What Is MC Cable and Why Is It Used in Commercial Projects?

MC cable is a type of armored electrical cable that consists of insulated conductors enclosed in a flexible metallic sheath, usually made of aluminum or steel. It is widely used in commercial and industrial applications because of its:

✅ Durability – The metal-clad design provides extra protection against physical damage.
✅ Fire Resistance – Helps reduce fire hazards by offering built-in grounding and insulation.
✅ Code Compliance – Approved for use in exposed or concealed locations, including direct burial and damp environments.
✅ Ease of Installation – Reduces the need for conduit in certain installations, making it faster and more cost-effective to install.

Common Applications:

• Power distribution in office buildings, hospitals, and retail spaces
• Feeder circuits for HVAC systems and industrial machinery
• Commercial lighting and electrical outlets
• Underground installations with NEC-approved MC cable

Step 1: Determining the Correct Size for MC Cable

Choosing the right size of MC cable is critical to ensuring proper electrical performance and compliance with NEC requirements. The size of the cable depends on several factors:

1. Calculate Electrical Load Requirements

The first step in sizing MC cable is determining the total electrical load that the cable will carry. This is measured in amperes (A) and depends on the number of devices, their voltage, and power consumption.

• Step 1: Identify the total wattage of the connected equipment.
• Step 2: Use the formula: Amperage=Total WattageVoltage\text{Amperage} = \frac{\text{Total Wattage}}{\text{Voltage}}Amperage=VoltageTotal Wattage​
• Step 3: Select an MC cable gauge that can safely handle this load based on the ampacity ratings in the NEC.

2. Select the Proper Wire Gauge

The American Wire Gauge (AWG) system determines the size of conductors inside MC cable. Common sizes for commercial projects include:

Copper vs. Aluminum Conductors:

• Copper conductors have higher conductivity and are typically used for critical circuits.
• Aluminum conductors are lighter and more cost-effective but require a larger gauge size to carry the same current.

3. Check Voltage Drop for Long Runs

If the MC cable run exceeds 100 feet, voltage drop can become an issue. The NEC recommends keeping voltage drop under 3% for branch circuits.

To compensate, increase the cable size for long-distance runs to prevent power loss and overheating.

Step 2: Proper Installation Techniques for MC Cable

Once you’ve selected the correct size, follow these best practices for installing MC cable in commercial settings.

1. Follow NEC Guidelines for Support and Securing

• MC cable must be supported at intervals of 6 feet or less.
• Secure MC cable within 12 inches of every junction box, panel, or fitting.
• Avoid excessive bending—MC cable has a minimum bending radius (typically 5 times the cable diameter).

2. Cutting and Stripping MC Cable

• Use MC cable cutters or a rotary cable cutter to avoid damaging internal conductors.
• Remove the armor sheath carefully and use anti-short bushings where required.
• Ensure the grounding conductor is properly exposed and ready for termination.

3. Proper Termination and Grounding

• Use listed MC connectors for metal-clad cable to secure terminations.
• Connect the grounding conductor to the panel ground bar or as per NEC Article 250.
• Never splice or extend MC cable without using NEC-approved junction boxes and fittings.

4. Fire-Rated and Damp Location Installations

• Use fire-rated MC cable when running wiring through plenum spaces or fire barriers.
• In damp or wet locations, use NEC-approved moisture-resistant MC cable and sealed connectors.

Step 3: Ensuring Code Compliance

To pass electrical inspections and meet safety standards, MC cable installations must comply with NEC requirements:

✅ Use the right size conductors for the ampacity requirements.
✅ Secure and support cables as per NEC guidelines.
✅ Follow grounding and bonding rules to prevent electrical hazards.
✅ Check insulation ratings for commercial environments (e.g., fire-rated or moisture-resistant MC cable).

Final Thoughts: Choosing and Installing MC Cable for Commercial Projects

Properly sizing and installing MC cable is essential for safe, efficient, and code-compliant commercial electrical systems. By selecting the right cable size, ensuring proper support and terminations, and following NEC guidelines, contractors and electricians can ensure a reliable and long-lasting electrical installation.

Before starting any project, always refer to the latest NEC updates and consult with a licensed electrician to ensure compliance with local regulations.