Plastic vs. Metal Electrical Boxes: Choosing the Right One for Your Project
Understanding Electrical Boxes
Electrical boxes are essential components of any electrical system, serving as junction points for electrical cables and providing support for outlets, switches, and lighting fixtures. They come in a variety of sizes and shapes to accommodate different applications.
Types of Electrical Boxes
There are two main types of electrical boxes: plastic and metal. Each type has its own advantages and disadvantages, making it suitable for specific applications.
Plastic Electrical Boxes
- Advantages:
- Lightweight and easy to handle
- Economical
- No sharp edges
- Built-in clamps for cable attachment
- Easy to modify with knockouts
- Disadvantages:
- Can warp or crack under stress
- Not as secure as metal boxes
- May not provide adequate grounding
Metal Electrical Boxes
- Advantages:
- Strong and durable
- Fire-resistant
- Can be grounded
- Gangable for multiple connections
- Disadvantages:
- Heavier and more difficult to handle
- More expensive than plastic boxes
- Sharp edges can be hazardous
- Requires separate clamps for cable attachment
When to Use Plastic Electrical Boxes
Plastic electrical boxes are typically used in the following situations:
- When using Romex (NM) cable, which has a plastic sheath
- When grounding is independent of the box
- For old work or remodel installations where the box is attached to drywall
- When the wall covering thickness is undetermined (adjustable plastic boxes can be used)
- By do-it-yourself electricians who prefer ease of installation
When to Use Metal Electrical Boxes
Metal electrical boxes are typically used in the following situations:
- When using metallic sheathed cable (BX cable) or metal conduit
- When grounding depends on the box
- For exposed locations where the box is not recessed into the wall
- For stud attachment rather than drywall attachment
- For gangable installations where multiple boxes need to be connected
- By experienced do-it-yourself electricians or licensed electricians
Other Considerations
Metal Electrical Boxes
- Metal boxes provide a stronger attachment to studs, making them ideal for heavy items like ceiling fans or light fixtures.
- They can be used with Romex or NM wiring, but special precautions must be taken to ensure proper grounding.
- Some metal boxes have pre-attached clamps for gripping the electrical cable, while others require separate clamps.
Plastic Electrical Boxes
- Plastic boxes are lightweight and easy to work with, making them popular for do-it-yourself projects.
- They often come with built-in clamps for the wires, eliminating the need for additional components.
- Old work or remodel boxes have wings for attachment to drywall when there is no access to a stud.
Troubleshooting Electrical Box Installation
- If a plastic box becomes misshapen or cracked, it may need to be replaced.
- Pre-attached door clamps on plastic boxes can sometimes make it difficult to remove cables.
- Old work or remodel boxes attached to drywall can pull away and break if not properly supported.
Conclusion
Choosing the right electrical box for your project depends on the type of wiring, grounding requirements, and installation location. Plastic boxes are lightweight, economical, and easy to work with, while metal boxes are stronger, more secure, and can be grounded. By understanding the differences between the two types, you can make an informed decision that meets the needs of your project.