What is the proper way to wire a sub-panel from the main panel?
2 Answers
Wiring a sub-panel from a main panel requires careful attention to electrical safety and code compliance. Here’s a detailed step-by-step guide for wiring a sub-panel properly:
### 1. **Plan the Installation**
- **Determine the sub-panel's purpose**: Identify what the sub-panel will power (e.g., a garage, workshop, or additional circuits).
- **Choose the right sub-panel**: The sub-panel’s amperage rating must match the load it will carry. Typically, sub-panels are rated at 50, 60, 100, or 125 amps.
### 2. **Turn Off Power**
- **Shut off power** to the main panel before working. This is critical for safety.
- **Test with a voltage tester** to ensure there’s no live electricity where you’ll be working.
### 3. **Select the Correct Breaker**
- You need to install a **double-pole breaker** in the main panel that corresponds to the amperage of the sub-panel (e.g., if installing a 60-amp sub-panel, use a 60-amp breaker).
- Make sure the breaker matches the main panel’s brand and type for compatibility.
### 4. **Choose the Proper Cable**
- Use appropriate-sized wires for the sub-panel's load. Common wire sizes for copper conductors are:
- **60-amp sub-panel**: Use 6-gauge wire.
- **100-amp sub-panel**: Use 4-gauge wire.
- **125-amp sub-panel**: Use 2-gauge wire.
- The wire should have four conductors: two hot wires, one neutral wire, and one ground wire.
### 5. **Run the Cable to the Sub-Panel**
- **Route the wire** from the main panel to the sub-panel. Use an appropriate path (such as through walls, ceilings, or conduit) and ensure the wire is protected from damage.
- **Conduit protection**: If the wire runs outside or underground, it must be protected in conduit.
### 6. **Install the Sub-Panel**
- Mount the sub-panel in a location that’s easily accessible and compliant with local codes (typically 48" to 72" from the ground to the top of the panel).
- Ensure the sub-panel is securely mounted and level.
### 7. **Connect Wires to the Main Panel**
- **Neutral wire**: Connect the neutral wire (white) to the neutral bus bar in the main panel.
- **Ground wire**: Connect the ground wire (bare copper or green) to the ground bus bar in the main panel.
- **Hot wires**: Connect the two hot wires (usually black and red) to the double-pole breaker installed in the main panel.
### 8. **Connect Wires to the Sub-Panel**
- In the sub-panel, there are two bus bars: one for neutral and one for ground.
- **Neutral wire (white)**: Connect to the neutral bus bar in the sub-panel.
- **Ground wire (bare or green)**: Connect to the ground bus bar in the sub-panel.
- **Hot wires (black and red)**: Connect to the main lugs or the main breaker in the sub-panel.
- **Important**: In a sub-panel, the neutral and ground must be separated. Ensure the neutral bus bar is isolated from the ground.
### 9. **Bonding the Ground Bar**
- The **ground bus bar** in the sub-panel should be bonded to the metal sub-panel case.
- The **neutral bus bar** should **not** be bonded to the case in the sub-panel. There should be no electrical connection between neutral and ground in the sub-panel.
### 10. **Check Circuit Breakers and Wiring**
- Install individual circuit breakers in the sub-panel as needed for the new circuits.
- **Double-check** all connections to ensure they’re tight and correct.
### 11. **Turn on the Power**
- Turn the main breaker back on at the main panel.
- Flip the breaker that feeds the sub-panel.
- Test the sub-panel with a **voltage tester** or multimeter to ensure it’s receiving the correct voltage (typically 240 volts between the two hot wires and 120 volts between each hot and neutral).
### 12. **Inspection and Compliance**
- Before using the sub-panel, it’s important to have the installation **inspected** by a licensed electrician or local building inspector to ensure it complies with the local electrical code.
### Key Considerations
- **Grounding**: If the sub-panel is in a separate building, install a grounding rod and connect it to the sub-panel ground bus bar.
- **Ampacity**: Ensure the wire gauge and breaker size are adequate for the sub-panel's load.
- **Clearance**: Ensure sufficient space around the sub-panel for working and ventilation.
