How to wire an intermediate switch to control bulb from three different positions.

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Have you been in a house where you notice that a bulb or set of electrical bulbs have more than two control switches? Yes, This is achieved with the help of an intermediate switch. This switch helps us have control of electrical bulbs from almost the existing doors or house corridors. As we go further on the post, we will understand the construction and how to install an intermediate switch. where to install them and how to install them on our installation work.

How to install a 2-way switch, controlling one lamp

The intermediate switch is an electrical switch that is used to control electrical bulbs from different positions. With intermediate switches, the lighting point can be controlled from two or more different positions.

These types of switches are seen at the staircase, hospital rooms, and other places it found to be useful. The intermediate switch is different from the normal switch we are used to.

Construction of an intermediate switch.

Intermediate switch internal construction
intermediate switch

the intermediate switch is a four-terminal switch, constructed in such a way that it changes the flowing of current in two directions. When the switch is turned ON, it interchanges the connections and makes the current flow from another direction.

Fig (b) of the diagrams above, is the internal position of the switch when turned ON or up position. While fig(c) shows the internal position when turned to OFF or down position.

From the diagram above, we can see how the switch changes the path of the current to another path. That is just the exact operation and construction of an intermediate switch.

Where to install an intermediate switch.

The intermediate switch is the only switch that made it possible for a light bulb or set of bulbs to have more than two control. In the sense that we can ON or OFF the bulbs from three or more different positions. So the intermediate switches are normally installed in the step case, hall room, hospital rooms or passage on our buildings.

Installation a 3-ways switch using SPDT switch and an intermediate switch.

To install the intermediate switch, we will be needing the following equipment.

  • One intermediate switch.
  • Two SPDT (single pole double throw switch) switch.
  • Lamb holder and lamp/bulb.
  • 1mm cable.


strictly follow the diagram below to make the connection.

3 ways intermediate switch controlling one lamp/light.

3 way switch wiring using intermediate switch.
3 way switch at OFF state
3 way switch wiring using intermediate switch
3 way switch at ON state.

Step 1.

Follow the diagram above. Place the intermediate switch in between the two SPDT switch. The switches should be at a convenient place where they should be accessible.

Step 2.

use a cable wire to connect from the life wire to the common of the SPTD switch. Then from the SPDT switch connect the L1 and L2 to the L1 and L2 of the intermediate switch.

step 3.

From the traveler of the intermediate switch, connect the two travelers to L1 and L2 of the second SPDT switch. And connect from the common of the second SPDT to one terminal of the lamp holder.

step 4.

Connect from the neutral point to the second terminal of the lamp holder. Now the circuit ok to run and control the bulb from the three different switches. use an appropriate circuit breaker to protect the circuit on the distribution box. How to calculate loads to assign to the circuit breaker.

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