Pot lights from halogen to LED and DC driver

[Kitchen Panda]

I've swapped most of the halogen MR 16 bulbs in my kitchen with LED near-equivalents; can't quite get to 700 lumens in an LED but I figure getting rid of the cover glass makes up some of that. The halogens have been OK, the LEDs have been great. But I have one spot in the kitchen that has burned up three transformers in 14 years. The last one went for two years less a day - and it was operating a 7.5 watt LED, not a 50 watt halogen. None of the other 20 or so lamps in the house have had a transformer fail, even those with LEDs and dimmers.

I purchased an LED 12 V solid-state driver ( which claims on the box to have ULC approval) from a certain online store and have replaced the iron transformer with this DC supply. I checked it on the bench, wiring up to a lamp and letting it run for 3 hours - it was scarcely warmer than room temperature, and measuring power into the driver shows 8 watts while running a 7.5 watt rated bulb. So, my hope is that this electronic driver will stay cooler and so last longer than the expensive transformers (which aren't even available as a renewal part from the maker!).

Now, I see the LED bulbs are stamped 12 VAC - they seem to light fine on DC, and draw as much power. At least for the Phillips lamp I tested. Will other types of LED perhaps not work on DC? The other thing I'm not entirely happy with is putting these electronic drivers in a closed ceiling box - the power dissipation is much less than an iron transformer, and I also kept the over-temperature cutout in the box.

I wonder why the original transformers fail so often in just one spot in the house, and not elsewhere? I wonder if after 14 years I'm going to have a wave of transformer failures?

Oh well, at least I've got one DC driver conversion to use as a pilot model.

 

[JoakimFlorence]

That spot might get more vibration (perhaps from a nearby fan) or get more exposure to moisture. This could lead to loose or corroded connections in the wires. This can then lead to resistive overheating and a burnout.
It's also possible when you have been replacing those transformers you have not been properly connecting them in a way that maximizes surface area between the contact points.

One more possibility (unlikely I think) is the metal housing might be grounded (somehow in contact with some other metal) or not adequately grounded, different from the housing of the other transformers.

Is that one light fixture on a dimmer? Iron core transformers do not like to run on some types of dimmers. When they do, they run much hotter than usual due to the extra high frequency the dimmer generates.

Now, I see the LED bulbs are stamped 12 VAC - they seem to light fine on DC, and draw as much power. Will other types of LED perhaps not work on DC?

I imagine the ones meant to run on lower voltages will. But not all of the bulbs meant to run on higher (normal plug-in) voltages.