# How To Determine Amperage of Circuit Breaker

The amount of current is rated by the circuit breaker.The circuit breaker shuts down the flow of current in a circuit to prevent damage to the wiring and appliances.You can avoid unnecessary power interruptions and fire hazard by learning how to calculate the actual amperage of devices on the circuit.

### Step 1: Examine the panel.

The amperage should be marked on the handle.Before the circuit breaker trips, the maximum amperage is taken.Standard household circuits can be used for 15 or 20 Amps.Specific appliances may need dedicated high-load circuits.If you don’t know where your circuit breaker is, check your basement.You could look in your utility room, garage, or outside of your house.

### Step 2: Give the amperage by 0.8.

It’s a good idea to expose the breaker to 80% of the rated power.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.When you divide the breaker size by 0.8, you get the same result for a continuous load and a non-continuous load.

### Step 3: Understand the double-pole breakers.

Two standard circuit breakers share a handle, and some high-voltage devices may be wired to a double-pole circuit breaker.The amperage of the two breakers should not be combined.Both circuits will be tripped at the same time.A two-pole breaker at 15 Amp on each pole would supply the appliance on the branch up to 30 Amps, not 30.A single breaker has 120V.A double pole breaker is tied together with a handle tie, so it can deliver 240V.

### Step 4: The current on the circuit is compared to this.

How much your wiring and circuit breaker can handle is now known.Continue to the next method to find out if your circuit exceeds this amperage.

### Step 5: You can find the device’s wattage.

Pick the device that is attached to the circuit.The data plate can be found on the back or underside of the device, or near where the power cord is connected.This is the maximum power rating of the device.”Full Load Amps” is the name of the device that will list the amperage directly.If it does, you should go to the next section to read that rating.

### Step 6: The circuit’s voltage should be checked.

When it comes to household circuits, you can assume your house is in line with your country’s standards.120V in North America and Central America, or 220V to 230V for most other countries.Measure the voltage using a multimeter if you think you are working with an exception.If you use one, make sure it’s set to AC or DC.If you’re measuring a device that uses a transformer to convert the power to DC, you need to set the multimeter accordingly.The label will state whether the device is AC or DC.

### Step 7: The wattage is divided by the voltage.

The answer is how much power the device draws on your circuit.A 150 watt device on a 120-volt circuit will draw 120 120.

### Step 8: For every device on the circuit, repeat.

The calculation for each other device on the circuit should be the same.Next to the name of the device, write down each answer.

### Step 9: The devices are always running.

Take the continuously running devices, or the devices that are expected to use the maximum current for 3 hours or more at a time.Add their power levels together.Plug one of the devices into an outlet on a different circuit if the result is more than 80% of your circuit breaker’s rated amperage.

### Step 10: Add more power.

Add the amperage of other devices that might be on at the same time.The circuit will trip if any combination gets above 100% of the circuit breaker’s rating.You can either move a device to a different circuit or remember not to use high-power devices at the same time.circuits don’t operate perfectlyDevices may draw more current to make up for some of the lost energy.It is possible to trip the breaker if the total amperage calculated on paper is slightly below the rating.

### Step 11: You can measure the amperage with a multimeter.

A multimeter has a pair of jaws at the top that close to encircle a wire.The number of Amps running through that wire will be displayed when the device is set to measure.If you want to test a circuit, expose the wire leading to the load side of the circuit breaker.A friend can turn on other devices in the house with the set up of the multimeter.The display will increase if the device is on the same circuit.Unless you have a basic understanding of electrical safety, you shouldn’t attempt this.If you remove the front panel of a breaker panel, you will expose yourself to dangerous voltages, so use extreme caution.

### Step 12: The data plate is something to look for.

The electrical information should be on the data plate.The back or underside of the device is where the cord enters.The rating you need for the circuit breaker will be determined by the information on this plate.All appliances with a motor should be covered by this section because they list the amperage directly on the data plate.If your device only lists the watt, you should calculate the amperage.The method of determining safety features for the motor is not appropriate.The wiring of the electrical supply is protected by the circuit breaker.Air conditioning units and ovens should be installed by a trained electrician.

### Step 13: The device’s rating should be checked.

The voltage of your electrical circuit is what determines the amperage drawn.If the intended V of the device is listed, you can confirm that it matches the electrical system.The device will usually list two values if it can run at two different voltages.The first number listed on each line is what you would refer to if you were running the device on a 120-volt supply.There is a 5% tolerance for the voltage in most electrical codes.Don’t run a device on a supply outside the range.In North America and some other countries, household outlets are on a 120V standard.Most of the world uses 220V.Many homes have 30-A or 50-A breakers that are dedicated to larger appliances.25% of the continuous load and 100% of a non-continuous load are required for the wiring and breakers to be designed.

### Step 14: The FLA or “full load Amp” is what you should look for.

The rated horsepower is the number of Amps the motor will draw.If this device is left on for more than three hours, the circuit breaker should be rated at 125% of this value.Take the FLA and add it to 1.25.This allows for more load due to other factors.This value can also be listed as running Amp, rated Amp or just Amp.You can skip the 125% calculation if the circuit breakers are rated to 100%.If you have a type of breaker, this information will be listed on the electrical panel.

### Step 15: Take a look at the LRA.

The amount of current drawn when the motor is not turning is called the locked rotor Amp.A brief surge of current is required to start the motor.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.An electrician can inspect your wiring or you can move the device to another circuit.The value of internal forces listed on air conditioner units is not the same as this.If the circuit is designed strictly for motors, you can oversize the breaker to 125% to prevent it from tripping.

### Step 16: Take other devices into account.

The NEC says branch circuits are sized at 125% of the continuous load and 100% of non-continuous load.If multiple devices are running on the same circuit, add them together as follows: If your circuit breaker is rated at 100%, just add all of the amperages together.If your circuit breaker is rated for continuous loads at 80% or you don’t know, add the amperages of all devices running for more than three hours at a time and multiply by 1.25.For shorter periods of time, add the amperage of all devices.If the answer exceeds the circuit breaker amperage, move the device to another circuit.

### Step 17: The ratings for the air conditioning unit can be used.

Most of the time, these values are not listed in North American air conditioning units.The Minimum Circuit Ampacity tells you the minimum wire size.The maximum overcurrent protection is the highest allowable.The MOP value is used when choosing a circuit breaker.If you don’t have experience with heating and cooling, these values can be surprising and complicated by new technologies.If you don’t have experience in the area, consider hiring a professional.