robbob2112
Doing more research, mosty harmless
Just to add to the discussion....
I'm 100% off-grid with grid-assist via ATS(s) - e.g. PV (15kw) -> Charge Controllers -> Battery (121kwh) -> Inverters (24,000w). I wire the inverter outputs to ATS(s) where the ATS(s) have inverter input and grid input (with grid as the default) and the output goes to the home circuits.
Effectively, when the solar system has enough battery charge, the inverters turn on and power the 'solar' leg of the ATS(s). This causes the ATSs to switch to 'solar power' to energize the circuits around the home. When the battery runs down and the inverters shut off, the ATSs automatically switch back to grid to energize the circuits around the home
Couple of pros...
1) No chance of backfeeding the grid / no interaction with power company required.
2) My home continues to function whenever I shut off the solar system to work on it / expand it (happy wife = happy life )
3) The ATSs are UL listed and easy to replace the internals.
Couple of cons...
1) ATS switching requires a UPS on sensitive circuits like computers.
2) ATSs are mechanically linked relays and I've had 3 of 5 fail after 4-5 years (~3,000 cycles). I didn't orient them as instructed so that might be part of the issue.
My system is individual components but.....
They make off-grid AIOs these days that include ATSs and UPSs as part of the internals and operate as I've described above. For example, I use an MPP Solar 3048LV in my trailer that is off-grid with ATS and UPS built-in.
Essentially, these units invert off the battery all the time and take PV and grid input to charge the battery as it's inverting which effectively takes care of the UPS issue. This is a little different than my system in that the MPP Solar unit must be operational all the time whereas it's only the ATSs that must be operational 'all the time' in my system.
Do you have design docs posted? Or can you share privately? I have been trying to figure out how to have power from the grid when the house is built and then add my own solar later.
Is your ATS using contactors or relays?