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HomeTips & GuidesAmp Circuit Breaker: How To Determine Your Home’s Electrical Load

Amp Circuit Breaker: How To Determine Your Home’s Electrical Load

Let’s look at the amp circuit breaker ratings in this article.

While you can use fuses to protect electrical circuits and devices in your home, you must replace them once they burn.

Circuit breakers are better options because you can reset them after tripping. This mechanism saves you the cost of buying a new device and the labor of fitting it.

But you must get their ampere rating right before installation, and we’ll help you determine your home’s electrical load below. Read on to learn more!

What Are Circuit Breakers?

Circuit breakers are electrical switches that protect electrical circuits from damage caused by electrical faults like short-circuiting and overloading.

They have tripping mechanisms that interrupt the flow of electricity if they detect a higher amperage draw (excess current) than their ratings.

Therefore, you should install a circuit breaker with the correct rating to prevent tripping due to a load exceeding its current rating. When buying one for your circuit, it should meet these criteria.

  • Feature a higher amp rating than the circuit it is protecting.
  • Be capable of handling the amp draw from all appliances in the circuit when turned on concurrently.

Circuit Breaker Types: By Protection

These devices come in the following types when considering the kind of protection they provide.

  • Standard: These circuit breakers offer the least protection because they only cover short circuits and overloads.
  • GFCI: Ground Fault Circuit Interrupters can detect if there is a ground fault, which is a direct link between the live power supply and the earth. Such issues usually occur in kitchens, bathrooms, or areas with high moisture levels. 
An earth leakage circuit breaker

An earth leakage circuit breaker

  • AFCI: Arc Fault Circuit Interrupters are some of the safest circuit breakers because they safeguard against electrical arcing. This issue occurs due to large sparking in faulty sockets or switches.

Circuit Breaker Types: By Poles

Single pole circuit breakers connect only a single wire, usually the live cable, from source to load. But double pole circuit breakers cover the live and neutral wires.

Multiple single-pole circuit breakers

Multiple single-pole circuit breakers

Tandem breakers are double-pole variants that are as compact as the single-pole type. Therefore, they are ideal for breaker panels with limited space.

Circuit Breaker Amp Ratings

A main service panel or breaker box houses all the circuit breakers and acts as a distribution center to split the AC power supply to individual circuits running through your home.

Power flows through the primary double-pole electrical circuit breaker, which then powers single or double busbars to connect to the secondary breakers.

So, the primary or central circuit breaker amperage rating should be higher than your household’s entire power consumption. On the other hand, the secondary individual circuit breakers should meet and slightly exceed the amperage of the devices connected in that circuit.

Going by this explanation, the rating of the primary circuit breaker should be equal to or exceed the total of the sum of the individual branch circuit breakers.

A main switch circuit breaker rated at 63 amps

A main switch circuit breaker rated at 63 amps

How To Determine Your Circuit’s Electrical Load

Before going into this calculation, let’s demystify the technical jargon relating to electrical load capacity.

  • Ampere: Amp measures the electrical charge or current flowing past one point in a circuit per second.
  • Voltage: This factor defines the potential difference between two points in a circuit, which indicates the force pushing the electrons through the system.
  • Wattage: Watt is the electrical power that devices consume in circuits. Therefore, electrical appliances have wattage ratings.

Circuit breakers don’t consume electricity, meaning they have ampere and voltage ratings. On the other hand, home electrical appliances and other devices consume power. Therefore, they have wattage and voltage ratings.

So, how do you reconcile the two? Use the formula Wattage = Ampere x Voltage.

Therefore, if the circuit handles larger appliances, such as a washing machine, air conditioner unit, or heater, it will need a circuit breaker with a higher amp rating than one for the lights.

A central air conditioning unit consumes about 3500 watts per hour, while a washing machine uses about 850 watts. With these two only, the circuit draws 4350 watts when both are on, and you should use this figure to calculate the amperage rating.

