Circuits, Outlets, And Cords: How Power Capacities Interact
Posted on: 24 December 2018
The number of personal electronic devices in use today means that everyone has to have power cords plugged into most outlets in their homes and offices. Unfortunately these outlets aren't always placed in the most convenient spots, leading people to put as much as they can on certain outlets. If you grew up in a family where you were taught basic electrical safety, you know how to do that correctly, but if you didn't learn much about how power cords and outlets work together, here's your chance. The circuits, outlets, and power cords you use all have an effect on what you can use and what you should get if you need to buy spare power cords.
Total Power Available on the Circuit
Your home allows in a certain amount of power, listed in amperes, or amps. These amps are divided up by circuits. In most homes now, you'll have a circuit-breaker box that holds all the switches that control the power to individual rooms (much older homes may still have fuse boxes). You'll see that certain areas are lumped together on one circuit while other rooms have a couple of circuits.
For example, you may see that all the outlets in your bedroom are on one circuit, the living room and hallway are on another circuit, and your kitchen has three circuits (major appliances like the refrigerator usually have a dedicated circuit that is separate from the general circuit running to other outlets). Each circuit can't provide any more than what it's been set up for -- a 20-amp circuit provides only 20 amps total, and if you try to draw more, you'll trip the breaker and the power will go out. So on one circuit, all the outlets draw from a pool of 15 or 20 amps.
What the Outlet Can Deliver
Each outlet on the circuit is itself rated to allow a certain number of amps through, either 15 or 20. So if you have a 15-amp outlet installed on a 20-amp circuit, you can get only 15 amps total through that outlet. But you can draw 20 amps total from all the outlets on that circuit.
It's easy to tell which one you have; 20-amp outlets have a slightly different pin configuration. You'll see the basic hot-neutral-ground three-prong setup, but the neutral pin -- the big one on the left -- will have a horizontal slot aded on, making the opening look like a sideways T. So you never have to worry about accidentally putting a 20-amp appliance into a 15-amp outlet as it simply won't fit.
What the Cord Can Handle
Then you have the load for the cord, which, like outlets, allows a certain amount of power to be drawn from the cord. For specific power cords to items like computers, the cords will be rated for the power drawn by that specific computer. For general cords, like surge suppressors and extension cords, you'll again have a specific rating like 15 amps. That means you can draw only a total of 15 amps through that cord.
This sounds complicated at first, but once you get used to the names and numbers -- and once you create an outlet and circuit map for your home -- all you really need to know is that the power draw should not exceed the cord, outlet, and circuit numbers. If you're not sure what type of cords to get, ask an electrician or the staff at a home improvement or hardware store.
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