A simple way to tell if a main circuit breaker is bad

By
Real Estate Agent with DeLex Realty

On most electrical panels there is a main breaker. The main breaker does as the name implies, it is a main disconnect for the entire panel board. Today, this breaker is typically 200 amps or more and is normally located at the top of the electrical panel or on the bottom.

A home electrical panel is made of two bus bars located behind the circuit breakers. Each of these bus bars are 110 volts and are a separate phase. If you were to look at the power on an oscilloscope, you would see the two phases are exactly 180 degrees out of phase. This is how you make 220 volts, by using the two phases.

Often when a main breaker fails, only one phase is effected by the failure. Thus it is not uncommon to have power to one half of the house. When one finds power to have of the house a simple way to check if it is a lost phase is to turn on the electric stove, if a phase has been "lost" the other half of the 110 volt outlets in the home will begin to work. The reason is the power is passing through the elements on the stove and to the un-powered phase in the electrical panel. When this occurs there can only be two possible causes, either the power company lost a phase coming into the panel or the main breaker has gone bad.

Posted by

James (Jim) Lord

jim@jimlordregroup.com

www.jimlordregroup.com

480-648-3378

Comments (2)

Anonymous
Ned

I spent the better part of the weekend dealing with this exact issue. I installed some new kitchen lights and a dimmer switch. It worked for a while, then I lost the electricity in several rooms of my house. After troubleshooting everything I could think of, from searching for a short to replacing an old stuck breaker, I fired up my dryer just out of curiosity. And that's when the dead half of my outlets and lights came back to life. I turned off the dryer and did the math: I must have lost half of my outlets, which meant one of the two legs of my panel wasn't getting power. As you point out, there can only be two causes: either the power company lost a leg, or half of my main breaker was defective. I very carefully (rubber gloves and electrical tape to mask off nearby terminals and buses) removed the main breaker and reinstalled it up side down. The dead outlets came back, and the ones that were live went dead. Bingo! I knew it was the main breaker. Best I can figure, the new lights overloaded the very old main breaker, but it wouldn't reset properly. I installed a new one and everything is back to normal. I wish I'd found your article sooner. Thanks anyway!

Feb 04, 2018 10:35 PM
#1
Anonymous
Gregory Allen Hudson

That really helps me I'm sitting here with the dryer running so I can watch tv. Just started washing a comforter to last till I find a meter and home depot opens you save me hundreds. Thanks

May 15, 2020 09:38 PM
#2