Know Your Electrical Panel

We've talked about the basic electrical tools used to diagnose issues; now let's look at your electrical panel, which is what distributes all the electrical power for your home. If you have outbuildings with power, these may have their own sub-panels that distribute power just to that building. Knowing the location of these panels is critically important to being able to safely work on the electrical circuits in your home.

Inside your panel, you'll find either circuit breakers or fuses. Resettable circuit breakers are used in all modern construction projects; fuses are found in much older homes, usually dating to the 1950s or earlier. Some of these buildings have had update and refit work done, however, and if so they will have modern circuit breakers. I discussed the basics of fuses and circuit breakers here and here, and they're worth a quick review.

A residential breaker panel, pictured closed.

Breakers inside a panel.

The pictured panel is the one in my own home. Notice that there are both single and two-handle breakers: the single-space breakers supply 120V power to lights and normal outlets, and the two-space breakers supply 240V power to things like ovens, clothes dryers, and electric HVAC systems. There should be a schematic inside the panel door listing what each circuit powers, but these are sometimes out of date or inaccurate.

Knowing a few things about your panel can help you isolate which circuit you need to disconnect:

• Breakers marked as 15 amps are almost always lighting. 
• 20 amp breakers can be lights or outlets. 
• As mentioned above, two-space breakers (referred to in the trade as two-pole breakers) power high-draw items like ovens and clothes dryers. These breakers are the top two breakers in my panel as pictured. 
• Some panels will also have a breaker marked as "Main." This breaker kills all power to the entire house, and will be labeled with a higher amperage than any of the other breakers, almost always 100 amps or more. If the main breaker isn't in the panel, it will be located near the electrical meter, as noted here.

Find your own panel and take a look inside. Be familiar with your breakers so that when you need to flip one, you've got nothing to be afraid of.

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