Determine Amperage of Circuit Breaker

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←Older revision		Revision as of 00:13, 2 July 2019
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	== Steps ==		== Steps ==
	===Finding the Amperage Rating of a Circuit Breaker===		===Finding the Amperage Rating of a Circuit Breaker===
−	#Examine the electric panel. Each circuit breaker should have its amperage marked on the handle. This is the maximum amperage that circuit can take before the circuit breaker trips.[[Image:Determine Amperage of Circuit Breaker Step 1 Version 2.jpg|center]]	+	#Examine the electric panel. Each circuit breaker should have its amperage marked on the handle. This is the maximum amperage that the circuit can take before the circuit breaker trips.[[Image:Determine Amperage of Circuit Breaker Step 1 Version 2.jpg|center]]
	#*In the United States, standard household circuits are rated for 15 or 20 amps. Specific appliances may need dedicated, high-load circuits for 30 or 50 amps.		#*In the United States, standard household circuits are rated for 15 or 20 amps. Specific appliances may need dedicated, high-load circuits for 30 or 50 amps.
−	#Multiply the amperage by 0'''.8'''. For everyday use, it's a good idea to expose the breaker to a maximum of 80% of the rated amperage. It's fine to exceed this for short periods of time, but continuous current above this amount could trip the breaker.[[Image:Determine Amperage of Circuit Breaker Step 2 Version 2.jpg|center]]	+	#Multiply the amperage by 0'''.8'''. For everyday use, it's a good idea to expose the breaker to a maximum of 80% of the rated amperage. It's fine to exceed this for short periods of time, but continuous current above this amount could cause enough heat to trip the breaker.<ref>https://ift.tt/2RMEEXv>[[Image:Determine Amperage of Circuit Breaker Step 2 Version 2.jpg|center]]
−	#*Your electrical panel might have a note about the breakers operating at 100% of the rated value. If it does, you may skip this step.	+	#*Breakers should be sized at 125% for a continuous load and 100% for a non-continuous load, which comes out the same when you multiply the breaker size by 0.8.
	#Understand double-pole breakers. Some high-voltage devices may be wired to a double-pole circuit breaker — two standard circuit breakers sharing a handle. Do ''not'' add together the amperage of the two breakers. Both circuits will be tripped simultaneously by the amperage displayed on one circuit breaker handle.[[Image:Determine Amperage of Circuit Breaker Step 3 Version 2.jpg|center]]		#Understand double-pole breakers. Some high-voltage devices may be wired to a double-pole circuit breaker — two standard circuit breakers sharing a handle. Do ''not'' add together the amperage of the two breakers. Both circuits will be tripped simultaneously by the amperage displayed on one circuit breaker handle.[[Image:Determine Amperage of Circuit Breaker Step 3 Version 2.jpg|center]]
	#*For example, a two-pole breaker at 15 amps on each pole (breaker handle) would supply 240 volts to the appliance on that branch at up to 15 amps, not 30.		#*For example, a two-pole breaker at 15 amps on each pole (breaker handle) would supply 240 volts to the appliance on that branch at up to 15 amps, not 30.
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	#*Some devices will list the amperage directly, often labeled FLA, meaning "Full Load Amps". If it does, [[#ampdata|skip down to the next section]] to interpret that rating.		#*Some devices will list the amperage directly, often labeled FLA, meaning "Full Load Amps". If it does, [[#ampdata|skip down to the next section]] to interpret that rating.
	#Check the voltage on the circuit. For household circuits, you can usually assume your house follows the voltage standards of your country. (For example, 120V in North America and Central America, or around 220V to 230V for most other countries.<ref>https://ift.tt/2KOYpNn) If you think you are working with an exception, [[Use-a-Multimeter|measure the voltage]] using a multimeter.[[Image:Determine Amperage of Circuit Breaker Step 6.jpg|center]]		#Check the voltage on the circuit. For household circuits, you can usually assume your house follows the voltage standards of your country. (For example, 120V in North America and Central America, or around 220V to 230V for most other countries.<ref>https://ift.tt/2KOYpNn) If you think you are working with an exception, [[Use-a-Multimeter|measure the voltage]] using a multimeter.[[Image:Determine Amperage of Circuit Breaker Step 6.jpg|center]]
−	#Divide the wattage by the voltage. The answer will be the amperage the device draws on your circuit. For example, a 150 watt device on a 120 volt circuit will draw 150 ÷ 120 = 1.25 amps.[[Image:Determine Amperage of Circuit Breaker Step 7.jpg|center]]	+	#Divide the wattage by the voltage. The answer will be the amperage the device draws on your circuit. For example, a 150-watt device on a 120-volt circuit will draw 150 ÷ 120 = 1.25 amps.[[Image:Determine Amperage of Circuit Breaker Step 7.jpg|center]]
	#Repeat for each device on the circuit. Perform the same calculation for each other device on the circuit, or at least the ones with the highest wattage. Write down each answer next to the name of the device.[[Image:Determine Amperage of Circuit Breaker Step 8.jpg|center]]		#Repeat for each device on the circuit. Perform the same calculation for each other device on the circuit, or at least the ones with the highest wattage. Write down each answer next to the name of the device.[[Image:Determine Amperage of Circuit Breaker Step 8.jpg|center]]
