Light Fixtures 240V fixtures on 208V circuit?

[plangetee]

Hello all

I've got a 208V power source single-phase. Turns out the light fixtures I have are 240V. Any harm in powering the 240V light fixtures from a 208V power source?

Let me know if I can clarify anything.

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[davidbeach]

It depends. What are they? What actually gets connected to the circuit (lamp, ballast, etc.)? What is the actual voltage rating of what gets connected? Etc., etc.?

 

[cranky108]

Many high energy fixtures are changable. Do a little homework.

 

[undervoltage]

No harm, the output lux level will be less then what it should be at rated voltage.

 

[waross]

the output lux level will be less then what it should be at rated voltage

Yes. I have seen the lux output of fluorescent fixtures cycle between low and lower (zero, as low as you can get) as the thermal protection cycled on and off under low voltage conditions.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[jmbelectrical]

Since the fixture is rated at a line-to-line voltage (240V), I am assuming that it uses an HID lamp. At a reduced voltage, the ballast will likely be unable to start or maintain the arc required for proper operation of the lamp.

Many HID ballasts are equipped with multiple taps to allow for operation at 120V, 208V, 240V, 277V, or 480V. Verify that this is not the case before doing anything else. Otherwise, the ballasts will need to be replaced. Buck-boost transformers are another option, as well.

 

[plangetee]

These lights do not have ballasts. They are incandescent lights. The lights are being used in a Beacon Flasher Assembly. The lights are being installed at various places on a silo.

What we are more than likely going to have to do is change the entire assembly to 208V...per the recommendation of the manufacturer of the lights. Adding transformers I'm being told is going to be more expensive than just changing the entire assembly.

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[ThePunisher]

I they are incandescent lamps, the lamp intensity will decrease due to a lower voltage applied.

Do you want to consider the equivalent lux output due to a lower nominal voltage applied and see whether it is still complying with your requirement before to paddle to an endeavor to change all of them?

 

[PHovnanian]

Beacon Flasher as in FAA required structure marking lights?

I'd replace them with 208V fixtures. The problems you might encounter with using 240V marked equipment improperly include visibility and/or flashing rate out of spec. The biggest risk is that some doctor will fly his Cessna into your silo and, following the subsequent investigation, his heirs will sue you, the silo owner and anyone else they can find for his death.

 

[BJC]

"The lights are being used in a Beacon Flasher Assembly. The lights are being installed at various places on a silo."
It may have been designed that way. You get longer bulb life with 208 volts. I have seen it on stack lighting.

 

[cranky108]

incandescent lights? They aren't the type congress is outlawing are they?

That would be insane for one goverment agency to recommend, and another to outlaw.

 

[waross]

That would be insane for one goverment agency to recommend, and another to outlaw.

Sadly, that is the nature of many government agencies.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[cranky108]

Sarcasim, is just another way of showing disgust with things.

 

[eeprom]

According to IEEE 241, under powering an incandescent bulb will prolong the bulb life and decrease the illumination, no damage done. For a 120V bulb powered at 105V, the lifespan increases to 575%, and the illumination goes down to 64%.

I had a project years ago where we had dozens of 120V indicator bulbs on a series of control panels. The distribution transformer was tapped up to help the starting of 480V motors. The result was that our tiny 120V bulbs were burning out at a disappointing rate. We put in a transformer with an 88V secondary, and we never had another problem.

 

[waross]

I supervised a department store project. There were a lot of ceiling mounted 150 Watt accent spot lights. The issue was the labor cost to replace lamps. Because of the location above displays, it could take two or more men several hours to access some of the fixtures for relamping. We installed auto-transformers to drop the voltage to about 108 volts. The lamps lasted for years.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[plangetee]

The installation is actually in Canada. I'm not sure what Canada's government is doing as far as legislation goes.

For the comment regarding the life expectancy of a bulb based on voltage: where would Ifind this in the NEC?

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[eeprom]

I don't think there is anything in NEC for bulb longevity. Take a look at "IEEE Recommended Practice for Electric Power Systems in Commercial Buildings". Chapters 3 and 10.

 

[PHovnanian]

Contact a reputable bulb manufacturer for life vs voltage figures. There are 'long life' bulbs, bulbs rated at higher voltages (130V instead of 120 or 125, for example).

I have a fixture (with bulbs) that I brought back from Paris rated at 220V. Just for kicks, I put it in a hallway in my house about 20 years ago. The light is dim (but good enough for the hallway) and the bulbs have never been replaced.