Hi All, I am working on sorting out equipment for a roughly 70kw 208V three phase system, where they also want a very small battery backup for some 120V loads. It seems like it may be a bit overkill to have all 70kw worth of solar going through battery based inverters, when I need only a small amount of backup power. But I would also like to keep the whole system with the same manufacturer inverter for monitoring simplicity.
I am considering two Sol-Ark 30K inverters, but their L3 battery system will do a minimum of 40kWh. I need to keep it under 20kWh because of permitting issues. I am leaning towards Enphase, because their commercial MI's are high powered and surprisingly low cost. Especially since this is a roof mount on a pitched roof, and that will take care of rapid shutdown. But in order to use their batteries, we need a 240V split phase system. I am thinking of using a couple strings of IQ8's to integrate with their batteries, and then use a 208V to 240V transformer to hook into the rest of the electrical system in the building. Something like this: https://store.maddoxtransformer.com/products/d7271c82-ce60-5b76-8198-4a9150263607 My only concern here is wondering whether there will be phase issues, if I am taking two legs from the 208V primary at 120 degrees from each other and turning that into 240V for the IQ system controller. I would love to hear if someone has done something like this successfully. I don't want to find out during installation if it wont work. Or, if anyone has other equipment suggestions, I am open to that too. Thanks! -Dave -- [image: Logo] <https://www.sungineersolar.com/> Dave Tedeyan, P.E. Owner | Sungineer Solar p: he | him | his a: 1653 Slaterville Rd. | Ithaca, NY 14850 w: www.sungineersolar.com <http://www.sungineersolar.com/> c: (607) 270-0370
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