The Household Power System
Electricity flows to the appliances in your house from power lines running along the street. Before reaching your home, these wires pass through a meter box where an electric meter records your power usage.
Your home’s service panel contains a main switch and individual switches (circuit breakers) that control the flow of electricity to different circuits.
Electrical Wiring
Unlike the electricity that flows from battery-powered devices, which only has one direction of flow, household power alternates directions 60 times per second. That’s why we need a grounding system to keep electricity from flowing back toward the source.
This circuitry begins with a large metal box Household Power System with a hinged cover called the service panel, fuse box or (in older houses with fuse-controlled circuits) breaker box. It contains a main switch that shuts down the flow of power and switches (circuit breakers) that control power to individual circuits.
Each of these circuits distributes electricity to lighting fixtures, receptacles (aka outlets) and appliances. Its hot wire has black, red or some other color insulation; the neutral wire is white or bare. The neutral and ground wires connect to separate bus bars in the service panel.
Older homes may have aluminum wiring, which is less flexible than copper and can cause fires at connections between wire and devices (switches, outlets, light bulbs) or splices. This hazard has been mitigated since the introduction of an aluminum alloy that reduces conductor expansion to prevent fires, but not enough to eliminate them completely.
Electrical Outlets
An electrical outlet, or receptacle, lets you plug devices and appliances into your home’s power system. It’s where electricity comes in from the grid and then exits back out into the circuit.
Residential electricians install outlets in wall spaces around your house for you to use. They typically accept three-prong plugs and include a round third hole for the grounding wire that protects you from electric shock.
These electrical outlets are the most common type you’ll see in most homes. They support a standard 110 volt circuit and are ideal for most household devices and appliances.
This type of electrical outlet has a built-in breaker that can shut off the power to prevent dangerous arcing in the socket. Arcing can be caused by overheating appliances, hammering nails through the wiring, or rodents chewing on wires.
This type of electrical outlet is often found in bathrooms, kitchens, and laundry rooms. It monitors the current that goes into and then returns from a device Household Power System or appliance plugged in and trips the circuit if it senses that the returning current is too high.
Electrical Circuits
The power that flows through your electrical system is alternating current; it goes back and forth between the power source and your household items 60 times per second. There are two wires that carry this energy: a hot conductor and a neutral one. The hot conductor powers switches and outlets in your home, and the neutral conductor carries electricity back to the service panel. A third, or grounding, wire adds critical protection against electric shock and fire.
Most residential electricity systems have a voltage of 120 volts with a frequency of 60 Hz. Some homes may be supplied with 240-volt circuits using both the hot and neutral wires; these are required for some large appliances, such as electric water heaters and clothes dryers.
If too much current passes through a wire, it can overheat and melt the insulation. This is a serious hazard and could cause a fire or injury. The electrical system contains circuit breakers and fuses that protect the wires by shutting off power if they overheat. See The Path of a Circuit to learn how these safety devices work.
Electrical Breakers
All the wiring in your house runs through a central panel (or fuse box panel for older houses) with a dozen or more circuit breakers. Circuit breakers are rated based on how much current they can safely carry. If they ever see a current higher than their ratings, they interrupt it to prevent electrical fires.
Most of the time, a breaker trips due to overloading (too many things drawing power on one circuit) or a short circuit (two wires that have made contact). Some circuit breakers are AFCI, which protect against additional fire hazards like arc faults.
Fuses were common in older service panels, but today new homes use circuit breakers instead. Your service panel has a main switch that shuts off all the electricity coming in, and a series of individual switches (circuit breakers) for each of its circuits. Breakers that feed receptacles are usually rated at 15 or 20 amps, while larger “double-pole” breakers have higher amperage ratings for appliances like stoves and clothes dryers. When you need to reset your breaker panel, start by shutting off the single-pole breakers first, then double-clicking the main breaker on again.
Backup Power
Ms Henderson knows that frequent power outages aren’t just frustrating, but can also be life-threatening. That’s why she has a home backup system in place, to keep her lights and fridge on.
There are different kinds of home backup power systems, from a generator that runs on gas to battery-based solutions that use solar energy to create electricity in the event of a grid outage. The size of a backup power system depends on how much electricity you want to use during an outage and how long you need it to last. The key is to add up all the electrical appliances in your household and check that this peak demand is lower than the backup power capacity of your solution.
Lumin’s smart energy storage solution provides both backup power and load management all in one, using responsive technology that reacts to a variety of energy conditions across the house including grid outages, circuit schedules, demand limits and battery charge state. It also allows you to reconfigure your power backup plans on the go from a smartphone app and offers more ways to save energy costs in your house.