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What is a 3 way box?

A 3 way box, also known as a 3 way electrical box, is a type of junction box used in electrical wiring. It allows for the connection of 3 separate electrical circuits in one single box. A 3 way box gets its name from the fact that it interconnects 3 “ways” – meaning 3 separate cables or wires. This allows a 3 way box to enable 3 way switching, a setup used to control a light fixture from two different locations.

What is a Junction Box?

Before diving into what specifically a 3 way box is, it helps to understand what a junction box in general is. A junction box is an enclosure in electrical and construction systems that allows for the connection and branching of circuits. It is essentially a containment device that provides protection and organization for wire connections.

Junction boxes allow electricians to access and modify electrical wiring by housing and connecting endpoints of multiple wires/cables. This aids in installation, circuit splitting, and overall maintenance of electrical systems. Junction boxes come in many shapes and sizes for different purposes, but generally consist of a housing or frame made from plastic or metal. The front cover can be removed to provide access to the interior space where wires are connected.

Key reasons junction boxes are vital components in electrical wiring:

  • Safety – They prevent exposed wires, contain shorts/faults, and reduce fire hazards.
  • Accessibility – They allow access to wire connections for modifications or troubleshooting.
  • Organization – They neatly contain and separate different circuits.
  • Load support – They structurally support the weight of conductors and devices.
  • Isolation – Separates disconnected neutrals, hot wires, and other conductive parts.
  • Protection – Shields wires from damage and environmental factors.

By providing these crucial functions, junction boxes enable complex yet safe electrical networks in residential, commercial, and industrial settings.

What is a 3 Way Switch?

Now that you understand the role of a junction box, what exactly is a “3 way switch” in electrical wiring?

A 3 way switch allows control of a light or other electrical load from two separate locations, like opposite ends of a hallway or large room. Switches of this type are connected with a 3 wire cable consisting of a power wire (typically black), a neutral wire (typically white), and a traveler wire (typically red).

In a basic 2 way switch setup, flipping the switch connects or disconnects the power wire to turn a light on and off. In a 3 way switch system, power continuously runs to one switch box and gets transferred to the light fixture via the traveler wire running between switches. The key benefit is you can turn the light on or off from either switch by flipping one or both of them.

Common examples where 3 way switches provide convenient control include:

  • Hallways with switches at each end
  • Large rooms with multiple entryways
  • Staircases with switches at top and bottom
  • Any other location needing multi-point control

An electrician would install 3 way switches and run the necessary 3 wire cables to create this adjustable multi-location control. Now that you understand what a 3 way switch setup entails, a 3 way box is simply a special junction box that allows wire connections for this type of switching.

What is a 3 Way Box?

A 3 way box, also called a 3 way junction box, is a specific type of electrical junction box designed to accommodate the wiring of 3 way switch circuits. It contains 3 distinct sections that allow for the proper termination of all wires involved in 3 way switching.

The defining features and components of a 3 way junction box include:

  • Three separate compartments/sections – One for each of the 3 cable wires: grounded (neutral), power, traveler.
  • Multiple knockouts – Knockout holes allow entry of the 3 cables into the proper sections.
  • Clamps – A clamp in each section firmly secures the wires entering that compartment.
  • Larger capacity – They are deeper than normal boxes to fit more wires and connections.
  • Sturdy mounting tabs – Allow secure surface or recessed mounting in walls.

These specialized boxes come in both metal and plastic forms. Metal types offer maximum durability for heavy wiring loads. Plastic varieties feature built-in clamps and quick cable insertion for faster installation. UL and NEMA rating codes indicate safety and compliance approvals.

Typical Specifications of a 3 Way Box Include:

  • 10-12 gauge wire capacity
  • Voltage ratings up to 600V
  • 1/2 to 1 inch knockout sizes
  • Dimension range from 2 x 3 x 3 inches up to 4 x 4 x 3 inches

With its separated compartments and capacity to handle multiple thick wires, a properly installed 3 way box creates a safe, contained environment for the 3 way switching wiring arrangement.

