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To connect home electrical wiring from a house panel to a garage panel, follow these steps:
1. Determine the power requirements: Calculate the total electrical load for the garage panel to ensure it doesn’t exceed the capacity of the house panel.
2. Install a subpanel in the garage: Mount a subpanel near the main house panel, ensuring it’s properly grounded.
3. Run electrical cables: Use appropriate cables, such as NM-B or THHN, to connect the subpanel to the house panel. Run the cables through conduit for protection.
4. Make connections: Connect the hot wires (black or red) from the house panel to the corresponding breaker in the subpanel. Connect the neutral wires (white or gray) and the ground wires (green or bare) to their respective bus bars.
5. Test the connection: Before turning on the power, double-check all connections and tighten them securely. Use a voltage tester to ensure there’s no electricity flow before working on the wiring.
By following these steps, you can safely connect home electrical wiring from a house panel to a garage panel. Always consult a licensed electrician if you are unsure about any part of the process.
Many homeowners utilize their garage for more than just parking cars. It often serves as storage for a water heater, extra refrigerator or freezer, garage door opener, and sometimes even a workshop. Due to the circuitry required for these functions, as well as the lights, it is a wise decision to install a garage subpanel.
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When planning the installation of a subpanel, there are two factors to consider. The first is the size of the panel, which includes its capacity for circuit breakers and its current rating. The second consideration is the distance between the main panel and the subpanel, as this determines the size of the cable used to connect them. The subpanel can be located inside the garage or on an exterior wall. If it is installed outside, a waterproof panel enclosure rated for exterior use is necessary.
Determining the Size of the Breaker Box
During the planning process of the subpanel installation, it is important to calculate the expected load. The National Electrical Code provides a calculation form for this purpose. This process is similar to doing your taxes. The basic idea is to measure the square footage of the area that the subpanel will serve and multiply it by 3 watts to account for lighting. Additionally, include a minimum of two 1,500-watt appliance circuits (or more if necessary) and the power draw in watts of each large appliance that is permanently wired to the panel. This information can be found on the label attached to each appliance.
After adding up the total power draw, divide it by 240 volts. Round up the resulting amps of current to the nearest breaker size. For example, if the result is 42 amps, a 50-amp breaker is required in the main panel to serve the subpanel. Additionally, a panel rated for that amount of current must be purchased. If unsure, consult the NEC’s load calculation form or seek advice from an electrician.
Choosing and Installing the Cable
The subpanel is connected to the house electrical wiring through a double-pole breaker in the main panel. The size of this breaker is determined by the current draw, as explained above. The wire gauge of the cable used to connect the subpanel to the main panel depends on the size of the breaker and the distance between the panels. In general, a 30-amp subpanel requires 10-gauge wire, a 40-amp subpanel requires 8-gauge wire, and a 50-amp subpanel requires 6-gauge wire. For a 100-amp subpanel, thicker 3- or 4-gauge cable with a 6-gauge ground wire is needed.
Over longer distances, voltage drop becomes a concern, typically occurring after 100 to 150 feet, depending on the cable size. If cable needs to be run for a longer distance, it is recommended to upgrade to the next wire gauge.
UF cable can be directly run in a 24-inch-deep trench, but it must pass through a vertical PVC conduit that extends at least 18 inches into the ground on both ends. The conduit must have waterproof connections to the walls or panels it passes through.
Installation of the Subpanel and Circuit Breaker
The metal panel enclosure can be installed on any stable vertical surface, as long as there is a clearance of at least 3 feet in front and on either side. The panel should be easily accessible and ideally not more than 5 feet above the ground.
The subpanel is controlled by a double-pole breaker, which takes up two slots in the main panel. If the main panel is overloaded, it may be necessary to rearrange the breakers to create more space. Wiring the circuit breakers is not complex, but it can be dangerous. It is recommended to hire an electrician to handle this aspect of the panel installation.
