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Electrical Panels 101: A Homeowner’s Guide to Breaker Boxes

Electrical Panel

In this article, we’ll attempt to remove some of the mystery of your breaker box by explaining:

  • What it is and why it’s important
  • The different parts of the breaker box and what they do
  • The different sizes of panels
  • The lifespan of panels and circuit breakers

What’s a breaker box?

Electric panels take incoming electricity from your electric company and safely redistribute the electric current throughout your home through circuits.

The breaker box also houses safety devices known as circuit breakers. Circuit breakers cut the power whenever electrical wiring in your home has too much electric current running through it.

Related: Why Does My Circuit Breaker Keep Tripping?

The parts of your breaker box


1. Circuit breakers

Each circuit in your home has a corresponding breaker. If there’s an electric overload on a circuit (whether from a short circuit or too many appliances running at once), the corresponding breaker automatically trips to shut off the flow of electricity to that circuit.

There are 2 main types of standard breakers:

  • Single pole – These are single switches and likely make up most of the breakers in your breaker box. In the photo above, all the circuit breakers on the left side, except the service disconnect, are single pole. They can handle 120 volts and are either 15 amps or 20 amps. (See the numbers on top of the switches?)
  • Double pole – These look like two switches joined together. They can handle 240 volts and are usually between 15-125 amps. These are for your large appliances like stoves, dryers, air conditioners and water heaters.

There are also other types of special purpose breakers such as Arc Fault Circuit Interrupters (AFCI) and Ground Fault Circuit Interrupters (GFCI)  that are designed to provide additional safety protection from fire (AFCI) and electrocution (GFCI).  These are not in the picture above.

2. Service disconnect

You can, in the case of an emergency, shut off the electricity to your entire home by flipping the service disconnect.

It’s the biggest breaker in your box, usually 100 to 200 amps. It’s sometimes also called the ‘electrical main’. Most often it’s at the top or bottom of your box, though it can also be in the middle, as in this example.

This is where the power from the electric company flows into the box. It goes through this switch and into the rest of the circuits.

3. Expansion slots

Many breaker boxes have empty slots so that you can have a licensed electrician add additional circuits, as needed. This comes in handy if you add new appliances to your home or need to add electricity to a room that doesn’t have it (like a garage, basement, or room addition).

In the photo above, there are many slots for additional breakers.

The difference between breaker box “sizes”

When you hear someone say they need a “larger” electrical panel or breaker box, there are 2 things they could be referring to:

  • The amount of electricity the panel can handle – This is measured in amps. Most homes have either 100-amp or 200-amp breaker boxes.
  • The number of circuits a panel can handle – If you don’t have space for new circuits but need to add one, you can either add a sub-panel or upgrade your breaker box to handle more circuits.

If you have questions about the size panel you need, get help from a licensed electrician.

Will I ever need to replace my breaker box?

Typical electrical panels last up to 60 years throughout the country. However, Phoenix’s heat can cut that lifespan down to 25-30 years, in some circumstances.

The circuit breakers can also go bad due to tripping too many times or because it has baked  in the Arizona heat. If a breaker goes bad, it won’t trip even when there’s too much electricity going through the wires.

This can be a real fire danger. An overloaded circuit will overheat the wires, breaking down the insulation, which can cause a fire.

Here’s a thermal image of a bad breaker. Notice the heat created from too much electrical current.
This is why we recommend you have your electrical panel checked yearly to make sure all your breakers are working and keeping you safe.

George Brazil Plumbing & Electrical serves Phoenix, Scottsdale, Mesa, Tempe, Chandler, Glendale and the entire Phoenix metro area.

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