Ballast Stray Voltage.

[wireddd]

We are in the process of converting 150 fixtures from T12 to T8 lamps and electronic ballast. On several of the fixtures one of my electricians got a shock from the ballast housing to the threaded rod supporting the fixture. So we started checking and found that the ballast case to ground registered
4 volts. We did find that the conduit feeding these fixtures had somewhat loose locknuts at the junction box. After tightening the voltage dissapeared. So I checked several ballast at our shop and found that when energized the ballast case to ground was 3.76 volts. Enough to give you a shock. I then talked to tech service at Phillips/Advance and was told that yes indeed the ballast gives off a "radiated type pulse voltage" and that 4 volts was within the UL requirements for leakage. I was also told that some ballast may be as high as 60 volts. I then asked what effect this many ballast may have on the grounding system if they all leaked 4 volts. I was told that because you can't touch all the fixtures at once it's not a problem.
Has anybody had any similar situations along this line?

 

[Electric-Light]

We are in the process of converting 150 fixtures from T12 to T8 lamps and electronic ballast. On several of the fixtures one of my electricians got a shock from the ballast housing to the threaded rod supporting the fixture. So we started checking and found that the ballast case to ground registered
4 volts. We did find that the conduit feeding these fixtures had somewhat loose locknuts at the junction box. After tightening the voltage dissapeared. So I checked several ballast at our shop and found that when energized the ballast case to ground was 3.76 volts. Enough to give you a shock. I then talked to tech service at Phillips/Advance and was told that yes indeed the ballast gives off a "radiated type pulse voltage" and that 4 volts was within the UL requirements for leakage. I was also told that some ballast may be as high as 60 volts. I then asked what effect this many ballast may have on the grounding system if they all leaked 4 volts. I was told that because you can't touch all the fixtures at once it's not a problem.
Has anybody had any similar situations along this line?

See: http://www.westbay.ndirect.co.uk/images/Figure5.jpg
Almost all switch mode power supplies have a front end common mode filter like that. This includes electronic ballasts. The voltage you're seeing is due to capacitive coupling.

 

[templdl]

And the voltage is measured with a digital multimeter which will read a voltage across just about anything. Should you take a common 2 cell flashlight light with a 3v band palce it across the points which you are measuring it will with almost all certainty not light up.

 

[jeremysterling]

And the voltage is measured with a digital multimeter which will read a voltage across just about anything. Should you take a common 2 cell flashlight light with a 3v band palce it across the points which you are measuring it will with almost all certainty not light up.

Since the probability is high that the 4 volt leakage potential of the service ballast is not the source of the electrician's shock, the OP may need to explore alternate theories for the source of the shock.

Line voltage or battery ballast are two good places to start.