series circuits for Sunny Boy [RE-wrenches]

[Jeffrey Wolfe, Global Resources]

Travis,

One fine print note on using some of  the SqD disconnects. The 600VDC 
rating on some of them depends upon breaking BOTH the hot and the negative, 
using the outside poles of a three phase unit. The only unit I see in my 
Grainger book that avoids this requirement is the 200A 4-wire switch, (but 
it's not really clear it's listed for DC, and the Square D catalog does not 
rate it for DC>)

So you're into either multiple switches or ignoring the rating. The rating 
is *probably* made in consideration of breaking the DC under load at a 
level of 200A, but still and all, that's the rating.

I'd stick with the combiner box.

Jeff

On Sunday, December 02, 2001 6:53 PM, Travis Creswell, Ozark Solar 
[SMTP:ozsolar at ipa.net] wrote:
> Check out page 458 of the Grainger No. 392 catalog.  You'll have to buy a 
3
> phase model and that will give you 3 sub arrays.  You can get a  Nema 3R
> Rainproof ST/3P 600 VDC fusible disconnect (30 amp, Square D flavor) for
> $401.75.
>
> Does the Trace Tech model have a handle or do you have to open the box 
and
> remove the fuses.
>
> And be ever so careful about trying to "educate inspectors".  Do want he
> wants on this job with a big smile on your face then carefully challenge 
him
> next time.  Tell him how smart he is and thank him (for making life
> difficult) and your life will be so much easier next time.  They are the
> final authority so if they feel like it they can make your life very
> difficult.
>
> Travis Creswell
> Ozark Solar
> ----------
> From: "Mangelsdorf, Marco" <mmangelsdorf at hei.com>
> To: RE-wrenches at topica.com
> Subject: series circuits for Sunny Boy [RE-wrenches]
> Date: Sun, Dec 2, 2001, 5:14 PM
>
>
>
> Aloha Wrenches,
>
> Does anyone know of a relatively low cost high voltage (up to 600 VDC)
> combiner box that has, say, two or three fuse holders?
>
> We've finished the first Sunny Boy 2500U installation here in the islands
> with two parallel series-wired sets of (10) BP 150-watt 24 VDC modules.
> According to a reasonable interpretation of the NEC 690-9 (b), there is 
no
> need for fuse protection of each series circuit of modules.  So, in the
> install, I have both sets of modules wired directly to a single pair of
> #10CU conductors with no fuses.  The inspection did not pass last friday
> with the notation being that there was no overcurrent protection on the
> roof, i.e., no combiner box with separate fuses to protect each series
> string.  I'm going to try and educate our local authorities tomorrow on 
the
> lack of need for fuses on the roof with a cover letter of my own and a
> two-page letter that John Berdner of SMA-America has been kind enough to
> supply me with.  BUT....in case I don't prevail in my education process, 
I'm
> looking for a low cost plan B.  I know that I can get a 10-circuit 
combiner
> from Trace Tech. that's rated at the high DC voltage.  But I'd like to 
avoid
> spending $400 or more bucks for it.
>
> Any ideas?
>
> thanks,
> marco
>
> Marco Mangelsdorf, Ph.D.
> Marketing and Sales
> ProVision Technologies, Inc.
> 69 Railroad Avenue, Suite A-7
> Hilo, Hawaii 96720 USA
> (808) 969-3281, fax 934-7462
> www.provisiontechnologies.com - - - -
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