Siemens SR90 wiring

NZRR
NZRR Registered Users Posts: 28 ✭✭
in PV Installers Forum - NEC, Wiring, Installation #1
I am looking for advice on wiring Siemens SR90 modules into two high voltage strings to for use with a Xantrex 60-150 CC. There are currently two 10-modules arrays that are wired in strings of six and four (I am not yet sure how), and I would like to wire them into four strings of five modules. On the data sheet for the module is the following warning:

"If the designer chooses to use the 6-volt version in a high voltage array configuration, the designer must install custom large bypass diodes and heat sinks around every 6-volt parallel string."

What does this mean?

Also, there are six terminal screws in the junction box - two for positive and two for negative - not sure what the other two are for. Any thoughts?

Module specs are (12V/6V): Vmp 17.0/8.5; Voc 21.6/10.8; Imp 5.4/10.8; Isc 6.1/12.2.

Thanks for your help.
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Comments

  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    #2
    Re: Siemens SR90 wiring

    Could you post a link to the full document?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,639 admin
    #3
    Re: Siemens SR90 wiring

    Here is one web page where that phrase is used on the SR90 data sheet:

    http://www.oksolar.com/panels/sr50.htm

    I am guessing that these panels do not have bypass diodes:

    Tech Tips - Northern Arizona Wind & Sun
    The diodes ACROSS each panel are the bypass diodes. Most medium and larger panels come with these already installed. The purpose of bypass diodes is to shunt the current around a shaded, weak, or damaged panel. If the full current passes through a shaded or weak panel, overheating and damage may occur. Bypass diodes are not needed on 12 volt systems, optional on 24 volt, and should always be used on 36 volt or higher systems. See also our tip on shading. For another perspective, see the Sandia Labs IEEE paper on blocking diodes (PDF file). Bypass diodes may be ordered from our online webstore at 8 Amp bypass diode

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    #4
    Re: Siemens SR90 wiring

    Looks like each panel has two separate strings of cells with separate terminals. You can wire them in parallel, making a 6V panels, or in series, making 12V panels. It's very handy. If you wire them as 6V panels, you can make a really long string.

    It's easy to see if bypass diodes are in the box or not. If they're not there, there could be a space where you can install them inside the box.

    Heat sinks will dissipate heat produced by diodes. They may have built-in versions too,
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