SWR2500U Some derating likely [RE-wrenches]

[jberdner at sma-america.com]

Joel:

As Mo pointed out it is all about airflow.
This is why it is difficult for us to quantify exactly when and how much
derating at what power level.

How much does the wind blow ?
How much does the sun shine ?
How hot does it get and when ?

These are all critical variables that are up to Ma Nature.
Beyond that we can only go with experience (2.8 to 3 kW STC max) and
provide solutions, i.e. a fan, when we are wrong.  What I can say
conclusively is: a 12 Vdc 3" muffin fan, running at 9 Vdc, draws about
1.5 Watts, is virtually silent, and  drops the heatsink temperature by
about 15 C.  This simple solution is enough to solve any derating issue
we have seen to date. 

If you have any questions, or if I can be of any further assistance,
please do not hesitate to contact me.

Best Regards,

John Berdner

SMA America, Inc.
12438 Loma Rica Drive, Unit C
Grass Valley, CA  95945
530.273.4595 (voice)
530.274.7271 (fax) 


-----Original Message-----
From: Joel Davidson [mailto:joeldavidson at earthlink.net] 
Sent: Thursday, November 21, 2002 6:36 PM
To: RE-wrenches at topica.com
Subject: Re: SWR2500U Some derating likely [RE-wrenches]

Mo,
Thanks for the solid feedback!
Joel Davidson

Mo Rousso wrote:

> I know Joel is looking for some hard data, but I can only offer my
> observations.
>
> We installed 24 BP MSX-120 (12VDC nom) on 1 SB 2500 on an open
southern
> exposure roof with a pitch angle of 18 degrees.  The owner wanted to
push
> the inverter to the max and we added a 25th panel to the string.
>
> The inverter is mounted on an interior south facing wall of the garage
> (please don't yell at me John!!!) in Fallbrook, CA.
>
> On those days when we had nice bright skies and cool temps the
inverter
> would go into derate mode.  However, we added a fan to the heat sink
and the
> derate issue has been completely eliminated.  The customer is getting
every
> erg he can out of the set-up and is now a happy camper.
>
> I decided to add a fan to my SB to see what would happen.  My home has
20 BP
> 2150s modules with 10 modules per pole on DP&W TPM racks.  Both poles
feed a
> single SB2500.  In the past, I would occasionally  see derates maybe
20
> times per year for a 1 to 2 hour period each.  The fans I mounted are
DC and
> are powered by a 10W PV module that is oriented so that it powers up
the
> fans around 10 AM until dark.  All deratings have ceased and I have
actually
> seen my SB display post an output reading of 2507 watts.
>
> My goal is to build a small DAQ system and actively log my system
> performance so that I have hard data to analyze.  Until then, if
derating is
> an issue, put on a fan - it works.
>
> Mo
> --
> Mo Rousso
> HelioPower
> Renewable Energy Systems
> Remote Power Solutions
> mrousso at heliopower
> www.heliopower.com
> 760.845.8843
>
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