Allen,
I agree with Kirpal's comments. In fact, because the 300-volt breakers
take up so much extra space, I'd stay with the three-modules-in-series
design even if using the Classic charge controller; unless the PV array
was so far away that you need the extra voltage to reduce wiring losses.
But, for the example you are talking about with four modules in series
you would want a Classic 200 not the Classic 150 because the Classic 150
would goes into non-operational hyper-Voc mode at 28°C (82°F), measured
at the cell.
The fact that the FM charge controller will talk to the Mate has
advantages: 1) Only one temperature sensor is needed, 2) Voltage
adjustment for grid-tie mode, and 3) Synchronization of equalize,
absorb, and float modes. Not one of these is a significant enough issue
to merit choosing the FM, and suffering from it's lower efficiency and
poor MPPT tracking, over the Midnite Classic or Morningstar TriStar MPPT
charge controllers.
Kent Osterberg
Blue Mountain Solar, Inc.
www.bluemountainsolar.com
On 12/16/2012 10:51 AM, Kirpal Khalsa wrote:
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
<[email protected] <mailto:[email protected]>>
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*
[email protected]_ <mailto:[email protected]>
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 <tel:505%20424-1112>*
_www.positiveenergysolar.com_ <http://www.positiveenergysolar.com/>
*
*
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