3 Ways to Use Copper MC Cable
1. Indoors Without Conduit
MC stands for Metal Clad due to the aluminum wrapped jacket called aluminum interlocked armor. The metal clad jacket was designed to be used indoors as a cable that replaces NMB cable in conduit. The armor is approved by the NEC to be used indoors without conduit because the jacket protects in the same way that conduit does. Romex® NMB cable can still be used when conduit is not required because it's cheaper than MC cable.
2. Outdoors Above Ground
NMB cable uses a basic PVC jacket and has a bare copper ground wire, which are two reasons it cannot be used outdoors. Copper MC cable on the other hand has an insulated ground wire and a metal clad jacket that allow it to be used outdoors. The conductors inside the aluminum armor are THHN THWN-2 rated which means that don't even need the jacket to be used outdoors. If you want to save money on the cable you can purchase 3 or 4 THHN wires and run them individually to get the same affect.
3. Outdoors Underground With Conduit
Again, with the use of THHN THWN-2 wires inside MC cable it can be used outdoors or in conduit underground. It cannot be directly buried in the ground without conduit because it will start to decay much earlier than expected. Remember, using MC cable in conduit is more expensive than running all separate THHN wires. You would be paying a premium to install one cable instead of 4 single wires which may or may not benefit your situation.
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