Perhaps you've always wondered what's in the mysterious metal box on the basement wall. It's a circuit breaker box, and without it your whole home electric system would be unsafe, leaving you in danger.

Circuit box repairs or upgrades require an expert, but you don't need to be a master electrician to understand the basics of how it functions. The most common problem is a tripped circuit, and you can usually reset it yourself.

What's in the Box?

The circuit box is frequently found in the basement, although it could also be in a garage, closet, utility room or even outside. All the electricity coming into your house flows through the box.

If you open the metal door, you see a bank of switches. Each one corresponds roughly to a room in the house, while certain outlets for major appliances like the washer or furnace probably have their own switch. They should be labeled.

There also may be a main disconnect breaker, usually at the top of the box, which allows you to cut off power to the entire house. In many newer homes the main disconnect may be outside near the electric meter. Some homes do not even have one. This is useful if you are doing electrical work in your house, or in the circuit box itself. The switch should be labeled “main” or something similar.

How It Works

Why do you need a circuit box? When an electrical device malfunctions, such as the motor in your freezer overheating, wires can get crossed, creating a huge spike in electric charge. That puts you at risk of overloading your electrical system, and unchecked overloads can cause lead excess heat stress on wires, or worse.

Fortunately, your circuit breakers are on the job. There is an electromagnet or bimetallic strip inside each breaker. If the current moving through the circuit gets too high the device flips a switch, disconnecting the circuit. No more electricity can flow to the part of your home where the problem is, so the danger is averted.

So if the power goes off in one part of your house but still works in the rest, a tripped circuit breaker is the most likely culprit. The switches in your electrical panel should be labeled; if not you can still tell which one got tripped, because it will be flipped part way toward the off position. Some switches also show red when they've been tripped.

How Do I Fix It?

All you have to do to restore power is flip the switch all the way to the off position, then back to on. If flipping the circuit back on doesn't solve the problem, it might be something more serious. In that case, it's time to call a licensed electrician.

Some newer circuit breakers have advanced features, such as the ability to detect when a person makes contact with a live wire and automatically cut off the current, potentially preventing injury or death by electrocution.

If you live in an older home you may still have a fuse box. It operates on the same principle as a circuit box, with one major difference -- the wire inside the fuse actually burns up if too much current passes through it, so if the fuse blows, you need to replace it. Most fuse-style panel are maxed out, so if you have one it would be a good idea to consult your electrician and see if it’s time to consider a replacement.

Need Some Professional Guidance?

Your local Mister Sparky® electricians are always here to help. If you're having problems with your circuit breakers or fuse box, give us a call.