Koneka [RE-wrenches]

Darryl Thayer daryl_solar at yahoo.com
Tue May 27 11:09:09 PDT 2008


Hello
I would calculate it differently, the concern is the
back feed current, the current back feed is the
maximum possible current or 1.25* Isc.  The second
1.25 is for continuous current derating and used in
wire sizing and fuse sizing.  
  
2 strings: 1.25*2.38 (2-1)= 2.87 amps no fuse required
3 strings: 1.25*2.38 *(3-1)=5.74 still no fuse
required
4 strings 1.25*2.38*(4-1)=8.61 Fusing required.  

CAUTION this is not the end of the calculation!!
Where does the power go from here?  Does it connect
with a charge controller? IS the charge controller
rated for NO BACK feed?  Billl Brooks says most are
not!  Further does it go to an inverter? Bill says
many inverters are not rated for no back feed. 

Therefore I tend to use fusing always.  The sum of the
possible back feed to a module must not exceed the
fuse rating of the module.  Remember the lessons of
the BP Millennia modules.  
Darryl

--- Mark Frye <markf at berkeleysolar.com> wrote:

> 
> Kaneka T-SC120: Isc = 2.38 A, "Series Fuse" = 7.0 A
> 
> 2 Strings: 1.56 * 2.38 A (2-1) = 3.7 A < 7.0 A = no
> fuses required
> 
> 3 Strings: 1.56 * 2.38 A (3-1) = 7.4 A > 7.0 A =
> fuses required on each
> string, max 7 A
>  
> Mark Frye
> Berkeley Solar Electric Systems
> 271 Vistamont Dr
> Grass Valley CA 95945
> (530) 401-8024
> www.berkeleysolar.com 
> 
> -----Original Message-----
> From: Mark Frye [mailto:markf at berkeleysolar.com] 
> Sent: Monday, May 26, 2008 2:27 PM
> To: RE-wrenches at topica.com
> Subject: RE: Koneka [RE-wrenches]
> 
> 
> Do you have  the Isc and "series fuse rating" for
> the modules?
>  
> Mark Frye
> Berkeley Solar Electric Systems
> 271 Vistamont Dr
> Grass Valley CA 95945
> (530) 401-8024
> www.berkeleysolar.com 
> 
> -----Original Message-----
> From: Marco Mangelsdorf [mailto:marco at pvthawaii.com]
> Sent: Monday, May 26, 2008 2:19 PM
> To: RE-wrenches at topica.com
> Subject: Koneka [RE-wrenches]
> 
> 
> Does any one have a system schematic of a 20-module
> or something similar
> Koneka 2.4 kW system with a 2.5 kW Xantrex GT or
> Sunny Boy inverter that
> they'd be willing to share with me?  With these A-si
> modules having a high
> voltage and low amperage, I'm wondering if I can
> parallel four or five
> strings or whether I need to fuse the individual
> strings.
> 
> Please contact me off-list.
> 
> Thanks,
> marco
> 
> Marco Mangelsdorf, Ph.D., President
> Electrical Contractor License C-26351
> 69 Railroad Avenue, Suite A-7
> Hilo, Hawaii 96720 USA
> (808) 969-3281, fax 934-7462
> 
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