TC code reference [RE-wrenches]

Tue Feb 4 13:33:10 PST 2003

William,

I think John Wiles' message is pretty good. I would add that the main issue
with any cable--TC, UF, or USE is that it is: (1) Proper temperature rated
conductors (90C Wet), (2) Properly supported--no dangling in no-man's land,
and (3) Protected from physical damage--supported under modules or in
conduit if bridging between panels.

Messenger wires and cable trays are often used in industrial applications
where the wires are out of reach overhead typically.

Type TC comes in a variety of cross-sections including flat, oval, and
round. Several posts a year or so ago provided links for round TC. If a
round cable gland is used, then a round or oval cross section is necessary.
Flat is like Romex or UF and has different cable glands.

Bill.

-----Original Message-----
From: William Miller [mailto:wrmiller at slonet.org]
Sent: Monday, February 03, 2003 11:54 AM
To: RE-wrenches at topica.com
Subject: TC code reference [RE-wrenches]

At 09:34 AM 2/3/2003 -0800, you wrote:
>
>
>I was also told by an inspector that wire marked only TC must be
>supported by a cable tray or raceway - at least in Canada. Is there an
>exception in the NEC?
>

Eric:

>From the 2002 NEC:

First:

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

Directs you to:

340.10 Uses Permitted.
Type UF cable shall be permitted as follows:
(1) For use underground, including direct burial in the earth. For
underground requirements, see 300.5.
(2) As single-conductor cables. Where installed as single-conductor cables,
all conductors of the feeder grounded conductor or branch circuit,
including the grounded conductor and equipment grounding conductor, if any,
shall be installed in accordance with 300.3.
(3) For wiring in wet, dry, or corrosive locations under the recognized
wiring methods of this Code.
(4) Installed as nonmetallic-sheathed cable. Where so installed, the
installation and conductor requirements shall comply with the provisions of
Article 334 and shall be of the multiconductor type.
(5) For solar photovoltaic systems in accordance with 690.31.

Following the reference:

690.31 Methods Permitted.
(A) Wiring Systems. All raceway and cable wiring methods included in this
Code and other wiring systems and fittings specifically intended and
identified for use on photovoltaic arrays shall be permitted. Where wiring
devices with integral enclosures are used, sufficient length of cable shall
be provided to facilitate replacement.
(B) Single Conductor Cable. Types SE, UF, USE, and USE-2 single-conductor
cable shall be permitted in photovoltaic source circuits where installed in
the same manner as a Type UF multiconductor cable in accordance with
Article 339. Where exposed to sunlight, Type UF cable identified as
sunlight-resistant shall be used.
(C) Flexible Cords and Cables. Flexible cords and cables, where used to
connect the moving parts of tracking PV modules, shall comply with Article
400 and shall be of a type identified as a hard service cord or portable
power cable; they shall be suitable for extra-hard usage, listed for
outdoor use, water resistant, and sunlight resistant. Allowable ampacities
shall be in accordance with 400.5. For ambient temperatures exceeding 30°C
(86°F), the ampacities shall be derated by the appropriate factors given in
Table 690.31(C).
Table 690.31(C) Correction Factors

(Table omitted)

(D) Small-Conductor Cables. Single-conductor cables listed for outdoor use
that are sunlight resistant and moisture resistant in sizes 16 AWG and 18
AWG shall be permitted for module interconnections where such cables meet
the ampacity requirements of 690.8. Section 310.15 shall be used to
determine the cable ampacity and temperature derating factors.

Here is how I interpret this:  TC cable is allowed under D if it is rated
for outdoor use and if it is 14 or 16 AWG.  What is not clear to me is the
path the code takes by directing you to a section on UF cable and then to
section 690.31.  Also, I am not sure that 14 AWG is adequate size for this
purpose since the 60degreeC rating is only 18 amps.  This barely exceeds
the 15A series fuse rating for a Shell SP150, for example.

I've made up my mind on the suitability of TC cable, but I always want to
keep an open mind, so I will contribute to the discussion if I feel I have
something useful to contribute.

I am a code novice, so I await the words of those more wise, Bill Brooks
for example, or John Wiles.

William Miller

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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
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