I am also responsible for a 480 Volt ungrounded system. I am considering installing a line insulation monitor (Cutler-Hammer D64L2). Do any of you have any experience with these? I am assuming that it would be better than the PT-light bulb arrangement.
There is an exhaust fan motor at one of my facilities which has a "sagging" problem. The motor will be running fine at about 50 amps and then, for no reason, current will drop to about 38-40 amps and hang out there for a minute or two. Flow also reduces during this time period...
