4-Way & Intermediate Switch Diagrams
Dear Mr. Electrician: How do I wire additional light switches to control the same light fixture from multiple locations?
Answer: If more than two light switch locations are wanted, one or more four-way switches would need to be installed in between two 3-way switches. In some countries the four-way is called an intermediate switch. You would just continue from one 3-way switch box with the 14/3 three conductor cable (Two colored traveler wires, a white neutral, and a bare or green ground wire) in and out of each four-way switch box. The white wires get spliced through. The red and black wires are connected to the four-way switches. Follow the switch manufacturer’s instructions and wiring diagram as the connections on the switch vary by manufacturer. Sometimes the switch wiring connection diagram is printed on the inside of the 4-way switch packaging box. At the other end you connect the other 3-way switch with either the LINE or the LOAD. See the light switch wiring diagrams above and below. Ground wires are spliced together with a pigtail or two and then bonded to the metal switch box and to the green screw on the switch.
You must use electrical boxes for your light switches that are approved for the number of wires and devices that you will be installing. See article 314 in the National Electrical Code (NFPA 70) to determine what size electrical boxes you should use. Keep in mind that each light switch will count as two wires when calculating your box fill. In addition any clamps inside of the box will count as one wire. Connectors that are outside the electrical box with only the locknut inside do not count as a wire.
Below is another method for wiring 4-way switches. The electrical switch box that contains the LINE and LOAD wires may need to be bigger than the other switch boxes, especially if there are other wires going into the switch box. Whenever the white wire in a cable is not being used as a neutral conductor, it must be re-identified with a different color other than white, gray, or green. There is no limit as to how many 4-way switches can be used in a lighting switch circuit.
When 3-way switches are used, the LINE and LOAD wires can only go onto one specific switch screw terminal. It is a different color screw from the other two screw terminals. With 4-way switches you must read the manufacturer’s instructions or wiring diagram. Sometimes there is only a switch wiring diagram printed on the inside of the 4-way switch package box. The wiring connections on 4-way switches varies between manufacturers.
It is possible to bring all of the wiring into the ceiling light electrical box and wire your 3-ways and 4-ways from there. It can get crowded with wires in the ceiling box so you must use a larger size electrical box to be code compliant. Two cubic inches are required by the National electrical code for each #14 wire. See Tables 314.16(A) & (B). I have a diagram for this light switch wiring method on my 3-way page (Link Below).
I did not include grounding conductors on the 4-way switch wiring diagrams in order to keep them simple. However each switch and metal electrical box is required to be grounded. This is commonly achieved by splicing all of the ground wires together and than adding a pigtail to them for each switch at that location.
My post depicting 3-way switch and 2-way switch wiring diagrams will be helpful to you.