Connecting two lights controlled by two separate switches to one branch circuit is a relatively easy project even for the new DIY electrician. The most difficult part of this project will be routing the individual "Switch Legs," the cables carrying the power from the switches to the lights they control. Routing wire through finished walls and floors can be challenging for even the experienced electrician so I will assume that you are installing these circuits in a new room addition where the framing is still exposed.
Mount the double-gang device box 46-inches above the finished floor. The NEC doesn't specify a specific height for switches but 46-inches is standard. Mount the box so that the front lip of the box will be flush with the finished wall surface. This is required by Article 314.20 of the NEC.
Mount the lighting outlet boxes where the fixtures are to be located per Article 314.20 of the NEC.
Route the cable from the service panel to the 2-gang device/switch box.
Route the cables from the 2-gang device box to the individual lighting outlet boxes.
When routing NMC through hole drilled through framing members, the front edge of the hole must be at least 1 and ¼-inches from the nearest edge of the framing member; if this depth can't be maintained a 1/16-inch thick steel nail plate must be installed on the framing member per NEC Article 310.4.
When routing NMC along the sides of framing members the front edge of the cable must be at least 1 and ¼-inches from the nearest edge of the framing member per NEC Article 310.4.
Support the cable within 12-inches of each box with a cable staple or strap and at a maximum 4 and ½ foot intervals between boxes, per NEC Article 334.30.
Using the cable ripper, remove the jacket from the cable leave ¼-inch of the jacket intact where it enters each box. Using the diagonal pliers or razor knife, remove the slit jacket from the cable. Cut the individual conductors so that there's 6 to 8-inches of free conductors in each box per NEC Article 300.14.
Cut two 6-inch lengths of Black wire to use as pigtail splices at the 2-gang device box.
Strip ¾-inches of insulation from both ends of these pigtails.
Using the needle nose pliers, form a loop in one end of each pigtail.
Using the Lineman pliers, form a three way splice with the black conductor bringing power into the device box by twisting them together in a clockwise direction. Once the conductors are twisted together, screw a yellow wire nut over the splice. Check to be sure that no bare copper is exposed outside the wire nut. If necessary remove the wire nut and trim the splice as needed until no bare copper shows. Wrap the splice with tape for extra protection.
Using the Lineman's pliers, splice the three white, neutral conductors together. After screwing on a wire nut and taping the splice as you did above, fold this splice into the back of the device box as far as possible.
Cut two pieces of bare copper grounding conductor and make a 5-way splice with the three grounding conductors entering the device box. Form a clockwise loop on the opposite ends of the pigtails.
Form a clockwise loop on the two remaining black conductors that are part of the two switch legs.
Attach the two grounding pigtails to the green grounding screws on the switches.
Attach the two black pigtails bringing power to the switches to the bottom brass screws on the switches.
Attach one black wire from the switch legs to each switch.
Wrap the switches with tape for extra protection.
Secure the switches in the box.
Remove the cover and trim of the service panel.
Install the 3/8-inch cable connector in an available knockout in the panel and carefully route the cable inside the panel. Use caution here. Remember you are working on a live service panel.
Install the new CB.
Strip off the cable jacket and route the white, neutral conductor down to the panel's neutral bar. Cut it to length. Strip off ¾-inches of insulation and fasten securely to the neutral bar. Repeat this step with the bare neutral conductor. If you installed this circuit into the main service panel and not a sub-panel, the neutral bar is bonded to the panel ground bar so the bare grounding conductor can be connected to either bar. If you are working with a sub-panel, the neutral bar is isolated from the grounding bar so the bare conductor must be attached to the grounding bar to meet Code requirements.
Install the panel trim and cover.
Tape the CB in the off position until you have installed the light fixtures
Remember to pull a permit and to have the required inspections performed. As a rule there will be two inspections, a rough in inspection and a final inspection. The rough-in inspection will be performed after you mount the boxes and run the cable, before the walls are closed up. The final inspection will be made after all connections have been made but are still accessible for inspection
Tips and warnings
- Remember to pull a permit and to have the required inspections performed. As a rule there will be two inspections, a rough in inspection and a final inspection. The rough-in inspection will be performed after you mount the boxes and run the cable, before the walls are closed up. The final inspection will be made after all connections have been made but are still accessible for inspection
Things you need
- 2008 Revision of the NEC (National Electric Code)
- Double-gang "New Work" device box
- Two 4-inch round lighting outlet boxes
- 12/2 w/Gr. NMC (Non-Metallic Sheathed Cable), Romex
- 3/8-inch drill/driver
- Spade bits
- Romex cable staples
- 3/8-inch cable connector
- Lineman's pliers/Electrician's pliers
- Cable ripper or razor knife
- Diagonal pliers/wire cutters
- Wire strippers
- Needle nose pliers
- Electrician's screwdrivers
- Yellow wire nuts
- Green wire nuts
- Two, SPST (Single-Pole, Single-Throw) toggle switches
- Black plastic electrical tape
- 20A, SP CB (Circuit Breaker)
- Double switch cover plate