This process is designed to follow **NEC (National Electrical Code)** standards, but always consult local building codes for additional requirements or variations.
### 1. **Plan the Installation**
- **Determine the sub-panel's purpose**: Identify what the sub-panel will power (e.g., a garage, workshop, or additional circuits).
- **Choose the right sub-panel**: The sub-panel’s amperage rating must match the load it will carry. Typically, sub-panels are rated at 50, 60, 100, or 125 amps.
### 2. **Turn Off Power**
- **Shut off power** to the main panel before working. This is critical for safety.
- **Test with a voltage tester** to ensure there’s no live electricity where you’ll be working.
### 3. **Select the Correct Breaker**
- You need to install a **double-pole breaker** in the main panel that corresponds to the amperage of the sub-panel (e.g., if installing a 60-amp sub-panel, use a 60-amp breaker).
- Make sure the breaker matches the main panel’s brand and type for compatibility.
### 4. **Choose the Proper Cable**
- Use appropriate-sized wires for the sub-panel's load. Common wire sizes for copper conductors are:
- **60-amp sub-panel**: Use 6-gauge wire.
- **100-amp sub-panel**: Use 4-gauge wire.
- **125-amp sub-panel**: Use 2-gauge wire.
- The wire should have four conductors: two hot wires, one neutral wire, and one ground wire.
### 5. **Run the Cable to the Sub-Panel**
- **Route the wire** from the main panel to the sub-panel. Use an appropriate path (such as through walls, ceilings, or conduit) and ensure the wire is protected from damage.
- **Conduit protection**: If the wire runs outside or underground, it must be protected in conduit.
### 6. **Install the Sub-Panel**
- Mount the sub-panel in a location that’s easily accessible and compliant with local codes (typically 48" to 72" from the ground to the top of the panel).
- Ensure the sub-panel is securely mounted and level.
### 7. **Connect Wires to the Main Panel**
- **Neutral wire**: Connect the neutral wire (white) to the neutral bus bar in the main panel.
- **Ground wire**: Connect the ground wire (bare copper or green) to the ground bus bar in the main panel.
- **Hot wires**: Connect the two hot wires (usually black and red) to the double-pole breaker installed in the main panel.
### 8. **Connect Wires to the Sub-Panel**
- In the sub-panel, there are two bus bars: one for neutral and one for ground.
- **Neutral wire (white)**: Connect to the neutral bus bar in the sub-panel.
- **Ground wire (bare or green)**: Connect to the ground bus bar in the sub-panel.
- **Hot wires (black and red)**: Connect to the main lugs or the main breaker in the sub-panel.
- **Important**: In a sub-panel, the neutral and ground must be separated. Ensure the neutral bus bar is isolated from the ground.
### 9. **Bonding the Ground Bar**
- The **ground bus bar** in the sub-panel should be bonded to the metal sub-panel case.
- The **neutral bus bar** should **not** be bonded to the case in the sub-panel. There should be no electrical connection between neutral and ground in the sub-panel.
### 10. **Check Circuit Breakers and Wiring**
- Install individual circuit breakers in the sub-panel as needed for the new circuits.
- **Double-check** all connections to ensure they’re tight and correct.
### 11. **Turn on the Power**
- Turn the main breaker back on at the main panel.
- Flip the breaker that feeds the sub-panel.
- Test the sub-panel with a **voltage tester** or multimeter to ensure it’s receiving the correct voltage (typically 240 volts between the two hot wires and 120 volts between each hot and neutral).
### 12. **Inspection and Compliance**
- Before using the sub-panel, it’s important to have the installation **inspected** by a licensed electrician or local building inspector to ensure it complies with the local electrical code.
### Key Considerations
- **Grounding**: If the sub-panel is in a separate building, install a grounding rod and connect it to the sub-panel ground bus bar.
- **Ampacity**: Ensure the wire gauge and breaker size are adequate for the sub-panel's load.
- **Clearance**: Ensure sufficient space around the sub-panel for working and ventilation.
This process is designed to follow **NEC (National Electrical Code)** standards, but always consult local building codes for additional requirements or variations.