Sometimes, the choice is clear-cut and obvious, mainly forgrounding.
Other times, it’s a matter of personal preference.
Generally, do-it-yourselfers prefer plastic electrical boxes, andelectriciansuse both metal and plastic boxes.
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Plastic and metal electrical boxes sometimes have crossover uses.
Grounding is one situation where you must use the correct box.
So, metallic-sheathed cable must contact a metallic box for proper grounding.
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Metal electrical boxes can be more difficult for do-it-yourselfers to work with.
They have rear and side knockouts that require supplementary clamps, and these knockouts can be hard to remove.
In addition, their sharp edges can injure hands.
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It’s usually best to wear gloves when working with metal boxes.
Use metal boxes with interior exposed applications.
Typically, electrical boxes are recessed in walls.
A typical installation involves attaching the exposed box directly to a masonry wall.
Because the wires are also exposed, metal conduit is required.
Many metal electrical boxes can be ganged, while most plastic boxes cannot.
Some metal boxes have side walls that can be removed to create duplex or triplex boxes.
What Is Gang?
Togangelectrical boxes means to attach two or more boxes to create a single box.
This provides the user with the flexibility to construct boxes as needed.
When attachment to the stud is a major worry, choose a metal box.
Metal boxes mean you might drive strong screws into the studs, ensuring a maximum amount of holding power.
Metal boxes will not warp.
With their high-stress material, metal boxes are often stronger than the work material built around them.
Some metal boxes have pre-attached clamps for gripping the electrical cable.
Other boxes require you to purchase separate clamps, driving up the total cost of the box.
Generally,do-it-yourself electriciansmay find metal boxes slightly more cumbersome to work with than plastic boxes.
Wearing gloves will make it more comfortable to work with metal boxes.
Plastic boxes are lightweight, cheap, and simple to work with.
Holes are easy to punch out in the back or sides.
PVC can melt when subjected to sufficiently high temperatures but it does not conduct electricity.
Many plastic boxes come with built-in clamps for the wires, further lowering the overall project cost.
The electrical code does not require that you use NM cable with plastic boxes.
The overriding concern is grounding.
Metal-sheathed wiring depends on bonding with the metal electrical box for grounding.
Electrical boxesserve as end or junction points for electrical cables.
Outlets, light switches, ceiling lights, ceiling fans, and transition wires are installed in electrical boxes.
Other Plastic Box Considerations
Plastic electrical boxes are easy for do-it-yourself home remodelers to work with.
The least expensive plastic boxes come with pre-attached nails for nailing into studs.
Old work or remodel boxes have wings so they can be attached directly to drywall.
These are used when there is no free access to a stud.
Gangable plastic electrical boxes do exist but they are not common.
So, you will need to know the required size of box in advance.
You cannot disassemble and reassemble plastic boxes to gang them into double or triple-sized boxes.
On the downside, plastic boxes tend to become misshapen when stressed.
When plastic boxes receive a sharp blow, they can crack.
Old work or remodel boxes attached to drywall can pull away from thedrywalland their attachment wings often break.
A junction box is an electrical box that allowed two or more electrical cables to be safely spliced together.
Metallic cable is self-grounding, as long as the cable is properly secured to the box.
NM cables are not self-grounding.
Your local electrical code may allow you to place a junction box in the attic.
Check with the permitting office before you do this.
Metal boxes are stronger, so they will resist damage better than plastic boxes.
National Fire Protection Association.
