LED floodlight failure

[hbiss]

So, I stop by to see my buddy, a fellow EC the other day and he says let me show you something. He has an LED flood light, your typical cobra head- only with a bracket to mount to a wall. Lithonia I think. Anyway, he removed it from a gas station because the owner complained that after around 20 minutes it went out. It was in service for about 3 years with no issues. So he brought it back to check it out. On the top there is a compartment that contains the power supply and he figures it must be bad so he orders a new one. When he shows it to me the new PS has already been installed and he says that it still goes off after 20 minutes. You have to remove power and it lights again. Hmmm.

He takes the cover off and I check if it's the same as the old one, and it is. Mean Well HLG-320 here:

http://www.meanwellusa.com/productPdf.aspx?i=337#1

So I figure let's plug it in with the power supply sitting on the bench outside the fixture and see what happens. After awhile I touch the PS case feel very little temperature rise but the fixture is as hot as hell. My hunch was that the power supply was being overheated, and sure enough, with the power supply out of the fixture it continued to operate just fine.

For giggles, I say lets measure the 120V line current draw and it's an amp more than the 3.5A rating on the label. I don't know if that means anything, but for sure the fixture LEDs are generating too much heat. If you look at the spec sheet under protection, when an over temperature condition is detected it's designed to shut down and latch off output voltage, re-power on to recover. Which is exactly what it's doing.

So what about the LEDs? When they age do they draw more current and generate more heat? This power supply is a constant voltage design, perhaps a constant current supply would have been better suited?

I just advised that he try and return the replacement power supply and get his $100 back then tell the customer he needs to replace the fixture.

-Hal

 

[SparkyTrev]

My guess will be that an LED in the fixture (assuming that they're "china brand") has broke down enough to cause it to draw more current to fire. As an LED wears down, its internal resistance will rise.
That constant voltage meanwell driver doesn't mind and outputs current to keep the voltage the same, which in turn overheats it.
Ide return the driver, advise the HO of a defective fixture, and depending the cost of the fixture decide if rebuilding it with fresh LEDs from a name brand mfg would be cost effective. Good LEDs are pennies on the dollar still.

 

[hbiss]

... depending the cost of the fixture decide if rebuilding it with fresh LEDs from a name brand mfg would be cost effective. Good LEDs are pennies on the dollar still.

Thought about replacing the LEDs for about a second. There are three arrays made to fit that fixture so you would have to obtain them from Lithonia. Betcha it would be almost as expensive as a new fixture if they even sell them. And as far as I'm concerned, if it were me I wouldn't want to bother with it. I've already wasted enough time on this thing. Had to use the bucket truck to get at it. Just tell the customer that the fixture is defective, replace it, collect your money and move on.

-Hal

 

[SparkyTrev]

Agreed. Before apprenticing and still, I repair and rebuild LED lights as a tech. More fixtures now are only made to be put together and not come apart. Its good to see the meanwell driver, more often than not I pull fried drivers; the diodes are pretty stout compared to whats pushing them.