Be careful when using D.E. filters.
After fixing our overvoltage problem due to a bad contactor for our generator autoswitch box, we ran a test on generator power. I had been noticing higher voltages when running on generator before all that happened, but I didn't think much of it. Sometimes loads are unbalanced, or whatever... On power grid, volts were stable.
Long story short, we now have whole-house over/undervoltage protection thanks to @fabric
. The only trouble was that this new protection kept tripping when we switched over to genny power. Measuring indicated that the V on phase 1 was 252V, with obviously higher spikes that triggered the new over-V protection. Should be 230!
I looked up the datasheet for the Linz 20kVA alternator we have, and the troubleshooting section said that if you have overvoltage problems, the load capacitance may be too high. D'OH! Cue lightbulb over my head...
We had 12 DE filters on phase1, and 6 and 5 on the other phases. Phase 1 voltage was highest on genny power...
Removed the filters, and problem is gone... So D.E. filters are a no-no when running on a generator. Here's why (simplified explanation of course):
I'm pretty sure it would be worse
on a smaller generator. Also, the same is true of inverter outputs according to at least one of my viewers.
I don't believe the DE filters ruined the grid contactor for the simple reason that while we were using the filters, we didn't have any power outages - except for the zapping events. Upon switching to genny power, a different contactor is engaged, and that one is NOT burned. I'm gonna clean it a bit and store it as a backup.
Best case, the genny has high voltage or shuts down. Worst case, it can be damaged due to high currents in windings.
So, I guess that lesson #2 is don't assume there's only one problem when there are actually 2 different ones! 🤓