Your Electrical System Is Complex
Your electrical system doesn’t have a complex, but with all those wires and components, it is complex. That doesn’t mean you can’t hope to get to know or even understand it, however. We’re going to do our best to break things down as simply as possible.
In part one, you learned about Ben Franklin’s famous kite, how we produce electricity, and how that electricity gets to your. Part two is about how the electricity safely travels from your breaker panel to your outlets and appliances. In other words, this is how the electricity the power company supplies you with actually powering your home.
Your home’s electrical system includes:
- a line or service drop
- a meter that keeps track of how much electricity you use
- the main circuit breaker panel or fuse box that protects the system from getting overloaded
- the wiring circuits to the outlets, light fixtures, and hard-wired appliances.
Let’s take a look at each component, one by one.
The service drop
A service drop is the main electrical line that runs from transmission lines to the service head at your house. It’s called a “service drop” because it’s higher than your home, so the feeder line literally drops.
Meters are usually installed outside the house so meter-readers can record your usage. Most are mechanical, with spinning wheels that display the numbers. Some newer meters are digital with an LCD screen. Either way, the meter measures electricity usage in units of kilowatt hours (kWh). To find out how much you used in one month, just take the number of kilowatt hours your meter shows today and subtract the number it displayed at the beginning of the month.
For example: If your meter reads 50,500 today and it was 50000 a month ago, then you used 500kWh this month. In 2017, the average U.S. residential utility customer used 10,399 kilowatt hours (kWh) per year. Louisiana was highest at 14,242 kWh per year, and Hawaii was lowest at 6,074 kWh.
The Main Breaker Panel
When the main electric supply line leaves the meter, it enters the home and arrives at the main circuit breaker. The bigger the main breaker, the more electricity your home gets. Most homes have 200 amps, older homes only have 100, and really large homes could have up to 400. The breaker itself functions like a power switch. If it senses an overload, it turns the power off to reduce the risk of fire or electrocution. Fuses function the same way as breakers, except they burn out instead of simply switching off.
Below the main breaker, smaller circuit breakers control electricity going to individual rooms or hard-wired appliances like your air-conditioner. At this point, your home’s 200 amps are distributed to these different areas by passing through circuits. Your kitchen probably has two 20 amp circuits or so, the bedroom has one 15 amp circuit, the air conditioner gets its own 30 amp circuit, and so on. To get more specific, on one of the two 20 amp circuits in the kitchen probably powers the lights, the outlets, and the refrigerator. The other 20 amp circuit probably powers the stove, microwave and dishwasher.
Smaller circuit breakers function the same way as the main breaker. If there’s an overload in the specific circuit attached to the small breaker, it’ll automatically turn off. That will cut off the flow of electricity to that circuit, without cutting off power for your whole home. Make sure each circuit is appropriately labeled on the inside of the main breaker panel door. That way you’ll know which breakers to flip back on (or which fuses to replace) when there’s an overload. Helpful labelling will also help you if you ever need to turn power off to a particular part of your home. It certainly helps us when we’re installing new electrical equipment!
Fuses serve the same function as breaker switches, but the way they perform that function is a bit different. If you have fuses instead of breaker switches, you won’t be able to turn power on and off quite as easily. Instead of simply toggling a switch, you’ll have to replace a burnt-out fuse after the breaker trips. When replacing fuses, make sure your new fuse has the SAME amp rating as the last fuse you used. This is important, because a 30 amp fuse cannot handle a load that needs a 50 amp fuse.
It’s like these classic lyrics from the Rolling Stones.
“And I went down to the demonstration
to get my fair share of abuse
We’re gonna vent our frustration
If we don’t we’re gonna blow a 50-amp fuse.”
Jagger’s “frustration” is overloading so much, he’s going to blow a 50-amp fuse. Mick could have used a 100-amp but, you can’t always get what you want.
Now you have your smaller circuit breakers and you need to get the electricity to each room or hard-wired appliance. For that, you have bundles of wires that snake through walls, ceilings, and floors. Each bundle has at least three wires:
1. The black wires are insulated and “hot.” They bring electricity directly from the circuit breakers.
2. The white wires are insulated and “neutral.” They carry the current back to the electrical source at the panel.
3. The bare copper wire is the grounding wire, which is included for safety.
When the black and white insulated wires are attached to outlets or switches they don’t quite connect. By plugging something in or flipping the switch, you’re completing that near-connection. When the wires connect the circuit completes and power flows into the outlet or fixture.
If the fixture is faulty, the wire is frayed, or the system is wet, the ground wire becomes the path of least resistance. Instead of following through the circuit, the current flows into the ground wire–and the actual ground. That triggers the circuit breaker to shut off or the fuse to burn out to prevent fire or electrocution.
Between parts 1 and 2, we’ve taught you all the basics of electricity. You know how it’s created, how it gets to your home, and how it powers your stuff. You also know how awesome and powerful it is. Hopefully, when you’re working on a project that includes electricity, you’ll give it the respect it deserves. Stay safe!
Remember: when it doubt, call a professional electrician. If you’re working on an electrical project or dealing with an electrical problem, EarlyBird always has your back. We can help make sure your project goes off without a hitch.