There are different opinions about Romex, so it’s tough to distinguish between right and wrong. It’s a non-metallic sheathed wire used for common circuit wiring. But can you run Romex in a conduit? Let’s find out.
The NEC recommends using Romex in the conduit to protect the wires from physical damage, especially if you have stripped the wires. Also, using a conduit can significantly improve the wire’s lifespan and prevent potential hazards if you are using it outdoors or for underground wiring.
There are multiple intricacies involved regarding using Romex in a conduit. If you are new to it, go through this guide till the end to gather detailed knowledge about Romex wires, their pros and cons, the NEC rules, and the steps to run the wire in a conduit.
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This post includes some affiliate links.What is a Romex cable?
Romex is the name of the brand for non-metallic sheathed electrical wires used in residential unit wirings.
Most people do not call the wires’ Romex’, but only non-metallic.
Besides, Romex is not any standard type of wire. So, people need clarification.
The wires are generally in-home standard wirings.
These non-metallic sheathed wires are also classified as underground feeders.
The wires are non-conducting and flame-resistant with a moisture-resistant coating.
Therefore, they are good for wet areas, like basements.
The wires are covered with papers inside.
The outside sheathing is made of woven rayon.
The paper inside the wires prevents the wires from sticking to each other after heating up and maintains flexibility during installation.
You will find the wires inside the PVC plastic jacket that prevents threats.
Romex has three different wires-
- A negative wire in white
- A positive wire in black
- A bare copper wire
The sheathing comes in 3 different colors suggesting three different gauges:
- 14 gauge wire: The sheathing is white in this gauge wire. It is used in 15 amp circuits.
- 12 gauge wire: The sheathing is yellow and is used in 20 amp circuits.
- 10 gauge wire: The sheathing is orange, and the wire is used for 30 amp circuits.
Can I run Romex in a conduit?
There is no problem in running Romex in a conduit.
Since the wires are non-metallic, it is suggested by the NEC to use them in a conduit to prevent physical damage.
The conduits protect the weak and vulnerable wires from the harmful and eroding factors that are responsible for damaging the wires.
So, if you use a conduit, it will extend the life of the Romex wires.
Installing Romex is quite dangerous and expensive because the wires will keep deteriorating over time.
So, you will have to buy them often for replacements, especially if you don’t use conduits.
But sometimes, using the Romex in a conduit is unsafe because it generates more heat than expected.
The Romex wires cannot breathe inside the conduit.
As a result, it will suffocate and start holding more heat than its actual level.
That is why using other insulated wires in a conduit is recommended.
Besides, the cost will be less.
Can you strip the Romex in the conduit?
You can use stripped Romex in the conduit.
Using a conduit becomes more vital when you strip the Romex wires.
If you use these wires outside or underground, use weather-resistant conduits to protect the wires, especially the bare wire.
When you strip Romex wires, you will find three wires – white negative, black positive, and a bare copper wire.
The negative and positive wires are insulated with papers inside the sheath.
The papers help prevent the wires from sticking to each other while heating.
Does Romex need a conduit?
The necessity for conduit while running Romex wires depends on the location of the wire installation.
Concrete
While running the wires on concrete areas, the wires will be exposed.
So, you must use a conduit while running Romex along the concrete walls.
However, you can avoid the conduit while running the wires through the walls.
You will also require running the Romex in conduit if you run them through the floor.
Ceiling joists
Generally, there is no need for a conduit while running Romex in ceiling joists.
The wire installation here is concealed, and the cables will remain safe.
But, you will require guard strips if you use the wires in an attic.
Outside or exposed locations.
As mentioned, the conduit protects the wires from physical damage.
Since the wires will face several issues outside or exposed areas, it is good to use a conduit outside.
Why should I run Romex wires in a conduit?
As mentioned earlier, Romex has three wires wrapped in a PVC plastic jacket.
So, if there is already an outer jacket, why run them inside the tube?
Here is why:
The law
No law gives strong and detailed information about Romex and conduits.
So, it is not mandatory to run Romex in conduit.
You can also run other insulated wires inside the conduit, which will be much cheaper than Romex.
No law prohibits the practice of running Romex in conduit.
That is why people are fine with using them in the conduit.
If you have faith in the outer sheaths of the Romex wires, ignore the usage of conduits.
Otherwise, use the conduit to protect the wires.
Safety
The PVC sheaths cannot save the bare copper wire in the Romex cables.
The other two wires will remain fine.
That is why contractors use conduits to protect all wires from physical injury.
If you have Romex wires in a threatening location without protection, things like oil or gas can enter the jacket and harm the bare copper wire.
So, you must use the conduit to protect the wires, especially if you have used them outdoors or underground.
The bare ground wire is more exposed to outdoor elements.
