[RE-wrenches] transformerless inverters and conductor colors

[August Goers]

Hi All -



Refer to NEC 690.35 Ungrounded Photovoltaic Power Systems. 690.35(D)
specifies the types of PV source conductors required. For standard 600 V
ungrounded systems it is typical to use PV wire (which may or may not be
double insulated) under the arrays where installed exposed and then
transition to THWN-2 or equivalent once going into a raceway such as EMT.
We have many systems installed this way which are working just fine. It is
true that the ground fault protection is more sensitive on ungrounded
inverters but THWN-2 when installed with good workmanship should be just
fine in raceways. We buy only black PV wire and phase tape at the ends. For
larger arrays we use number labels for each string. My opinion is that
buying and stocking different colors of PV wire is not worth the hassle and
that good simple labeling makes up for it.



1000 V ungrounded systems are a different beast and the only viable option
I've found to date is to run 1000 V PV wire all the way from the array to
the inverters.



Best,



August





*August Goers*



Luminalt Energy Corporation

o: 415.641.4000

m: 415.559.1525





*From:* re-wrenches-bounces at lists.re-wrenches.org [mailto:
re-wrenches-bounces at lists.re-wrenches.org] *On Behalf Of *Marco Mangelsdorf
*Sent:* Monday, September 23, 2013 10:09 PM
*To:* 'RE-wrenches'
*Subject:* [RE-wrenches] transformerless inverters and conductor colors



Can you, Don, or someone else please cite the specific code language where
double-insulated conductors are required from beginning to end in such DC
circuits?



Thanks.



Marco- You should not transition to THHN wire at all for the DC run. The PV
wire is double insulated for a good reason- the transformerless inverters
are such suckers for a ground fault that they need the extra protection.
That's why the NEC specifies PV wire.

I recently did an installation like you wrote, with a transition at the
j-box. This developed an intermittent ground fault when wet, and when the
P1 inverter failed it was deemed out of warranty.  Learn from my mistake--
use PV wire all the way to the inverter.



That said, does anyone know where to get 1000 volt PV wire in colors other
than red, black, and white?

It would be nice to color code the positive runs like is possible with
colors of THHN.

I'm thinking of buying spools of white and spraying plastic paint on them
for a striped color coding.



Don Barch

Energy Solar
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