Looks like the best answer to my question is to retrofit a transfer switch that switches the neutral as well as both lines but there's still a couple of things I'm not sure I've got my head wrapped around and maybe a couple of options I haven't thought of.
I'm planning to use an MPP LVX6048 with batteries and PV primarily for back up power. The plan was to feed the house sub panel through the existing generator transfer switch. In my application, that switch is placed immediately after the main panel which contains a 200A breaker and the neutral-ground bond for the house. The xfer switch operates on only L1 and L2, neutral passes through and the bare ground bonds to the switch case before going back to the main panel.
FWIW the generator is just a 5500W portable - suitable for a day if the power is out but not much more than that.
As backup power through a manual switch, I had not intended to connect the AC mains to the inverter at all. Operating off of DC inputs only, the inverter will bond N-G and as the transfer switch does not disconnect the neutral, I've got a loop. I had also not intended to have a separate critical loads panel. With the generator, I just kill the breakers in the sub panel for the loads I'm not powering with the generator prior to connecting with the transfer switch.
Option 1 is to get a new transfer switch which switches neutral as well as the lines. This seems to be the correct solution but likely the most expensive.
Option 2 is to disable the N-G bond in the inverter. Easier and cheaper, this seems like it would work for a back up power scenario but I'm not sure if this causes a real safety issue as:
1, The neutral would still be connected to the utility even with the lines disconnected. A danger external to the house???
2, I'm uncertain whether or not there's an issue with a breaker being able to clear a ground fault that occurred in the inverter. With no AC input to the inverter (and the internal N-G bond disabled) I'd have the N and Grnd from the inverter both connected to the point where the N-G bond in the main panel occurs. Wouldn't that provide a sufficient pathway back to the source?
Option 3, abandon the back up power only idea, run AC to the inverter and add a separate sub-panel that the inverter is always powering some of the loads in the house. This seems like the most common way of using these things but in going with this option, It dawns on me that if the utility power goes out, I'm kind of right back to square one.
I'm going to get a price on changing out my transfer switch. Thoughts on options 2 and 3?
I'm planning to use an MPP LVX6048 with batteries and PV primarily for back up power. The plan was to feed the house sub panel through the existing generator transfer switch. In my application, that switch is placed immediately after the main panel which contains a 200A breaker and the neutral-ground bond for the house. The xfer switch operates on only L1 and L2, neutral passes through and the bare ground bonds to the switch case before going back to the main panel.
FWIW the generator is just a 5500W portable - suitable for a day if the power is out but not much more than that.
As backup power through a manual switch, I had not intended to connect the AC mains to the inverter at all. Operating off of DC inputs only, the inverter will bond N-G and as the transfer switch does not disconnect the neutral, I've got a loop. I had also not intended to have a separate critical loads panel. With the generator, I just kill the breakers in the sub panel for the loads I'm not powering with the generator prior to connecting with the transfer switch.
Option 1 is to get a new transfer switch which switches neutral as well as the lines. This seems to be the correct solution but likely the most expensive.
Option 2 is to disable the N-G bond in the inverter. Easier and cheaper, this seems like it would work for a back up power scenario but I'm not sure if this causes a real safety issue as:
1, The neutral would still be connected to the utility even with the lines disconnected. A danger external to the house???
2, I'm uncertain whether or not there's an issue with a breaker being able to clear a ground fault that occurred in the inverter. With no AC input to the inverter (and the internal N-G bond disabled) I'd have the N and Grnd from the inverter both connected to the point where the N-G bond in the main panel occurs. Wouldn't that provide a sufficient pathway back to the source?
Option 3, abandon the back up power only idea, run AC to the inverter and add a separate sub-panel that the inverter is always powering some of the loads in the house. This seems like the most common way of using these things but in going with this option, It dawns on me that if the utility power goes out, I'm kind of right back to square one.
I'm going to get a price on changing out my transfer switch. Thoughts on options 2 and 3?