conduit vs tray cable [RE-wrenches]

[Bill Brooks]

Kelly and Larry,

Just a little note on conduit. Larry mentioned the problem of not having the
right temperature rating, but the bigger problem in my opinion is that many
manufacturers do not rate their junction boxes for conduit. It must be
explicitely called out in the installation instructions otherwise it
violates the UL listing of the module. Those cute little 0.75" holes on most
junction boxes are not designed for conduit but for cable glands.

Larry, I'm sure that your conduit installations are of the highest quality,
but field experience with average installations on rooftops is far from
encouraging. I have seen conduit pull out of connectors, pull out of
junction boxes, and pop the whole junction box off the back of the module.
Siemens sells their module as "conduit rated" and they are one of the few
companies that has gone through UL to get their modules approved for
conduit. There are very few things more dangerous in a PV system than an
open junction box laying on a roof.

Bill.



-----Original Message-----
From: Kelly Keilwitz [mailto:kelly at whidbeysunwind.com]
Sent: Tuesday, April 16, 2002 10:25 AM
To: RE-wrenches at topica.com
Subject: Re: conduit vs tray cable [RE-wrenches]


Larry,
Thanks for the idea of simply gluing male (PVC?) ends to your carflex. I too
like the clean and tight installation that results from using 1/2" flex
between module J-boxes. However, I'm uneasy with the stress that is put on
adjacent boxes by the short runs of flex that must curve around the module
frames (because of the long liquid-tight connectors). It seems as though it
would be cheaper, simpler, and faster to use your method. And, because there
would be more length of flex (because of the shorter connectors) to curve
around the module frames there should be less stress on the J-boxes.

Are you still using this method? Other wrenches? Anyone see any problem with
this?

--Kelly

Kelly Keilwitz
Whidbey Sun & Wind
Renewable Energy Systems
kelly at whidbeysunwind.com
Ph & Fax: 360-678-7131
Renewable Energy Now!

----- Original Message -----
Thanks Jeffery for bringing up this issue of liquid tight conduit.

When I first started using conduit  I simply glued male threaded ends to
the Carflex and used a standard nut with a silicone O ring to seal.

I had a supplier who found an obscure but valid reference in one of the
CarFlex tech sheets that actually allowed this and was listed by UL.
I also had it confirmed by a Portland  Oregon Code Inspector who
attended the referenced tech forum

I have yet to see one of these glued conduits fail but I have seen
expensive Thomas and Betts, Bridegport  and Hubble ends separated and in
some cases UV has made them very brittle with the non silicone O ring
turned to powder.

I have been back to some of my sites that have been in extreme heat,cold
and wet for 13 years and see absolutely no signs of a degraded wire or
conduit.
In some cases I have seen USE or RHW used by others at the same site
looking pretty ratty.

Larry Elliott

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