Safely running electrical wire outside requires knowing and following National Electric Code (NEC) guidelines for installation. Knowing the required steps will also make it easier for you to gather all the materials you need to reduce the time required for the conduit installation process. Using the right conduit can ensure protection against moisture and corrosion and reduce your efforts in installing it.
Table of Contents
Applications for Outdoor Wiring
Using outdoor wiring is essential in a variety of industries. Here are some of the most common reasons to run electrical wire outside:
Installing junction boxes makes access to electrical junctions for future repairs easier. Almost every sector that needs outdoor electrical installation will have use for junction boxes to connect and protect electrical wiring and equipment. These boxes protect the conduit by keeping moisture away from the wires.
Outdoor Control Boxes
Outdoor control boxes permit quick access to the operation of a variety of systems. The types of control boxes typically installed outside include:
- Controls for lights and video
- Irrigation controls or timers
- Programmable logic controls used to operate heavy machinery
- Local electrical controls
- Security system controls
Like junction boxes, outdoor control boxes must have protection from corrosion and moisture intrusion, part of which includes tightly fitting conduit electrical wires to them.
Automatic sensors for gates, lights and other exterior electrical devices require reliable wiring protected from the elements to power them. As with all outdoor electrical equipment, conduit protecting the wiring leading to the sensors must have water-tight seals and provide protection from corrosion and ultraviolet (UV) damage.
Marine equipment must stand up to some of the harshest elements. Salt spray, total immersion, wind and UV rays can breach standard outdoor equipment enclosures. Electrical protection for marine use must offer the highest level of moisture protection to prevent damage to the equipment. The conduit holding the electrical wiring going to these devices must be equally robust.
Telecommunications equipment for delivering Wi-Fi signals outside requires the same protection from moisture intrusion as any other powered device. Routers that deliver faster 5G broadband signals require less space between the devices that use them. Many businesses will need to install more of these devices to improve wireless connectivity throughout their properties.
Outdoor Chemical Injection Pumps
Outdoor control boxes often regulate when and how to inject chemicals into treatment tanks, wells or other sites. These electrical boxes need robust protection from the elements and any corrosive chemicals in use by the injection system.
Wastewater Processing Equipment
The waterproofing of outdoor controls and electrical wiring at wastewater facilities prevents damage to the system that could disrupt operations. Conduit and enclosures must hold up to outdoor use and chemical exposure while staying waterproof and corrosion-proof.
Alternative Energy Equipment
Solar and wind energy need reliable electrical wiring to deliver power. Conduit used for these applications should perform exceptionally well in protecting against UV damage from exposure to direct sunlight.
Scientific equipment might require long-term operation in harsh environments to collect data. Devices may need constant powering in locations such as forests, deserts, swamps and other extreme environments.
In such locations, the abilities to protect against moisture and temperature extremes and resist corrosion are important for both conduit and electrical enclosures for scientific equipment.
6 Important Rules to Know Before Installing Electrical Wire Outside
Brush up on your knowledge of NEC requirements for installing electrical wiring outside. The following are important rules to know before you begin:
1. Depth for Buried Conduit Depends on Type
You can’t use a standard depth for the trench you bury your electrical conduit in. The depth of the trench depends on the material used for the construction of the conduit.
A rigid metal conduit (RMC) requires digging a trench only 6 inches below the surface compared to a minimum 24-inch deep trench for underground feeder (UF) cable without conduit. PVC conduit needs at least 18 inches of soil above it.
2. Soil Covering the Trench Can’t Have Stones
The backfill material used to cover the trench can’t have stones or rocks in it. It must consist of smooth materials.
3. All Underground Electrical Cable Will Need Some Form of Conduit
Even UF cable needs a conduit to support it and protect it for a length of at least 18 inches underground to its connection at the LB conduit body or box.
4. You Need GFCI Protection on Outdoor Receptacles and Circuits
To add more protection against short circuiting from moisture, the NEC requires ground fault circuit interrupter (GFCI) protectors on outdoor outlets or circuits. The protection may be at the circuit breaker or receptacle.
5. Pipe Bends Can’t Add to More Than 360 Degrees
When creating bends in your conduit, the total can’t add to more than 360 degrees. For instance, you can’t have more than four 90-degree turns in the conduit.
6. You Must Verify Underground Structures Before Digging
Don’t start trenching before verifying the exact locations of other conduits, gas lines, water lines, waste pipes and other utilities. A severed electrical line while digging could be fatal. A broken gas line could shut down operations until gas shutoff and repairs are completed.
Use Call 811 to connect with local utility providers several business days before you intend to begin trenching. This time will allow local utility providers to connect with you about where their underground service lines are on your property.
Calling is a safety measure to take for yourself and your company.
How to Install Electrical Conduit Outdoors
To install electrical conduits outdoors, start with the right materials and a clear idea of where to install the raceways. Follow these steps to ensure proper installation that meets NEC requirements for safety:
1. Plan the Installation Process
Create a diagram outlining the exact route for the conduit and the length of conduit and wiring needed. This plan will facilitate getting adequate materials without wasting money.
2. Obtain Any Required Permits for Construction
Depending on your industry and location, you may need permits for installing buried electrical wire or outdoor electrical equipment. Get the required permits from your local government before starting so that you can avoid fines.
