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diy solar

PV system Switch

pbuck00

Bucky
Joined
Jan 2, 2020
Messages
31
Location
California North Coast
I currently have two solar systems. The first one is a 6 year old grid tie 3500 w PV system going into a Fronius inverter. Feeds back any excess to the power company. When the power company started doing their safety shutoffs I found the drawback of grid tie.. (i.e. no power... no solar either), so I put together an "off grid" smaller system with 1800 watt system going to a MPPSolar 2424LV-MSD and 6kw battery bank, which feeds an off grid sub panel for critical devices.
Both systems have been working just fine... except ... the second system potential harvest is much more that I actually use and there are many times I am not making full use of my panels.
So I had a thought. Could I wire all panels to the Fronius inverter and be able to take full advantage of all harvesting. Use that power to also keep the batteries topped off and feed back the excess to the power company. That part seems pretty straight forward and for MOST short duration power outages (less than 2 days) that would work just fine through the second 2424LV-MSD/Battery bank system and subpanel.....

but what if I put in some type of box where I could switch the 1800 watt PV system back to the MPPSolar for when the power goes off for a couple of days or a week... disconnect it from the original grid tie system and back over to the original design to power the 2424LV-MSD/battery bank to power just my critical loads.

After that lengthy intro... my primary question is... what would that switch be called... I have no idea what I am even looking for. Closest idea I have come up with is a 2 battery switch box but that doesn't seem right..

any ideas or recommendations? Thanks in advance.
 
Interesting, sorry I had not seen this post earlier, hope you're still around.

I'll get to the "switch" later, first what about the voltage your Fronius inverter is using? Generally these (Fronius) inverters can operate with higher maximum open circuit voltages than the LV2424 (145V). How are your panels wired (series/parallel); the question is what voltage can the Fronius 'see' from your configuration?

Can the LV2424 handle the voltage of your current panel configuration?

I've got a Fronius operating at 310 VDC and have LV2424 (2) for major emergency backups, BUT I have to manually re-configure the panels (less in series/more in parallel) to operate the LV2424.

If the voltage is 'proper' for both inverters I think a DPDT, double pole, double throw switch could conveniently work. Here's and example (PV would hook to BAT terminals):
1633545454326.png
 
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