Main Circuit Breakers

Main breakers are the breakers that disconnect electricity to all the branch circuits in the panel, and hence to the entire home, usually. I say usually because some panels have what is called a ‘split-bus’, or a solar system installed. I’ll discuss those below. Branch circuits are all the branches of the electrical system that power different areas of your home and each branch circuit has its own circuit breaker.

Main breakers come in a number of different sizes. Older homes may have had 70 amp main breakers, but these are rare. The standards today are 100, 125, 150, and 200 amp mains. You’ll find 100 amp service in smaller homes or condos, 150 amp service in many homes built in the 1970’s through today. If a home is very large or is designed to have a large electric load, like a home with electric heat, you’ll see a 200 amp main breaker.

In houses you’ll usually find the main breaker inside the electrical panel with all the branch circuit breakers. If you live in a condo or town home you will often find no main breaker in the electrical panel for that unit, it will be in a central location where all the electric meters are for the rest of the units in the building.

Sometimes you will even find homes with no main circuit breaker. This was done in the ‘old days’, 1960’s and before. My first home built in the 1960’s was like this. This is not done today as electric code requires there be no more than 6 ‘throws’ to turn off all the electricity in the home. A ‘throw’ is usually 1 circuit breaker, but it can be two breakers if their switches are tied together so the turn on and off together. Breakers that are tied together in this way are usually for high voltage circuits for dryers, water heaters, etc.

Split Bus Main Breakers

Some main panels contain what is called a split bus. This is where several breakers are plugged into a bus (normally in the top of the panel) that is directly connected to the power company with no main breaker to protect them. Then there there is another bus (usually a lower section) that is protected by a breaker in the first section. Hence the name split-bus. The top section usually has breakers in it for 240 volt appliances like your dryer, range, water heater (if electric). The bottom bus contains breakers that serve all the 120 volt devices in your home like lights, outlets, dishwasher, etc. The breaker in the top section that controls all of the breakers in the lower section can be considered the main breaker, but you also need to know to turn off all the other breakers in the top section to turn off all electricity to the home.

These split-bus panels were common many years ago, but this system is no longer used. There’s generally no problem with this type of panel but it’s helpful to know if your home has one because to turn off all the power to the home all you have to do is turn off the breakers in the top section in the panel.

Solar System Installed

If a home has a solar system the main breaker only cuts off power from the power company. It doesn’t cut off electricity coming in from the solar system. To do this you need to find a circuit breaker amongst all the other breakers in the panel that is labeled ‘solar system’ in some way, and turn it off. Before working inside an electrical panel always test with a voltage sniffer that power is actually off.

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