3. Choose the Type of Conduit to Use
Select the best conduit for the project. RMC requires a shallower trench due to its extra strength and wire protection. UF cable doesn’t require conduit for its entire underground length but still needs it when transitioning from underground to above the soil. UF cable requires a conduit to protect it from its buried depth to the final point above ground.
If you have plans for expansion in the future, choose a conduit that completely encloses the electrical cable through the whole trench. The use of continuous conduit through a trench facilitates the addition of future electrical cables through the conduit without needing to dig again.
4. Dig Trenches for Underground Conduit Runs
Dig trenches to the required depth based on the type of conduit used. Powered trench diggers speed up this process. For smaller projects, a shovel will suffice for digging shallower or shorter trenches.
5. Install LB Conduit Bodies for Feeding Rigid Conduit Into a Building
Prepare the site for feeding conduit through an exterior wall. Drill a 1-inch hole into the wall where the electrical wire needs to come from the inside to the outside through the LB conduit body. Place a short piece of RMC through the hole in the wall. Install a conduit connector on both ends of the conduit.
The side on the exterior of the wall will attach to the LB conduit body. This attachment will hold the fitting in place while measuring the distance from the LB conduit body to the bottom of the trench. Connect the interior connector to an electrical box to ensure the conduit has a secure connection to the box on the inside of the building.
Follow the same process to connect the other end of the conduit to an LB conduit body at another exterior building. Use a piece of threaded conduit at either end, which will screw into the bases of the LB conduit bodies or the weather-proof boxes at either end.
6. Bend RMC Conduit and Lay It Into the Trench
If using RMC conduit, bend it and use couplers to connect pieces together. Add ¾-inch to the last length of conduit that will thread into the LB conduit bodies or boxes at the ends of the conduit. Adjust the total length for the required bend to bring the conduit from underground to the terminus. Lay the conduit into the trench and thread the end into the LB conduit bodies or boxes.
As for how to install electrical wiring outdoors with PVC conduit, the pipes will need to connect to elbow joints for bends with glue to hold the parts together. Glue joints to PVC conduit to create bends in this type of conduit. Attach expansion joints at the terminus of the PVC conduit where it feeds into a box or goes into a building
Lay the conduit into the trench and attach a male coupling to the end of the PVC conduit with glue. This allows you to screw the end of the conduit into the bottom of the electrical boxes or LB conduit bodies at the start and end of the line.
For gray Schedule 40 PVC for electrical work, you can bend it by heating the material and gently moving it into the needed position. This allows for fewer joints in the conduit.
7. Feed the Wires Through the Conduit
Open the back of the LB conduit bodies or leave the electrical box open to feed the electrical wires through. Push a snake through the conduit until it reaches the other end.
Connect the wires to the end of the snake and tape them together. Slowly pull the other end of the snake out of the conduit to drag the wires through. A second person at the other end helping to feed the wire into the conduit can reduce snags.
8. Affix Straps to Support Vertical Conduit on Walls
Attach straps across the conduit before it enters the LB conduit body or box. Affix the straps to the building with the material-appropriate screws to hold them in place. For higher vertical runs, place a strap at least every 30 to 36 inches for support.
9. Shut Off Power and Connect the Wires to the Source and End Device
Cut off the power and connect the wires to the power source and the end device. Wire the device as needed to provide power.
10. Get an Inspection and Refill the Trench
Depending on your sector and location, you may need an electrical inspector to verify your trenching and conduit placement. After approval, add sand or caution tape over the conduit before refilling the trench to warn future diggers of the presence of electrical conduit.
Materials for Outdoor Wiring and Conduit
Before starting the installation of the electrical conduit outside, gather the essentials to reduce time at the job site. The following should be among your supplies prior to digging trenches for underground installation:
- Conduit rated for outdoor use: Not all conduit materials will suffice for outdoor or underground use. Only conduit approved for these applications can safely house outdoor electrical wiring. Selecting durable, moisture-proof conduit for use outside and underground will ensure project success.
- Conduit connectors: Connectors tightly join conduit to LB conduit bodies or boxes that have threaded openings.
- Cable entry systems: Passing cables or electrical wires through or into cabinets is easier with cable entry systems that include both terminated and non-terminated for use in electrical cabinets or equipment.
- Cable glands: Cable glands include indoor and outdoor types for connecting cables to equipment.
- Trenching equipment: Use either a powered trencher or a shovel for digging trenches for the conduit.
- Weatherproof LB conduit bodies or receptacle boxes: These terminal sites for outdoor electrical connections need solid seals that protect the interiors from moisture.
- Snake or fish tape: The length of this tool should be longer than the entire distance of the conduit through which you feed the electrical wire.
- Conduit bender or heat gun: You only need a bender if you intend to use RMC conduit. Use a heat gun to warm and bend gray PVC for electrical use. For flexible outdoor conduit, you don’t need either tool.
The above tools make the process of installing electrical conduits simple and fast.
Trust AerosUSA for Electrical Conduit and Other Outdoor Wiring Essentials
Our products are made for the high standards and heavy use of numerous industries, from marine and offshore to food and beverage. We have conduits and accessories needed for running electrical wire safely outdoors for nearly every application. Contact us at AerosUSA to request a quote or for more information about our products.