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-boun...@lists.re-wrenches.org [mailto: re-wrenches-boun...@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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