What Is the Difference Between a 120V and 240V Breaker?

What Is the Difference Between a 120V and 240V Breaker?

In Ontario, residential electrical service is single-phase 240V. The panel’s two hot buses each carry 120V to neutral — devices that operate at 120V connect to one hot bus, while 240V devices connect to both hot buses simultaneously. The type of breaker determines which voltage a circuit operates at.

120V Breakers (Single-Pole)

• Occupies one slot in the panel and connects to one hot bus bar — provides 120V between the hot and neutral conductors
• Used for standard lighting circuits, outlet circuits, and appliances that plug into standard outlets
• Common sizes: 15A (lighting and general outlets) and 20A (kitchen counter, bathroom, laundry)
• The circuit cable carries one hot, one neutral, and one ground — typically NMD-90 14/2 or 12/2

240V Breakers (Double-Pole)

• Occupies two adjacent slots and connects to both hot bus bars — provides 240V between the two hot conductors
• Used for electric ranges, dryers, electric water heaters, air conditioners, EV chargers, hot tubs, and baseboard heater circuits
• Common sizes: 30A (dryer, EV Level 2 charger), 40A (range), 50A (larger EV chargers, hot tub), and higher
• The circuit cable carries two hots, one neutral (for appliances that need 120V functions like oven lights), and one ground — typically NMD-90 10/3 or 8/3 depending on amperage
• A double-pole breaker physically ties both poles together so that a fault on either leg trips both simultaneously

Any new 240V circuit requires an ESA permit in Ontario. EZSMART installs 240V circuits for EV chargers, ranges, dryers, hot tubs, and other high-demand appliances across Ontario. Contact us for a quote.

Amir Azimipour

Electrician Since 2008 Journeyman Electrician Designated Master Electrician at EZSMART Corp