How To Wire Switches in Series?

Electrical Technology

How to Connect Two Switches in Series to Control a Single Load?

In today’s basic home electrical wiring installation tutorial, we will learn how to wire and connect two switches in series to control and operate a single light point.

Mostly, this is not a proffered method to wire single way switches in series as parallel or series-parallel connection is used in common electrical wiring installation. In some cases, it may seem a useless connection, but there are some possibilities where we have to control a single load from two places while both switches must be switched ON to operate the load.

Related Post: How To Wire Switches in Parallel?

Before go in details, we will see the basic construction and operating mechanism of single way (2-Way in North America) switch which is shown in fig below:

Below is a simple step by step tutorial with schematic and wiring diagram which shows how to wire single way switches in series ?

Requirements:

Single Way Switches (SPST = Single Pole Single Through) x 2 No
Lamp (Light Bulb) x 1 No
Short pieces of cables x 4 No

Procedure:

Connect the two single way switches, light bulb in series to the power supply as shown in fig below. Keep in mind that both switches S₁ and S₂ must be closed to complete the circuit.

If there are more switches connected in series with electrical appliances i.e. light point, all of them must be at ON position to operate the load. If one of the single switches is open, the circuit won’t work then.

Click image to enlarge

The circuit will only complete if both of the switches are at ON position. In other words, If one of the switches are open or at OFF position, the light bulb will not glow. This is the same case for other loads as well which are connected in series to control by two single way switches.

Related Wiring Diagrams:

Below are the different positions of single way switches and light point when connected in series.

Click image to enlarge

Switches in Series Different Positions of Switches & Light Bulb

To get the switching position in ON condition for the light bulb, the above operation is the same as the Digital Logic AND Gate truth table which is given below.

Switch ₁	Switch ₂	Lamp Position
0 = OFF	0 = OFF	0 = OFF
0 = OFF	1 = ON	0 = OFF
1 = ON	0 = OFF	0 = OFF
1 = ON	1 = ON	1 = ON

In simple words, there are four switching positions and if both the switches are at ON position, the light bulb will glow. On the other hand, if one of the switches is at OFF position, the current will not flow in the circuit as the circuit behaves like an open circuit, hence the bulb will not glow. No matter what, all of the other connected switches are at OFF or ON positions.

The following gif shows the all positions of switches connected in series to a light bulb. It clearly shows that the light bulb is ON when both the switches are at ON position. If any one of the switches is at OFF position, The light bulb will not glow.

Here is the short video version:

How To wire Lamps in Series?
How To Wire Lamps in Parallel?

Good to know:

Switches and fuses must be connected through line (Live) wire.
Switching connections in series is not a preferred way to wire home appliances, a parallel or series-parallel wiring method is more reliable instead.
Less wires and cables are required in this kind of wiring connection.
It is not a reliable and comfortable method of wiring.
Use this wiring connection when only and only it is needed to be done.

Warning:

Electricity is Our Enemy, if you give it a chance to kill you, Remember, they will never miss it. Please read all caution and instructions while doing this tutorial in practical.
Disconnect the power source before servicing, repairing or installing electrical equipment.
Never try to work on electricity without proper guidance and care.
Work with electricity only in presence of those persons who have good knowledge and practical work and experience who know how to deal with electricity.
Read all instructions and cautions and follow them strictly.
Contact the licensed electrician or the power supply company before practicing any change in electrical wiring connection.
The author will not be liable for any losses, injuries, or damages from the display or use of this information or if you try any circuit in the wrong format. So please! Be careful because it’s all about electricity and electricity is too dangerous.

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