NEC 2005 Handbook, Annex B, page 1204, Table B.310.11 I see now that 100% diversity applies to 4-6 and 7-9 ccc's but 50% above that. Sorry.
- Peter Peter T. Parrish, President California Solar Engineering, Inc. 820 Cynthia Ave., Los Angeles, CA 90065 Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885 CA Lic. 854779, NABCEP Cert. 031806-26 peter.parr...@calsolareng.com -----Original Message----- From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Bill Brooks Sent: Thursday, January 08, 2009 10:19 AM To: 'RE-wrenches'; exelt...@yahoo.com Cc: 'Will Logan' Subject: Re: [RE-wrenches] Cable Sizing Peter, Where do you read the 50% diversity? My 2005 NEC handbook clearly says that the raceway adjustment table is based on NO diversity--all conductors loaded at maximum. Bill. -----Original Message----- From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Peter Parrish Sent: Thursday, January 08, 2009 9:47 AM To: exelt...@yahoo.com; 'RE-wrenches' Cc: 'Will Logan' Subject: [RE-wrenches] Cable Sizing Here is an issue that has been bothering me for some time and I finally was asked to explain it to a junior member of our Company and had to admit ignorance... I am referring to the issue of derating the ampacity of wire in a raceway or conduit with other current carrying wires. I refer to Table B.310.11, Annex B of the 2005 NEC Handbook, but the same information occurs elsewhere in the HB as Table 310.15(B)(2)(a) and the CB. Table B.310.11 requires a 20% derating for four to six current carrying conductors. There is a note that this derating includes the effects of a "load diversity" of 50%. Am I to assume that 50% load diversity means that each current carrying wire is operating at 50% of its temperature-corrected ampacity (or less)? Does this table apply equally well to DC and AC circuits? What about 3-phase/3-conductor wiring? In specific: if we have two DC PV circuits (4 wires: 2 positive, 2 negative) in EMT and we have taken into account the "PV 125% circuit current calculation", "cable sizing of 125% for proper operation of overcurrent devices", and cable derating for temperature -- do we now apply the derating from B.310.11 for 4-6 wires? This is what we have been doing, and I'm looking for confirmation. - Peter Peter T. Parrish, President California Solar Engineering, Inc. 820 Cynthia Ave., Los Angeles, CA 90065 Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885 CA Lic. 854779, NABCEP Cert. 031806-26 peter.parr...@calsolareng.com -----Original Message----- From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Exeltech Sent: Wednesday, January 07, 2009 7:37 PM To: RE-wrenches Subject: Re: [RE-wrenches] fire safety vs. fire hysteria? Yes, it's made the rounds (13 total hits using the link Michael provided), but the entire list of 13 is actually comprised of only six websites. The originating site has two hits on the list, leaving five sites for the other 11 hits. One site is a BBS, similar to this one and would likely require a refuting post -- perhaps a copy/paste of the superb response posted earlier. The four remaining sites may respond and remove the inaccurate material and/or links if contacted in a similar positive tone. The sooner it's addressed, the fewer the links there will be for the crawlers to find... I've assembled a summary list of the sites if anyone wants to contact me off list for a copy. Dan --- On Wed, 1/7/09, Michael Welch <michael.we...@re-wrenches.org> wrote: > Right, but this piece has made the rounds on the internet. > > Check out this Google search > http://tinyurl.com/7amhk4 _______________________________________________ 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 _______________________________________________ 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 _______________________________________________ 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 _______________________________________________ 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