However, you can skip using the conduit for some wires.
The metal-clad wires can survive messy and rough conditions without wear and tear.
Location
If you install the Romex wires outside your house, they have to face the weather.
So, you must put these wires inside the weather-resistant conduits.
The same applies to underground wires because they will face conditions like pests and humidity.
Installing the wires inside your house is quite safer than those outdoors.
Conduits can be annoying because running the wires through those tubes is challenging.
But, the tube will increase the lifespan of the wires.
Why don’t people prefer using Romex in conduits?
Though the conduits can save these non-metallic wires from physical damage and increase their lifespan, many people prefer to avoid running these wires in the conduits.
Here are some common reasons behind it:
Complicated process
Installing the Romex wires inside the conduit is very difficult.
If you lack experience in it, it will take months to run the Romex wires, especially if you have chosen the wrong conduit.
Many contractors do not accept such installations.
Instead, they like to work with bare wires.
Durability
A conduit protects the Romex wires from physical damage.
You need to know the right process to avoid damaging the outer jacket of the wires while trying to pull them through the tube.
By doing it without experience, you are decreasing the wires’ durability.
Professionals can experiment with such things, but laypeople should ignore them.
Wire limitations
Conduits can limit the wire quantities after use.
You must follow the cable numbers regulations to pull through the conduit.
For example, you must make 31% fill for some wires.
In that case, you will require larger conduits, which means more money.
Now, if the wires do not fit properly in the conduits, you must reduce some wires to fit them in the available space.
Heating problems
Conduits can keep the Romex wires safe from physical damage and increase their lifespan.
But conduits can also increase the heat of the wires.
Running the wires through the conduits traps the heat inside and overheats the wires.
If the heat is too much to handle, it can destroy the wires, especially if the temperature rating of the wires is very high.
Wet areas
You cannot use the conduits near wet locations.
Moisture can harm the wires if they start building rust.
Rust indicates that the conduits are in bad condition.
Remember that you have to buy them again. So, do not only invest in the wires but also the conduits.
How many Romex should I use for one conduit?
The number of wires used in a conduit depends on the wire gauge sizes, conduit type, and conduit size.
Below, I shared detailed information about the number of wires to be used for one conduit:
14 gauge wires
EMT conduits
- ½ inch – 12 wires
- ¾ inch – 22 wires
- 1 inch – 35 wires
- 1½ inches – 84 wires
PVC – Sch 40 conduits
- ½ inch – 11 wires
- ¾ inch – 21 wires
- 1 inch – 34 wires
- 1½ inches – 82 wires
PVC – Sch 80
- ½ inch – 9 wires
- ¾ inch – 17 wires
- 1 inch – 28 wires
- 1½ inches – 70 wires
FMC conduits
- ½ inch – 13 wires
- ¾ inch – 22 wires
- 1 inch – 33 wires
12 gauge wires
EMT conduits
- ½ inch – 9 wires
- ¾ inch – 16 wires
- 1 inch – 26 wires
- 1½ inches – 61 wires
PVC – Sch 40 conduits
- ½ inch – 8 wires
- ¾ inch – 15 wires
- 1 inch – 25 wires
- 1½ inches – 59 wires
PVC – Sch 80 conduits
- ½ inch – 6 wires
- ¾ inch – 12 wires
- 1 inch – 20 wires
- 1½ inches – 51 wires
FMC conduits
- ½ inch – 9 wires
- ¾ inch – 16 wires
- 1 inch – 24 wires
10 gauge wires
EMT conduits
- ½ inch – 5 wires
- ¾ inch – 10 wires
- 1 inch – 16 wires
- 1½ inches – 38 wires
PVC – Sch 40 conduits
- ½ inch – 5 wires
- ¾ inch – 9 wires
- 1 inch – 15 wires
- 1½ inches – 37 wires
PVC – Sch 80 conduits
- ½ inch – 4 wires
- ¾ inch – 7 wires
- 1 inch – 13 wires
- 1½ inches – 32 wires
FMC conduits
- ½ inch – 6 wires
- ¾ inch – 10 wires
- 1 inch – 15 wires
8 gauge wires
EMT conduits
- ½ inch – 3 wires
- ¾ inch – 6 wires
- 1 inch – 9 wires
- 1½ inches – 22 wires
PVC – Sch 40 conduits
- ½ inch – 3 wires
- ¾ inch – 5 wires
- 1 inch – 9 wires
- 1½ inches – 21 wires
PVC – Sch 80 conduits
- ½ inch – 2 wires
- ¾ inch – 4 wires
- 1 inch – 7 wires
- 1½ inches – 18 wires
FMC conduits
- ½ inch – 3 wires
- ¾ inch – 6 wires
- 1 inch – 9 wires
Conduit sizes for different wire size
Now let’s have a look at the conduit size (in inches) to use according to the wire size:
| Wire size | Conduit size (in inches) |
|---|---|
| 4/3 wire | 1-1¼ inch conduit |
| 6/3 wire | ¾-1¼ inches |
| 8/3 wire | ½-1 inches |
| 10/2 wire | ¾ inch |
| 10/3 wire | ½ inch |
| 12/2 wire | 1 inch |
| 12-3 wire | 1 inch |
| 14-3 wire | 1 inch |
The list above is to help you know which wire can be suitable for which conduit.
