Loose or high resistance neutral. Check ALL neutral and bonding jumpers, both in the distribution & branch panels. Also neutrals on the affected ckt, a loose or bad shared neutral on a 120/208 ckt will surely cause problems like this. Also look for a grounded neutral on a ckt. If you close a main breaker and there is a poor or undersized neutral, but also a ckt with a neutral to ground short, when the inrush current is present as the main is closed, it will try to get a ground (neutral) at the lowest resistance point. This can be the neutral to ground point. (and may be thru the affected equipment) Robert
