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Home » Electrical Wiring Installation » How To Wire Switches In Series?

How To Wire Switches In Series?

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

In today 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 case, it may seems useless connection, but there are some possibilities where we have to control single load from two places while both switches must be switch ON to operate the load.

Before go in details, we will see the basic construction and operating mechanism of single way switch which is shown in fig below:

Construction & Working of one way SPST (Single Pole Single Through) Switch
Construction & Working of one way SPST (Single Pole Single Through) Switch

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 appliance i.e. light point, all of them must be at ON position to operate the load. If one of the single switch is open, the circuit won’t work then.

How To Wire Switches In Series?
How To Wire Switches In Series?

The circuit will only complete if both of the switches are at ON position. In other words, If one of the switch 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.

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
Switches in Series Different Positions of Switches & Light Bulb

To get the switching position in ON condition for light bulb, the above operation is 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 = ON
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 switch is at OFF position, the current will not flow in the circuit as the circuit behaves like an open circuit, hence bulb will not glow. No matter all of other connected switches are at OFF or ON positions.

Good to know:

  • Switches and fuses must be connected through line (Live) wire.
  • Switches connection in series is not a prefer way to wire home appliances. parallel or series-parallel wiring method is more reliable.
  • 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 instruction while doing this tutorial in practical.
  • Disconnect the power source before servicing, repairing or installing electrical equipments.
  • Never try to work on electricity without proper guidance and care.
  • Work with electricity only in presence of those persons who has good knowledge and practical work and experience who know how to deal with electricity.
  • Read all instruction 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 wrong format. So please! Be careful because it’s all about electricity and electricity is too dangerous.

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18 comments

  1. i want to ask one question why we used heer two spst siwthes it can be made with one single spst

  2. Hello ET here Why u using 2 switches SPST switch and 2 switches in (figure 1)

  3. Its a two way switch ..<br /><br />Means that one light is being control from two swtiches <br /><br />( Stair case , from below turn it On from switch one , and when go up , turn it off from switch 2 )

    • This would be a crappy way of doing it. Once you turn it off at one switch, the only way to turn it back on is from that same switch. You might as well just have one switch to eliminate having to remember which switch turned it off

  4. ya I agree with chad.It&#39;s good for nothing to connect two switches in series

  5. How it will work, mean to say that in first both the switches will of then when we on switch one from below stairs then how we can off the lamp by switch 2 which is already in off position?

  6. way we use two switches in series sircuit….????

  7. 1 lamp 10 switch control &

  8. the point of two spst switches in series is that first one acts as a “master switch” so you can cut the power without turning off the breaker. You are then free to use the second switch for normal operation.

  9. SUB METER CONNECT HAI USKO MANE SOCKET SE DISCONNECT KARNA HAI

  10. I need a circuit diagram of a PFC using a dual boost converter

  11. Please define about SPST(single pole single through)

  12. eletrical map see

  13. Very useful website

  14. In series the lamp shall be made ON only if all the switches are ON position… In such case a all the floor switches has to be made ON. Then only the lamp can be made ON.

  15. its just an reference how to connect 2 SP switches in a series and both should ON to glow the Lamp., First Switch we can consider as first is the protection for second. If we use some protection unit like Fuse/MCB/RCCB etc instead of first switch den we can protect the circuit better.

    Difference B/w SP & DP?
    Ans: single-pole switch controls just one circuit. A double-pole switch controls two separate circuits. A double-pole switch is like two separate single-pole switches that are mechanically operated by the same lever, knob, button, or Switch.

  16. I wired a similar circuit, 120VAC with 2 switches in series, at school and I’m a little confused about something.. when both switches were open and I put my voltmeter across the 1st switch, I got a reading of 16V. Why? What is causeing me to get this reading?

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