NEC Article 720 Wiring Methods

[cmjones]

Does anyone have experience with allowed cabling for systems that fall under Article 720? ​

Section 720.11 has me wondering if the cabling can be simply installed exposed and supported by the building structure (i.e. not installed in conduit). A

re circuits installed under Article 720 required to be installed under the provisions of Chapter 3 wiring methods? ​

720.11 Mechanical Execution of Work. Circuits operating at less than 50 volts shall be installed in a neat and workmanlike manner. Cables shall be supported by the building structure in such a manner that the cable will not be damaged by normal building use.

 

[coffeebean]

The supporting would be found in the listing and labeling in the manufacturers installation instructions

 

[hbiss]

A better idea would be telling us what systems or equipment you are talking about. It looks like Art 720 exists because they were too lazy to include the applicable verbiage in each of the other Articles listed in 720.2. By itself 720 is useless.

Likely Art 725 will tell you how to determine what class your "less than 50 volts" application is and what wiring method you need to use.

-Hal

 

[cmjones]

Researching into designs involving higher power DC loads for office buildings which may not fall under any of articles under 720.2 (i.e. loads with power requirements greater than a Class 2 power source could supply).

Any opinions on if 720.11 allows for lenient wiring methods than that required in Chapter 3? Fore example: running the DC wires directly to the loads via J-hooks or cable tray without needing a conduit or other form of raceway.

 

[paulengr]

If you can’t meet chapter 7 you cannot use chapter 7 wiring methods, period.

Cable tray IS a raceway but the types of cables allowed is limited. And you have to account for entering and exiting it. So for instance type TC must be in a raceway but MC and TC-ER do not as long as it is supported every 3 feet, which is where your J hook concept would be correct.

Alternatively distribute power via AC then land at an AC/DC converter in a group of fixtures. That’s how a lot of landscaping retrofits do it. So the transformers and AC cabling is chapter 3. The DC side can become chapter 7.


Sent from my iPhone using Tapatalk

 

[hbiss]

Any opinions on if 720.11 allows for lenient wiring methods than that required in Chapter 3? Fore example: running the DC wires directly to the loads via J-hooks or cable tray without needing a conduit or other form of raceway.

Just forget that 720 exists!!!

Researching into designs involving higher power DC loads for office buildings which may not fall under any of articles under 720.2 (i.e. loads with power requirements greater than a Class 2 power source could supply).

Look, it's really quire simple. If your power source isn't CL2 or CL3 then you MUST use a Chapter 3 wiring method. There is NO distinction between AC or DC. Art. 725 is your reference.

Cable trays with suitable cables or conductors are a Chapter 3 wiring method. Individual conductors supported by J hooks are not.

-Hal

 

[don_resqcapt19]

...Cable tray IS a raceway ...

Cable tray is a support method for raceways and cables, it is not a raceway.