Electrical Conduit 101: Basics, Boxes, and Grounding

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Installing an electrical conduit can be daunting, especially if you have no experience. A faulty electrical conduit can be dangerous, resulting in a fire or even an electrocution

Most homeowners don't know where to start when installing an electrical conduit. This is because the process can seem complicated and confusing.

In this guide, we'll walk you through the basics of installing an electrical conduit, from choosing the right type to boxes and grounding. We'll also provide tips and advice for each step of the process.

What is Electrical Grounding?

Electrical grounding is one of the most important elements in electrical systems. However, many people do not know how it works. Well, electrical grounding is a procedure where the electrical currents transition from their use to the ground source below the electrical system.

Types of Conduit

Conduit used for residential wiring includes several types of metal and plastic materials designed for different applications. Here are some of the most common types of conduit available:

Electrical Metallic Tubing Conduit

An electrical metallic conduit is a thin, rigid walled metal conduit typically made of galvanized steel. Because the tubing is thin and lightweight, it's easy to bend with a special tool called conduit a bender. An electrical metallic conduit is best used indoors for residential and light commercial construction.

If installed outdoors, it needs to be assembled along with watertight fittings. Outdoors, EMT conduit will typically last a few years, while indoors, it will last indefinitely. EMT is permitted by the National Electrical Code for dry and wet locations but requires watertight fittings and connectors in wet locations.

Flexible Metal Conduit and Liquid Tight Flexible Metal Conduit

A flexible metal conduit, or FMC, is a corrugated tubing of aluminum or galvanized steel. It's more flexible than an electrical metallic conduit and can be used indoors and outdoors. It's also watertight so that it can be used in wet locations.

A liquid tight flexible metal conduit, or LFMC, is a Flexible Metal Conduit with a rubber liner that makes it watertight. It's typically used indoors, where moisture is a concern. FMT tubing is commonly used for short runs in exposed locations, such as wiring for garbage disposers and water heaters.

Liquid tight flexible metal conduit is a flexible metal conduit covered with plastic sheathing to make it watertight. It's used for outdoor wiring, serving air conditioning units, and other outdoor equipment.

Non Metallic Liquid Tight Flexible Conduit

Non metallic liquid tight conduit is often used in place of liquid tight flexible metal conduit. It has unique connectors, and it's used when less protection is needed for the conduit, as in indoor settings.

Non Metallic Liquid Tight Flexible Conduit
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Rigid Metal Conduit and Intermediate Metal Conduit

A rigid metal conduit is the most common type of metal conduit. It's made of galvanized steel and is available in thin-wall and heavy-wall varieties. Intermediate metal conduit is similar to rigid metal conduit, but it has a thicker wall and is used for heavier loads.

Rigid Metal Conduit and Intermediate Metal Conduit
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They're used for structural piping that houses the wiring for the home's connection to the utility service lines for many overhead services. Intermediate metal conduit has largely replaced rigid metal conduit in new construction, and both of them are joined with threaded connections.

Electrical Non Metallic Tubing

Electrical nonmetallic tubing is flexible plastic tubing designed for use inside residential walls or concrete block structures. Although the tubing is moisture resistant and flame retardant, it's not suitable for exposed locations and shouldn't be installed indoors or anywhere that may be exposed to elements.

Electrical Non Metallic Tubing
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This tubing is often called Smurf tubing for its blue color, although it also comes in gray and orange, depending on the manufacturer and use.

PVC Conduit

Rigid PVC is a plastic pipe similar in size to a rigid metal conduit. It can be heated, bent, and joined with glued or threaded connections. PVC is available in schedule 40 and schedule 80 options. Schedule 40 is used most often, while schedule 80 is used when there's a risk of damage to the pipes because it has thicker walls.

Conduit is Not the Same as BX

At first glance, an electrical conduit may seem similar to BX, also referred to as AC wiring for armored cable or MC for metal cable. Like conduit, loose but insulated individual wires are encased in BX's metal shell. Also, like a conduit, BX wiring can be used in exposed locations.

Conduit is Not the Same as BX
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According to NEC, the difference is that an armored cable may not be used in damp or wet locations, in places exposed to corrosive conditions, or in places where damage might occur. By contrast, certain types of conduits may be installed in such locations.

Wiring Used With Conduit

A conduit is a hollow tube that wires are pulled through during installation. This differs from cable, which is a group of wires encased inside a flexible protective sheathing. If you're using conduit, the National Electrical Code (NEC) requires that the wiring be Type NM-B type NMB.

Type NM-B is an armored cable with a rubber jacket and two-wire conductors. The armor protects the cable from damage, and the rubber jacket keeps moisture out. Type NMB is also an armored cable, but it has a thermoplastic sheath instead of a rubber jacket. The armor protects the cable from damage, and the thermoplastic sheath keeps moisture out.

Types NM-B and NMB are available in two thicknesses: standard and extra-thick. The thick cables are used when there's a high risk of damage, such as when the cable is run through a drilled hole in a concrete wall.

The National Electrical Code requires using a metal box to hold the electrical outlet or switch. The code also requires that the box be grounded. You can either use a grounding clip or by screwing a metal strap to the box and attach the strap to the grounding screw on the outlet or switch.

Grounding Conduit With Raceway

Conduit always terminates at some electrical box or at fixed equipment that serves as a box. Special connectors are used to secure conduits to boxes and join lengths of conduits together to form long straight runs or bends. The boxes, connectors, and conduits form a raceway wire enclosure system.

A raceway is an enclosed conduit that forms a physical pathway for the electrical wiring to follow. In this way, the metal raceway acts in the place of the grounding wire that is found in a non metallic cable. This is also the main reason why only metal boxes may be used with metal conduits.

This type of grounding system was more common in older construction than it is today. Today, many electricians include an insulated ground wire in a metal conduit as a preferred means of grounding the circuit. For a metal raceway to serve as a grounding system, all parts of the raceway must be electrically connected, with no interruptions.

If a remodeler unwittingly installs a plastic box in the raceway, or any connections come loose, the ground path will be broken, leaving the circuit ungrounded.

FAQs on Electrical Conduit 101

Do you need a ground in every conduit?

No, you do not need a ground in every conduit. The ground is only needed when a metal conduit is used. If a plastic conduit is used, no ground is necessary.

Can I use Romex wire in a metal conduit?

No, Romex wire should never be used in a metal conduit. Only use approved types of wire in a metal conduit.

Can I use a metal box in a plastic conduit?

Yes, you can use a metal box in a plastic conduit as long as the connections are tight and there are no interruptions in the raceway.

Final Thought on Electrical Conduit 101: Basics, Boxes, and Grounding

There you go! Electrical grounding is very important as it protects your home and family from potentially deadly shocks. Make sure you know how to wire an outlet before touching your electrical conduit, and if you have any questions, consult a professional. In addition, always be aware of your surroundings when working with electricity. Stay safe.

 

 

Kristina Perrin

Kristina Perrin

Kristina is an expert DIY home remodeler and mom to three. When she's not cooking or experimenting with new recipes, you can find her working on new home improvement projects or writing about her favorite kitchen appliances or DIY projects on Kitchen Infinity blog.

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