Shocking Truth: What You Need to Know About Your House's Electrical Circuits

Don't Be Shocked! What You need to Know About Electrical Circuits

Working with electricity can seem a little scary, especially if you have ever felt the sudden zap from an outlet or appliance. It's only natural to be hesitant, but with some basic information under your tool belt, you'll see that electricity, while something to respect, isn't something you need to fear. After all, electricity is similar to water. Once the flow of electricity is turned off, the area you're working in should be safe. So, once you know how to turn off the power, you can master any electrical project!

Jane Tip: If you are working on a circuit that powers computers or expensive electronics, it is best to unplug these components before turning the power off from the main circuits. Although most electronics have surge protectors, you can do damage if there is a surge after the power is restored and the electronic components are in the on position.


Although the power comes in from external power lines, the beginning of your electrical system really starts at the Main Service Panel, usually located in the basement, garage or interior closet of most homes. Inside the service panel, you'll find one of two things:

Circuit Breakers

If your home was built within the last few decades, you'll find your service panel has a couple (or more depending on the size of your home) rows of toggle switches. These switches are called circuit breakers and they serve two functions: 1) when a surge of power comes through a wire, then the switch "trips," literally breaking the circuit and cutting any power to the line and 2) these switches also enable you to turn off the power to a given area while working.


Older homes have fuse boxes, though these have pretty much been phased out. To turn off the power to a given area controlled by a fuse, you'll want to remove the fuse by unscrewing it or pulling it out. Screw-in fuses usually control wall outlets and light fixtures while "pull-out" fuses control areas that service large appliances.

"Blowing a Fuse" or "Tripping a Breaker"

When a circuit is carrying too much electricity, the circuit shuts itself off. This is a safety mechanism that keeps the surge of power from entering your home. A fuse has a thin piece of metal at the top that will melt away when too much current enters the line. When this occurs the fuse is "blown" and will need to be replaced.

Safety Check! When working with fuses, you want to be sure to only touch the insulated rim of the fuse. This will minimize your risk of shock.

During an unexpected surge of power a circuit breaker will "trip" into the off position. When this occurs, the easiest way to determine which of the breakers was affected is to feel for the switch that seems 'loose' to the touch. Simply flip it back into the "on" position and power will be restored to the area.

Safety Check! If you trip your circuit breaker or blow a fuse to a line that services large appliances or a computer, be sure that these items are turned off before restoring power to the area.

I Know Where to Turn Off the Power, but How do I know it's Off?

You can turn off the power to any given area in your home via the main service panel. But, you'll need to have two things to be sure you do this correctly: a circuit index and a current tester.

Mapping Your Panel

Safety Check! Before opening or even touching your main service panel, make absolutely sure there is no standing water under your feet.

Most main service panels have what's known as a circuit index that's attached to the inside door of the panel or to the panel itself. This is a map of which circuits provide power to the areas of your home. It's a smart idea to verify the accuracy of the map--circuits can be mislabeled, so a little experimentation is wise. If your home doesn't have a map already, you'll want to take a few minutes and make one yourself.

To make a map, flip all the switches on and off while a friend stands inside, calling out to you when the power goes out. Be sure to be careful that any computers or major appliances are turned off or unplugged during this test. You'll want to avoid any unnecessary surges of power when flipping the switch on and off.

Jane Tip: If no one is available to help you, use a radio turned up loud enough for you to hear when it goes off.

Keep in mind that if there is a circuit index from a previous owner you will want to be sure to verify their markings before doing any kind of electrical project. Never assume that they haven't since changed or are inaccurate.

A Current Affair

Current testers are a vital tool when doing any electrical work because they enable you to detect any live wires. Once you have turned off the power from the service panel, double check it with a current tester. If you are working on an outlet, you can insert the prongs of the tester into the outlet. If the tester lights up or beeps, the circuit is on. If there is more than one circuit in an outlet, test both of them before you go to work.

When it comes to purchasing a tester, we like the type known as "no-touch" current tester. These usually run around $20.00 or so, but they allow you to simply get the probe in the general vicinity of the wires in question, rather than having to actually touch the wires with the probe.

Jane Tip: Before starting a project, always test your tester in a working outlet before you turn off the power. A faulty tester will not react, making you think the power is off when it could still be on.

If you are working on a light fixture, the same basic rule applies. You can check a light fixture before dismantling it with current tester models that screw into an open light bulb socket. If the device lights up or beeps, the power is still on. A light fixture can also be tested by dismantling the fixture and exposing the wires. Remove the wire cap and test the wires.

Jane Tip: Be sure to tell everyone in the house that you're working with the electricity. Lock the panel or fuse box, if possible. The last thing you want is one of your family members accidentally turning the power back on while you're working!


Taking the tentative approach to fixing your home's electricity is only normal--hey, those are your survival instincts kicking in! But the good news is that after doing it a couple of times you will grow more confident. And by taking the preventative measures outlined above before any electrical project, you'll see just how easy electricity can be.

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Everything you Need to Know About Splicing Wires
How to Install a Dimmer
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