Chloe Zhang
Plastic electrical boxes are a popular choice for DIY enthusiasts as they are easy to work with and inexpensive. However, they have their limitations. Unlike metal boxes, plastic boxes cannot be grounded because they are non-conductive. This means that if you are using metal-sheathed wiring with a plastic box, you will need to take additional grounding measures to avoid a dangerous situation. While plastic boxes are convenient, they are also more prone to damage and can become misshapen or crack under stress. This raises the question: are plastic boxes a safe and viable option for electrical wiring, or is it better to opt for metal boxes that provide a stronger and more secure option?
Do plastic boxes need to be grounded?
| Characteristics | Values |
|---|---|
| Conductivity | Plastic boxes cannot be grounded because they are non-conductive |
| Safety | Using metal-sheathed wiring with plastic electrical boxes without other grounding measures is dangerous |
| Grounding | Plastic boxes cannot be grounded, but all the grounding conductors from the circuit are made together |
| Usage | Plastic boxes are preferred by do-it-yourselfers, while electricians use both metal and plastic boxes |
| Affordability | Plastic boxes are inexpensive and come with pre-attached nails for nailing into studs |
| Durability | Plastic boxes tend to become misshapen when stressed and can crack when hit |
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What You'll Learn
- Plastic boxes are non-conductive, so they can't be grounded
- Metal boxes are grounded by connecting the bare ground wire to the metal yoke
- Plastic boxes are preferred by DIYers, while electricians use both metal and plastic
- Metal boxes are stronger and provide a stronger attachment to the stud
- Metal boxes are required to be grounded, whether using NM or metallic cable
Plastic boxes are non-conductive, so they can't be grounded
Metal boxes are strong and provide a strong attachment to the stud. They can withstand high levels of stress and are less likely to warp or become misshapen than plastic boxes. For this reason, metal boxes are often the preferred choice when attachment to the stud is a major concern. Metal boxes also allow for the driving of strong screws into the studs, ensuring maximum holding power.
On the other hand, plastic boxes are easier for do-it-yourself home remodelers to work with. They often come with pre-attached nails for nailing into studs, and presets that indicate the thickness of drywall to prevent the box from being nailed too deeply. Plastic boxes with pre-attached doors can also eliminate the need for additional clamps to hold electrical cables in place.
However, plastic boxes have some drawbacks. They tend to become misshapen when stressed and can crack if they receive a sharp blow. The pre-attached door clamps can also make it difficult to remove cables. In terms of grounding, plastic boxes cannot be grounded because they are non-conductive. This means that if a ground is required, a metal box must be used.
It is worth noting that the choice between plastic and metal electrical boxes is not always clear-cut and can depend on personal preference. Both types of boxes have their advantages and disadvantages, and in some cases, it may be acceptable to use either type. However, when it comes to grounding, metal boxes are the only option as they are conductive and can be included in the equipment grounding path.
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Metal boxes are grounded by connecting the bare ground wire to the metal yoke
Plastic electrical boxes are commonly used by DIY enthusiasts and are also used by electricians. They are easy to work with and are the least expensive option. However, they tend to become misshapen when stressed and can crack when hit. Plastic boxes with pre-attached doors that act as clamps can hold electrical cables in place, but they can be stubborn and difficult to remove.
Metal electrical boxes, on the other hand, are generally stronger and provide a stronger attachment to the stud. They can withstand high stress and are less likely to warp or become misshapen. Metal boxes also allow for stronger screws to be driven into the studs, ensuring maximum holding power.
When it comes to grounding, metal boxes always need to be grounded, regardless of the type of cable used. This is done by connecting the bare ground wire to the metal yoke or strap of the box. The bare ground wire is usually green and can be attached with a screw. This provides an effective ground fault current path, protecting equipment from becoming energised in the event of a short circuit.
In contrast, plastic boxes do not inherently have a ground path and require additional measures to be grounded safely. Using metal-sheathed wiring with a plastic box without proper grounding can be highly dangerous. While it is possible to ground a plastic box, it requires more complex methods, such as using a pigtail to connect to a ground screw within the box.
