. If the dimmer 3-way is in the OFF position, the solid 3-way does nothing.

I figured that one of the 3-way went bad, so I replaced both switches - and everything is back to normal. I didn't troubleshoot which switch was bad, but I suspect it was the dimmer.

Now, exactly the same problem just occured on a different circuit in the basement.

What gives? Is it really possible that I had two dimmers go bad? These are both the same model lutron switches from Home Depot. Are 3-way dimmers notorious for burning out or something? I did notice that the dimmer switch appears to feel warm to the touch when on.

Before I go our and brute-force another replacement, I'd love a better theory than two bad dimmers :)

Oh - and I carefully marked the common and travellers at install-time, and as this worked for a period then failed - I'm pretty sure the wires aren't mixed up :)

Cheers,
-Brett

this is the specific model of dimmer:

http://www.lutron.com/ariadni/?s=17000&t=17200

I'm using the 600 watt incandescent one. The first circuit that burned out had 7 x 50 watt incandencet can lights on it. The second circuit had 2 x 35 watt halogen bulbs.

sparky rw
Re: 3 way dimmers. I'm feeling pretty dim.

do you have a continuity tester? if so check and be sure your travelers are correct. you might try puting the dimmer in the box with the switch leg. the warmth from a dimmer is normal.

brettmarl
Re: 3 way dimmers. I'm feeling pretty dim.

for the last one that died, i used my multimeter in resistance mode to ensure the travelers were correct.

any recommendations for validating a bad dimmer using a multimeter? i assume in OFF mode, there would no continuity on either traveler terminal.

Fencepost
Re: 3 way dimmers. I'm feeling pretty dim.

I'm not sure that you can use a multitester to evaluate a dimmer switch. Dimmers use "silicon controlled rectifiers" which chop the current -- that is, they rapidly turn on and off -- instead of presenting a varying resistance.

canuk
Re: 3 way dimmers. I'm feeling pretty dim.

brett ..... Lutron has a 24/7 tech support line 1-800-523-9466 . They will work with you from home to resolve things by providing them with all the numbers from the dimmer and exactly the wiring setup.

The output from those electronic dimmers are from a Triac.
An ohm check really will only verify the conductors and the mechanical toggle switch.

brettmarl
Re: 3 way dimmers. I'm feeling pretty dim.

oddly enough, everything is working fine again this morning. i'm suspicious that the dimmer is mis-behaving when overheated. i'm going to leave the lights on again for a while and see if i can reproduce the problem.

perplexedly yours,
-brett

JLMCDANIEL
Re: 3 way dimmers. I'm feeling pretty dim.

Brett when you installed the dimmers did you remove the side panel on them to put them in one box (called ganging)? If you did it reduces the wattage rating to 300 watts. What you might try is to put one dimmer and one 3-way in each box instead of 2 dimmers in one box and 2 3-ways in the other box..
Jack

canuk
Re: 3 way dimmers. I'm feeling pretty dim.

Jack .... I was wondering about that as well.
It might have some bearing on the one light circuit having the 7 x 50 watt = 350 watt ... but ... shouldn't be an issue with the other light circuit with the 2 x 35 watt.

JLMCDANIEL
Re: 3 way dimmers. I'm feeling pretty dim.

Canuk,
The problem is that you are putting 2 SCR circuits in one box. That concentrates the heat. It will depend on the temperature failure of the individual SCR.

As an example lets say the failure temp of SCR 1 is 122 degrees and SCR 2 is 125 degrees. As soon as the temp reaches 122 SCR one shuts down that allows the box to stay below 122 and SCR 2 continues to work. Install new dimmer 1 it's SCR failure temp is 127. So now as the temp rises SCR 2 fails because you reach 125 but SCR 1 still works. Let them cool down and they both work again. By putting the dimmers in separate boxes you do not combine the heating output of the two.
Jack

canuk
Re: 3 way dimmers. I'm feeling pretty dim.

Yep .... I fully understand what you're saying and it would also depend if the box was metal or plastic for heat sinking purposes.

I was thinking they may be in seperate boxes since they are 2 different circuits ... but you never know.

Also was curious if these circuits are dedicated for lights or if they may also be tied in with receptacles.

brettmarl
Re: 3 way dimmers. I'm feeling pretty dim.

Interesting overheating theory. Both the 3-way dimmers in question are each in their own individual box. They are both in a weird wall - it's a concrete wall that is fir'ed out with 2x2's. The box is a double-gang Carlon plastic shallow box (so it's only 1.5" deep) with a single-gang mud-ring on the front (i wanted enough room for the wires & dimmer). we used closed-cell spray foam insulation - in the walls - so it's pretty darn tight in there insulation-wise.

Pages

TV Listings

Find TV listings for This Old House and Ask This Old House in your area.