[RE-wrenches] Radian design limitation - am I missing something?

Sun Dec 16 12:05:05 PST 2012

Reading on Page 13 of the Radian Operator's manual;
"If the battery charger is not active, the target voltage used by the Radian inverter is Sell Voltage in the

Grid-Tie Sell menu. (See page 21 for more information on charging and selling. See the MATE3 Owner's

Manual to change any of these settings.)"

This scenario sounds very similar to the logic used by the old Trace 4024/4048 to GT.  It was completely irrelevant which CC was used with the 4024 as "selling" was based on the inverter's DC voltage sensing.  Am I missing something?  Quite frankly, I'm banking on a solution like this as I have just installed a Radian as my own upgrade here at my shop and am using a Classic 150 as CC.  

Bill

  ----- Original Message ----- 
  From: Kirpal Khalsa 
  To: Allan at positiveenergysolar.com ; RE-wrenches 
  Sent: Sunday, December 16, 2012 10:51 AM
  Subject: Re: [RE-wrenches] Radian design limitation - am I missing something?

  Allan...indeed this is a limitation....and yes i agree with you that a higher voltage charge controller would be a welcome update to Outbacks line up.....Looking at the DPW top of pole list, i would suggest to you a design using 15 255 watt modules with the FM80 charge controller which would both meet your total wattage requirements, would still only  need one charge controller, as well as conform to the 3 module multiplication requirement....additionally it would require less foundation/excavation work, but would in fact be a honker of an array....just an idea! Locally in your area I know Focused Energy has a good price and availability of the US made SolarWorld 255's which we use often...
  Good luck.
  Kirpal

  On Sun, Dec 16, 2012 at 10:41 AM, Allan Sindelar <allan at positiveenergysolar.com> wrote:

    Wrenches,
    Please tell me if I'm overlooking something, in what appears to be a design weakness:

    I would like to use an Outback Radian system for a standard GTBB system. In order to take full advantage of the system's capabilities, I have to use all of Outback's main components; in this case the FM60 or FM80 charge controller. The problem is that the most common (and lower-cost) modules today are 60-cell, meaning 20 Vnominal. Given the 150V DC hard maximum voltage limit of the FM-series charge controller, in our cold climate I can only use these 20V modules in 60 Vnominal series strings; that is, in multiples of three modules. As the Radian is (wisely) offered in 48V only, pairs of modules would provide too low a voltage, and series strings of four modules would exceed 150 Voc in cold weather. 

    The base Midnite Classic 150 will safely operate to 198 VDC in this application, but it won't communicate with the Mate3.

    Is this a fundamental design limitation in the Radian system, suggesting that Outback is due for a controller upgrade, or am I missing something obvious? It appears that arrays and racks have to be sized in ~720-watt sets of three-module series strings, which can be problematic in some designs. In the design in question I would like to use 16 240W modules on two 8-module pole-top racks (for seasonal adjustability); nothing in sets of three meets the customer's output and aesthetic needs. 

    Any solutions would be welcome.
    Thank you,
    Allan

    -- 
    Allan Sindelar
    Allan at positiveenergysolar.com
    NABCEP Certified Photovoltaic Installer
    NABCEP Certified Technical Sales Professional
    New Mexico EE98J Journeyman Electrician
    Founder and Chief Technology Officer
    Positive Energy, Inc.
    3209 Richards Lane (note new address)
    Santa Fe, New Mexico 87507
    505 424-1112
    www.positiveenergysolar.com 

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