3 Way Box Wiring

When wiring a new 3 way switch system, an electrician will utilize special 3 way boxes to cleanly install and connect the wiring. Here are the basic steps involved in wiring two 3 way switches using this type of box:

  1. Mount the 3 way boxes – Position the boxes for the two switches in the desired locations per the electrical plan.
  2. Install the wires into the boxes:
    • Feed the 3-wire cable between the boxes for traveler wire connection
    • Input the power wire and neutral wire into the proper box
  3. Clamp the wires into their designated box sections:
    • Line/power wire into the bottom section
    • Neutral/grounded wire into the middle section
    • Traveler wire into the top section
  4. Strip the wire insulation properly to make clean connections
  5. Anchor the wires by screwing down the clamps in each section
  6. Cut and connect the wires to the 3 way switches as dictated by the manufacturer
  7. Attach the faceplates and switches to operate the connected light

The separate channels confine and organize all the wires that need to link up in this circuit. This prevents unsafe exposed conductors. The ample space and gauge capacity provide room for stuffing extra wire length into the box as needed.

Overall, the design of a 3 way junction box lends itself nicely to fast yet reliable installation of 3 way switch electrical systems.

Types of 3 Way Boxes

There are a few common variations when it comes to the specific types and forms of 3 way junction boxes:

Metal 3 Way Boxes

  • Most durable and provide greatest protection in heavy use settings
  • Typically made from galvanized steel for corrosion resistance
  • Sturdy for supporting heavy fixture loads
  • Knockouts may need to be drilled out as needed
  • Common brands include Allied Moulded, Carlon, Raco

Plastic 3 Way Boxes

  • Quick wiring with built-in clamps and cable slots
  • Non-conductive and resistant to environmental factors
  • Cost effective while still durable
  • Stay cooler than metal when circuit loads increase
  • Popular brands include Allied Moulded, Carlon, Hubbell

Masonry 3 Way Boxes

  • Designed for installation in concrete, brick or other masonry
  • Have threaded bosses to screw box directly into the material
  • Prevent moister deterioration of the box
  • Common brands are Appleton, Crouse-Hinds, O-Z/Gedney

Low Voltage/Data 3 Way Boxes

  • For non-power wiring like data, phone, security systems
  • Plastic or metal with 2+ compartments
  • Often have low voltage mounting braces
  • Brands include Hubbell, Legrand, Leviton

So in summary, there are varied options when selecting a 3 way box for an application based on the wiring load, location, conductivity, and frequency of access needed. Professional electricians determine the optimal type for the job.

Plastic vs. Metal 3 Way Boxes

Two of the main decisions when picking a 3 way junction box are plastic vs. metal construction. Here is a brief comparison of plastic and metal boxes:

Plastic 3 Way Boxes


  • Lower cost
  • Lighter weight than metal
  • Corrosion resistant
  • Easy cable insertion into clamps
  • Non-conductive
  • Cooler operation with heavy loads


  • Less durable than metal
  • Not as sturdy for heavy fixtures
  • Can melt at extreme temperatures

Metal 3 Way Boxes


  • Very strong and durable
  • Ideal for heavy wiring applications
  • Superior protection from physical damage
  • Stable support for large fixtures
  • Grounds electrical system


  • Higher cost than plastic
  • Corrosion potential without galvanized coating
  • Heavier than plastic boxes
  • Can transfer heat to wires with high loads
  • Conductive so more caution is needed

In summary, plastic is lighter and easier to work with but metal is stronger. Metal boxes are better for heavy commercial and industrial uses, while plastic boxes suffice for typical residential wiring needs.

When to Use a 3 Way Box

Some common situations where you would want to utilize a 3 way junction box for an electrical project include:

  • Installing a new 3 way switch circuit – Provides appropriately separated channels
  • Replacing old 2 way switch boxes in a 3 way switching retrofit – Upgrades box to proper type
  • Repairing or modifying existing 3 way switch wiring – Allows maintenance access
  • Adding additional control locations to a 3 way circuit – Enables extra traveler wires
  • Converting between switch-controlled and always-on fixture – Accommodates line/load reversal
  • Powering a light fixture from multiple locations – Allows traveler wires between boxes
  • Troubleshooting and fixing faulty 3 way switching – Contains issue safely

Anytime you need to tap into the wiring of an existing 3 way switch setup, or are creating a new 3 way switching system, using the correct 3 way junction boxes ensures a safe enclosure for making those important line and traveler wire connections.

