TC-ER Control Cable Grounding NEC

[turtlepokerman]

Greetings,

I have a 120Vac Control Cable that runs from a small 100VA 1-Ph CPT located in a MCC to a Relay Panel. Am I required to run a equipment grounding conductor within the cable to consider it TC-ER rated? There are numerous of these cables that are running between the two pieces of equipment.

The section that confuses me is NEC 2011 section 336.10(7) which states that "Equipment grounding for the utilization equipment shall be provided by an equipment grounding conductor within the cable.". Currently both the MCC and the panel are located in the same building and both equipment are bonded to the ground ring that is run within the building. So if a short occurs in the panel or the MCC the fault path would be through the building ground ring. All raceway is bonded to the ground ring as well, but the raceway is not continuously run along the conductor.

All help is appreciated!

 

[7anoter4]

NEC 2017 Art.336.10(7)f requires the same for conductors more than 6awg.For 6 and less you may use also: " at the time of installation, one or more insulated conductors must be permanently identified as an equipment grounding conductor in accordance with 250.119(B)."
250.119(B): “Individually covered or insulated equipment grounding conductors shall have a continuous outer green or green with one or more yellow stripes except as permitted in this section.”

 

[rcw retired EE]

An equipment grounding conductor is needed to assure a low impedance fault current path back to the power source. It could be a green wire or otherwise identified wire in the TC/ER cable or an external wire or a combination of cable tray, conduit, bonding jumpers, and/or ground wires all bonded with approved connectors. Using the ground grid or building frame or the earth as the sole return path is not allowed due to the relatively high impedance of that path.

Seems like overkill for a 100 VA voltage transformer. (Can it be considered a Power Limited Cable?).

The section you referenced refers to cables that drop from cable tray to the equipment with out being in protected by conduit. A separate green or bare #12 awg ground wire run outside the cables would provide the ground path but be subject to damage. It would not meet code. A properly installed conduit or piece of tray enclosing/supporting the cables would make the installation compliant without the green wires in each cable.

Since there are numerous cables running between the two pieces of equipment, a single equipment grounding conductor in the tray with those cables might work, or the tray can be the ground path. A separate wire has to run in the same tray and conduits as the cables and be sized for the largest over current protection device of any cable, and be , #4 awg per 392-10 B 1) - (c ). If there are multiple conduit drops from the tray to the final enclosure, the ground wire has to run in each conduit without being reduced in size.

 

[turtlepokerman]

Doing a further dig into the NEC it looks like I am able to classify the circuits as Class 1 Remote-Control and Signaling circuit (assuming my CPT is a Class 1 transformer). I can't however find any grounding requirements that are associated with class 1 circuits. I have dug pretty deep into Article 725 and can't find anything that specifically calls it out. Since there are no amendments in Article 725, Chapter 2 still applies. Unless anyone knows of a location that specifically allows this.