−	#Add the amperages of devices that are always running. Take the continuously running devices, or the devices that run for more than a couple hours at a time. Add their amperages together. If the result is more than 80% of your circuit breaker's rated amperage, plug one of the devices into an outlet on a different circuit.[[Image:Determine Amperage of Circuit Breaker Step 9.jpg|center]]	+	#Add the amperages of devices that are always running. Take the continuously running devices, or the devices that run for more than 3 hours at a time. Add their amperages together. If the result is more than 80% of your circuit breaker's rated amperage, plug one of the devices into an outlet on a different circuit.[[Image:Determine Amperage of Circuit Breaker Step 9.jpg|center]]
	#Add additional amperages. On top of the continuous amperage, add the amperage of other devices that might be on at the same time. If any combination gets above 100% of the circuit breaker's rating, it will trip the circuit. You can solve this by moving a device to a different circuit, or by remembering not to use high-power devices at the same time.[[Image:Determine Amperage of Circuit Breaker Step 10.jpg|center]]		#Add additional amperages. On top of the continuous amperage, add the amperage of other devices that might be on at the same time. If any combination gets above 100% of the circuit breaker's rating, it will trip the circuit. You can solve this by moving a device to a different circuit, or by remembering not to use high-power devices at the same time.[[Image:Determine Amperage of Circuit Breaker Step 10.jpg|center]]
	#*Electrical circuits never operate perfectly. Some of the energy is lost to heat, and devices may draw more current to make up for this. Waste is low in most household circuits (below 10%), but it is still possible to trip the breaker if the total calculated amperage on paper is slightly below the breaker rating.		#*Electrical circuits never operate perfectly. Some of the energy is lost to heat, and devices may draw more current to make up for this. Waste is low in most household circuits (below 10%), but it is still possible to trip the breaker if the total calculated amperage on paper is slightly below the breaker rating.
	#Measure amperage directly with a clamp multimeter (optional). A clamp multimeter (or clamp ammeter) has a pair of "jaws" at the top that close shut to encircle a wire. When set to measure amps, the device will display the number of amps running through that wire.<ref>https://www.youtube.com/watch?v=ar7qkMHKw40</ref> To test a circuit, expose the wire leading to the load side of a circuit breaker. With the clamp multimeter set up as described, have a friend turn on other devices in the house. If the device is on the same circuit, you will see the amperage display increase.[[Image:Determine Amperage of Circuit Breaker Step 11.jpg|center]]		#Measure amperage directly with a clamp multimeter (optional). A clamp multimeter (or clamp ammeter) has a pair of "jaws" at the top that close shut to encircle a wire. When set to measure amps, the device will display the number of amps running through that wire.<ref>https://www.youtube.com/watch?v=ar7qkMHKw40</ref> To test a circuit, expose the wire leading to the load side of a circuit breaker. With the clamp multimeter set up as described, have a friend turn on other devices in the house. If the device is on the same circuit, you will see the amperage display increase.[[Image:Determine Amperage of Circuit Breaker Step 11.jpg|center]]
−	#*Do not attempt this unless you have electrician's gloves and a basic understanding of electrical safety. These wires are live and removing the front panel of a breaker panel can expose you to dangerous voltages.	+	#*Do not attempt this unless you have electrician's gloves and a basic understanding of electrical safety. These wires are live and removing the front panel of a breaker panel can expose you to dangerous voltages, so use extreme caution.
	<span id="ampdata"></span>		<span id="ampdata"></span>
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	#*Most electrical codes allow a ± 5% tolerance for the voltage (or slightly more).<ref>https://ift.tt/2RNrYQ2> Do not run a device on a voltage supply outside this range.		#*Most electrical codes allow a ± 5% tolerance for the voltage (or slightly more).<ref>https://ift.tt/2RNrYQ2> Do not run a device on a voltage supply outside this range.
	#*Household outlets in North America and some other countries are on a 120V standard. Most of the world uses 220–240V.<ref>https://ift.tt/2KYQEon>		#*Household outlets in North America and some other countries are on a 120V standard. Most of the world uses 220–240V.<ref>https://ift.tt/2KYQEon>
−	#*Many homes have 30-A or 50-A breakers dedicated to larger appliances such as water heaters, baseboard heaters, ovens, stoves, and heavy-duty power tools. The wiring and breakers for these circuits are required to be designed at 125 percent of the continuous load.	+	#*Many homes have 30-A or 50-A breakers dedicated to larger appliances such as water heaters, baseboard heaters, ovens, stoves, and heavy-duty power tools. The wiring and breakers for these circuits are required to be designed at 125% of the continuous load and 100% of a non-continuous load.
