I have two solar systems installed on my property and I'm wondering if I can use them for off-grid power. One system is an Enphase grid-tied setup that includes panels, micro inverters, and a combiner, while the second is a Victron grid-tied system featuring panels, an MPPT, a Multiplus II inverter, an autotransformer, a smart shunt, a grid meter, and about 20kWh of batteries. Everything runs fine as is, especially since the grid is stable, but I'm curious about my options in case of a sustained power outage.
I've checked the Victron materials and it seems like the Multiplus II might be able to run my house and keep a bit of power available, but it's not set up for that right now. I know that currently both systems shut down during a power outage to prevent sending power back into the grid. If I wanted to use the Victron to supply power to my home, I think I'd need to switch the AC in to AC out, but I'm worried about how to charge the batteries, especially since I don't want to lose the capability of the Enphase system. Can anyone advise on what options I have without requiring extensive rewiring?
1 Answer
If your Multiplus is wired correctly, it can disconnect from the grid and keep powering your home during an outage. You can have the Enphase system still operational and charging the batteries, but it depends a lot on how your wiring is configured. Generally, you want your grid connection to go to AC in on the Multiplus and load to AC out. If your Enphase system is connected on the IN side after measuring current transforms, it can keep charging the batteries while you’re on-grid. But if you want to have it working during an outage, it needs to be on the OUT side. Just make sure the frequency shifting is set up right and that your Multiplus can handle the peak output from the Enphase.
It sounds like your Multiplus isn't set up to keep anything powered if the grid goes down. The grid connects to AC in on your Multiplus, so unless you switch it to AC out, anything connected through it won’t work without grid power. I think if the grid went down for a long time, you could cut off the mains and switch those AC lines, but you'd have to lose that Enphase system's ability to charge the batteries while you are running off the Multiplus. You’re right, the Enphase does generate a lot more than the few hundred watts from the Multiplus' panels, so you'd likely be limited without rewiring. Maybe consider a critical loads panel if you want the backup capability?