[RE-wrenches] AL wire with DC

[Dana]

I cannot speak for what if.

I have seen CU & AL bolted in AL mechanical butt splices
where someone did not torque it to spec. and it went to
arcing. Both were a mess ; The butt splice was pitted /
damaged and needed replacement, the AL cable melted and the
copper cable did not.
It the same amperage, but both were 1,600+watt arrays. 
But AL is softer and the strands are larger for the same
size as CU wire. 

I think that there was a greater safety factor in the CU.
More strands, finer wires, a harder metal, therefore greater
contact area on the AL mechanical butt splice. I have seen
split bolts that were loose and you could pull the wire out
easily and no melting or arcing. 

Thanks,  Dana Orzel

Great Solar Works, Inc
E - dana at solarwork.com
V - 970.626.5253
F - 970.626.4140
C - 970.209.4076
web - www.solarwork.com

"Responsible Technologies for Responsible People since 1988"


-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf
Of Dana
Sent: Friday, July 23, 2010 4:24 PM
To: 'RE-wrenches'
Subject: Re: [RE-wrenches] AL wire with DC

OG - Off Grid

Thanks,  Dana Orzel

Great Solar Works, Inc
E - dana at solarwork.com
V - 970.626.5253
F - 970.626.4140
C - 970.209.4076
web - www.solarwork.com

"Responsible Technologies for Responsible People since 1988"

-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf
Of Richard L Ratico
Sent: Friday, July 23, 2010 4:18 PM
To: re-wrenches at lists.re-wrenches.org
Subject: Re: [RE-wrenches] AL wire with DC

Dana,

Thanks for the input. Excuse me please, "OG jobs" are?

If the wire had been copper and didn't melt, but instead
continued to arc,
would the resultant heat have eventually started a fire?
What type of splice was it?

Does no one else use Al for DC? Here in rocky Vermont/NH,
we use the same type aluminum URD cable for both AC and DC
runs, but,
always installed in PVC conduit, never direct buried.
Haven't seen
seen a problem yet.

Dick Ratico
Solarwind Electric

--- You wrote:
The problem with Al is that, IF there is ever a loose
connection, & associated arcing, that it melts not like
copper in the same situation which may arc but not melt.

I have come in on OG jobs where Al was employed and found J
boxes that were [sometimes wet] and had loose connections
and the splice was charred/melted and the AL wire was not
conducting & melted beyond use, directly at the splice. The
rubber linemen's tape was charred and there was a direct
short to the metal box which was at least grounded
correctly. I tend not to use Al based on this experience.

Thanks,  Dana Orzel

Great Solar Works, Inc
E - dana at solarwork.com
V - 970.626.5253
F - 970.626.4140
C - 970.209.4076
web - www.solarwork.com

"Responsible Technologies for Responsible People since 1988"

-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf
Of R Ray Walters
Sent: Friday, July 23, 2010 7:46 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] calculating DC voltage drop

I try to keep it in copper for DC, as I had always heard of
trouble with Aluminum on DC. (True or Old Wrenches Tale?)
We definitely go to Al on long AC runs, as its whats
available, and the cost difference becomes remarkable.
I've seen small cuts in Al, later corrode completely through
the conductor.(AC run) I'm not sure what would happen it
were DC.
Probably depend on whether it was positive or negative, and
which was bonded to ground? (either accelerate the
corrosion, or act as cathodic protection?)

R. Walters
ray at solarray.com
Solar Engineer
--- end of quote ---
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