TC code reference [RE-wrenches]

[Matt Lafferty]

Wrenches:

William wrote:

>690.31 Methods Permitted.
>(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.  

To clarify:

Tray cable is permitted under 336 & 340.10.

Article 690.31(D) refers to single conductor cables which are classified
as "free-air".  This classification gives them a higher ampacity rating
than ones in conduit or in a cable assembly, such as tray-cable. USE-2
is allowed, for instance.  Regarding their appropriate applications,
Thin-Film comes to mind.  TF's have a very low Isc and Series Fuse
rating.

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.

For the record:  The TC I've used in PV applications has never been
smaller than #12, and always sunlight resistant.

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


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