Preparation

• 1). Cut and mount a plywood backer for the sub panel to two studs, unless the sub panel will be mounted between two studs. The backer board should be wide and high enough to accommodate the sub panel and to mount cable straps to for each cable entering the sub panel.
  
  
• 2). Attach the sub panel to the plywood backer or mount it between two studs with screws. Remove a convenient knockout disk from the sub panel by holding the point of a screwdriver against it and tapping the screwdriver with a hammer. Grasp the disk with a pliers and twist it free. Install a cable clamp in the hole.
  
  
• 3). Remove a convenient knockout disk from the main panel box and install a cable clamp in the hole.
  
  
• 4). Position the work light to shine directly on the main circuit breaker panel. Turn off the main circuit breaker by moving it to the off position. Remove the main panel cover screws and set the cover aside. Note the two large wires coming into the panel and attaching to the large lugs near or on the main breaker. These wires and lugs are live even when the main is turned off. Never touch these lugs.
  
  

Installation

• 1). Install the double pole breaker on the main panel at two unused adjacent positions. Fit the mounting tabs on the breaker onto the panel mounting flange and press the breaker into place on the copper bus bar tabs. Move the new breaker to the off position.
  
  
• 2). Remove enough sheathing from the cable so that the wires may be routed inside the box in the same fashion as existing wires. Insert the cable through the cable clamp so that at least 1/2 inch of sheathing is inside the panel box. Tighten the clamp firmly, but not so the cable is crushed. Repeat this step at the sub panel, neatly routing the cable to it. Fasten the cable in place with cable straps within 12 inches of the boxes and every 4 feet thereafter.
  
  
• 3). Route the bare ground wire neatly to the ground bus bar in both panels. After routing the wire neatly, trim it to length and insert it into an empty hole on the bus bar. Note that in the main panel, the white neutral wires and the ground wires may both use the same bus. This is not true in the sub panel. Tighten the bus screws firmly to hold the wire in place.
  
  
• 4). Route the white neutral wire to the neutral bus in the main panel. Trim the wire to length, strip 3/4 inch of insulation from the end and insert it into a hole in the bus. Tighten the bus screw firmly. Repeat this step at the sub panel, keeping the neutral and ground bus bars separate.
  
  
• 5). Connect the two colored wires in the sub panel to the two panel lugs. Route the wires neatly, trim to length and strip 3/4 inch of insulation from the wires and insert them into the lugs. Tighten the lug screws firmly.
  
  
• 6). Route the colored wires in the main panel to the new double pole breaker. Trim to length, remove 3/4 inch of insulation and attach one wire to each terminal. Tighten the terminal lug screws firmly.
  
  
• 7). Remove two breaker knockouts from the panel cover to accommodate the new double pole breaker. Replace the cover on the main circuit panel and install all the screws. Verify the new double pole breaker is in the OFF position and turn on the main circuit breaker.