For smaller (<2000) Inverters, Victron used to suggest a simple bypass “mode” by pulling the AC IN cable plug, pulling the AC OUT receptacle, and connecting them together. Seems simple. The newer Multiplus Compact (12/2000)does not have the “plug” feature anymore, they use terminal blocks. I read that the reason for the change was simply the plugs were difficult to remove etc..? so I thought I would in effect do the same setup with some short pigtails, using NEMA L5-30R and L5-30P connectors. For arrival in extreme cold (remote off-grid cabin) I could manually bypass the inverter and run the AC panel straight off the small generator (which normally plugs into AC IN. But, as I sketched this out, it appears to me that in that condition, I would be losing the earth ground connection to the DC side of the Cabin. From all instructions I have seen, I am tieing DC negative bus, with all the DC enclosure grounds, to the Multiplus Chassis which is internally tied to AC Out ground, which then ends up at AC panel ground and then earth ground rod. If you (mechanically) disconnect AC out, you lose that ground path between DC- and AC Gnd. In the scenario described, Inverter would off, and likely Battery Bank Main Switch, until the cabin warmed above 32f. But, after reaching 32f, if someone turned the Battery Bank on, before reconnecting Inverter (and internal ground path), that “could” be a potential problem, couldn’t it?? So, I guess the next solution is 2 pole manual transfer switch, switching L & N from either AC In or AC Out to Panel (common side of transfer switch). The ground would remain intact through the Inverter Chassis. This would seem to work fine for Inverter “bypass”, but if the Inverter needed to be actually removed for service, I would need to mechanically join DC- and AC Gnd.
I was originally just trying to save the space of the MTS (good ones are not inexpensive either), by using the plug and receptacle approach, but MTS seems like best or certainly “better” practice. Again, Honda 2000 usually feeds Inverter AC IN, but in some very cold arrival conditions, I want to easily have the generator directly feed AC panel for 3-4 hours to warm up battery bank (and other electronics).
Am I technically correct that the plug and receptacle approach would have been slightly flawed? Or am I over-thinking this? Can create and share schematic if needed. Thanks all.
I think so, yes.
I guess that would help.
Thanks for taking the time to look! I am bonding N/G at the 120V panel.(1)Earth Gnd rod will be near panel. Ignore the 50A Main, I’ll change that to 30A. It appears to me, from everything I have found in wiring unlimited etc, that my DC- is tied to DC Chassis gnd. That in turn, is physically tied to AC Gnd (from factory) right at the Inverter AC terminals. It appears that if I use the “NEMA plug/receptacle” approach to manually bypass Inverter (conn B&D) on those extreme cold arrival nights, I would lose the connection from DC- & equipment gnds, that “normally” is tied to the AC panel through the inverter. If someone wakes up in the morning, and turns on main DC disconnect at battery, solar charger could start running, and that wouldn’t be completely safe to have DC gnd isolated from AC gnd (and earth). I know they “should” remember to bring the inverter back in to play (Conn A &B, C&D), but no guarantee.
And so, it seems to me, even though I originally wanted to avoid the MTS, its probably what I need to do; gnds will always remain intact, MTS switches N & L from either AC Out or Genset, to AC Panel In. In bypass mode, the Genset would still go to Inverter AC IN, but AC out would be “cut off” at MTS… This extreme cold scenario would be pretty rare (maybe 1-2) weekends a year, so I thought the NEMA plugs seemed easy enough, until I saw what I perceive as the gnds isolation problem. Am I wrong?
