NEC 410.130(G)(1)
- Thread starter anbm
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Possibly because when you insert one end of the bulb in its socket there can be a high voltage exposure at the pin(s) of the unconnected end.
If you hold one end and insert the other you can get zapped.
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With most double ended lamps, don't you have to take the lamps out to access the disconnect? And wouldn't you have to plug in the disconnect before installing the lamps?
So I don't think that explanation works.
I don't have a better answer though.
I have always though that it was because on the single pin lamps removing the lamp diconnects power to the ballast where as on a double pin the ballast gets power directly from the source.
That, however, is based on my antique knowledge of fixtures. Old men don;t climb ladders and change ballasts so things might have changed
That, however, is based on my antique knowledge of fixtures. Old men don;t climb ladders and change ballasts so things might have changed
qcroanoke
Sometimes I don't know if I'm the boxer or the bag
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I think its more for ballast replacement safety.
Maintenance men working them hot and getting hammered from grabbing a hot or neutral.
Maintenance men working them hot and getting hammered from grabbing a hot or neutral.
Yes, I'm sure that is the idea, but why limit it to double ended lamps? Why not require the same for compact fluorescent fixtures, or even LED fixtures?
I have always though that it was because on the single pin lamps removing the lamp diconnects power to the ballast where as on a double pin the ballast gets power directly from the source.
That, however, is based on my antique knowledge of fixtures. Old men don;t climb ladders and change ballasts so things might have changed
That's interesting. I never knew removing a single pin lamp removed power from the ballast. So by double ended, they don't mean lamps that connect on both ends, they mean lamps that have 2 pins on each end?
That sounds like a plausible explanation. Maintenance people who have worked on single pin lamps may not realize removing a double pin lamp doesn't remove power to the ballast.
I don't replace ballasts either, but I can confirm on most double ended lamp fixtures, power goes straight to the ballast.
Strathead
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OK, I am a cynic, but I believe that the reason is because Ideal had a strong lobby and they convinced the board that with all of the ballast changes from T12 to T8 in the 90's it was a great idea to install the disconnects. I seem to remember the logic was the safety of changing ballasts. Back then they were done quite unsafely. I am sure OSHA would have a fit today. They were mostly done hot even at 277 in the High Rises in Northern Ca at least.
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I was at the NFPA meeting where this proposal was brought up, long lines of persons testifying against it (Salt Lake City 2004)
And after it was adopted, many ads in trade magazines for ballast disconnects
And after it was adopted, many ads in trade magazines for ballast disconnects
Strathead
Senior Member
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- Ocala, Florida, USA
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- Electrician/Estimator/Project Manager/Superintendent
Someone else please, but I think your original impression of a double end lamp is correct. The speculation that the disconnect has anything to do with lamp change is false. You have to remove lamps to remove the cover to access the disconnect. It is there to facilitate changing the ballast only.
I guess it doesn't matter too much since I can't tell you the last time I saw a single pin lamp.
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