PV rating norms [RE-wrenches]

[Mark Edmunds]

Hi William,

The XW-SCC is rated and listed for 100% operation. As for the NEC temp
correction rating pushing 3 modules just over the max Voc limit of 150V
- you may want to ask your local inspector for an opinion. Our sizing
tool calculates the Voc based on the actual temperature data from the
manufacture, (44.6V + (-.145V/C x -35C)) x3modules =149.025V, where the
NEC has had to group values to simplify creating a table, giving a
slightly higher result. 

Regards,

Mark



Mark Edmunds
Xantrex Technology Inc.

-----Original Message-----
From: William Miller [mailto:wrmiller at charter.net] 
Sent: Tuesday, December 11, 2007 9:23 AM
To: RE-wrenches at topica.com
Subject: PV rating norms [RE-wrenches]


Friends:

First off, sorry about the long winded request for help on PV rating.
The discussion can be boiled down to this exception to
690(8):  Exception:  Circuits containing an assembly, together with its
overcurrent device(s), that is listed for continuous operation at 100
percent of its rating shall be permitted to be utilized at 100 percent
of its rating.

This exception specifies not just the device but also the circuit, so I
believe we can avoid use of the 125% factor when considering the charge
controller and the circuitry into and out of said charge controller.
This is assuming Xantrex listed their device for 100% duty, which I am
assuming.

Regarding open circuit volts:  Here is another case of the NEC being in
conflict with the manufacturer's sizing tool.  The NEC requires a
correction factor of 1.13 for our climate zone.  This puts three strings
just over the listing of 150 VDC, even though the manufacturer's sizing
tool allows strings of 3 (although just barely).  It is common sense
that I must satisfy both...

Thanks for the "input".

William


-- _________________________________
William Miller
Miller Power and Communications
Voice :805-438-5600     Fax: 805-438-4607
email: wrmiller at mpandc.com
http://mpandc.com
License No. C-10-773985


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