As a courtesy to the Wrenches who
posted in response to my request, a design followup:
I completed the design using two Midnite Classic 200s. I specified
one Classic Lite after learning that the Classic could be used to
program both units and both could send their data to the web. I'll
use one MNPV-6 on each 8-module subarray (each needs 4 spaces for
2P ganged high-voltage breakers, so MNPV-3s won't work). The
Classics can share a common negative, properly sized.
The rack issue had a fair amount to do with visual height in the
desired location. Four- and eight-module racks used modules in
landscape orientation. Six-module racks used landscape also, but
both three-module and nine-module racks are in portrait
orientation - both too high (taller than four modules in
landscape) and visually unappealing.
Re Kent's concerns below: Multiple temperature sensors are not an
issue. No equalization is necessary with sealed batteries in GTWB,
and synchronization of absorption and float modes will seldom
matter - when the utility is up the inverter determines modes of
both, and when the grid is down the Classics will determine the
modes of both.As far as voltage adjustment for grid-tie mode, I'm
not sure to what Kent is referring.
Until this design I had not realized the fundamental limitation of
the Outback controllers. At 48 Vnom, they will only work with 3
60-cell module series strings in a cold climate - no more, no
less. To me that quite limits their applicability. As Kent says,
even given certain disadvantages to mixing products, "Not one of
these is a significant enough issue to merit choosing the FM".
I'll offer that Outback is suddenly way behind the curve on this
one.
Allan
Allan Sindelar
[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
www.positiveenergysolar.com
On 12/16/2012 1:17 PM, Kent Osterberg wrote:
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]>
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]
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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