The appropriateness of ROMEX [RE-wrenches]

Mon Jul 2 20:48:50 PDT 2001

Hi Baran,

I'm not sure how you got to 396 VDC (unless the SX-120S is a 12V version of 
the SX-120?). My calcs show 24 SX-120 at 33.7Vmp each = 808.8Vmp.

For code, you also need to look at Voc.   24 SX-120 at 42.1Voc = 1010.4Voc. 
This puts the system well over 600V, and I think quite higher than you need 
to be for the Sunny Boy 2500. I think the Sunny Boy goes from 275 to 
550VDC. So I'd probably start by looking at 12 of the SX-120. John Berdner 
sent out a great spreadsheet a few weeks back that helps in determining the 
proper number of string modules.

The Romex can be rated for higher voltages, but I would probably put single 
conductors into conduit. We're looking at a voltage level here that could 
pretty easily hurt someone, and an attic usually is accessible to 
"untrained personnel". The chance of someone, someday, cutting, tearing, 
somehow invading that romex in an attic, is too high for me. You want to 
differentiate the higher voltage wiring from the standard house stuff. Even 
some Greenfield or liquid tight conduit, both fairly easy to work with, 
would do the trick. The code is a minimum. Sometimes it's overkill. 
Sometimes we should prudently go beyond it.

Remember my guiding principal for installation safety, "the a__ you save 
might be your own..."

Jeff

Jeffery D. Wolfe, P.E.
Global Resource Options, LLP
A Woman-Owned Limited Liability Partnership
4 Kibling Hill Road
P.O. Box 51
Strafford, VT 05072
800-374-4494 Toll Free
802-765-4632 Phone
802-765-9983 Fax
global at sover.net
http://www.GlobalResourceOptions.com

----------
From: 	Baran Galocy[SMTP:livewire at c-zone.net]
Reply To: 	RE-wrenches at topica.com
Sent: 	Monday, July 02, 2001 9:06 PM
To: 	RE-wrenches at topica.com
Subject: 	The appropriateness of ROMEX [RE-wrenches]

Fellow Wrenches,

Is there anything wrong, from a code point of view, with using ROMEX wire
for my dc photovoltaic hookup.  I have 24 SX-120S panels wired in series 
for
396 vdc @ 7.5 amps.  Since 12/4 ROMEX carries 16 amps with a 20% power
de-rating  and the rating on ROMEX wire is 600 volts - no ac or dc
specification, my 50'-0" run from the rooftop j-box to my inverter has a
fractional voltage drop.  I should note that the ROMEX is to be used in the
attic where it is considered code-appropriate for the location.  Also, of
course, there is proper ground fault protection in the Sunny Boy 2500
inverter.

I can find nothing disallowing this use of ROMEX in my NEC handbook, but am
I missing something?  Thank you in advance for appropriate information and
advice.

Baran Galocy DBA HelioElectric

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