Esteemed Wrenches, We are having a hard time finding a source of PV Wire with a 1000V rating that will fit into a two-hole 1/2" strain relief. It seems that all of the wire brands that are "double-insulated" just have too large of a diameter to get two of them though a 1/2" strain relief, needed since most common combiners have 1/2" knockouts for wire entry. However, we have found a source of single-insulated wire that is UL Listed and bears the "PV Wire" marking.
I've always been under the assumption that "double-insulated wire" was necessary when using transformerless grid-tie inverters, as it is with power tools that only have two-prong plugs on them. However I can't find that specific language in the Code. It just says "must be marked as PV Wire". I also found this quote about PV Wire from John Wiles (underlining mine): "The thickness is specified and there may be one or two layers of insulation. The insulation must pass an accelerated UV test of 720 hours and will be marked "Sunlight Resistant." PV cable/PV wire also has smoke and flame-retardants and may be used inside conduit inside buildings. In the U.S., it should not be called a 'double-insulated cable' as that is a purely European term." This appears to mean that double-insulation is not required for transformerless (non-isolated) inverters; just that it needs to be marked as "PV Wire". Can anyone here confirm, hopefully with documentation, that actually having "double-insulation" is not required when using non-isolated inverters? Thanks Brian Teitelbaum AEE Solar
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