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Old 05-09-2017, 03:03 PM
cmac2012's Avatar
Renaissance Dude
Join Date: Dec 2004
Location: Berkeley, CA
Posts: 24,061
LEDs and dimming - problem SOLVED

One of my best clients decided to put LEDs everywhere in his estate. It's about a half acre lot with a lot of exterior lighting. They operate their business out of their house, there's a stone sidewalk leading down to the house, steps of varying length - they have numerous footlights, etc. for safety.

He's tired of always replacing bulbs and wants to bring his elec bill down. Inside they have 3 areas with the L7MR16. We bought Luxrite brand, 7 watts, 500 lumens, 2700K on the heat/color scale. The latter important, I have yet to find a client who likes the blue white variety and 3000 and over is leaning that direction. Especially 3500 and up, nobody seems to like it. 2700 has enough red and yellow in the spectrum. 2800 good also.

In the kitchen are 5 can lights with this bulb. The bulbs are specified dimmable and I bought a dimmer that is rated for LEDs. But, oh dear, problems. Flickering, complete blackout if left in lowest dim setting, takes a few minutes to come back on when dialed up. At full bright is high frequency fluttering. Last night they all but one went out completely.

I had a hunch it was the transformers at fault and research backs that up:

10 things you MUST know before you dim LED lamps | Lux Magazine | | Americas | Home page

This is an interesting article and requires some digestion. I wouldn't expect anyone to read it unless they too are looking for LEDs with proper dimming ability.

There are thousands of different dimmable LED light fixtures on the market, but only three major types of dimming method: mains dimming, Dali or DMX.
The dimmer switch I bought has to be of the 'mains' type. The Dali type sounds superior but it requires an extra two core cable between the dimmer switch box and the driver/transformer. I might be able to fish one down to the box.

My hope is that I could buy a single transformer and get rid of all of the tungsten bulb transformers, each can having its own of course. The 5 cans are in a small area, wiring them with low voltage wire would be easy. If such an item can be found that uses the older style 'mains dimming' would be cheaper.

The article points out that this is largely unregulated market place. Manufacturers make claims that their LEDs are dimmable and the answer may be yes and no.

This client had two older fluorescent under-cab lights with the small 2 ft. bulbs. Always needing new bulbs, just unreliable. He bought two LED fixtures designed for the purpose. I put them in, they're controlled by the same dimmer. They are working great. More modern of a driver installed.

By contrast, the can lights have a transformer that was built before the LED retrofit market existed. Not really prudent to think it would be up for the task.

In summation, I still need some learning to know what transformers/drivers to get to solve my problem.


1986 300SDL, 351K
1984 300D, 133K

Last edited by cmac2012; 05-11-2017 at 03:06 AM.
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Old 05-11-2017, 03:05 AM
cmac2012's Avatar
Renaissance Dude
Join Date: Dec 2004
Location: Berkeley, CA
Posts: 24,061
Oh man, sometimes you get lucky. Turns out this guy did the trick for all five can lights. This is the 75 watt version, I got a 60 watt that looks nearly identical at a local lighting store. My research was making me paranoid. Five lights at 7 watts each, that's only 35 watts. I may buy the 75 watt-er from Amazon (for less than half of the store price) and put 3 of the lights on that on and the remaining two on the 60. Overkill. A sort of redundancy insurance.


1986 300SDL, 351K
1984 300D, 133K
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Old 05-17-2017, 02:46 PM
E150GT's Avatar
I'm a chicken
Join Date: Sep 2006
Posts: 1,148
I sell electrical supplies. I dont really get into things like this really but I run into dimming issues with LED's sometimes. I always suggest that you get with the manufacturer of the bulb. They usually test all their lamps with the various dimmers available and can tell you which ones work best with their product.
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Old 05-17-2017, 03:58 PM
is thinning the herd
Join Date: Mar 2010
Location: Columbus, Ohio
Posts: 3,340
We own a lighting company, we happen to sell mostly TCP LED bulbs (as well as Sylvania, and others), and like E150 mentioned all our manufacturers put out lists of what dimmers they have tested with their products. TCP happens to really like Lutron dimmers.

Its also important to remember a fair number of LEDs you will still find out on the market, usually cheaper big box store LEDs, or the ebay chinese $2 LED bulbs I regularly have thrown in my face simply are not dimmable. Make sure you've got a dimmable bulb.
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Old 05-17-2017, 06:09 PM
IMPEACH II 2021 +25A
Join Date: Jan 2014
Location: Honah Lee
Posts: 18,793
And for the first time ever a dim bulb is desirable !!

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