Article 336 Power and Control Tray Cable of Type TC [PDF]

We summarized main points of NEC Article 336 standards which is practically used in commercial building, plants, refineries and other projects.

Article 336 Power and Control Tray Cable of Type TC

Article 336 of the National Electrical Code (NEC) covers Power and Control Tray Cable, which is designated as Type TC. This type of cable is used for various electrical power and control applications and is designed to be installed in cable trays. Power and Control Tray Cable (Type TC) typically includes conductors for power transmission as well as control conductors for signaling and control purposes. These cables are commonly used in industrial and commercial settings where they can be installed in cable trays, conduit, or other approved raceways.

Type TC cables are known for their versatility and suitability for a wide range of applications. They are often used in power distribution, motor control, lighting systems, and various control circuits. These cables are designed to meet specific electrical and safety standards to ensure safe and reliable operation.

It’s important to consult the NEC and local electrical codes when specifying and installing Type TC cables to ensure compliance with regulations and to guarantee safe electrical installations.

NEC Article 336.1 Scope

It’s important to consult the NEC and local electrical codes when specifying and installing Type TC cables to ensure compliance with regulations and to guarantee safe electrical installations.

NEC Article 336.10 Uses Permitted

Article 336.10 of the National Electrical Code (NEC) outlines the permitted uses of Type TC (Power and Control Tray Cable). This section specifies where and how Type TC cables can be used in electrical installations. Here’s a breakdown of the permitted uses:

Power, Lighting, Control, and Signal Circuits: Type TC cable can be used for power, lighting, control, and signal circuits.
In Cable Trays: Type TC cables can be installed in cable trays, including those with mechanically discontinuous segments up to 300 mm (1 ft) in length.
In Raceways: Type TC cables can be installed in raceways.
Outdoor Locations with Messenger Wire: They can be used in outdoor locations when supported by a messenger wire.
Class 1 Circuits: Type TC cables are permitted for Class 1 circuits as allowed in Parts II and III of Article 725.
Non-Power-Limited Fire Alarm Circuits: Type TC cables can be used for non-power-limited fire alarm circuits if the conductors comply with the requirements of 760.49.
Between Cable Tray and Utilization Equipment: Type TC-ER (Type TC-Exposed Run) cable can be used between a cable tray and utilization equipment or devices under specific conditions:

The cable must be Type TC-ER.
It should be installed in industrial establishments with qualified personnel.
Continuous support and protection against physical damage are required using methods like struts, angles, or channels.
The cable must comply with the crush and impact requirements of Type MC cable and be marked “TC-ER.”
The cable should be secured at intervals not exceeding 1.8 m (6 ft).
Equipment grounding for the utilization equipment should be provided by an equipment grounding conductor within the cable. For cables with conductors sized 6 AWG or smaller, one or more insulated conductors can be permanently identified as an equipment grounding conductor. Exception: Type TC-ER can transition between cable trays and between cable trays and equipment or devices for a distance not exceeding 1.8 m (6 ft) without continuous support. Mechanical support is required where the cable exits the cable tray to ensure the minimum bending radius is not exceeded.

Moisture and Corrosive Agents Resistance: Type TC cable should be resistant to moisture and corrosive agents when installed in wet locations.
One- and Two-Family Dwelling Units: Type TC-ER-JP cable, containing conductors for power and control circuits, is permitted for branch circuits and feeders in one- and two-family dwelling units. Installation should follow the requirements of Part II of Article 334 for interior wiring and Part II of Article 340 for exterior wiring. Exception: When used to connect a generator and associated equipment with terminals rated at 75°C (140°F) or higher, the cable is not limited in ampacity by 334.80 or 340.80.
Direct Burial: Type TC cable can be directly buried if it is identified for such use.
Hazardous (Classified) Locations: Type TC cable can be used in hazardous (classified) locations where permitted by other articles in the NEC.
Service-Entrance Conductors: Type TC cable can be used for service-entrance conductors if identified for such use and marked as Type TC-ER.

This article provides comprehensive guidance on the acceptable applications and conditions for using Type TC cables in electrical installations, ensuring their safe and compliant use.

