[RE-wrenches] wire sizing question

Sat Jan 3 14:58:17 PST 2015

Yes, beautiful. But I am still trying to figure out if it is NEC 
compliant. At first pass, it seems like it is missing a few 
disconnecting means.

On 1/3/2015 10:48 AM, Larry wrote:
> Wow, Jarmo! That is some incredible workmanship and a great way to 
> interconnect multiple inverters and chargers. You can tell they have 
> done this a few times. Thanks for sharing those photos.
> Larry Crutcher
> Starlight Solar Power Systems
> On 1/3/15 9:16 AM, Jarmo.Venalainen at schneider-electric.com wrote:
>> Hi:
>>
>> This link takes you to a site in Romania so you (likely) wont be able 
>> to read the text, but  it does have a lot of good pictures.
>>
>> This installer has been using XW since about 2007 and has a tons of 
>> experience.  I like what he does with the DC wiring/busbars.  The 
>> breakers are in the box below the inverters and charge controllers.
>>
>> http://customer.lpelectric.ro/doc/sibiu2/sibiu2_28kw_fotovoltaic.html
>>
>> JARMO
>> _____________________________________________________________________________________
>> *
>> Jarmo Venalainen*  | *Schneider Electric **  |  Solar Business*  | 
>> *CANADA*  | *Training & Development Specialist - Senior* *
>> Phone:* +604-422-2528  | *Fax:* +604-420-1591  | *Mobile:* 
>> +604-505-0291 *
>> Email:* _jarmo.venalainen at schneider-electric.com_ 
>> <mailto:jarmo.venalainen at schneider-electric.com> | 
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>> _
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>>
>>
>> From: 	drake.chamberlin at redwoodalliance.org
>> To: 	"RE-wrenches" <re-wrenches at lists.re-wrenches.org>,
>> Date: 	01/02/2015 05:18 PM
>> Subject: 	Re: [RE-wrenches] wire sizing question
>> Sent by: 	"RE-wrenches" <re-wrenches-bounces at lists.re-wrenches.org>
>>
>>
>> ------------------------------------------------------------------------
>>
>>
>>
>> 4/0 copper is good for a 24V, 4000 W inverter. What is being used for
>> multiple inverters?
>>
>> I've paralleled 4/0 into outback boxes using 2, 2" PVC conduits. It gets
>> pretty messy trying to put 4 sets of 4/0s into enclosures and battery
>> boxes (although I have worked on such systems). Does anyone have clean
>> solutions for these systems?
>>
>> Thanks,
>>
>> Drake
>>
>>
>>
>>
>>
>> > Some other things:  If you keep the conduit less than 24" long, 
>> which is
>> > recommended anyway for main battery connections, the conduit fill
>> > requirements don't apply. (see exception: 310.15(B)3a2)
>> > Using table 310.15(B)16 yeilds 230 amps for 4/0 at 75 C.  Then 240.6
>> > lists 250 amp as the next standard size of OCPD which is allowed to be
>> > used by 240.4(B)  So you can just justify 4/0.
>> > Further, many manufacturers (like Midnite) use the open air ampacity
>> > table: 310.15(B)17, since the cable is not "in conduit" and 4/0 
>> cable at
>> > 75 C is rated to 360 amps.
>> > The Free Air interpretation is not completely substantiated in the code
>> > from my read of it though.  Maybe someone more knowledgable could cite
>> > the chapter and verse that defines when the free air rating can and
>> > cannot be used.
>> > Also remember those breakers are 100% duty cycle rated, and that the
>> > inverter usually can't run any where close to 250 amps continuously.
>> > Bottomline is we've been using 4/0 with 250 amp breakers for almost 20
>> > years, and I've never seen or heard of a problem.
>> >
>> > R.Ray Walters
>> > CTO, Solarray, Inc
>> > Nabcep Certified PV Installer,
>> > Licensed Master Electrician
>> > Solar Design Engineer
>> > 303 505-8760
>> >
>> > On 1/1/2015 7:23 PM, jay peltz wrote:
>> >> Happy new year all.
>> >>
>> >> I have a question on wire sizing for the following.
>> >>
>> >> 250 amp breaker, in a UL enclosure ( say midnite or outback etc)
>> >> conduit from battery box to enclosure
>> >>
>> >> I'm wondering how folks size this for ampacity not voltage drop.
>> >>
>> >> thanks
>> >>
>> >> jay
>> >>
>> >> peltz power
>> >>
>> >>
>> >>
>> >>
>> >>
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