DIY electrical projects require extensive research, and every aspect needs thorough consideration. Especially romex, one of the most common non-metallic wires, leaves DIY-ers wondering how to wire it.

So, before you proceed with your next project, let’s take a look at whether you can run romex in a conduit and its codes.

Can you run romex in conduit?

You can run romex in a conduit. This non-metallic wire is recommended to be run through conduits in order to protect it against physical damage. Otherwise, it remains more prone to damage than its metallic counterparts. While it is code to run romex in conduit outdoors, you can also do so indoors.

Running romex through various mediums can be tricky as not all of them are allowed to pass through. Let’s dig deep to know more about it.

Outside:

If you’re using romex outside, it’s a good idea to strip the romex and run it through a weather-resistant conduit.

This procedure should also be followed if you’re using romex near a utility line. It will keep the wire protected against the elements of nature and other external damages.

Southwire 28828228 100' 12/2 with ground Romex brand SIMpull residential indoor electricial wire type NM-B, Yellow

Underground:

Conduit is especially recommended if you’re using romex to run wire underground.

Otherwise, the romex wiring remains unprotected. In such a case, the wire might be exposed to water, pressure, pests, and roots, which may escalate damage.

Leaving it unprotected will eventually damage the wire a lot faster; it can even cause an accident. Running the romex through the conduit will ensure the wire’s durability. Moreover, it is code to run romex through conduit underground.

Indoors:

When wiring indoors, you have the freedom to choose whether you want to run the romex through a conduit.

Conduit is especially used to combat outdoor weather conditions and damages. But it also works as incredible protection when romex is run in conduit indoors.

Southwire 28827422 50' 14/2 with ground Romex brand SIMpull residential indoor electrical wire type NM-B, White

In PVC conduit:

Romex is not recommended in PVC conduit. There are several reasons behind it. It’s mostly because the PVC conduit traps heat inside and creates more heat than need be.

The romex wiring cannot breathe in such a case and retains too much heat. This is likely to cause faster damage to the wire.

In flexible conduit:

Flexible conduits are used to protect romex when you’re trying to isolate the wiring from vibrations.

It is also used when you need an excessive number of fittings. However, note that some local electrical codes may limit the length of romex wire when run through a conduit. 

In metal conduit:

It is not advisable to put romex in metal conduit. The reasons may include that metal conduit may damage the romex wiring, especially when there is a 90-degree bend.

It might even exceed the metal conduit fill, giving rise to heat retention issues. Length may also be an issue in such a case.

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Is it code to run romex in conduit?

It is code to run romex in a conduit when it is otherwise exposed to physical damage. It may be a flexible or rigid PVC conduit, depending on what your specifications are.

Most local codes enforce the use of conduit when you’re wiring outdoors. However, you’ll have the freedom to choose whether or not you want to use a conduit when you’re wiring indoors. There is typically no code enforced in this regard.

Using a conduit outside is necessary in order to improve the romex wire’s durability. It will otherwise be exposed to physical damages, water, natural elements, pests, and more.

Are you allowed to run romex in conduit?

You are allowed to run romex in a conduit. In fact, it is recommended to run these non-metallic cables through a conduit as they are more prone to damages than metallic ones.

The type of romex would depend on the location of wiring – whether you’re wiring indoors, outdoors, or underground.

You should also use a conduit around the romex cable when you’re wiring near a utility line. However, note that you are not allowed to run romex through a conduit in wet locations. It may result in fast damage or even an accident.

Flexible PVC Non Metallic UL Liquid Tight Electrical Conduit Kit with 2 Straight and 2 Angle Fittings Included (1" Dia. x 100 ft)

How to run romex in conduit?

Pulling and bending the romex wire may prove to be difficult due to the friction. Therefore, lubricating the wire is a good idea. You can use a wire-pulling compound as a lubricant.

These lubricants come in gel, soapy, and slimy forms. You can make the wire slick simply by applying a coat on top. This will make running the romex in conduit a lot easier.

But you can follow the following steps to learn how to run romex in conduit easily:

Tie pull strings to the romex wire:

Now tie a strong pull string with the romex wire’s loop. The loop runs through its mouse and is designed to pull the wire easily.

Insert the mouse in the conduit:

Now that you have attached the pull string to the mouse, insert it into the conduit. The mouse will go in head first, followed by the string.

Southwire 63946828 100' 14/3 with ground Romex SIMpull residential indoor electrical wire type NM-B, White

Use a shop vacuum hose over the conduit:

Attach the hose of a shop vacuum to the other end of the conduit. Turn it on. The vacuum will quickly pull the mouse to the other end. Once the mouse is out, turn off the shop vac. 

Secure the strings:

As soon as you have the mouse outside the other end, untie the string from its loop. Secure the strings to the romex wire and lubricate it if necessary. Now you can easily feed wires into the conduit. This is how you can run romex in conduit.

Why can’t you run romex in conduit?

While running a romex cable through a conduit is often recommended, there are a few cases where you cannot use a conduit. The reasons why you can’t run romex in the conduit are as follows:

Retains excessive heat:

Romex, when kept unstripped, is heat and weather resistant. So running it through a conduit may create and trap excessive heat. If such a case arises, damage to the wire may be irreversible, and it may even cause accidents. 

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Damages quickly in damp and wet locations:

Running a romex wire in conduit is not permitted in wet or damp locations. They sustain damage and rust when put under such conditions. Instead, running romex in conduit is allowed in a shallow, concrete, or adobe-protected location.

How far can you run romex in conduit?

There are some regulations regarding how far you can run romex in conduit. It largely depends on the diameter of the conduit.

If you have a conduit of diameter ½ inch, then you fit nine romex wires of 12 gauges. You can also go for 12 romex wires measuring 14 gauges.

If the conduit has a diameter of ¾ inches, you can run 16 wires of 12 gauges. Otherwise, you can opt for 22 wires of 14 gauges. The choice is yours.

Does Romex have to be in conduit in the garage?

Romex cables have to be in conduit in the garage. This is because you cannot leave romex exposed to the elements in a finished garage wall. It will require protection from any potential damage.

However, if the cable runs through the ceiling, you will not need a conduit.

What size conduit do I need for 6/3 romex?

You will always need to run quick calculations for conduit fills for romex cables, just like any other wires. These calculations mainly consider heat dissipation factors. 

To run a 6/3 nm romex wire, you will need a large conduit. A conduit measuring 2 inches will work best in this case. It will provide enough space to offer flexibility for the wire and allow excellent heat dissipation within the conduit.

SOUTHWIRE COMPANY LL 11579041 50' 14SOL BLK THHN Wire, 14 Guage, Black

What kind of wire to run in conduit?

A conduit is a hollow tube through which different types of wires are pulled during electrical installation. You can encase various kinds of wires in a conduit.

The most common type of wire run in a conduit is romex cables. It is a non-metallic wire. Besides, you can run the following kind of wires in a conduit:

  • Non-metallic or NM-B wire
  • Thermoplastic heat and water-resistant nylon-coated wire or THWN wire
  • Thermoplastic high heat-resistant wire or THHN wire

Final Thoughts:

You can run romex in a conduit. It’ll help protect the romex from external damages. While the size and type of conduit will vary with the wire’s length and location, running it through a conduit is generally encouraged. In fact, it’s code to use conduit when using romex outdoors.

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