Single-pole circuit breakers mounted on a DIN rail

Single-pole circuit breakers mounted on a DIN rail

Countries like the US use a 110/120V electrical system. Therefore, the ideal circuit breaker rating is 40 amps for this individual circuit (4350/120=36.25).

Circuit Breaker Capacity

It is vital to note that circuit breakers can only handle roughly 80% of their overall amp rating. Therefore, the 36 or 40 amps should be 80% of the rating.

With this calculation, the breaker should have a rating of at least 45 amps. Each breaker has its maximum amperage capacity printed on the housing.

If your country runs on a 240V system, the circuit breaker amperage rating should be at least 20 amps (4350/240=18.125). And going by the 80% rule above, you should get a breaker that can handle 23 amps.

What if I Want To Connect Additional Appliances to the Circuit?

The values we’ve given above cater to the exact load currently connected in the circuit. But what if you buy a heater or connect other appliances with a high wattage rating?

The solution is to replace the already installed breaker with a highly-rated unit. Or you can wire an additional circuit.

Therefore, consider leaving some allowance when doing your wiring in the first place. For instance, instead of using a 45-amp circuit breaker for the 120V example above, install a 60-amp unit.

And for the 23-amp breaker in the 240V system, consider a 30-amp or 40-amp unit.

How To Determine Your Home’s Electrical Load

The example above is only one of the circuits in your home that should have its separate breaker in the service panel. 

Calculating the total amp draw can be challenging at first, and you need this figure to determine the rating for the central circuit breaker.

A double pole circuit breaker

A double pole circuit breaker

You can use these approximation steps to get a rough figure.

Step 1: Calculate Total Consumption By Footage

Multiply the square footage of all living spaces in your home by three watts. The result should be a rough equivalent of the lighting and receptacle power consumption.

For instance, if your total living space is 1,000 square feet, the power needs will be 3,000 watts.

Step 2: Add 1,500 Watts for Laundry/Kitchen Appliances

Each kitchen appliance and laundry room circuit adds a 1,500-watt load. So, if you have one kitchen appliance and a laundry room, that is an extra 3,000 watts. 

Step 3: Include Other Appliances

Consider the wattage of other appliances that have high power ratings. For instance, if you have a water heater, dryer, and dishwasher, check the ratings on their labels or boxes.

Water heaters and dryers consume roughly 5,000 watts each. Dishwashers are more energy efficient because they consume only about 1,000 watts.

Therefore, the total of these three appliances is 11,000 watts.

Step 4: Add the Wattage Values

The total wattage at this point is 17,000 watts (3,000+3,000+11,000). Take the first 10,000 at 100% value, then the remainder at 40%.

 In this case, 7,000 is the remainder. 40% of 7,000 is 2,800 watts. Therefore, the total is 12,800 watts.

A wattmeter showing the wattage reading at a power plug

A wattmeter showing the wattage reading at a power plug

Step 5: Include the Central AC or Heater

If you have central air conditioning or electric heat, include the one with the highest value. The assumption is you can’t use both concurrently. 

One is for heating the house during winter and the other for cooling during summer. We’ll use 4,000 watts.

Step 6: Get the Total and Divide by the Voltage

12,800 + 4,000 is 16,800 watts. In a 120V system, the amperage will be 140 (16,800/120). But in a 240V system, it will be half that (70 amps).

240-volt circuits are better because they push the amperes (current) twice as hard as 120-volt circuits. 

Therefore, they use thinner wires (with a higher American Wire Gauge) and lower circuit breaker ratings, which are cheaper.

Wrap Up

Circuit breakers are critical in household electrical circuits but are only effective if you calculate their correct sizing or capacity. 

The steps above should help you get the most suitable rating for the primary and individual circuit breakers. 

That’s it for this article. You can find out more about circuit breaker resetting here

Remember to comment below to share your thoughts and sentiments because we appreciate your feedback.

I am Lillian Yang, having been a sales manager for over 10 years.

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