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

[Kirpal Khalsa]

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* <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* <http://www.positiveenergysolar.com/>****
>
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