Corn Cob LEDS

[McConnell]

I have a parking lot with 12 ea. 277 volt Lights. Retrofit with Corn Cob LEDs 5k and now once a month at least 1 burns out. Voltage is about 288. It's in the range of 10% plus or minus. Should I change the taps on the transformer? That's the only thing I can think of.

 

[GoldDigger]

Does the luminaire restrict ventilation or place the bulb in a non-recommended orientation for cooling air flow?

 

[hillbilly1]

Are they direct wire? Or lamp ballasted?

 

[sameguy]

Very windy in that area?

 

[ptonsparky]

Don’t use the old ballasts. Aren’t the lamps rated 277?

 

[SAAPI]

I've got two replacing metal halide - removed ballast - they die about once a year.

 

[ptonsparky]

Low quantity for us but I don't think we've had any fail yet. Fixtures from one particular mfg that haven't lived up to the five year expectations but not the after market lamps. That mfg has been replacing them.

Not 277 either.

 

[kwired]

I have a parking lot with 12 ea. 277 volt Lights. Retrofit with Corn Cob LEDs 5k and now once a month at least 1 burns out. Voltage is about 288. It's in the range of 10% plus or minus. Should I change the taps on the transformer? That's the only thing I can think of.

If talking about changing taps I presuming these are replacement lamps that still utilize the ballast. Your ballast taps are likely 120, 208, 240, 277, in some cases 480. The 277 volt tap is still the closest to applied voltage.

Something to consider and not sure how LED replacement would respond, but in metal halide systems there is a capacitor that is in series with the lamp don't know what failed capacitor will do and might depend on how it fails as well. Also pulse start metal halide has high pulse starting device that I could see giving problems with a LED. I haven't used any of those replacement LED's yet, but think I would seriously consider ballast bypass types if I were to install any.

 

[LarryFine]

In my opinion, any LED replacement should be the type that does not use the ballast.

 

[kwired]

and another possible issue is having a replacement lamp that is or is not designed to be used in your application. things like open or enclosed lamp, lamp orientation and such can effect how heat is dissipated from said replacement lamp and depending on what the replacement was designed for may impact how long it will last

 

[tom baker]

I saw a lot of failures with LED (company) corn cob lamps. Heat is always an issue and also the quality of the driver.
A replacement luminaire would come with a warranty...

 

[drcampbell]

... in metal halide systems there is a capacitor that is in series with the lamp don't know what failed capacitor will do and might depend on how it fails ...

I don't think I've ever seen an AC capacitor fail any other way but open.
(which may or may not be the actual capacitor's failure mode; they usually have an internal fuse)

Does "5k" refer to the manufacturer's lamp-life estimate?
12 lamps x 400 hours/month = 4800 total hours of on-time per month. One failure per month might be entirely normal & expected.

 

[ptonsparky]

I always thought the 5K was referring to color, especially since CFL and LED.

 

[GoldDigger]

I always thought the 5K was referring to color, especially since CFL and LED.

That would normally be 5000 K where the K indicates degrees Kelvin color temperature.

 

[ptonsparky]

That would normally be 5000 K where the K indicates degrees Kelvin color temperature.

What’s three decimal points...

 

[GoldDigger]

What’s three decimal points...

I guess three decimal points would indeed be "...". Three decimal positions (or even better three orders of magnitude) would probably be more appropriate.

 

[hillbilly1]

In my opinion, any LED replacement should be the type that does not use the ballast.

Yeah, one of our lighting distributors said the failure rate on the ballast type is pretty high.

 

[LarryFine]

What’s three decimal points...

"Three holes in the ground; well, well, well."

 

[kwired]

I don't think I've ever seen an AC capacitor fail any other way but open.
(which may or may not be the actual capacitor's failure mode; they usually have an internal fuse)

Does "5k" refer to the manufacturer's lamp-life estimate?
12 lamps x 400 hours/month = 4800 total hours of on-time per month. One failure per month might be entirely normal & expected.

I find motor capacitors that have bulging case quite often. I don't think the "fuse" is an overcurrent device as much as it is a mechanical fuse that pulls apart when the terminal end of the case pushes out from pressure building up inside. Would guess majority of those that fail in this manner probably was due to short circuit, though the external result is open circuit because the fuse opened.