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<p>boB,</p>
<p> To add to Drake's wonderings, I've had a few SMA
TL-40 inverters trip with an AFCI fault. Significant hassle to
get onsite and deal with it. Some with metal roofs some without,
may have been lightening in the area.</p>
<p>Bill<br>
</p>
<br>
<div class="moz-cite-prefix">On 10/9/2018 2:02 PM, Drake wrote:<br>
</div>
<blockquote type="cite"
cite="mid:20181009210241.61564106067@pdx1-mailman03.dreamhost.com">
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Hi boB,<br>
<br>
I will keep putting an SPD on each string and on the AC line.
Sometimes
my systems end up with a lot of blue lights hanging from a wiring
gutter!<br>
<br>
Have you ever heard of any problems using the Midnite SPDs with
Sunny Boy
TL series inverters? So far, I don't think I've had a problem,
although
one TL-22, on a large metal roof, had arc fault protector trips.
<br>
<br>
Thanks,<br>
<br>
Drake<br>
<br>
<a name="_MailAutoSig" moz-do-not-send="true"></a>Drake Chamberlin<br>
<i>Athens Electric LLC<br>
OH License 44810<br>
CO License 3773<br>
NABCEP Certified Solar PV <br>
740-448-7328<br>
</i><a href="http://athens-electric.com/" moz-do-not-send="true">http://athens-electric.com/</a>
<br>
<br>
<br>
<br>
At 01:39 PM 10/9/2018, you wrote:<br>
<blockquote type="cite" class="cite" cite="">Content-Type:
multipart/alternative;<br>
boundary="------------98C0DCEF93B9ECF248E0580B"<br>
Content-Language: en-US<br>
<br>
<br>
For an inverter with two MPPT inputs, you will need to treat the
negatives and positive lines separate unless<br>
the manufacturer says something else. That means one SPD per
array unfortunately. Negative and positive connect<br>
to separate leads of the SPD and then ground in the middle. As
both
positive and negative PV lines rise together<br>
relative to ground, the SPD is supposed to clamp that rise to
below the
equipment's hi-pot voltage that they test<br>
to at the factory. (i.e. common mode voltage rise) All wires
except
for ground (chassis) of the equipment are tied <br>
together and the hi-pot machine (sort of like a Megger ?)
applies the
high voltage between all those wires on one <br>
side and ground on the other to make sure the insulation doesn't
break
down inside the equipment. <br>
This hi-pot test goes for AC utility input/output connections
and
DC from the PV input side. <br>
<br>
The SPD has to clamp plus and minus and AC inputs to a lower
voltage than this hipot rating but higher voltage<br>
than lines will see differentially in voltage. Remember that in
a
3-wire SPD, there is two sets of MOVs in series and<br>
the center is tied to ground. If one MOV starts conducting at
say,
500 volts DC then you can apply up to 1000<br>
volts between the hot leads. Each plus and negative line can
rise up to 500 volts from the lightning before they<br>
start to clamp. The bigger the lightning strikes effect, the
more current will be applied to the MOVs though and<br>
the clamp voltage will rise somewhat. That's why the SPD
arrestor
voltage should be well below the hi-pot voltage,<br>
whatever that is... Hi-pot voltages are quite a bit higher than
the
operating voltage. For example, All Classic CC's<br>
are tested to 2270 volts DC from hot lines to ground. It's
something like double the operating voltage plus 1000V<br>
and multiply by 1.414 for DC rating..... I'm going off memory
so
don't quote me on that but something like that.<br>
<br>
I think that Ray has the right idea about short connections like
from the
local generator. Battery also.<br>
Just apply SPDs to anything that goes outside like an antenna.<br>
<br>
boB<br>
<br>
<br>
On 10/9/2018 8:26 AM, cwarfel wrote:<br>
<blockquote type="cite" class="cite" cite=""><br>
<font face="Verdana">I think something on the order of 90+%
lightning
strikes come from the utility feed, not the dc side. That
has to be
ignored if in a high strike area or grid isolated. </font><br>
<br>
On 10/8/2018 10:37 PM, Ray wrote:<br>
<blockquote type="cite" class="cite" cite=""><br>
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.<br>
<br>
Maybe someone from Midnite can clarify this.<br>
<br>
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.<br>
<br>
<br>
<br>
<pre>Ray Walters
Remote Solar
303 505-8760</pre>
On 10/8/18
4:03 PM, Drake wrote:<br>
<blockquote type="cite" class="cite" cite="">Hello Wrenches,<br>
<br>
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? <br>
<br>
I believe the Midnite units are the best. Are they worth
the
expense?<br>
<br>
Thank you,<br>
<br>
Drake<br>
<br>
<br>
<a name="_MailAutoSig" moz-do-not-send="true"></a>Drake
Chamberlin<br>
<i>Athens Electric LLC<br>
OH License 44810<br>
CO License 3773<br>
NABCEP Certified Solar PV <br>
740-448-7328<br>
</i><a href="http://athens-electric.com/"
moz-do-not-send="true">http://athens-electric.com/</a>
<br>
<br>
<br>
<br>
<br>
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