Mercury light bulbs ballasted?

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Old 02-26-14, 09:37 PM
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Mercury light bulbs ballasted?

Greetings,

I am doing some troubleshooting on some exterior area lighting at my place of business. There are several flush mounted "can" type fixtures in the ceiling of the walkway that use 100W mercury vapor medium base bulbs. There are some other surface mounted fixtures on the side of the building that have incandescent flood lights in them, (medium base, PAR type, I think they are called).

The question is, don't all mercury bulbs (& sodium bulbs, for that matter) require ballasts, just like fluorescent tubes? I don't want to test these fixtures with bulbs that were not intended to be used with them. A friend told me that any medium base will be straight 120VAC (in the USA) and that whether you screw in a mercury, sodium CFL, LED, incandescent, as long as the wattage does not exceed the fixture's rating, will work fine. He said it's only when you get into Mogul or other than medium base sockets that ballasts are used. Is this correct?
 
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Old 02-26-14, 10:20 PM
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There are some discharge lamps that were called self-ballasting.

Your 100w medium based mercury lamps more than likely are ballasted and a regular bulb cannot be used in that socket. You should replace the lamps with the proper part number.
 
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Old 02-27-14, 08:29 AM
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A friend told me that any medium base will be straight 120VAC (in the USA) and that whether you screw in a mercury, sodium CFL, LED, incandescent, as long as the wattage does not exceed the fixture's rating, will work fine. He said it's only when you get into Mogul or other than medium base sockets that ballasts are used. Is this correct?
INCORRECT! There are many medium base mercury, metal halide and high pressure sodium lamps that all require the approriate ballast.
 
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Old 02-27-14, 11:09 AM
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It's fine here. Same members in both forums.
 
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Old 02-27-14, 07:07 PM
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That's what I was afraid of....so, next question: What happens when you screw in a regular 120VAC incandescent or CFL into a ballasted socket, designed for the aforementioned 100W mercury bulb? Similarly, what happens if you screw in a mercury bulb into a regular 120VAC socket? And lastly, since one cannot see behind the socket in many cases, how do you know if the socket is for ballasted bulbs or not, and if ballasted,presuming different ballasts are for different wattages, how do you know what discharge lamp to use?

(I just realized this post should have been in the Lighting section....if one of the moderators wants to move it there, I'll watch for a continuation there, as well.)
 
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Old 02-27-14, 09:50 PM
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OCV on a 50 and 175V mercury ballast (what I have) are in the 220-240V range. When I screw a mercury vapor bulb into a 120V socket the arc does not strike.
 
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Old 02-28-14, 05:44 AM
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What happens if you screw a mercury or sodium or other "high intensity discharge" lamp into a socket intended for an incandescent lamp (fixture without ballast)?

1. Nothing might happen and the lamp remains dark.

2. (more likely) The lamp starts seemingly normally but as it warms up it gets brighter and brighter and burns out, possibly explosively.


What happens if you screw an incandescent lamp into a socket intended for a mercury, etc. lamp?

3. Nothing might happen and the lamp remains dark.

4. The lamp lights up but may not be at the proper brightness. There is a (small) chance the voltage is too high and the lamp burns out even though the source voltage was correct for the lamp.

4a. The lamp lights up for awhile but then shuts off because the ballast has failed due to too much amperage.
 

Last edited by ray2047; 02-28-14 at 07:07 AM. Reason: Correct BB code.
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