NEC Article 336.12 Uses Not Permitted

Article 336.12 of the National Electrical Code (NEC) lists the uses that are not permitted for Type TC (Power and Control Tray Cable). These restrictions help ensure the safe and compliant use of Type TC cable. Here are the prohibited uses:

Installed Where Exposed to Physical Damage: Type TC tray cable should not be installed in locations where it will be exposed to physical damage. This restriction aims to prevent damage to the cable that could compromise its integrity or electrical safety.
Installed Outside a Raceway or Cable Tray System: Type TC cable should not be installed outside a raceway or cable tray system, except in specific situations outlined in 336.10(4), 336.10(7), 336.10(9), and 336.10(10). These exceptions define scenarios where outdoor or exposed installations are allowed.
Used Where Exposed to Direct Rays of the Sun: Type TC cable should not be used in locations exposed to direct sunlight unless it is specifically identified as sunlight resistant. This requirement ensures that the cable maintains its properties and safety when exposed to sunlight.

Adhering to these prohibitions helps prevent potential hazards and ensures that Type TC cable is used appropriately in electrical installations.

NEC Article 336.24 Bending Radius

Article 336.24 of the National Electrical Code (NEC) provides guidelines for the minimum bending radius for Type TC (Power and Control Tray Cable). Proper bending radius is essential to prevent damage to the cable, maintain its electrical integrity, and ensure safety. Here are the specified minimum bending radii for Type TC cable:

Type TC Cable Without Metal Shielding:

For cables with a diameter of 25 mm (1 in.) or less: The minimum bending radius should be four times the overall diameter of the cable.
For cables larger than 25 mm (1 in.) but not more than 50 mm (2 in.): The minimum bending radius should be five times the overall diameter of the cable.
For cables larger than 50 mm (2 in.): The minimum bending radius should be six times the overall diameter of the cable.

Type TC Cables With Metallic Shielding:

Type TC cables that have metallic shielding should have a minimum bending radius of not less than 12 times the overall diameter of the cable.

These bending radius requirements help ensure that Type TC cables are installed and bent in a way that doesn’t cause damage, kinking, or stress that could lead to electrical or mechanical issues. Proper cable handling is essential to maintain the cable’s performance and safety characteristics.

NEC Article 336.80 Ampacity

Article 336.80 of the National Electrical Code (NEC) specifies the ampacity requirements for Type TC (Power and Control Tray Cable). The ampacity of Type TC tray cable should be determined based on the following criteria:

Conductors 14 AWG and Larger: For conductors with a size of 14 AWG (American Wire Gauge) and larger, the ampacity of Type TC tray cable should be determined in accordance with the guidelines provided in NEC 392.80(A).
Conductors 18 AWG through 16 AWG in Cable Trays: For conductors with sizes ranging from 18 AWG through 16 AWG and installed within cable trays, the ampacity should be determined in accordance with NEC 402.5.
Conductors Outside of Cable Trays: When Type TC tray cable is installed outside of cable trays (where permitted), the ampacity calculation should follow the guidelines outlined in NEC 310.14.

These ampacity requirements are essential to ensure that the Type TC tray cable is appropriately sized to carry the electrical load without exceeding its current-carrying capacity. Adhering to these guidelines helps maintain the safety and performance of the electrical installation.

Part III Construction Specifications

NEC Article 336.100 Construction

Article 336.100 of the National Electrical Code (NEC) outlines construction specifications for Type TC (Power and Control Tray Cable). This section specifies the following regarding the construction of Type TC cable:

Prohibition of Metallic Sheath or Armor Under or Over Nonmetallic Jacket: Type TC cable should not have a metallic sheath or armor either under or over the nonmetallic jacket. In other words, there should not be a layer of metal sheathing or armor surrounding the entire cable, both inside and outside of the nonmetallic jacket.
Permitted Use of Metallic Shield(s): Metallic shield(s) are allowed in Type TC cable construction. These metallic shields can be positioned over groups of conductors within the cable, under the outer jacket, or in some cases, both. This means that metallic shielding can be selectively applied to certain portions of the cable to provide protection or other specific electrical characteristics.

