What Size Circuit Breaker Do I Need?

When creating a new electrical circuit in your home or business, you will need to make a lot of decisions. What will the primary purpose of the circuit be? What voltage will it carry? Will it need to expand at any point in the future? However, there is one vitally important question you will need to ask yourself at one point: what kind of circuit breaker should protect this new circuit? Circuit breakers are extremely important, as they protect electrical circuits and everything connected to them from overdrawing what the electrical infrastructure is capable of.

Why Breaker Size Is Important

A circuit breaker is an important safety check for any electrical circuit, so improper sizing can have some fairly significant consequences. A breaker that is too large can cause too much current to flow through a particular circuit, creating the risk for damage to electrical infrastructure. Too much current creates excessive heat in everything from connections to wires themselves, and that can cause injury or spark fires before the breaker can trip and shut off.

Conversely, using too small of a breaker means your breaker will be tripping almost constantly, and you’ll find yourself making a trip to the panel to reset the breaker during what you would otherwise consider “normal” use. Nobody wants to have to reset the breaker every time they use something like a microwave or a vacuum cleaner, but too small of a breaker will do exactly that.

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Proper Breaker Sizing

So how do you know what size breaker you need for a particular application? Part of it comes from experience, but you can actually answer this question rather easily by simply thinking about a few factors that may or may not be present in your circuit.

Circuit Location

Is your circuit going to be entirely indoors or will it cover an outdoor location? Will it cover some of both? While the latter certainly isn’t advised, outdoor breakers should generally be somewhat larger in size (think 25 amps or more). When you think about what you use an outdoor electrical outlet for (ceiling fans, light fixtures, yard care tools, pool pumps, etc.) you’ll see that the majority of your uses will probably require a pretty substantial amount of current. For example, a plug-in electric lawnmower may pull 10 to 15 amps or more all on its own, and that leaves you very little wiggle room without risking tripping your breaker. Likewise, running several things at once may require a higher amount of power, and that means you should plan to have extra capacity (and build your circuit to be able to support that capacity as well).

Circuit Purpose

A circuit that powers outlets and a ceiling fan for a small bedroom does not need to be the same size as a circuit used to power a spa heating and pumping system. A spa circuit will need a breaker as large as 50 amps or more, while a bedroom will generally need no more than 10 to 15 amps at the absolute most. Therefore, it’s not a good idea to install a 50-amp breaker for a bedroom or choose a smaller breaker for a pool house. Know what you intend to do with a particular circuit and use that knowledge to choose a breaker appropriately.

Circuit Size

It is never a good idea to build a circuit to be too large or to cover too many features of your home. The more you load onto a single circuit, the greater the chance that a problem takes that circuit offline, and the harder it is to determine what that problem is. However, sometimes you need to build a circuit to handle a larger number of features, and thus you should pick a breaker that is capable of handling that electrical demand. If you know that you are going to regularly need several high-energy devices over a bigger area at the same time in one area (such is the case with many garages or workshops) then choose a larger breaker to sustain that circuit. However, we do recommend splitting larger circuits if possible to minimize the amount of current draw over any one circuit.