[RE-wrenches] Inverter for Switch to GT

[Allan Sindelar]

Wrenches,
Occasionally, but more frequently recently, we get requests to turn off-grid
systems into grid-tie systems. Usually this involves sale of a property to a
new owner, and either grid is brought in to facilitate an easier sale or the
new owner brings it in. Once grid is in, the off-grid-based system is of
limited utility, as the equipment won't sell back. Most of these new owners
want a maintenance-free batteryless system.

Unfortunately, most off-grid arrays don't easily convert, as the string
sizing doesn't match. Here's my question: I have two of these requests right
now. Both are systems we installed in the late 90s. One has ten BP 275s, one
has twelve. These are standard 12V 75W modules common to that time. I need
advice on inverters that will work with these strings.

The Sunny Boy 700, which is the only small inverter model SMA still offers,
will handle one string of up to nine of these in our temperature range.
Larger models require higher string voltage. Fronius also requires higher
voltage.

You know, it's a real problem to have to explain to new green-oriented
homeowners that there's nothing I can do with their ten-year-old PV system
to make it spin their new meter backward. It doesn't do much for the
mainstream perception of PV for these folks.

What will work with these existing arrays, please?

Allan Sindelar
allan_(at)_positiveenergysolar.com <mailto:allan at positiveenergysolar.com> 
NABCEP certified solar PV installer
Positive Energy, Inc.
3225A Richards Lane
Santa Fe NM 87507
505 424-1112

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