	#Look for the FLA, or "full load amps". This is the number of amps the motor will draw at the rated horsepower. In the United States, if this device will be left on for more than three hours, the circuit breaker should be rated at 125% of this value. (Multiply the FLA by 1.25.) This allows for additional load due to other factors, mainly heat.<ref>https://ift.tt/2RO7S8a Amperage of Circuit Breaker Step 14.jpg|center]]		#Look for the FLA, or "full load amps". This is the number of amps the motor will draw at the rated horsepower. In the United States, if this device will be left on for more than three hours, the circuit breaker should be rated at 125% of this value. (Multiply the FLA by 1.25.) This allows for additional load due to other factors, mainly heat.<ref>https://ift.tt/2RO7S8a Amperage of Circuit Breaker Step 14.jpg|center]]
	#*This value may also be listed as full load amperage, running amps, rated amp, or just amps.<ref>https://ift.tt/2KUwCej>		#*This value may also be listed as full load amperage, running amps, rated amp, or just amps.<ref>https://ift.tt/2KUwCej>
−	#*Some circuit breakers are rated to 100% of the listed amperage, meaning you can skip the 125% calculation. This information will be clearly listed on the circuit breaker electrical panel if you have this type of breaker.<ref>https://ift.tt/2RNhwYM>	+	#*Circuit breakers are rated to 100% of the listed amperage, meaning you can skip the 125% calculation. This information will be clearly listed on the circuit breaker electrical panel if you have this type of breaker.<ref>https://ift.tt/2RNhwYM>
−	#Check the LRA. The LRA, or locked rotor amps, is the amount of current drawn when the motor is not turning. This is required to start the motor, and can be much higher than the FLA.<ref>https://ift.tt/2KOPziR> Modern circuit breakers are designed to allow this brief surge of current. If your circuit breaker is rated high enough for the FLA but still trips when the device is plugged in, it could be a faulty breaker, or just an old model. Move the device with high LRA to another circuit or have an electrician inspect your wiring.[[Image:Determine Amperage of Circuit Breaker Step 15.jpg|center]]	+	#Check the LRA. The LRA, or locked rotor amps, is the amount of current drawn when the motor is not turning. This is required to start the motor and can be much higher than the FLA.<ref>https://ift.tt/2KOPziR> Modern circuit breakers are designed to allow this brief surge of current. If your circuit breaker is rated high enough for the FLA but still trips when the device is plugged in, it could be a faulty breaker, another device plugged into the circuit that causes an overload, or just an old model. Move the device with high LRA to another circuit or have an electrician inspect your wiring.[[Image:Determine Amperage of Circuit Breaker Step 15.jpg|center]]
	#*Do not confuse this with the RLA, a specially derived value of internal forces, listed on air conditioner units.		#*Do not confuse this with the RLA, a specially derived value of internal forces, listed on air conditioner units.
		+	#*You can oversize a breaker to 125% to help prevent your breaker from tripping.
	#Take other devices into account. If multiple devices are running on the same circuit, add them together as follows:[[Image:Determine Amperage of Circuit Breaker Step 16.jpg|center]]		#Take other devices into account. If multiple devices are running on the same circuit, add them together as follows:[[Image:Determine Amperage of Circuit Breaker Step 16.jpg|center]]
	#*If your circuit breaker is rated at 100%, just add all of the amperages together.		#*If your circuit breaker is rated at 100%, just add all of the amperages together.
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	*The total of all breakers in a panel may exceed the rating of the "main" breaker. This is normal in residential systems where it is unlikely that all loads on all circuits will be operating simultaneously.		*The total of all breakers in a panel may exceed the rating of the "main" breaker. This is normal in residential systems where it is unlikely that all loads on all circuits will be operating simultaneously.
	*There are consumer devices for easy measurement of the actual wattage or amps being used by a cord-connected appliance. They are sold as "plug-in watt meters". You plug it into a receptacle, then plug an appliance into the watt meter to directly read how much power it is using, as displayed on the meter.  This may not provide a convenient branch-circuit total load, but it avoids the risk of trying to use a clamping ammeter on live wires inside a breaker panel.		*There are consumer devices for easy measurement of the actual wattage or amps being used by a cord-connected appliance. They are sold as "plug-in watt meters". You plug it into a receptacle, then plug an appliance into the watt meter to directly read how much power it is using, as displayed on the meter.  This may not provide a convenient branch-circuit total load, but it avoids the risk of trying to use a clamping ammeter on live wires inside a breaker panel.
−	*The National Electrical Code® (NFPA 70®) is available online for free viewing <ref> https://ift.tt/2RPNUKh </ref> (with minimal sign-up) or you may find a copy in a well stocked library or bookstore.	+	*The National Electrical Code® (NFPA 70®) is available online for free viewing <ref> https://ift.tt/2RPNUKh </ref> (with minimal sign-up) or you may find a copy in a well-stocked library or bookstore.
	== Warnings ==		== Warnings ==

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