How do you attach conduit to a box?

Attaching conduit to an electrical box is an important step when running new electrical wiring through your home. Proper conduit installation ensures a safe and secure connection between the conduit and box. There are a few key things to keep in mind when learning how to attach conduit to a box.

Types of Electrical Boxes

There are three main types of electrical boxes that conduit can be attached to:

• Plastic electrical boxes – These are made of PVC plastic and are lightweight and corrosion resistant. Plastic boxes are common in residential wiring.
• Metal electrical boxes – Typically made from steel, metal boxes are very durable and provide excellent protection. They are more common in commercial/industrial wiring.
• Conduit bodies – Unlike regular electrical boxes, conduit bodies are used specifically for connecting multiple conduit runs. They allow flexible conduit routing options.

The specific type of electrical box will determine what fittings and methods should be used to attach the conduit. Metal and plastic boxes have slightly different installation requirements.

Conduit Fittings

There are conduit fittings made specifically for connecting conduit to electrical boxes. The most common types are:

• Conduit connectors – Threaded fittings with a locknut for securing conduit to knockouts
• Conduit bushings – Threaded plastic bushings that protect conduit ends from sharp edges
• Conduit hubs – Allow conduit to be attached at the rear or sides of an electrical box

Using the proper conduit fitting ensures a solid, safe connection. The type needed depends on factors like the conduit size and material and box type.

Attaching Conduit to a Plastic Electrical Box

Follow these basic steps to attach conduit to a plastic electrical box:

1. Select an appropriate knockout – Choose a knockout sized for the conduit diameter. Remove it using a hammer and screwdriver.
2. Install a conduit connector – Secure the connector threads through the knockout hole. Use a locknut to tighten it in place.
3. Install a conduit bushing – For an extra layer of protection, attach a plastic bushing to the end of the conduit.
4. Connect the conduit – Thread the conduit onto the connector. Keep turning until it’s tightened securely.

Be sure to hold the electrical box steady as you turn the conduit to avoid cracking the plastic. The locknut should hold the connector tightly in place when finished.

Attaching Conduit to a Metal Electrical Box

Follow these steps to attach conduit to a metal electrical box:

1. Select an appropriate knockout – Use a flathead screwdriver and hammer to pry open the thin knockout plate.
2. Install a conduit connector – Turn the locknut 2-3 threads onto the connector. Insert the connector through the knockout.
3. Tighten the locknut – Tighten the locknut with adjustable pliers until it’s snug against the outside of the box.
4. Install a conduit bushing – For metal boxes, use an insulated bushing to prevent wire damage.
5. Connect the conduit – Thread the conduit onto the connector until tight. Use pipe wrenches to secure it.

Take care not to overtighten the fittings or you can warp the box. Be sure to attach the ground wire per NEC code requirements.

Securing the Conduit

Properly securing conduit provides protection and resilience:

• Use strap hangers – Secure conduit runs to joists and beams with 1-hole or 2-hole straps.
• Support vertical runs – Use conduit straps spaced every 10 feet for straight vertical runs.
• Support elbows and turns – Use hangers to support significant conduit bends.

Sturdy conduit support prevents movement and detachment from fittings. It also maintains proper spacing from other building components.

Common Code Requirements

Comply with the following code requirements when attaching conduit:

• Size conduits and knockouts properly – Conduit should be the same size as the knockout hole.
• Use suitable fittings – Fittings must be appropriate for the conduit and box types.
• Secure boxes firmly – Support boxes adequately to hold the weight of wires and conduit.
• Use approved methods only – Confirm all techniques meet National Electrical Code standards.

Contact a qualified electrician or consult the NEC handbook for clarification on any wiring best practices.

Tips for Attaching Conduit

Follow these tips for the best results when attaching conduit to an electrical box:

• Use quality fittings – Don’t rely on subpar connectors or bushings that can loosen over time.
• Deburr cut conduit – Use a deburring tool to smooth cut conduit ends for easy fitting insertion.
• Match trade sizes – If a 3/4″ knockout is required, use 3/4″ conduit fittings even if the actual conduit diameter differs.
• Allow elbow room – Leave space for inserting wires around bends and fittings inside boxes.
• Support heavy conduit – Use extra hangers and straps to provide solid support for large conduit sizes.

Taking extra care during the conduit installation process will ensure long-lasting, trouble-free electrical connections.

Conclusion

Learning how to properly attach conduit to an electrical box is a useful skill for DIYers. The key is using the right type of fittings for the specific box style. Securing the conduit firmly helps minimize safety risks and electrical issues in the future. With the proper materials and good workmanship, you can make durable conduit connections that will last.