Three Way or Four Way?

Three Way

The light, or electrical load, is controlled from two locations. Usually the top and bottom of a staircase, or two entrances to a hallway. By code, in Canada, hallways and stairwells must be controlled by three way switches. It can be dangerous to be walking up or down a dark stairwell searching for a light switch at the opposite end.

The question, or puzzled look, we get is why are they called three way switches when the light is controlled from two locations? Why isn’t it a two way?

The term three way refers to the construction of the switch, not what it does. There are three terminals or connection points on a three way switch.  “Common”. Two  “travellers”. The bond/ground and the neutral are independent of any switching, or at least they should be! Sometimes we find neutral wires which are switched. A dangerous situation which is prohibited in the electrical code because of the increased danger of electrocution to service technicians.

Four Way

A four way switch is needed when the light, or electrical load, is controlled from more than two locations. Generally a hallway with three entrances. Kitchens as well with more than two entry points.

In theory, and also bending a few physics laws, you could have an infinite number of switches to control a light fixture. Just keep adding four way switches between two three way switches. The “travellers” from the three way switches connect on either side of the four way switch.

Two way switch? Five way switch? They don’t exist. Just three way and four way switches.

A common call we get from customers is when their three way switches don’t work. 90% of the time a “handyman” has been doing electrical work in the house. The travellers and common have been improperly connected during a switch change. In this case, it is a quick diagnosis and repair by one of our technicians.