120V incandescent and 12V halogen with same dimmer?


Old 03-27-11, 03:41 PM
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Join Date: Jun 2007
Location: Seattle
Posts: 2
Question 120V incandescent and 12V halogen with same dimmer?

My kitchen lights consist of 6 overhead 120V (60W) lights and 2 halogen 12V (50W) lights, all controlled by a single switch.

The lights are dimmed by a Lutron Maestro incandescent dimmer, and the lights have worked fine in the 4 years we've lived here, so I never really thought about it.

Flash forward to yesterday. One of the halogen bulbs burns out and I go to replace it.

I assumed the lamp was a 120V halogen, but I discover that it's a 12V.

I put in a new 12V lamp and it doesn't work. So I open up the fixture and see the transformer and it hits me something must have gone wrong in the transformer. (The wiring looks fine, and the light worked until yesterday.) I notice the transformer has a warning "dimmable only with ELV dimmer."

So my questions:

1) I assume the person who installed the dimmer (not me) shouldn't have done so? Could this have been why the transformer is now broken?

2) Is there any kind of dimmer that can dim both 120V and 12V lights on the same switch?

4) It is safe to continue using the lights with the dimmer (the other 12V halogen is still working) until I can get a new fixture to replace the broken one?

Thanks for your help!
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Old 03-27-11, 04:19 PM
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Join Date: Sep 2005
Location: USA
Posts: 4,259
It shouldn't be an issue. The Maestro dimmers support both incandescent and electronic loads, so it should be fine as is. It's likely that the transformer just reached the end of its life.

As long as the total wattage isn't exceeded, you should be fine simply replacing the transformer.
Old 03-27-11, 08:49 PM
Join Date: Oct 2005
Location: Milwaukee WI
Posts: 1,338
Are you saying that the 12V fixtures each have their own transformer?

In my experience, this could be a problem. When the bulb burns out, there is no longer a load on the transformer. I am not sure about the physics of what's different when there's a dimmer vs. straight 120VAC on the line side, but you might want to check this out with the fixture manufacturer.

My Lutron magnetic dimmer instructions told me to never operate a 12V lighting transformer without load. Unfortunately I did not read that until after I had connected the transformer and powered it up without any bulbs installed. Poof. Lucky for me I had an extra transformer.

My landscape lighting transformer said the same thing. Don't operate a transformer without a load. Intermatic goes into considerable detail about all the conditions required to protect the transformer from overcurrent and to protect the bulbs from overvoltage.

Hard to believe this would be the case for your fixture, because regardless of whether you had a dimmer connected, how would you ensure that the bulb never burns out?

So, have you checked for a circuit breaker or fuse on the transformer?

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