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How to Wire Single Pole, Single Throw (SPST) as 2-Way Switch?

Installation of SPST – 2-Way Switch (NEC) AKA 1-Way Switch (IEC) for 120/240V & 230V AC – 2-Way & 1-Way Circuits

What is SPST Switch?

SPST (stands for Single Pole Single Throw) switch is the most commonly used switch to control the ON and OFF operations of household appliances such as lighting points and fans etc. It is used to control a single operation either ON or OFF in an electric circuit.

Good to know: SPST switch is known as single pole, single throw, Two Way switch, toggle switch or Light switch in North America (US – NEC). While it is known as One Way Switch, Single Way Switch or 1-Gang, 1-Way Switch (where Gang represent the number of throw or switches on the plate) in the Europe, UK and IEC following countries.

Caution: Switches are always wired on the Phase (Line or Hot) wires same as fuses.

Symbol of SPST Switch

The following symbols represent the basic single pole single throw switches.

SPST - Single Pole Single Throw Switch

Construction of Single Pole, Single Throw Switch

The Single Pole Single Throw switch has mainly two terminals for Hot IN and Hot OUT and an extra terminal as ground pin in North America. In the UK and IEC following counties, the single pole switch has only two terminals without ground pin.

Construction-Working-of-one-way-SPST-Single-Pole-Single-Throw-Switch

The following two figures show the main difference between US and UK single pole, single throw (SPST) switches.

Two-Way Switch – SPST, Single Pole, Single Throw – US – NEC

Two-Way Switch - SPST - Single Pole - US - NEC

One Way Switch – SPST, Single Pole, Single Throw – UK – IEC

One Way Switch - UK - IEC

Let’s see how to wire them one by one for different appliances.

Click image to enlarge

How to Wire a Single Pole Switch - IEC & NEC

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Wiring Single Pole, Single Throw Light Switches for 120V/240V Circuits – NEC

How to Wire a Single Pole, Single Throw Switch to a Light Bulb?

The following wiring diagram shows that how to wire and control a light bulb using an SPST switch. As shown in the fig below, there are three incoming wires from the breaker in the electrical box (junction box) viz, G (Ground), L (Line or Hot) and N (Neutral).

The ground wire is connected to the Ground terminal on the switch (Green with yellow stripe). The Line (as hot) is connected to the line terminal of the switch. Keep in mind that neutral wire is never connected to the switch.

Click image to enlarge

How to Wire a Single Pole Switch to a Light Bulb?

To control the light bulb using a single way switch, the ground wire (using wire nut in the electrical box) is connected to the bulb holder. Similarly, both Neutral and Hot wires are also connected to the LED light bulb. This way, the bulb is controlled via a single pole switch i.e. when the switch is ON, the light bulb will glow. If the switch is OFF, the light bulb will also OFF.

How to Wire a SPST Switch to an Outlet?

The SPST switch can be used for different appliances such as fans, standard outlets receptacles etc. The following fig shows how to wire a single pole, single throw switch to an outlet (for switched outlet) operation. In other words, the SPST switch is controlling the ON and OFF operation of the receptacle.

Click image to enlarge

How to Wire a Single Pole Switch to an Outlet

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Wiring Single-Way (One-Way or 1-Gang, 1-Way) SPST Light Switches for 230V Circuits – IEC

A 1-Gang, single pole, single throw (also known as One-Gang, One-Way switch) followed by IEC (International Electrotechnical Commission) is totally different from SPST toggle & light switches by NEC (National Electrical Code) standards.

The one way switch has two terminals as shown in the above fig. The first terminal should be connected to the incoming phase wire and the second terminal should be connected to the load point e.g. lighting points etc.

How to Wire a One-Way (1-Gang, 1-Way) Switch to a Light Bulb?

In the following wiring diagram for 230V AC supply system – IEC, a 1-gang one way switch is used to control a CFL or LED light bulb. It clearly shows that the incoming Phase (Line) wire (brown Color) is connected directly to the first terminal of the switch. The second terminal of the switch is connected to the light bulb through brown color.

Click image to enlarge

How to Wire a One-Way Switch to a Bulb?

Similarly, the Neutral wire (blue or sky blue color) is directly connected to the light bulb from the junction box. Finally, the green wire is connected to the bulb holder.

Keep in mind that Green as Ground wire never connects to the light switch as compared to the NEC Codes.

How to Wire a One-Way Switch to a Socket?

As mentioned above, the one-way switch can be used for different appliances such as light bulbs, fans, socket outlets etc. The following fig shows how to wire a one-way switch to 230V British socket (for switched socket) operation.

Click image to enlarge

How to Wire a One-Way Switch to a Socket?

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  • The brass screws should be connected to the Hot (line, live or phase) wire using the IEC & NEC Wire color codes. In case of SPDT and 4-Way (Intermediate switches), black colored screws are used for Hot or common terminals. In short, the color for common terminal is different than other terminals.
  • The silver screws should be connected to the Neutral wire (in case of switched outlet)
  • The green screw should be connected to the ground / earth wire (Green/Yellow or naked wire)
  • If there are no color coded screws on outlets, refer to the user manual or contact a licensed electrician.
  • Neutral Wire is not required in 240V outlets wiring (US) Also, Neutral is never connected to the switches.
  • Use the suitable voltage and ampere rating of switch with appropriate wire size and proper size MCB according to the load rating.

Precautions:

  • Switch off the main circuit breaker to make sure the power supply is OFF before wiring an existing or new outlet or switch with an electrical/junction box.
  • Contact the authorized and licensed electrician for switch installation if you are not sure about the wiring diagrams.
  • 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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