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Electrical boxes come in various types, but they can generally be classified into two main categories: plastic boxes and metal boxes.
At times, the decision is straightforward and evident, particularly for foundational purposes. In other instances, it boils down to individual taste. Typically, DIY enthusiasts lean towards plastic electrical boxes, while electricians utilize both metal and plastic options.
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When to Choose Plastic or Metal Electrical Boxes
Utilize plastic or metal electrical enclosures for various typical scenarios.
When the Use of Metal Containers is Necessary or Suggested
Utilize a metal electrical enclosure when dealing with metal-sheathed cables, often referred to as armored BX cables, or when metal conduits enter or exit the enclosure. The grounding of metal cables and conduits relies on the connection between their metal sheathing and the metal enclosure.
Utilize metal enclosures featuring visible internal components. Generally, electrical boxes are installed within the walls. However, spaces like unfinished basements and mudrooms might lack a fully developed wall structure, preventing the boxes from being covered by drywall.
A standard installation consists of securing the open box directly onto a brick or stone wall. Since the wires are also visible, the use of metal conduit is necessary.
Tip
The durability of metal boxes proves beneficial when installing particularly heavy objects, such as ceiling fans or substantial light fixtures.
Metal enclosures can be utilized with Romex or NM wiring if preferred, but it is essential to take specific precautions to guarantee adequate grounding. The grounding connection is established when a connected device, like a light switch or outlet, makes contact with the metal box.
Even in cases where the device lacks a proper ground connection, Romex or NM wiring can still be utilized with metal electrical boxes by securing the bare or green grounding wire to the box using a screw.
Numerous metal electrical boxes can be combined, whereas the majority of plastic boxes are not designed for this purpose. Certain metal boxes feature removable side walls, allowing for the formation of duplex or triplex configurations.
What does the term gang refer to?
Ganging electrical boxes involves connecting two or more boxes together to form a single unit. This approach offers users the versatility to build boxes according to their requirements.
Additional Factors to Consider for Metal Boxes
Metal boxes are durable and offer a robust connection to the stud. If securing to the stud is a primary concern, opt for a metal box. These boxes allow for the use of sturdy screws, maximizing the holding strength.
Metal enclosures are resistant to warping. Due to their robust construction, metal boxes typically offer greater strength compared to the surrounding materials. Certain metal boxes come with built-in clamps to secure the electrical cables, while others necessitate the purchase of additional clamps, which can increase the overall expense of the box.
In general, DIY electricians might find metal boxes a bit more challenging to handle compared to plastic ones. Using gloves can enhance comfort when working with metal boxes.
Plastic Electrical Enclosures
- Hinged doors
- Lightweight
- Smooth contours
- More affordable
- Can bend
- Cables with lower security features
- No grounding for the box.
- Can dissolve in flames.
Plastic, specifically polyvinyl chloride (PVC), is increasingly becoming the preferred choice for electrical boxes, particularly among DIY enthusiasts.
Plastic containers are affordable, easy to handle, and lightweight. Creating holes in the back or sides is a straightforward process. While PVC can melt at high temperatures, it is a poor conductor of electricity. Additionally, many plastic boxes are designed with integrated clamps for wires, which can help reduce the total cost of a project.
When the Use of Plastic Containers is Necessary or Advised
While it is advisable to utilize a plastic electrical box when connecting Romex (or NM) cables, it is not mandatory. The electrical code does not stipulate the use of NM cables with plastic boxes.
The primary issue at hand is grounding. Wiring that is encased in metal relies on a connection with a metal electrical box for proper grounding. When metal-sheathed wiring is used with plastic electrical boxes, and no additional grounding precautions are implemented, it disrupts that grounding connection, posing a significant safety risk.
Electrical boxes function as termination or connection points for electrical wiring. They house outlets, light switches, ceiling fixtures, ceiling fans, and wiring transitions.
Additional Factors to Consider for Plastic Boxes
Plastic electrical boxes are user-friendly for home improvement enthusiasts. The most affordable options feature pre-attached nails for easy installation into studs. Markings on the boxes indicate the appropriate thickness for 1/2-inch drywall, ensuring that the box face does not sit flush against the stud during installation.
Renovation or existing work boxes feature wings that allow for direct attachment to drywall. They are utilized in situations where access to a stud is limited.
Gangable plastic electrical boxes are available, but they are relatively rare. Therefore, it’s important to determine the necessary box size beforehand. Unlike metal boxes, plastic boxes cannot be taken apart and reconfigured to create larger, double, or triple-sized boxes.
A different variety of plastic box features metal brackets that connect to the studs and can be adjusted both forward and backward using a Phillips screwdriver. Although these are the priciest option among plastic boxes, they provide the greatest adaptability when the final wall thickness has yet to be decided.
Numerous plastic containers feature doors designed to secure the electrical cable to the box, removing the necessity for extra clamps.
One drawback of plastic boxes is their tendency to lose shape under pressure. A sudden impact can cause them to crack. Although the pre-installed door clamps offer convenience, they can be quite resistant when you try to detach the cable. Additionally, older work or remodeling boxes that are mounted on drywall may detach from the surface, and their attachment wings are prone to breaking.
What distinguishes a junction box from a breaker box?
A junction box is a type of electrical enclosure designed to securely connect two or more electrical wires. In contrast, a breaker box, also known as an electrical service panel, is a substantial metal enclosure that houses circuit breakers or fuses, serving as the control center for a home’s electrical system.
Are metal junction boxes required to be grounded at all times?
Metal junction boxes must always be grounded, regardless of whether you are using NM (non-metallic) plastic-sheathed cable or metallic cable. Metallic cables are inherently grounded, provided they are correctly fastened to the junction box. In contrast, NM cables do not have this self-grounding feature. To ground NM cable, you need to connect the internal bare copper wire to a screw within the metal junction box.
Is it advisable to install a plastic junction box in the attic?
Local electrical regulations might permit the installation of a junction box in the attic. It’s advisable to consult the permitting office prior to proceeding. Metal junction boxes offer greater durability and are less prone to damage compared to their plastic counterparts. If the attic is not easily reachable, it is generally safer to position ceiling junction boxes with the opening facing downwards, allowing for easier access from below.
