[RE-wrenches] AL wire with DC

Mon Jul 26 04:37:04 PDT 2010

I don't think most of the breakers and wire ends we use (or at least I) are
rated for Al use. I don't use Al at all and try to have as few splices as
possible. Each splice is a potential problem and with Al a failure in the
insulation can result in the wire just corroding away if it's buried. I
don't think it makes a difference if it's the + or - wire.

Later,
Bob

-----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 8:25 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] AL wire with DC

I think some of the advantage of the Cu in a bad connection is that it
dissipates heat better. That might explain the melting Al, but not the Cu.
Cu will melt and cook the insulation if the connection is loose enough at
high enough amperage.
Again, I have not personally seen a problem with Al on DC runs, I just
haven't done it.
110.14 just specifies what we already know( I think), that you have to use
special connectors that isolate the cu from direct contact with the Al.
The new splice block type connectors are great for this.

R. Walters
ray at solarray.com
Solar Engineer

On Jul 23, 2010, at 4:54 PM, Dana wrote:

> 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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