Installing a 3 Way Box

When installing a new 3 way junction box, either in new construction or a rewiring project, there are several key steps electricians take:

  1. Choose box location – Pick areas that allow convenient wiring runs and access to switches.
  2. Select proper box – Match the box to the wiring gauge and load requirements.
  3. Mount the box – Securely fasten to studs or wall surface with appropriate method.
  4. Install cables – Route lines through knockouts to proper box sections.
  5. Clamp the wires – Isolate and anchor each conductor separately.
  6. Connect switches – Join travelers, line, load per manufacturer diagrams.
  7. Verify operation – Test that the lighting functions properly from both switch locations.
  8. Attach cover plate – Secure switch and plate to the flush mounted box.

Following professional standards for box mounting, wire routing/separation, and connections ensures a safe and working 3 way switch wiring installation.

3 Way Box Code Requirements

Certain legal regulations apply when working with electrical boxes, including 3 way boxes. Relevant electrical codes include:

  • NEC 314 – National Electrical Code for junction box requirements
  • NEC 300.3 – Secure and appropriate wiring methods
  • NEC 404.2(C) – Neutral connections in switch boxes
  • NEC 110.3 (B) – Proper installation and service access
  • NEC 314.16 – Volume requirements for box fill
  • NEC 314.17(A) – Suitable box support and covers
  • NEC 110.12 – Mechanical execution of work

Always consult the latest electrical code edition for your region to ensure compliant and safe 3 way box installation. Licensed electricians are trained on proper application of all requirements.

3 Way Box Installation Tips

Here are some helpful tips electricians follow when wiring 3 way boxes specifically:

  • Use deep 2x3x3 inch boxes to provide ample room
  • Keep all wires trimmed to proper length for neater connections
  • Arrange wires to minimize crossing paths in the box
  • Route the incoming power through the bottom section
  • Connect the neutral wire to the white screw on the switch
  • Label wires with colored tape for easier identification
  • Test operation frequently during installation to catch issues early
  • Refer to manufacturer diagrams for recommended switch terminals
  • Fold and stuff excess ground wires into the back of the box
  • Use wire nuts to join multiple ground wires exiting the box

Thoughtful planning of the box placement combined with orderly wire management inside the box results in the most clearly understandable and successful 3 way switch wiring jobs.

Cost of a 3 Way Box

What is the typical cost of a 3 way electrical junction box? Here is an overview of price ranges:

  • Standard plastic – $1 to $3 per box
  • Heavy-duty plastic – $4 to $8 per box
  • Standard metal – $2 to $5 per box
  • Heavy-duty metal – $6 to $12 per box
  • Masonry – $5 to $15 per box
  • Low voltage – $1 to $10 per box

In most cases, plastic boxes are the most economical, while heavy duty metal boxes are typically the most expensive. Prices also depend on the size of the box. Additional costs will apply for packaging on multi-box orders and any applicable taxes and shipping.

Factors that add cost include extra heavy duty ratings, lugs vs. clamps, modular vs. standard designs, higher wire capacity, and quantity. For professional contractors buying boxes in bulk for larger jobs, you may be able to get discounts off regular retail unit pricing.

Overall, prices for basic 3 way boxes are very reasonable for the value they provide in building safe and functional electrical switch systems.


In summary, a 3 way electrical box is a specialized junction box designed specifically to handle the wiring connections required for 3 way switch circuits. It neatly separates and secures the grounded/neutral, line/hot, and traveler wires necessary in 3 way switch wiring systems that control lights from two locations. Professional electricians rely on the proper selection and installation of these boxes to safely build complex switching systems in residential and commercial settings. A quality 3 way box ensures reliable access to clean connections so switches can operate lighting safely and conveniently.