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

[Andrew Truitt]

Allan - I've installed a number of the DPW 15 module TPMs with Outback CC's
and inverters in exactly the configuration that Kirpal mentions and they
have worked well.  The 15 module TPM does require a deep hole so make sure
you don't have shallow bedrock.  Another option is to use the Xantrex
XW-MPPT80-600 (which has an input voltage range of 195-550V) with an XW
inverter.  I'm no huge fan of Xantrex but I've actually had good
experiences with the XW.  Finally, if I were you I would seriously consider
an AC coupled system which would likely increase your overall system
efficiency and decrease the amount of copper you have to run.  A pole
mounted SB 4000US coupled with a Sunny Island co-located with the battery
bank might work well.


For a brighter energy future,


Andrew Truitt
NABCEP Certified PV Installer™ (ID# 032407-66)****

Principal
Truitt Renewable Energy Consulting****

(202) 486-7507****

http://www.linkedin.com/pub/andrew-truitt/8/622/713


"Don't get me wrong: I love nuclear energy! It's just that I prefer fusion
to fission. And it just so happens that there's an enormous fusion reactor
safely banked a few million miles from us. It delivers more than we could
ever use in just about 8 minutes. And it's wireless!"

~William McDonough





On Sun, Dec 16, 2012 at 11:51 AM, Kirpal Khalsa <solarworks at gmail.com>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 <
> 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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