Electrical codes generally require that all electrical devices, and the wiring connections to those devices, must be enclosed in an approved electrical box. Often known as a junction box, this metal or plastic box includes a cover to protect the wiring within and protect you from the wiring. This rule is demonstrated nicely by wall switches, receptacles, and standard light fixtures, all of which require a junction box to mount the device and house the wiring connections.
But there are some devices that require no traditional junction box, for the simple reason that they have their own integrated boxes or enclosures for making the wire connections. Generally, these are devices that are mounted securely to a surface, allowing them to serve the same basic function as a junction box.
What Junction Boxes Do
A junction box performs several essential functions:
- Encloses the wiring connections and protects them from physical damage
- Provides a means for mounting the electrical device and securing the electrical cable(s) serving the device
- Prevents accidental contact with live wires and terminals
- Protects against fires by containing live wires that may come loose from the device
If you intend to use any device without a junction box, it's critical that its wire connection system serves all these necessary functions provided by a standard junction box. For example, if you have a light fixture that doesn't need a box for mounting, but the wiring connections are not protected by some kind of cover, then you can't use the fixture without a junction box. Or, if a fixture meets all of the criteria of a box but lacks a cable clamp, don't use it without a box.
Types of Devices That Don't Need Boxes
The first clue that a device is designed to be used without a junction box is that it has its own complete housing. And it generally will not have any wire leads extruding from it, because these wires are contained inside a wire connection compartment. Common examples of electrical devices that require no junction boxes include:
- Recessed lights ("can lights")
- Bathroom ventilation fans
- Wall-mounted heaters
- Fluorescent tube-style light fixtures
- Garbage disposals
- Baseboard heaters
Many permanently installed appliances, such as kitchen vent hoods, dishwashers, and hot water heaters, also don't require junction boxes. With these devices, if the electrical wires will be exposed or run outside of a wall, ceiling, or floor cavity, the wires must be contained inside some type of flexible conduit or be metal armored cable rather than in standard non-metallic (NM) cable.
Make Sure Cables Are Clamped
If you're adding a new device or replacing an old device that doesn't need a junction box, don't forget to secure the incoming cable with a cable clamp. If the device has its own clamp, use it following the manufacturer's instructions. Some devices do not have clamps, but the wire connection box will have a knockout hole that you can open up and fit with the proper metal or plastic cable clamp.
NEVER run the cable through the hole in the wire connection box without a clamp. Knockout holes in fixtures can have sharp edges that can cut through the cable sheathing if the cable is pulled or if there is movement or vibration of the device itself. If bare wiring comes in contact with a metal housing, the entire fixture can become electrified.
NFPA 731 Section 188.8.131.52. National Fire Protection Agency.
Exposed, Energized Wiring and Electrical Components. Office of Congressional Workplace Rights.