Yeah, I assumed you meant the four conductors. The exception would solve your problem if it's physically possible.
How long of a run are we talking about? The cost difference shouldn't be bad for a short distance. Jason Szumlansk i Fafco Solar On Tue, Mar 4, 2014 at 3:34 PM, Kirk Herander <k...@vtsolar.com> wrote: > Whether or not a further derate has to be applied is the killer here, as I > am working with existing panels and conductors. In an old Code > Corner(HP140) J. Wiles goes through a similar scenario and calls out the > allowable current rating and conductor in 310.15, but makes no mention of > applying additional derate factors. The .8 derate for 4-6 > conductors(l1,l2,l3, & n) will put the existing 4/0 cable between feed-in > and main panel at 208 amps, less than the allowable 217. I'd hate to need > to upsize the wire to 250 mcm. > > > > Kirk Herander > > VT Solar, LLC > > dba Vermont Solar Engineering > > NABCEPTM Certified Inaugural Certificant > > NYSERDA-eligible Installer > > VT RE Incentive Program Partner > > 802.863.1202 > > > > *From:* re-wrenches-boun...@lists.re-wrenches.org [mailto: > re-wrenches-boun...@lists.re-wrenches.org] *On Behalf Of *Jason Szumlanski > *Sent:* Tuesday, March 04, 2014 2:57 PM > *To:* RE-wrenches > *Subject:* Re: [RE-wrenches] conductors and the 120% rule > > > > Both the bus and conductors need to be rated for 217 amps minimum. As you > mentioned, the bus is not a problem. The way I interpret it, the conductor > size required would be after derate factors are applied. The rating of the > conductor is ultimately dependent on the derate factors. > > > > If you can locate your subpanel adjacent to the main distribution panel, > you may be able to use Exception #3 to 310.15(B)(2) by connecting the > panels with a short nipple. I assume you are just looking at a number of > conductor derate and not an ambient temperature derate. > > > > Jason Szumlanski > > Fafco Solar > > > > > [image: Description: Image removed by sender.] > > > > On Tue, Mar 4, 2014 at 12:05 PM, Kirk Herander <k...@vtsolar.com> wrote: > > Hello, > > I have a 225 amp 3-phase main lug sub-panel protected by a 200 amp > breaker. My inverter breaker feeding the sub panel is 60 amps. So 225 a bus > x 1.2 = 270 amps. That's less than the sum of the two breakers of 260 amps, > so no issue there. The conductors between sub and main panel have to be > rated for at least 260/1.2 = 217 amps, correct? Is this 217 amps before or > after derating the conductor? > > > > > > Kirk Herander > > VT Solar, LLC > > dba Vermont Solar Engineering > > NABCEPTM Certified Inaugural Certificant > > NYSERDA-eligible Installer > > VT RE Incentive Program Partner > > 802.863.1202 > > > > > > _______________________________________________ > List sponsored by Home Power magazine > > List Address: RE-wrenches@lists.re-wrenches.org > > Change email address & 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 > > >
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