NM cable vs. conduit wiring

[DarkKnight]

What's the difference between NM cable and conduit wiring methods, and when is each approach most appropriate?

[machinist]

NM cable is generally used in dry indoor spaces because it’s simple and affordable. Conduit provides extra protection and is often required outdoors or in areas exposed to damage. The exact method depends on electrical codes, since rules about where each type can be used vary by location.

[DarkKnight]

What is armored cable used for in residential wiring?

[machinist]

Armored cable is used in residential wiring where the conductors need extra mechanical protection but running conduit isn’t practical. It’s commonly found in places like unfinished basements, garages, or areas where wiring may be more exposed to impact. As with other wiring methods, the exact situations where armored cable is allowed or required depend on local electrical codes.

[DarkKnight]

How are transitions between different wiring methods done?

[machinist]

Transitions between different wiring methods are usually made inside an accessible junction box where the cables are properly connected using approved connectors. Each wiring type must be secured and grounded according to local electrical codes which can vary by location. For example, NM cable typically cannot be run inside conduit for long distances. Usually, the NM cable ends in a box and individual conductors continue in conduit. Using the right fittings and keeping the transition accessible helps ensure safety and makes future maintenance easier.

[DarkKnight]

How does wire gauge selection differ between conduit and cable installations?

[machinist]

The size of wire needed depends on how much electricity it carries, how long the wire runs, and how it's installed. In conduit systems, individual wires are placed inside a protective tube. This setup provides good physical protection, but when multiple wires are grouped together in the same conduit, it can trap heat. Because of this, the amount of current each wire can safely carry may need to be reduced. To stay safe and meet code, larger wire sizes are often used in these situations.

In cable assemblies like NM cable, the wires are bundled together inside a plastic sheath, which also holds in heat. These cables usually have more limited options for installation, and similar rules apply when many cables are grouped closely together. In both methods, choosing the correct wire size is important to prevent overheating and reduce voltage drop, especially over long distances.

Local electrical codes and safety standards always determine the exact requirements, so wire size must be chosen according to the rules in place for each location.