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I just bought my first house and found that all of the breakers in the circuit breaker box are not marked. what is the best way to find out which breaker goes to what outlet in my house?
There are a few ways to determine the circuits. I like to create a map of the entire house with all the electrical devices shown in their current location. That way I can label the devices with the circuit number. Also, as I determine the circuit number, I remove the device cover and label the back side of the cover with the circuit number.
FIrst step is to make sure that all the devices are energized. Use a multi-meter for this. It is easier with two people, or you do a lot of walking. In the breaker box, you can easily pick out the 240 volt circuits. There are only a few items in a house that use 240 volts. Electric oven(s), electric stove, electric clothes dryer, electric water heater are the most common appliances. So these circuits can be labeled first. Turn off the breaker, one breaker at a time, verify the appliance, and then label the panel, the house layout map and the device cover. Turn the breaker on, and move to the next. I use either a label machine, or have small, permanent labels made for my electrical panels. I have more than one electrical panel in my house. I have a 600 amp service, so I have 3 panels, and a lot of labels.
For the other devices thoughout the house, It is easy if you can plug in a lamp, radio, or something electrical into every outlet. Turn off one single pole breaker, walk thru the house to find the item that is no longer energized. Look for other outlets near this one, Use a multi-meter to verify that the device is not energized. Turn the breaker on, then verify the same device(s) to verify that the device is energized once again. Label your house map with the circuit number, label the back side of the cover on the device. I would wait to label the entire panel until last. You may decide on a different naming convention, or size of the letters to use. Repeat this same process thru the entire house making sure that you check each and every device.
You may also use another method. If you have, or want to purchase a telcom "toner and wand" you can use this to verify every device and circuit. It is a little faster because you will not have to actually test every single device. The toner creates a distinct tone and the wand allows one to hear that tone. This will require that you turn off power to the entire house, remove the panel cover so that the breakers and all wiring the panel are exposed. Create a plug from an extension cord, leave the wires on the plug exposed and stripped. Attach the toner to the wires, it does not matter what one goes to what, and plug the toner into the outlet. You Must ensure that the power at least to that circuit is off, it is easier if you turn off the main breaker. Go to the breaker box, and run the wand down the breakers close to where the wires are connected. You will eventually hear the tone that the tone generator is producing. Label your circuit map. Go to the outlets that are close to this one, and place the wand against the outlet, you should hear the tone there as well. Repeat at each outlet that is close. There may be lights on the same circuit, so you will hear the tone there as well.
The best, and most relaible means is to use a multi-meter and the same extension cord plug with the wires stripped. This will also be done with the power to the house off. Twist the two conductors together, do not include the ground wire. Plug the plug into an outlet, go to the breaker box with the cover removed, place one probe of the multi-meter on the neutral bar, and the other on a single pole breaker. Move the probe to another breaker until you find continuity. The needle on the meter will move, or the digits will change, showing the amount of resistance. It is the same as touching the two probe ends together. Label your house map with the circuit number, move the next outlet device and verify that one the same way.
Once you get every device verifed with a circuit number, make sure that you have all breakers are accounted for that have a wire attached. I just re-wired our house replacing the original 60 amp service with 600 amp service. I was able to label everything on paper first, and then it was simple to pull the correct circuit.
Handy Andy In Mt Airy NC
Get a plug-in Radio. Plug it into an outlet , turn on to favorite station and loud enough to be heard at the breaker box. Start turning off breakers until the raidio turns off. Same thing can be done for light fixtures with the use of a light socket receptacle adapter.