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What Is Electrical Conduit

Oct 26, 2020

In general, “conduit” is a channel or pathway that can apply to many different areas. Roadways can be traffic conduits, ditches can be conduits for water, websites are a conduit for information.

What are the Major Types of Electrical Conduit?

You’ll hear several acronyms tossed around when you’re talking about types of electrical conduit along with terms like “rigid” and “flexible”. Here’s a breakdown of the most common types of electrical conduit.

RMC: Rigid Metal Conduit

RMC stands for “rigid metal conduit”. It’s one of the most heavy-duty types of electrical conduit and uses galvanized steel for its construction. As an outdoor-friendly conduit, it provides outstanding protection from environmental and physical damage. It’s also capable of providing structural support for boxes, cables, and other electrical equipment.

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· Typical Fastening Style: Threaded

· Common Sizes: 1/2″ – 2-1/2″

· Common Applications: Outdoor installations

IMC: Intermediate Metal Conduit

Intermediate metal conduit (IMC) is a toned-down version of RMC that’s thinner and lighter. Even though it’s not as thick, it’s typically approved for all of the same applications as RMC. Given the choice between the two, our electricians prefer IMC simply because its lighter weight makes it much easier to deal with.

· Typical Fastening Style: Threaded

· Common Sizes: 1/2″ – 2-1/2″

· Common Applications: Outdoor installations

EMT: Electrical Metallic Tubing

Around our Pro team, EMT is the most common term thrown around when we’re talking about types of electrical conduit. Some of the new guys and gals use it as a catch-all term for all metal conduit, but that’s not actually correct.

EMT stands for “electrical metallic tubing” and is a type of rigid metal conduit. You normally see it made from galvanized steel and it also shows up as aluminum in some cases.

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As a thinner metal tube, it’s easy to bend and kink. When you’re installing EMT, you use a conduit bender to make your bends without kinking and a compact or 12V reciprocating saw with a high TPI blade is all you need to cut it.

· Typical Fastening Style: Compression

· Common Sizes: 1/2″ – 1″

· Common Applications: Residential and light commercial indoor (watertight fittings required for outdoor use)

FMC: Flexible Metal Conduit

Way back before most of us were born (the early 1900s), Harry Greenfield invented a flexible metal conduit (FMC).  Using steel or aluminum for construction, it has a distinct spiral look to it that allows it to flex over short distances much easier than EMT. It has a big advantage when you need to add conduit in tight spaces or around existing equipment.

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· Typical Fastening Style: Threaded

· Common Sizes: 1/2″ – 4″

· Common Applications: Indoor

LFMC: Liquid-Tight Flexible Metal Conduit

LFMC, or liquid-tight flexible metal conduit, is similar to FMC but covered in a waterproofing coating. It’s useful for outdoor applications and wet interior areas and requires fittings that are also watertight.

· Typical Fastening Style: Threaded

· Common Sizes: 1/2″ – 4″

· Common Applications: Outdoor and indoor wet areas

ENT: Electrical Non-Metallic Tubing

Electrical non-metal tubing (ENT conduit) is different from the other types of electrical conduit we’ve discussing so far in several ways. It’s a flexible PVC tubing that looks a lot like a pool hose.You can encase it in concrete, run it behind walls and under floors, and use it as a replacement for EMT. The major manufacturer for ENT uses 2-hour fire resistant rated materials. ENT is not UV-resistant, though, so using it where it will be exposed to UV rays is out.

· Typical Fastening Style: Snap-lock or glue

· Common Sizes: 1/2″ – 2″

· Common Applications: Indoor


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Rigid PVC Conduit

Rigid PVC is a very familiar material to many folks thanks to its similarities to the PVC we use in plumbing and irrigation. Unlike EMT, you can’t use a conduit bender to manipulate it. PVC needs to be heated before in order to bend it. Typically that happens using a heater box but you can use a heat gun as an alternative in the field.

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As a conduit, rigid PVC shares the same characteristics as water pipe: you glue it together and it’s water-tight when you install it correctly. That makes it useful for direct burial underground and it’s allowable in corrosive environments. You can also encase it in concrete, conceal it in walls, or leave it exposed.

· Typical Fastening Style: Glue

· Common Sizes: 1/2″ – 5″

· Common Applications: Outdoor, indoor, underground