Gray Flex - Radiational Cooling [RE-wrenches]

[Rob Wills]

Jay said "and will fill with water ( I
punch a small hole in the bottom of the loops as a drain hole when possible)
over time"

Many people do not know that a common mechanism for water in conduits and
junction boxes on
PV modules is to do with the optical behavior of the cells - being good
solar absorbers,
they also have very good emissivity, which means on a clear night they will
cool to below ambient.

If they cool to below dew point, moisture will condense on the backs of the
modules, and especially
in junction boxes. It's something to think of when designing wiring systems
(and equipment that mounts
to PV modules and frames).  The drain holes are important as hermetic
sealing is not possible.

Rob Wills



-----Original Message-----
From: jay peltz [mailto:jay at asis.com]
Sent: Thursday, April 26, 2001 10:29 AM
To: RE-wrenches at topica.com
Subject: Re: Gray Flex [RE-wrenches]


Hi Bill,

Well actually I am implying that the code doesn't always make sense, but
that
isn't anything new in life or in book of code that's hundreds of pages long.
And as you know you can ask 4 people and get 5 answers about the safety of
almost any issue.

But  there will always be different points of view that have good data to
back
them up as well. The guys in charge have to listen to the points of view,
then
decide what they think is best and act on it. What they decide is what we
are to
do.


What I was trying to point out only was the seeming inconsistency of some
things, such as flex conduit use for PV vs say Air Conditioning installs.
Yes I
know that conduit is only a physical protector, and will fill with water ( I
punch a small hole in the bottom of the loops as a drain hole when possible)
over time.

I  accept your data but I would like to know if you have measured the
temperature of a black rooftop AC install?  how does this compare with a PV
system?

QUESTION:
As the flex is rated for a given temperature, then give the geographical
range
of the country, is it possible to use different rated flex in different
parts
just like we derate for geographical temps?  For example up here on the
northcoast, in Arcata the hi temperature for the year might be 80 degrees F,
where as in Sac its probably like 110 or so?

I am trying to do the best work possible and to do that I need the most
information possible.

Thanks Bill I really do appreciate it,

Sincerely,

jay

Peltz Power

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