NEC Article 336.104 Conductors

Article 336.104 of the National Electrical Code (NEC) provides detailed specifications regarding the conductors used in Type TC (Power and Control Tray Cable). Here are the key points outlined in this section:

Conductor Sizes: Type TC cable may have various types of conductors for different applications:

Ungrounded, Grounded, and Equipment Grounding Conductors: These conductors can be in sizes ranging from 14 AWG through 1000 kcmil for copper, nickel, or nickel-coated copper conductors, and 12 AWG through 1000 kcmil for aluminum or copper-clad aluminum conductors.
Control and Signal Conductors: The minimum conductor sizes for control and signal conductors are specified as 18 AWG for copper, nickel, or nickel-coated copper, 14 AWG for copper-clad aluminum, and 12 AWG for aluminum.

Insulation Types: The insulation on these conductors should be one of the types listed in Table 310.4(1) or Table 310.4(2) that is suitable for branch circuit and feeder circuits. Alternatively, it should be an insulation type that is specifically identified for such use. This ensures that the insulation material is appropriate for the intended application.
Special Cases:

Fire Alarm Systems: When Type TC cable is used for fire alarm systems, the conductors must also comply with the requirements of 760.49.
Thermocouple Circuits: Type TC cable used for thermocouple circuits, as per Part III of Article 724, may have conductors made of materials suitable for thermocouple extension wire.
Class 1 Circuit Conductors: Insulated conductors of 18 AWG and 16 AWG copper must also meet the requirements of 724.49 when used in Class 1 circuits.

These specifications ensure that the conductors used in Type TC cable meet the necessary size and insulation requirements for various electrical applications, including power, control, signals, fire alarms, thermocouple circuits, and Class 1 circuits. Complying with these standards helps ensure the safe and reliable operation of electrical systems.

NEC Article 336.116 Jacket

Article 336.116 of the National Electrical Code (NEC) outlines the requirements for the outer jacket of Type TC (Power and Control Tray Cable). Here’s a summary of this section:

Outer Jacket Material: The outer jacket of Type TC cable must be made of a flame-retardant, nonmetallic material. This requirement is essential to enhance the fire safety properties of the cable. The use of a flame-retardant jacket helps reduce the spread of fire and smoke in the event of a fire-related incident.

Complying with this standard ensures that the outer jacket of Type TC cable contributes to overall safety by minimizing the fire hazard associated with electrical installations. Flame-retardant materials are designed to inhibit the ignition and propagation of flames, providing an additional layer of protection in case of a fire.

NEC Article 336.120 Marking

Article 336.120 of the National Electrical Code (NEC) specifies the marking requirements for Type TC (Power and Control Tray Cable) when it employs thermocouple extension wire. Here’s a summary of this section:

No Voltage Marking: When a Type TC cable incorporates thermocouple extension wire, there should be no voltage marking on the cable. In other words, the cable should not be marked with voltage information. This requirement is specific to Type TC cables that are used in conjunction with thermocouple extension wire.

The absence of voltage markings on such cables helps prevent confusion and ensures that users or installers do not mistake the cable for having voltage-carrying conductors. Thermocouple extension wires are typically used for temperature measurement and control systems and do not carry voltage for power distribution or other electrical functions.

NEC Article 336.130 Hazardous (Classified) Location Cable

Article 336.130 of the National Electrical Code (NEC) outlines the requirements for hazardous (classified) location cable listed and marked as Type TC-ER-HL. Here’s a summary of these requirements:

1. Suitable Nonmetallic Jacket: Type TC-ER-HL cables must have an overall nonmetallic jacket that is suitable for the specific environment in which they will be installed. This means the jacket material should be chosen to withstand the conditions and hazards present in hazardous locations.

2. Circular Cross-Section: The overall construction of Type TC-ER-HL cables should be essentially circular in cross-section. This circular shape ensures consistent and reliable performance in hazardous environments.

3. Continuous and Gas/Vapor Tight Jacket: The nonmetallic jacket of these cables must be continuous and gas/vapor tight. This requirement is crucial for preventing the intrusion of gases or vapors into the cable, which could lead to safety hazards or cable damage.

4. Equipment Grounding Conductor: For cables with a construction diameter greater than 25.4 mm (1 inch), the equipment grounding conductor shall be bare. This bare conductor provides a reliable path for grounding and helps ensure the safety of the cable and equipment in hazardous locations.

5. Metallic Shield: Additionally, a metallic shield shall be included over all conductors under the outer jacket for cables with a construction diameter greater than 25.4 mm (1 inch). This shield serves to protect the conductors from external interference and provides an added layer of safety.