>600 Voc (was Uni-Solar and SMA and Xantrex PV inverters) [RE-wrenches]

[Bill Brooks]

Joel,

You bring up a tough question. The code clearly states:

"...where other than crystalline or multicrystalline silicon photovoltaic
modules
are used, the system voltage adjustment shall be made in accordance with the
manufacturer's instructions." [NEC 690.7].

That being said, the manufacturer of the PVL-128 provides the following
information in their literature.

Open-Circuit Voltage (Volts)			             47.6V
Open-Circuit Voltage (Volts)at -10?C and 1250 W/m2     54.2V

Without temperature effects, the voltage of 12 modules in series is 571.2V.
The voltage goes up when it gets colder and when irradiance increases, so
how do you read the information? So according to their data the voltage can
reach 650.4V at cold, high irradiance conditions. What happens at -10C and
1000W/m2? Don't know since there are no coefficients. That should come from
the manufacturer. However, SMA's string sizing chart says max is 11 modules
in series and they have the right coefficients.

Clearly, in most parts of the U.S., including California, 12 modules in
series exceeds the 600Volt number--particularly if you consider the higher
initial voltage. Also, UniSolar is getting better at making triple-junction
so their voltages are going up, not down.

This is not a table 690.7 problem. This is a section 690.7 and UL problem.

Bill.




-----Original Message-----
From: Joel Davidson [mailto:joeldavidson at earthlink.net]
Sent: Wednesday, August 20, 2003 10:01 AM
To: RE-wrenches at topica.com
Subject: Re: >600 Voc (was Uni-Solar and SMA and Xantrex PV inverters)
[RE-wrenches]


Roy,
Thanks for the feedback. Anyone have problems with Building and Planning
regarding greater than 600 Voc based on NEC 690.7 correction factors? Thanks
in advance.
Joel Davidson

Roy Dyngen wrote:

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