TC code reference [RE-wrenches]

Matt Lafferty pvpro at attbi.com
Tue Feb 4 20:30:06 PST 2003


William:

The one & only "Code" thing I find to be a potential "issue" with TC is
the "not allowed to be supported by brackets or cleats" thing.
Functionally it's way sufficient for PV applications.  

I believe that we must adhere to the NEC for the "greater good" of what
we do....When it recognizes the aspects of what we do.  By this I mean
that "the Code doesn't know everything".  If it did, we wouldn't have a
new one with updates every 3 years.  This doesn't mean we should ignore
it, just work to change it where it conflicts reality.

The distance between J-Boxes is negligible when considering the
stiffness of multi-conductor TC. Well within the "6 feet between
supports" required.   If you throw a UV resistant, quality cable-tie
around it, the wire doesn't move.  Personally, on a longevity/functional
level, the wire-tie isn't necessary.  By installing it, you ensure that
the sheathing is in contact with the module frame, potential for
"rubbing" over time.   At least until the wire-tie goes away....lol 

I don't support or allow "out in the open" wiring.  By this I mean that
TC should be inside flexible conduit when it leaves the periphery of the
array to go to a J-Box.

As far as "how do you seal it up when you get to the J-Box" goes.  A
good cable gland, plastic, not metal, by the way....seals and supports
TC very well.  It is my belief that it will hold up for as long as any
of us can reasonably expect, too.  The ones that come standard in the
KC-120 work extremely well.  They seal up so well, you wouldn't believe
it.  Even around "flat" cable.  Round cable is better in this respect
because you don't have to tighten up the compression nut so much, but
you wouldn't believe how well the flat seals unless you see or do it
yourself.  I sure didn't.

Anyway, I had the same "conduit or nothing" mindset that you have.  I
truly respect (probably more than just about anybody here) that way of
thinking.  I still have a "you gotta show me first" attitude....Always
will.

Bottom line:  We have to look for ways to keep what we call "making a
living" sustainable.  That means we have to look for ways to lower costs
without sacrificing integrity of installations.  I know this works.
There are other ways, to.  That ol' cat can get skinned in more ways
than one!

As far as the single-conductor TC.  I was wrong with what I said
yesterday.  It didn't even dawn on me that some of the wire I've used
has had multiple ratings.  I was only looking for the "others" when I
got it and used it.

UF refers to "Underground Feeder".  I hope nobody here is putting their
glass underground!

Pray for Sun!

Matt Lafferty
pvpro at attbi.com
(916) 422-9772
(916) 628-7694 Cell
(916) 914-2247 Fax

Note: For your security a Veri-Sign Certificate is embedded in this
message to verify it came from me personally. - Matt


-----Original Message-----
From: William Miller [mailto:wrmiller at slonet.org] 
Sent: Monday, February 03, 2003 9:32 PM
To: RE-wrenches at topica.com
Subject: RE: TC code reference [RE-wrenches]


Matt:

I have a few questions as I try to ratify my decision, or not:

At 02:54 PM 2/3/2003 -0800, you wrote:
>
>To clarify:
>
>Tray cable is permitted under 336 & 340.10.
>

336.10 Uses Permitted.
Type TC tray cable shall be permitted to be used in the following:  
(1) For power, lighting, control, and signal circuits.
(2) In cable trays, or in raceways, or where supported in outdoor
locations by a messenger wire.
(3) In cable trays in hazardous (classified) locations as permitted in
Articles 392, 501, 502, 504, and 505 in industrial establishments where
the conditions of maintenance and supervision ensure that only qualified
persons service the installation.
(4) For Class I circuits as permitted in Article 725.
(5) For non-power-limited fire alarm circuits if conductors comply with
the requirements of 760.27.
(6) In industrial establishments where the conditions of maintenance and
supervision ensure that only qualified persons service the installation,
and where the cable is continuously supported and protected against
physical damage using mechanical protection, such as struts, angles, or
channel, Type TC tray cable that complies with the crush and impact
requirements of Type MC cable and is identified for such use shall be
permitted between a cable tray and the utilization equipment or device.
The cable shall be secured at intervals not exceeding 1.8 m (6 ft).
Equipment grounding for the utilization equipment shall be provided by
an equipment grounding conductor within the cable.
(7) Where installed in wet locations, Type TC cable shall also be
resistant to moisture and corrosive agents.
FPN: See 310.10 for temperature limitation of conductors. 


336.12 Uses Not Permitted.
Type TC tray cable shall not be used in the following:  
(1) Installed where it will be exposed to physical damage
(2) Installed as open cable on brackets or cleats, except as permitted
in
340.10(6)
(3) Used where exposed to direct rays of the sun, unless identified as
sunlight resistant
(4) Direct buried, unless identified for such use


Does this fall under the "power, lighting and control"?  Outdoor use
requires a messenger.

ARTICLE 340 Underground Feeder and Branch-Circuit Cable: Type UF

Is TC Cable the same s UF?

>
>In my experience, every piece of tray-cable I've ever touched has been 
>multi-conductor.  If they even made a small-conductor configured TC, it

>would not be allowed due to the sheathing, as I understand it. 
>Furthermore, buying such an animal would be hard to find and probably 
>2-3 times as expensive.
>

I must have used a different cable, it was single conductor.  Here is
where I found it:

http://www.bpsolar.com/ContentDocuments/84/MC%20Wire%20Kit%20diagrams.pd
f

According to the above, it's RHW-2.  I've seen samples of
multi-conductor TC cable.  How in the world do you seal this into a
j-box, being not round?

Thanks,

William

__________________________________________________________________
William Miller
Miller Power and Communications
PO Box 50, Santa Margarita, CA 93453
Voice :805-438-5600     Fax: 805-438-4607	
email: wrmiller at slonet.org
http://millerpowerandcomm.com

[Non-text portions of this message have been removed]

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