Drake, it's as quick as V=IR. So taking the 11A from your evergreens,
and a #10 interconnect wire at 1.24Ohm/kft (NEC Table 8):
Vdrop = (11A) (0.00124Ohm/ft) (36 ft) = 0.5V. If the modules are hot,
you're looking at a Vmp around 265V- so your worst-case Vdrop% in that
jumper wire is just 0.5V/265V = 0.2%.
You're not using the voltage of the entire array to figure the drop on
the interconnect; you're just using the string current. You use the
array voltage just to see whether the voltage drop is significant (as
David Katz wrote).
That answer your question?
DKC (just to add another Dave to the thread)
-------- Original Message --------
Subject: Re: [RE-wrenches] Long MC Cable Mid String
From: Drake Chamberlin <[email protected]>
To: [email protected], RE-wrenches <[email protected]>
Date: 2009/04/22 10:15
I have scratched my head on this one before, because it seems that two
terminals bonded together by a wire are essentially the same terminal.
The theoretical voltage difference on a terminal is zero. How do we
figure a voltage drop on a wire that has near zero volt potential
between the ends of the wire. Can we really use the voltage of the
entire array to figure the drop on an interconnect between two
modules? If so, why can we do this?
Thanks,
Drake
At 07:49 PM 4/21/2009, you wrote:
David,
There will be less than a 1 volt drop in 36 feet of 10 AWG at the 11
amps you get from the Evergreen modules. I don't think anyone will
notice.
David
David Katz
David Palumbo wrote:
Does the following series string wiring cause a problem? With (18)
Evergreen ES-A 205’s (low voltage modules 18.4Vmp) in series feeding
a grid tie inverter with a long series connector in the middle of the
string. (2) Top Of Pole 9 module mounts with the series connection
from module #8 on the first pole to module #9 on the second pole.
This MC cable connection would be, about, 36 feet in length to go 10’
down the pole below grade 18” for 13’ and back up the second pole 10’
(in conduit all the way) .
Will this extra long series wire cause problems?
I could use other modules of course but that would raise the cost per
watt by 70 cents.
Dave
/David Palumbo, President
Independent Power LLC
462 Solar Way Drive
Hyde Park, VT 05655
/NABCEP Certified
/ www.independentpowerllc.com <http://www.independentpowerllc.com>
/
_______________________________________________
List sponsored by Home Power magazine
List Address: [email protected]
Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive:
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules & etiquette:
www.re-wrenches.org/etiquette.htm
<http://www.re-wrenches.org/etiquette.htm>
Check out participant bios:
www.members.re-wrenches.org <http://www.members.re-wrenches.org/>
Drake Chamberlin
Athens Electric
OH License 44810
CO License 3773
740-448-7328
740-856-9648
------------------------------------------------------------------------
_______________________________________________
List sponsored by Home Power magazine
List Address: [email protected]
Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules & etiquette:
www.re-wrenches.org/etiquette.htm
Check out participant bios:
www.members.re-wrenches.org
_______________________________________________
List sponsored by Home Power magazine
List Address: [email protected]
Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules & etiquette:
www.re-wrenches.org/etiquette.htm
Check out participant bios:
www.members.re-wrenches.org
