Peter, There was a change in the 2008 NEC (I know - CA is just getting to this Code cycle) that won't allow THHN inside conduit when the conduit is installed in wet locations, 300.9 (300.5 for underground):
300.9 Raceways in Wet Locations Above Grade. Where raceways are installed in wet locations abovegrade, the interior of these raceways shall be considered to be a wet location. Insulated conductors and cables installed in raceways in wet locations abovegrade shall comply with 310.8(C). And 310.8(C): (C) Wet Locations. Insulated conductors and cables used in wet locations shall comply with one of the following: (1) Be moisture-impervious metal-sheathed (2) Be types MTW, RHW, RHW-2, TW, THW, THW-2, THHW, THWN, THWN-2, XHHW, XHHW-2, ZW (3) Be of a type listed for use in wet locations So for an attic run, it wouldn't be considered a wet location but for the outdoor runs it would be. And since so many runs will be exposed to both types of locations, it only makes sense to me to keep it all THWN-2. I like your position of only stocking one wire type to reduce the possibility of confusion in the field. Ryan -----Original Message----- From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Peter Parrish Sent: Friday, July 23, 2010 11:28 AM To: al...@positiveenergysolar.com; 'RE-wrenches' Subject: Re: [RE-wrenches] #10 THWN-2 Just a minor point: the dash-two appendage brings a wet-rated wire from 75 deg C to 90 deg C. If you are not in a locale that argues for wet-rated wire and your specific application does not argue for wet-rated wire, IMHO it is perfectly acceptable to use THHN wire (90 deg C rated for damp environments) for outdoors, attics and other extreme temperature conditions. Of course you have to use good 3R boxes and rain-tight EMT connectors. For us, it is easier to purchase and inventory just one wire type for conduit runs, and we usually get the same price for THWN-2 as we do for THHN, or close enough. In fact we almost never use #12 either for the same reason. _______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
