2nd EG4 3000 needed due to MWBCs?

Greetings,
I'm building a small solar system (1 x EG4 3000, 1 x EG4-LL, 2kW PV) to power a critical loads panel for a couple of hours max. In my area in NJ we get short power outages due to storms etc that this setup will cover, I've mapped out power usage via an emporia vue. EG4 will prioritize utility power over battery. Anything longer than that I can fire up the 240V generator and power up the main panel via interlock.

I was planning to move 4 loads (fridge, chest freezer, furnace, 1 set of LEDs) on a single phase critical loads panel, without bridging to the other phase, fed by a single 120V EG4 3000. But as part of my prep work I realized the 2 kitchen circuits for the fridge and the freezer are MWBCs. Fridge 20A circuit is sharing neutral with the gas range/range fan circuit and the freezer is on the kitchen outlets 20A GFCI circuits.

I could "undo" the MWBCs by running 2 new 12/2s but cost and labor-wise it may be much easier to buy a 2nd EG4 3000 and configure it for split phase, purely to handle the MWBCs as there won't be any 240V loads. I'm comfortable doing the work myself and have it inspected/permitted.

Would that work? Is there a better way to deal with MWBCs?

I'll let one of the electricians answer you on the MWBC question but assuming it's as you say and too much trouble to rewire it, the dual inverters would be a relatively inexpensive option. Otherwise this seems like a very manageable load for this inverter and with two you could certainly add a few more circuits, especially if you added another battery or two. I'm assuming the furnace is a gas furnace and you only need AC to operate it? Because a high resistive load like an electric furnace is going to be a lot for even two of these inverters.

EastTexCowboy said:

I'll let one of the electricians answer you on the MWBC question but assuming it's as you say and too much trouble to rewire it, the dual inverters would be a relatively inexpensive option. Otherwise this seems like a very manageable load for this inverter and with two you could certainly add a few more circuits, especially if you added another battery or two. I'm assuming the furnace is a gas furnace and you only need AC to operate it? Because a high resistive load like an electric furnace is going to be a lot for even two of these inverters.

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yes, gas furnace, minor AC draw

any feedback on the MWBC question would be greatly appreciated! Is there a better/alternate design in dealing with these MWBCs?

thank you

What is a MWBC dont remember any of those around in my travels?

Johno1066 said:

What is a MWBC dont remember any of those around in my travels?

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Multi Wire Branch Circuit. It's where two or more circuits use a shared neutral.

Split phase or 3 phase circuits probably can do that with the neutral sometimes half the cross sectional area of the live conductors. I did not realize that this was done in domestic circuits in this country. Generally this could be done with the supply to a stand alone machine or appliance. By using both cables through the inverter at the same phase angle it could be possible that the neutral is not large enough to carry the current from both circuits. The problem with running 2 inverters in split phase is that you will have twice the idling current even if you are not using those circuits. what is the load on those 2 circuits? you may get away with both on a single 20 amp breaker. I think the full load on the EG4 3000 is about 25 amps so you will have to do your math . I can manage most of my home on a single inverter but for a small water heater and well pump coming on at the same time so I have 2 EG4 3000 in parallel during the day and one gets shut down at 10pm until 7 am to save a little battery power. I still use grid power for a 240 volt drier but do not want to run the inverters in split phase as it really complicates the distribution panel.

Johno1066 said:

Split phase or 3 phase circuits probably can do that with the neutral sometimes half the cross sectional area of the live conductors. I did not realize that this was done in domestic circuits in this country. Generally this could be done with the supply to a stand alone machine or appliance. By using both cables through the inverter at the same phase angle it could be possible that the neutral is not large enough to carry the current from both circuits. The problem with running 2 inverters in split phase is that you will have twice the idling current even if you are not using those circuits. what is the load on those 2 circuits? you may get away with both on a single 20 amp breaker. I think the full load on the EG4 3000 is about 25 amps so you will have to do your math . I can manage most of my home on a single inverter but for a small water heater and well pump coming on at the same time so I have 2 EG4 3000 in parallel during the day and one gets shut down at 10pm until 7 am to save a little battery power. I still use grid power for a 240 volt drier but do not want to run the inverters in split phase as it really complicates the distribution panel.

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I wouldn't share the neutral on a 120v circuit myself. I was only stating what the abbreviation stands for.

You could also just get an EG4 6000ex, or any of the other split phase inverters with a transformer and accomplish everything with just one inverter.

Johno1066 said:

The problem with running 2 inverters in split phase is that you will have twice the idling current even if you are not using those circuits. what is the load on those 2 circuits? you may get away with both on a single 20 amp breaker. I think the full load on the EG4 3000 is about 25 amps so you will have to do your math .

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That's a good point and based on the reviews I've seen so far each 3k inverter would be consuming ~1.2A @ idle.
I can't combine the circuits, as starting current could trip a 20A breaker, running afterwards is fine. I think I'll revisit the idea of running additional 12/2s, there'll be an upfront cost but it'll keep the design rather simple.

thanks all!

shopman said:

You could also just get an EG4 6000ex, or any of the other split phase inverters with a transformer and accomplish everything with just one inverter.

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unfortunately I already received the 3k, but yeah, based on the above a 6k may have been a better starting choice. thanks!

The problem with the 6k inverter is that they do not seem to be as reliable as the 3k, and not a great difference in price for two of the 3k's against one 6K. I also felt that if one of mine failed I could limp along with the other until I could get one repaired or replaced. With one 6k it is all or nothing.