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Plastic boxes are preferred by DIYers, while electricians use both metal and plastic
Plastic boxes are generally preferred by DIYers due to their ease of use and cost-effectiveness. They often come with pre-attached nails for nailing into studs, and indicators on the box help prevent the installer from nailing the box face flush with the stud. Plastic boxes with doors can also hold electrical cables in place without the need for additional clamps.
However, plastic boxes have some drawbacks. They tend to become misshapen when stressed and can crack when subjected to sharp blows. The pre-attached door clamps can also make it difficult to remove cables.
On the other hand, electricians use both metal and plastic boxes depending on the specific requirements of the project. Metal boxes are known for their strength and provide a strong attachment to the stud. They are less likely to warp or become misshapen compared to plastic boxes. Metal boxes also allow for the driving of strong screws into studs, ensuring maximum holding power. Additionally, some metal boxes have pre-attached clamps for gripping electrical cables and removable side walls that offer flexibility in creating duplex or triplex boxes.
When it comes to grounding, metal boxes always need to be grounded, regardless of the type of cable used. Plastic boxes, on the other hand, cannot be grounded because they are non-conductive. This means that the ground is severed when using metal-sheathed wiring with plastic boxes, which can be highly dangerous.
In situations where a plastic box is used in a circuit with metal boxes, it is important to ensure that the metal boxes are included in the equipment grounding path with a pigtail to a ground screw within the box. This helps protect the equipment in the event of a short circuit.
Overall, while plastic boxes are preferred by DIYers for their convenience and affordability, electricians may choose either metal or plastic boxes based on the specific requirements of the electrical installation.
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Metal boxes are stronger and provide a stronger attachment to the stud
Metal boxes are inherently stronger than plastic boxes, which tend to become misshapen when stressed and can crack under sharp blows. Metal boxes are also more durable and fire-resistant than plastic, making them ideal for commercial use and areas requiring more durability.
Metal boxes provide a stronger attachment to the stud in several ways. Firstly, they allow for the use of strong screws that can be driven into the studs, ensuring maximum holding power. Metal boxes with pre-attached clamps can also securely grip electrical cables. Metal boxes with side tabs, longer straps, or bendable tabs can be securely attached to the stud with screws. The bendable tabs, for example, can be wrapped around the stud and then secured with screws. Metal boxes with mounting features designed for metal studs, such as metal tabs, attached tabs, or bendable tabs, can also provide a secure fit.
Metal boxes are also less cumbersome to work with than plastic boxes, especially when wearing gloves. They are often the preferred choice when attachment to the stud is a major concern or when working with heavy items like ceiling fans or heavy light fixtures.
While plastic boxes are easier for do-it-yourself home remodelers to work with and are less expensive, metal boxes offer superior strength and attachment options, making them a more reliable choice for certain applications.
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Metal boxes are required to be grounded, whether using NM or metallic cable
Metal boxes are grounded through their sheathing. When using metallic cable, also known as BX cable, the cable is grounded via its metal sheathing, and therefore the cable must be properly secured to the box for correct grounding. NM cable, on the other hand, is not self-grounding and must be grounded by attaching the cable's internal bare copper wire to a screw located inside the metal box.
It is important to note that the National Electrical Code (NEC) mandates that all electrical conduits and boxes must have a grounding method to ensure safety. This is to prevent electrical faults from causing shocks or fires. In the case of a fault, the grounding path created by the screw allows the fault current to return to the earth, rather than creating a potential shock hazard.
When using metal-sheathed wiring, it is highly dangerous to use plastic electrical boxes without taking other grounding measures, as this severs the ground. Therefore, it is crucial to ensure proper grounding when using metal boxes, regardless of the type of cable, to comply with electrical safety regulations and prevent potential hazards.
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Frequently asked questions
No, plastic boxes cannot be grounded because they are non-conductive. However, all the grounding conductors from the circuit are made together.
You can add a ground lead for the particular outlet or provide grounds all around the unit. Ground wires do not need to be insulated or run in a conduit but should run to an approved ground bus or rod.
You can run a "ground bus" along the bottom of the structure and then run ground spurs off that to each box you want to protect.
