I started using the wet rated wire nuts, because I've found some
corrosion in old connectors in outdoor boxes. BTW, why don't you
like the goo filled wire nuts? They seem a decent and cost effective
solution.
I agree with your idea that condensation and moisture buildup can
occur even in a NEMA 4 box, and the issue that I have is that
breakers and fuse holders in combiner boxes are definitely not wet
rated. I wonder what happens to the internal workings of a breaker
after decades in an outdoor box, but considering there are an awful
lot of them around (at least AC) I guess I'll get another night's
sleep in our less than perfect world of PV wiring.
Ray
On 10/21/2011 9:05 AM, Jamie Johnson wrote:
William, the only explanation that I have found for using
THWN-2 in conduit run through the attic is that during the day
as the temperature in the attic increases, the air in the
conduit expands, at night the opposite effect happens, the
temperature in the attic decreases and the volume of air in
the conduit contracts with the potential to bring in what ever
climate conditions exist outside the conduit (In FL this could
be humid air).
Over time if there is humid air present, this could form
condensation in the conduit or NEMA 4 rated enclosure, hence
the need for wire and connections rated for a wet location.
I have seen photos at inspectors meetings of NEMA 4
enclosures and conduit that contained water although I am not
sure how often this would normally happen.
Jamie Johnson
NABCEP Certified PV Technical Sales Professional
NABCEP Certified Solar PV Installer
General Manager
SOLAR POWER ELECTRIC
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