Hi everyone. I have been having some problem with some 2x4 troffers. Customer called last week a bunch of fixtures are out I changed 6 of the ballasts. a few days later they tell me the breaker keeps tripping so I put my amp meter on it it was pulling 24a so I split the circuits instead of 2 circuits now there are 4 for all the lights. I come this morning I see 2 ballasts are out one is one I just changed. What am i looking for?
Need more information to really help..how many fixtures were on each circuit, is the panel serving them 3 phase, were the circuits sharing a neutral?
Shared neutrals are a big no-no with ballasts, especially electronic ones. Harmonic currents add up rapidly and cause no end of problems and repeated ballast failures.
And any loose connections can kill e-ballasts rapidly. Had one case personally where we went through 3 ballasts on the same fixture until I pulled on the whip and the loose wirenut fell off in ther j-box. Fixed that and no more failures since (about 6 years now.)
That shared neutral is doing twice the work of either of the ungrounded conductors.
If it's single phase (pair of 120Vs 180 degrees out of phase) electronic ballasts on both sides should be drawing their spikes of current at the same time (in respect to the timing of a 60 cycle waveform) and thus the neutral should be sharing/splitting the spikes the same way it would if the loads were just resistors. When you get neutral overload is when you have multiple phases, 120 degrees out of phase. Then the loads on phase A draw their spikes of current at a different time then those of phase B.
A bad connection on a neutral could cause problems like those you normally see with neutrals serving other kinds of loads.
[This message has been edited by wa2ise (edited 01-13-2006).]
20 ballasts per circuit? check the amount of current each is pullin, it can add up. As long as they are not on the same phase, the neutral in the 3wire circuit should only have the imbalance on it, if they are on the same phase, the current in the neutral will be the sum of the current on both phases.