The electrical system in your home is quite complicated; it is made up of many individual circuits that supply power to different rooms or different parts of the house. Most of the circuits provide electricity to the lights and power outlets in each room or area. However, all homes also have at least a few dedicated circuits that only power a single appliance. In this guide, we’ll explain which appliances are typically on a dedicated circuit, as well as how to know if you need to move certain appliances to a new dedicated circuit.
Understanding 120-Volt and 240-Volt Circuits
Electrical systems in the United States are 120 and 240 volts. The majority of the circuits in a home are 120 volts. This includes all of the circuits that supply electricity to your lighting and power outlets. Modern residential electrical systems usually have at least two or three 240-volt circuits, depending on the size of the home and how many high-power appliances it has.
The National Electric Code requires that all 240-volt appliances be on a dedicated circuit. If your home has central air conditioning, the AC compressor or heat pump will function on an independent 240-volt circuit. If you have central AC and central heating with a gas furnace, the furnace will often be wired to the same circuit as the AC unit. If you only have central heating, the furnace will likely be on a dedicated 120-volt circuit instead.
Electric furnaces, electric water heaters, electric clothes dryers, and electric ranges and ovens all run on 240 volts as well. This means each one needs a dedicated circuit. If you have a hot tub or home EV charging station, they will also be on a 240-volt dedicated circuit.
Which 120-Volt Appliances Require a Dedicated Circuit?
Other than the stove and oven, most of your other kitchen appliances, like the refrigerator, freezer, dishwasher, and microwave, usually run on 120 volts. One possible exception is your dishwasher, as some large, high-end models have 240 volts.
Despite the fact that refrigerators, standalone freezers, and most dishwashers are only 120 volts, they should still be wired to a dedicated circuit. If the refrigerator shared a circuit with other things in your kitchen, it would often draw so much power that it would overload the circuit and cause the breaker to trip. Compact or countertop microwaves can sometimes share the same circuit as the lights and outlets in the kitchen, as they typically draw 700 watts at the most. Larger or built-in microwaves draw a minimum of 1,000 watts, so it’s always best that they are on a dedicated circuit.
Washing machines are also only 120 volts, but they still need to be on a dedicated 20-amp circuit. The reason for this is that washing machines and other more powerful appliances like AC units and refrigerators require much more current when starting. This extra current draw is known as the start-up load. It is typically around three times as high as the running load, or how much current it draws when running.
Understanding Watts, Amps and Volts
All 120-volt circuits are either 15 or 20 amps. Most 240-volt circuits are either 30 or 50 amps, but you’ll occasionally see some that are only 15 or 20 amps or as high as 60 amps. The amperage and voltage of a circuit determine how many watts of electricity it can safely supply without being overloaded and causing the circuit breaker to trip. To determine how many watts a circuit can provide, all you need to do is multiply its amperage by its voltage.
A 120-volt, 15-amp circuit can technically provide 1,800 watts of electricity. However, if the current ever spiked above 1,800 watts, the circuit breaker would instantly trip. This is why you should never exceed 80% of a circuit’s maximum capacity, which means you never want to pull more than 1,440 watts at one time on a 120-volt, 15-amp circuit. A 120-volt, 20-amp circuit can provide 2,400 watts, but you never want to exceed 1,920 watts to be safe.
It’s important to understand that some kitchen appliances can draw more watts than their ratings shows. For instance, a 1,000-watt microwave can sometimes draw around 1,500 watts when cooking on full power. Even though your main kitchen circuit is usually 20 amps, the microwave could still easily overload the circuit if you tried to run it at the same time as another appliance. In fact, this could even happen if you ran the microwave when all of your kitchen lights were on. Though, this depends on how many lights you have and what type of bulbs they use.
A double-door refrigerator and freezer typically uses somewhere between 350 and 800 watts. However, its peak power draw or start-up load can sometimes be as high as 15 amps (1,800 watts). This means it could easily trip the breaker if it wasn’t on a dedicated 120-volt, 20-amp circuit.
How to Prevent Overloads and Other Electrical Issues
If you frequently have issues with a circuit breaker tripping when you run the vacuum or use a hair dryer, it means that that particular circuit is overloaded. You’re trying to draw too much power at once. This usually happens because you have too many things plugged in and turned on at one time. This can include a TV, stereo, lights, computer, etc. In this case, you can try to unplug everything and see if the breaker trips a second time.
A breaker that keeps tripping even when you’re not trying to power many things on that circuit can indicate that there is a damaged wire or loose connection that is causing a short circuit. This is something you’ll want to have an electrician check out immediately, as a short circuit can easily cause a fire.
If your microwave keeps causing the breaker to trip, the only real solution is to have an electrician run wires from the electrical panel. Then, the installation of a new dedicated circuit that only powers the microwave can take place. As long as there is room in your electrical panel for an additional circuit and circuit breaker, installing a new circuit is usually a fairly simple task. Having a dedicated circuit will also make your home safer. This is because overloading a circuit can cause the wiring to become extremely hot and potentially cause an electrical fire.
Many homes also have issues with things like lights dimming or a TV flickering when the AC first turns on or when they start the dryer. If you notice these issues, it indicates that your electrical service doesn’t have sufficient amperage. You may need to upgrade to a higher-amp service panel. Older homes usually only have a 100-amp service panel, whereas most newer homes have 150-, 200-, or even 400-amp panels.
The amperage of your service panel dictates how many total amps or watts your electrical system can supply at any given time. If you only have 100-amp service, the start-up load can use so much of the available current that it leads to less power temporarily flowing through the other circuits. This power drop is what can cause issues like a flickering TV or dimming lights.
If you need to install a new dedicated circuit in your home or upgrade your electrical panel, you can count on the expert electricians at Potts Electric for help. We are a local, family-owned company. We’re ready to help if you need an electrical inspection or any electrical installation or repair services in Ellisville or the St. Louis Metro area. No matter what type of electrical service you need, give us a call to get the expert help your home deserves.