THHN Open wiring

[bnewport]

What NEC section(s) pertain(s) to open runs of THHN? The application involves a transition from cable tray to a switchboard with chase nipples in the top. At what distance between the tray and panel is the cable required to be in conduit?

Bryan

 

[barbeer]

300.3 - as it leaves the tray it should transition to a chapter 3 method. The installation does not sound NEC compliant to me.

 

[Dennis Alwon]

I am no expert on cable tray but art. 392,3(A) & (B)(1) may help.

(A) Wiring Methods. The wiring methods in Table 392.3(A) shall be permitted to be installed in cable tray systems under the conditions described in their respective articles and sections.

Table 392.3(A) Wiring Methods

Wiring Method Article
Armored cable 320
CATV cables 820
CATV raceways 820
Class 2 and Class 3 cables 725
Communications cables 800
Communications raceways 800
Electrical metallic tubing 358
Electrical nonmetallic tubing 362
Fire alarm cables 760
Flexible metal conduit 348
Flexible metallic tubing 360
Instrumentation tray cable 727
Intermediate metal conduit 342
Liquidtight flexible metal conduit 350
Liquidtight flexible nonmetallic conduit 356
Metal-clad cable 330
Mineral-insulated, metal-sheathed cable 332
Multiconductor service-entrance cable 338
Multiconductor underground feeder and branch-circuit cable 340
Network-powered broadband communications cables 830
Nonmetallic-sheathed cable 334
Non-power-limited fire alarm cable 760
Optical fiber cables 770
Optical fiber raceways 770
Other factory-assembled, multiconductor control, signal, or power cables that are specifically approved for installation in cable trays
Polyvinyl chloride PVC conduit 352
Power and control tray cable 336
Power-limited fire alarm cable 760
Power-limited tray cable 725
Rigid metal conduit 344
Rigid nonmetallic conduit 352
RTRC 355
Signaling raceway 725

(1) Single Conductors. Single-conductor cables shall be permitted to be installed in accordance with (B)(1)(a) through (B)(1)(c).
(a) Single-conductor cable shall be 1/0 AWG or larger and shall be of a type listed and marked on the surface for use in cable trays. Where 1/0 AWG through 4/0 AWG single-conductor cables are installed in ladder cable tray, the maximum allowable rung spacing for the ladder cable tray shall be 225 mm (9 in.).
(b) Welding cables shall comply with the provisions of Article 630, Part IV.
(c) Single conductors used as equipment grounding conductors shall be insulated, covered, or bare, and they shall be 4 AWG or larger.