[RE-wrenches] Dual Sol-Ark - not paralleled - backing up separate 200-amp panels, with one AC-coupled input:

[scot.arey at solarcentex.com]

Background: New customer wants both 200-amp panels backed up and neither can be "slimmed down" to allow just one backup panel so looking at dual, but not paralleled, SA15 (or 18).

The design / cost-reduction opportunity: There is one 100-amp set of inground conductors already going out to where ground mount would be. My immediate thought is to use this wire already in ground to transport output of solar ground mount. I'd put a large grid-tied inverter at the ground mount and "de-aggregate" the AC via a load center by the Sol-Arks, and AC couple half to each Sol-Ark. No trenching...both Sol-Arks have AC-coupled input

The question I need help/ideas on: What happens to frequency shift if just one Sol-Ark /battery combo is near-full SoC during backup ops and shifts to 62hz to shutdown the AC-coupled GTI. Seems it would shift the ac-couple POI to 62hz but the other inverter would still be at 60hz still and this conflict might not "mix well" getting back to the grid-tied inverter at the ground mount.

I may well come back to the option of new trenching and pulling separate DC conductors to each Sol-Ark and get the simplest, least complex design but I'm exploring all design options to use existing wire and not have to trench.

Best analogy I can come up with, is that like an Outback system having "float charging coordination," I could have "freq shift coordination" between the Sol-Arks and of course that is not a feature in non-paralleled inverters.

I suppose combining the separate 200-amp services and then paralleling the Sol-Ark inverters to this might be the necessary actions if I want to avoid trenching and still back up all.

Howard "Scot" Arey
Owner, Solar CenTex

NABCEP PV Installation Professional
TECL 29755
254-300-1228
[cid:0f1e27ac-55b6-4c2c-add4-8077cad0c1ac]

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