Gray Flex [RE-wrenches]

Sun Apr 22 11:07:03 PDT 2001

Bill you can't be serious about AC units not getting as hot as PV modules?
Can you?  Have you never been on a flat mopped black tar roof of a business
or a school in the middle of the summer.  No shade, no wind just lots of sun
and the AC unit running as hard as it can.  In my mind that is much worse
conditions than the back of a solar module and there is millions of
installations of gray flex on flat tar roofs.

And yes even thought "carflex" is only 60c wet rated I still use it for
module interconnects.  I feel it is the best is terms of durability and
looks.  I have seen the insulation on too many wires on generators and in
attics chewed off by curious squirrels or whatever creature chews wires in
two.

Travis Creswell
----- Original Message -----
From: "Bill Brooks" <billbrooks7 at earthlink.net>
To: <RE-wrenches at topica.com>
Sent: Saturday, April 21, 2001 11:43 PM
Subject: RE: Gray Flex [RE-wrenches]

> Joel and others,
>
> The point is not that air conditioners don't get got and wet, they just
> don't get nearly as hot as the back side of a PV module. For roof mounted
> arrays in warm climates (Los Angeles), it is best to use 75C as the
hottest
> ambient temperature (on the back of the module). This means that the
conduit
> must be rated for at least 80C (wet since it is outdoors). The conductors
we
> use to connect to the module must be at least 90C rated to allow current
> flow (a 75C wire at 75C has zero ampacity by definition). Non-Metallic
> Flexible Conduit is normally 60C wet rated but can be purchased in 80C,
> which is fine to use.
>
> If you are mounting the modules in an open rack like most of our off-grid,
> ground-mount and pole mount systems, the hottest temperature never go
above
> about 65C, so 75C wire is okay, but the 0.33 multiplier must be applied to
> the ampacity calculation (e.g. 10 ga. wire has a 16 amp ampacity at these
> temps).
>
> Bill.
>
> -----Original Message-----
> From: Joel Davidson [mailto:joeldavidson at earthlink.net]
> Sent: Saturday, April 21, 2001 10:05 AM
> To: RE-wrenches at topica.com
> Subject: Re: Gray Flex [RE-wrenches]
>
>
> Gray flex on air conditioner installations gets hot and wet. For many
years,
> manufacturers, distributors, installers and inspectors have accepted gray
> flex.
> What should be used on air conditioner installations that would be better,
> cheaper and faster than current practices?
>
> Bill Brooks wrote:
>
> > Answer,
> >
> > USE-2 cable or Tray Cable without conduit using cable glands to connect
to
> > the junction boxes is cheaper than conduit and more appropriate in many
> > cases. Many modules are not "conduit ready". Just because it has a 3/4"
> > knockout, does not mean you can put a piece of conduit on it. We have
many
> > examples of conduit causing junction boxes to pop off the backside of
the
> > module. If the installation directions don't mention conduit you CANNOT
> put
> > conduit on them.
> >
> > If you put conduit on a module it must be a minimum of 80C wet-rated.
The
> > stuff you buy at HOME DESPOT is 60C rated and can weaken and fall apart
at
> > the temperatures we work with. I'm not making this stuff up or just
> > regurgitating John Wiles stuff, I've seen it on several occasions in the
> > field. The crap they often put on A/C units rated for lower temperatures
> > should NEVER be used on PV system.
> >
> > Now that oughta get some reaction--anyone care to take me to task on
this
> > one? (in good fun of course)
> >
> > Bill.
> >
> > -----Original Message-----
> > From: Joel Davidson [mailto:joeldavidson at earthlink.net]
> > Sent: Saturday, April 21, 2001 9:17 AM
> > To: RE-wrenches at topica.com
> > Subject: Gray Flex [RE-wrenches]
> >
> > Flexible conduit is used almost always to wire outdoor air conditioners
> > and passes inspection. Yet some designers say do not use gray flex for
> > PV module interconnects and short sub-panel whips. What is better,
> > faster, cheaper than gray flex?
> >
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