I believe you can use the SPD 300 AC on 2 strings, if PV neg is
grounded. You would connect the green to ground (or PV neg) and then
connect the red to one string pos, and connect the black to the other
string pos. This would be limited to 300 v also. I haven't tried that
exact configuration, but I have used the 300 AC to protect both the AC
in and AC out on 120 vac inverters. I also believe you can use a 600 DC
version, and wire as I mentioned, but the LEDs won't light. If you are
using ungrounded inverters, then I think you would need an SPD for each
string in order to protect both the pos and neg of each string, like
you've been doing.
Maybe someone from Midnite can clarify this.
As far as it being worth it, I haven't had lightning related damage
since I started using the Midnite SPDs, and I used to have system damage
every year. If you are not in lightning country, or the install is in a
low spot with less likelihood of taking a hit, you might be able to
skimp. But for some of these off grid ridge top installs, I consider it
a must. Some times I don't install one on the gen circuit, if its really
close.
Ray Walters
Remote Solar
303 505-8760
On 10/8/18 4:03 PM, Drake wrote:
Hello Wrenches,
Do you use surge arrestors with multi MPPT input string inverters? Do
you put a separate arrestor on each MPPT input? I find it sort of
pricey using a Midnite Solar arrestor on each string, but have been
doing that. Is there a less expensive approach that is effective?
I believe the Midnite units are the best. Are they worth the expense?
Thank you,
Drake
Drake Chamberlin
/Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV
740-448-7328
/http://athens-electric.com/
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