While the National Electrical Code does not officially prohibit placing NM cable inside conduit, it is extremely difficult to do so in practice, and very few experienced electricians will do so. The main reason for this is that most conduits are made of steel or aluminum, which will react with some components of the cable such as insulation and ground wires to create an electrical hazard. However, many buildings use plastic conduit, which is immune to these effects.
The only situation under which it is permissible to place NM cable in conduit is if the cable is being used as a protective wiring method around power lines. In this case, all metal connections to other cables or equipment must be made outside of the conduit-and any nonmetallic connections such as tapered screws must be used-but the cable itself can be placed within the conduit.
This type of installation is called "conduit protected wiring." Conduit protected wiring is required by code in areas where there are no distribution centers available off the street side of the building. These areas include factories, warehouses, schools, hospitals, and nursing homes. They also include any building over 5 stories high or with complex wiring systems.
In conclusion, NM cable may be run inside conduit only if it is being used as protective wiring. Otherwise, it should be allowed to hang freely from ceiling to floor.
Type MC cable has an outside PVC jacket and can be put in parking decks, concrete pours, and direct ground burial if it is labeled for such purpose. While NM wire may be routed via conduit, it is rarely done. The main reason is that most conduit is made from vinyl and this does not bond well to other materials. The plastic insulation on the conductor would likely cause it to break down over time as it bends inside the conduit.
If you do decide to use conduit, try to use larger size conduits to give the cable more space to move. Concrete tends to be tight when poured so there isn't much room for error. If the conduit is too small, the cable won't be able to move enough to prevent damage to it.
Also make sure that the type of conduit you are using is approved for MC cable. Some types of conduit are designed to resist corrosion from water but not all are created equal. Check with your conduit installer about which types of conduit they recommend for MC cables.
Finally, make sure that you follow the instructions that come with the cable package. Most MC cables are designed to be installed by a professional wiring contractor or electrical engineer. Unless they specify otherwise, don't attempt to install these cables yourself.
Conduit Wiring Is Used Non-metallic (NM) or Romex cable is the most often used type of cable in household wiring. THHN and THWN wire are the most regularly used wire kinds within conduit. Other types of cable, such as metal core, can be routed within conduit but they are more commonly used outside of conduit because they're less likely to cause damage to other wires if they get pinched.
The main advantage of using conduit for wiring is that it provides a protected environment for the wiring to live in. If there were no way to protect the wiring inside walls and floors, people would have a right to be upset if their electricity stopped working one day. Within conduit, however, the wiring is completely hidden from view, which makes it easier for homeowners to do business with instead of risk damaging it themselves.
Another advantage of using conduit is that it allows for the installation of multiple cables within the same hole, providing many options for routing these cables. Any openings in the conduit wall need to be large enough to fit a cable through, so if there are any obstructions in the path of a cable, this will need to be taken into consideration when planning where it should be run. For example, if there's an existing radio frequency (RF) outlet nearby, it might not be a good idea to route your cable next to it because it could cause interference with it.
Conduit, on the other hand, is needed for all residential and commercial wiring in some regions of the country, increasing the cost and difficulty of house wiring for the typical homeowner. Wiring without conduit is called "rough-in" wiring. The term refers to the fact that before any wiring is done, the walls and floors of the room being wired are opened up and inspected for holes or cracks that would lead to electrical problems later.
The best way to avoid having to use conduit is to select suitable materials for your home's construction. For example, if you pick drywall over wood paneling, you don't have to worry about damage to the wall panel causing a leak that would require conduit to fix.
You also want to make sure that your home was built according to code. Some codes require certain types of wiring to be put in conduit, while others allow any type of wiring to be done without it if code violations don't exist. Check with your local building department to make sure you're not violating any rules by doing your own wiring.
Finally, label everything! Use marker or tape to identify what each wire is for - hot, neutral, and ground - and keep them in their respective boxes.
When inserting wire into conduit, it is critical to understand the limits. The amount of heat that wire insulation may safely endure is graded. Heat is produced as electricity flows via wires. To prevent overheating of the wires inside the conduit, wire fill inside the conduit must never exceed the prescribed level. This prevents the situation where a section of conduit contains enough wire to cause an electrical hazard if some of it was removed or damaged.
Conduit is designed to carry electric current and support mechanical stress without breaking down. However, too much pressure or force applied to the conduit can break it down eventually. Also, if you cut into the conduit with a knife or other cutting tool, you could reach deep enough to cut through the outer covering and injure yourself on the metal core.
So, the answer is yes, it is safe to put wire in conduit. But first, make sure that there is enough space for the cable to fit comfortably. If not, try again with a smaller size conduit. And also make sure that you don't go over the fill limit, otherwise you might be exposing yourself to an electrical hazard.