How to Identify Single Phase or 3 Phase

How to Identify Single Phase or 3 Phase

If you’re planning on installing an appliance that needs a lot of power, or you have a blown fuse or electrical issue, knowing whether or not your building uses a single-phase or 3-phase power supply is important. Generally, most residential homes use a single-phase circuit and commercial properties that use high-powered machinery and equipment will have a 3-phase circuit.[1] X Research source But, there are a few ways you can check to be sure which type you have.

Method 1 of 2:
Looking for Clues

1
Read your electrical meter to see if it says single or 3-phase. Look near your fuse box to see if your meter is mounted next to it. Some homes may have their electrical meter in the basement, on the side of the home, or even in the front yard for energy companies to easily check them. When you find your meter, the face will include information such as the wattage and the identification number. Look for a description such as “Single Phase” or “1-Phase” to identify a single-phase or “3-Phase” or “Tri-Phase” for a 3-phase supply. [2] X Research source The meter could also read “Mono-Phase” for single-phase or “Polyphase” for 3-phase.

Tip: Your utility bill may also say what type of power you have. Check out a recent bill to see if it says single or 3-phase on it.

2
Look at the width of the main switch in your switchboard. Find the main switchboard in your fuse box, which is the largest fuse usually located directly in the center of the box. Look at the width and the number of “poles” which are the individual circuits that the switch controls. A single-phase circuit will have a 1-pole width and a 3-phase circuit will have a width of 3 poles. [3] X Research source If you can’t find your fuse box, try looking for a metal box in your garage or basement, or check the side of your home outside.
3
Count the wires connected to an appliance or the main switch. Look at the wires connected to an appliance such as a water heater or oven. If you can’t see the wires connected to a device, look in your fuse box and find your main power supply switch, which is the largest switch that’s generally located in the center of the box. If there are 2 wires, then you have a single-phase circuit. If there are 3 or 4 wires, then you have a 3-phase circuit. [4] X Research source In a single-phase circuit, there’s 1 live wire and 1 neutral wire. In a 3-phase circuit, there are 2 or 3 live wires and 1 neutral wire.
4
Check the number of fuses in the switchboard. The service fuses for your main power supply are usually located in your fuse box or mounted near it. They’re black and rectangular in shape. Single-phase circuits use 1 service fuse and 3-phase circuits use 3 service fuses. Count the fuses to determine what type of system you have. [5] X Research source
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Method 2 of 2:
Checking the Voltage

1
Set a digital multimeter to the AC volts setting. Use a digital multimeter with 2 leads to check the voltage of your electrical system, which will tell you whether you have a single or a 3-phase circuit. Turn on your multimeter and set the setting to read AC power in volts. [6] X Research source Make sure the red and black leads are plugged in correctly. The black lead goes into the terminal labeled “COM” and the red lead goes into the terminal labeled “V.”
2
Hold your black lead to the ground wire connector. On your main electrical circuit board, the wire connector is a plate with a screw that holds the wire in place and is useful for taking readings. Locate the wire connectors attached to your main power switch. The connector on the far left is the neutral or ground connector. Hold the end of your black test lead against the connector. [7] X Research source Keep the black lead pressed against the connector.
3
Touch the red wire to 1 of the hot wire connectors to take a reading. Take your red test lead and hold it against 1 of the hot wire connectors near the ground wire connector. Your digital multimeter will give you a reading of 120 volts. [8] X Research source Both single and 3-phase circuits have a reading of 120 volts between a hot and ground wire.

Tip: If you don’t have an accurate reading or any reading at all, your black lead may not be connected to the ground. Lift up your black lead and press it against the connector again.

4
Place the black lead against another hot wire connector. Lift up your black lead from the ground connector and touch it to another hot wire connector so both of your leads are touching 2 separate connectors. Your digital multimeter will give you a reading of 206 volts if you have a 3-phase circuit and a reading of 240 volts if you have a single-phase. [9] X Research source
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Method 1 of 2:
Looking for Clues

1
Read your electrical meter to see if it says single or 3-phase. Look near your fuse box to see if your meter is mounted next to it. Some homes may have their electrical meter in the basement, on the side of the home, or even in the front yard for energy companies to easily check them. When you find your meter, the face will include information such as the wattage and the identification number. Look for a description such as “Single Phase” or “1-Phase” to identify a single-phase or “3-Phase” or “Tri-Phase” for a 3-phase supply. [2] X Research source The meter could also read “Mono-Phase” for single-phase or “Polyphase” for 3-phase.

Tip: Your utility bill may also say what type of power you have. Check out a recent bill to see if it says single or 3-phase on it.

2
Look at the width of the main switch in your switchboard. Find the main switchboard in your fuse box, which is the largest fuse usually located directly in the center of the box. Look at the width and the number of “poles” which are the individual circuits that the switch controls. A single-phase circuit will have a 1-pole width and a 3-phase circuit will have a width of 3 poles. [3] X Research source If you can’t find your fuse box, try looking for a metal box in your garage or basement, or check the side of your home outside.
3
Count the wires connected to an appliance or the main switch. Look at the wires connected to an appliance such as a water heater or oven. If you can’t see the wires connected to a device, look in your fuse box and find your main power supply switch, which is the largest switch that’s generally located in the center of the box. If there are 2 wires, then you have a single-phase circuit. If there are 3 or 4 wires, then you have a 3-phase circuit. [4] X Research source In a single-phase circuit, there’s 1 live wire and 1 neutral wire. In a 3-phase circuit, there are 2 or 3 live wires and 1 neutral wire.
4
Check the number of fuses in the switchboard. The service fuses for your main power supply are usually located in your fuse box or mounted near it. They’re black and rectangular in shape. Single-phase circuits use 1 service fuse and 3-phase circuits use 3 service fuses. Count the fuses to determine what type of system you have. [5] X Research source
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Method 2 of 2:
Checking the Voltage

1
Set a digital multimeter to the AC volts setting. Use a digital multimeter with 2 leads to check the voltage of your electrical system, which will tell you whether you have a single or a 3-phase circuit. Turn on your multimeter and set the setting to read AC power in volts. [6] X Research source Make sure the red and black leads are plugged in correctly. The black lead goes into the terminal labeled “COM” and the red lead goes into the terminal labeled “V.”
2
Hold your black lead to the ground wire connector. On your main electrical circuit board, the wire connector is a plate with a screw that holds the wire in place and is useful for taking readings. Locate the wire connectors attached to your main power switch. The connector on the far left is the neutral or ground connector. Hold the end of your black test lead against the connector. [7] X Research source Keep the black lead pressed against the connector.
3
Touch the red wire to 1 of the hot wire connectors to take a reading. Take your red test lead and hold it against 1 of the hot wire connectors near the ground wire connector. Your digital multimeter will give you a reading of 120 volts. [8] X Research source Both single and 3-phase circuits have a reading of 120 volts between a hot and ground wire.

Tip: If you don’t have an accurate reading or any reading at all, your black lead may not be connected to the ground. Lift up your black lead and press it against the connector again.

4
Place the black lead against another hot wire connector. Lift up your black lead from the ground connector and touch it to another hot wire connector so both of your leads are touching 2 separate connectors. Your digital multimeter will give you a reading of 206 volts if you have a 3-phase circuit and a reading of 240 volts if you have a single-phase. [9] X Research source
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