Wire nuts in DC? was (Re: Fried Combinor Box) [RE-wrenches]

[Bill Brooks]

Wrenches with wire nuts,

The problem with wire nuts from the beginning has been installation
technique. If you read the directions on proper installation of wire nuts
(twist-on wire splices), you find that most people are too lazy to install
them properly. We get away with this in AC systems, not because there is any
kind of "self-cleaning" going, but because arching in AC systems is usually
less destructive than with DC. It may take 30-years for a wire nut in an AC
system to break down, but the installation technique in a 12- or 24-volt
system will fail in less than 5 years.

A similar problem we have is the use of indoor wire nuts in outdoor junction
boxes. All wire nuts in Rainproof and waterproof boxes outside must be of
the waterproof type (designed for wet locations). If we put an indoor wire
nut, slopily installed in an outdoor enclosure, we have almost guaranteed
failure.

This has caused many in the PV field to warn against the use of wire nuts
with PV systems. I think we are beginning to tone down that rhetoric, but
add many stipulations so that people are clear on the fact that any
connector improperly applied and installed can cause problems.

Bill.


> -----Original Message-----
> From: Travis Creswell, Ozark Solar [mailto:ozsolar at ipa.net]
> Sent: Monday, April 02, 2001 5:46 AM
> To: RE-wrenches at topica.com
> Subject: Re: Wire nuts in DC? was (Re: Fried Combinor Box) [RE-wrenches]
>
>
> Hey Jerry,
>
> Actaully I was hoping someone could explain it to me.  I have heard that
> self cleaning bit several times but never realy undersood it.  What I had
> figured was that AC went back and forth 60 times a second (in the
> USA) while
> DC only goes on one direction (unless you are talking about the battery
> cables charge-discharge).
>
> Could I have read it in Wiles book?
>
> Travis Creswell
> Ozark Solar
> ----- Original Message -----
> From: "Jerry Caldwell" <solarcowboy at yahoo.com>
> To: <RE-wrenches at topica.com>
> Sent: Monday, April 02, 2001 1:43 AM
> Subject: Re: Wire nuts in DC? was (Re: Fried Combinor Box) [RE-wrenches]
>
>
> > Travis,
> >
> > can you explain what you mean by "self cleaning"?
> > this is a new one for me.
> >
> > Jerry
> >
> > --- "Travis Creswell, Ozark Solar" <ozsolar at ipa.net>
> > wrote:
> >   I had heard that you weren't
> > > supposed to use wire nuts in
> > > DC because DC wasn't self cleaning and AC was self
> > > cleaning.  That self
> > > cleaning bit seemed to make some sense but  now as I
> > > look at it in writing
> > > it sounds kinda shaky.  Any body else heard that?
> > >
>
>
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