I went to replace an electronic ballast in a standard 2'x 4'troffer. Once I opened it, I realized that it had only three tubes, not the four that I was expecting. The ballast had three blue wires and one red, assuming that the red was common to all three tubes and the each blue went to the opposite end of each tube.
The replacement ballast said on the box that it supports either three or four tubes, however the wiring diagram only showed it wired to four and the supporting documentation was just safety information, etc. This one looked more traditional: Two red wires, two blues and two yellows. My question is how to wire this thing to only three tubes. My experience has always been that tubes on these ballasts work in pairs. Any ideas?