However, avoid following this blindly.
The measurements may vary if you have a different conduit size, type, or wire size and gauge that is not mentioned here.
How to run Romex wires through a conduit?
Installing wires in the conduit takes work.
It is quite tricky and expensive.
So, you should call an electrician if you have a conduit for Romex wires.
For running Romex wires in the conduit, you start by pulling the wires through the conduit pipe.
However, an experienced person can help you with easier steps to pull the wires.
Use lubricant because the wires sometimes respond little to the pulling.
They are either very flexible or the pipe is small for them.
For running the Romex wires through the conduit, try the string method:
- Tie a string with the rod and push it inside the pipe.
- Now, connect the lower side of the string with the wire cable and use the upper end to pull it through the conduit.
You can also use a conduit mouse. It helps in guiding the wires to go through the conduit safely.
Be gentle and patient.
What kind of conduits should I choose for Romex wires?
There are conduits for every Romex size.
You can ask for suggestions from your electrician if you need to learn about it.
However, to help you a little, I have listed some best conduits for Romex wires.
Metal conduits
Metal conduits are rigid and strong and perfect for rough areas.
The intermediate metal is lightweight and thin.
You can use these conduits for areas that need such rigid metals.
The liquid flexible metal conduits are mostly used near the AC units.
PVC conduit
PVC conduits are the second best because they are strong enough to survive a corrosive atmosphere.
PVC conduits and plastic plumbing pipes have many common things.
Flex conduits
Flex has some spiral structures, which increases the conduit flexibility.
These spiral constructions make the conduit easy to use and manipulate.
Liquid tight conduits
These conduits are mostly used for outdoor purposes.
Some makers also pair them with plastic coating to help fight outside weather conditions.
Romex’s pros and cons
Romex wires have both merits and demerits.
| Pros | Cons |
|---|---|
| You get Romex wires in bundles. You can use multiple wires in the conduits simultaneously. | You cannot use Romex for outdoor purposes because they are not long-lasting like the other insulated wires. Besides, the harsh outside weather can easily and quickly damage the wires. |
| You can receive multiple gauges of Romex wires, starting from 14 till 2 AWG. | Romex has weak entry and exit points. So, if you install the wires roughly and carelessly, you will hurt the points. |
| Romex wires are ideal for houses and small offices. | Romex wires require specific conduits. If the wire and conduit sizes do not match, you must buy them again. |
| Romex wires have multiple color codes to help you understand the wire sizes. | Installation is quite expensive and complicated. |
How long will Romex last?
Romex wires are indeed dangerous, and installing them is more dangerous.
You cannot use the Romex wires by burying them or installing them anywhere.
Moisture can enter the wires and damage them.
If your Romex wires are kept with proper protection, the wires will last up to 20 to 30 years.
However, it may start deteriorating before time.
It will degenerate faster if you do not use conduits.
So, to increase the wires’ lifespan, use conduits.
What does the NEC say about running Romex wires in a conduit?
The National Electric Code does not prevent you or the contractors from running Romex wires in the conduit.
Instead, the NEC wants the customers to run these non-metallic wires through the conduits to protect them from physical harm and increase their lifespan.
So, if you have a stripped Romex cable, conduits are a must, especially for outdoor settings.
However, if you have separate local codes, you should consult your local authorities before you approach.
If your local codes do not match with the NEC code, you have to abide by the rules and regulations of the local codes and ignore the NEC codes.
Local codes always have more priority than NEC codes.
Final thoughts
There is no objection to running Romex wires in the conduit. Instead, the NEC code recommends using conduits for these wires.
Conduits keep the wires from faster deterioration and physical damage, especially if you use the wires somewhere outdoors or for underground purposes.
But, many people avoid it because the Romex wires warm up much more than expected inside the conduits. The heat remains trapped inside the tube, and the wires get overheated.
The number of wires used in a conduit depends on the wire sizes, types, conduit sizes, and conduit types.
The Romex wires can last up to 20-30 years if kept properly. However, degradation may start before that.
Data Source: National Electrical Code, NEC Wire Table, Electrical wiring, Home wiring.
