Long distance DC feeders [RE-wrenches]

[Matt Lafferty]

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All:

Quick "chime-in"... Regardless!!!!!! of how you interpret the NEC on
"Grounding Separate Structures", as long as you are using currently
configured US compatible equipment and system grounding schemes, BOND ALL
GROUNDS PARALELL AND PROPERLY SIZED IF YOU WANT IT TO WORK AND NOT SCRATCH
YOUR HEAD LATER!  (Sorry for all the caps... Trust me here or suffer...)

Two Cents (Guess you all know by now that I didn't have any winning Lotto
Tix)

Matt Lafferty
Universal Energies Institute
mlafferty at universalenergies.com
(916) 422-9772
(916) 628-7694 Cell
(916) 914-2247 Fax
www.universalenergies.com


-----Original Message-----
From: John Berdner [mailto:jberdner at sma-america.com] 
Sent: Monday, June 07, 2004 1:40 PM
To: RE-wrenches at topica.com; RE-wrenches at topica.com
Subject: RE: Long distance DC feeders [RE-wrenches]

Marco:
 
By home runs I meant a separate dc positive and dc negative for each
inverter. In contrast you could have a dc combiner with multiple sub-array's
in parallel then a single pair of bigger wires running the long distance
then split out to feed multiple inverters.  
 
A separate ground rod at the array can be used >> but << you probably have
to run a separate ground wire back to the house UFER to bond the two
grounding systems together.  
Some have argued that this is not required because at 200' it is a
"seperately derived system". I don't read the Code that way any more (after
repeated spirited discussions with J. Wiles) We have also seen some some
GFDI issues in this set up. My guess is circulating ground currents caused
by the array frames being referenced to one rod and the array negative to a
different rod at a different potential.
 
Best Regards,
 
John Berdner
 
>>>>

John,

'Sorry to be dense here. "Home runs" for each array? For example, I'm going
to be doing a SB array that's about 200' from the inverter. The array is
going to be mounted on a barn roof. The barn will have its own UFER ground.
Twas my plan to ground the array frames to the barn UFER ground and run the
+ and - (adequately sized, of course) to the inverter. The inverter will be
grounded to the UFER ground at the house.

Am I missing somethin'?

aloha,
marco

- Have to pull home runs for each array.
(Since we ground our arrays here in the USofA the GFDI circuits see the
other GFDI as a ground fault) (In the ROW, with floating arrays you can
parallel the arrays and use Sunny Team for higher efficiency and N+1
redendancy)

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