# ballast



## Dennis Alwon (May 9, 2009)

I am curious as to why it did not trip the OCPD.


----------



## jbfan (Jan 22, 2007)

If you are doing it hot, at least cut the feed before removing the ballast!


----------



## Dennis Alwon (May 9, 2009)

Sounds like if the ballast is floating and you read 133v from steel to the casing on the ballast then the ballast must be shorting to the case.


----------



## Big John (May 23, 2010)

I'm gonna guess this was a magnetic ballast, and the case was had voltage on it from some sort of coupling. Think of induced voltage on the dead travelers of 3-wire Romex. Same thing.


----------



## bill4807 (Jan 4, 2013)

Dennis: I do not believe the protection device tripped.
Jbfan: I don't know I was not there, I think he was just curious as to why it was happening as he was testing it.

So the engineer at this place allegedly said that all their ballasts do that since once you unscrew the casing from the light fixture mount u break the ground. And there is a "floating potential of 133V" I do not know if it is tied in on the inside of the ballast or not. But if its all of them there has to be some explanation of how its there.

Big John: I do not know if it is magnetic.But if it was coupled, i dont know i think thats alot of voltage to get coupled without a larger magnetic field between the two. 

I think since u undo the case which is grounding the ballast, u are basically floating the "neutral" and when measured from that to ground u get half the supply on that circuit, then when reconnected it shunts the "133 floating voltage potential back to ground where it is suppose to be. Any thoughts? lol


----------



## Skooby (May 3, 2012)

I once found 120v from the ECG from 4lamp T8 fixtures. Only happened with three or more in a run, ENT was between fixtures. Went to tie in a switch leg and I got buzzed when I twisted the EGC's together in a jbox. I opened every jbox in the path to the service, thinking I had a crossed wire to the grounded conductor, found none. Further investigation found it was coming from electronic ballasts. Called the engineering number on the ballast, they suggested I check out the frequency, and said as long as it was above 12,000hz it shouldn't hurt anything. So checked the frequency, found it to be 26,000+hz. Asked the local inspector in, we were both concerned but be let it pass.... Still confused a little, again it only happened with three or more 4lamp T8 ballasts, since that incident, I use metal conduit/emt and have not found this problem again....


----------

