electricalwiring
I just barely finished re-wiring my bathroom on a circuit that connects to the hall light. So currently is is composed of the hall 1)light/switch 2)bathroom light/switch 3) bathroom receptacle. I would like to add another light fixture above the vanity in the bathroom because the overhead light casts a shadow.
Here is a diagram of the current setup:
Is it possible for me to add another light fixture off of the switch in the bathroom? And if so what would I need to do?
Basically, you want to start with a switch. You run a black and white wire in from the bottom of the switch box (from the panel). This will take the form of 12/2 or 14/2 cable. You run another 12/2 or 14/2 cable from the top of the switch box to the first light. You connect the black wire to the switch. You connect the 2 white wires together, and then connect the other terminal on the switch to the black wire of the cable leaving this junction box towards the first light. The ground wire should also be connected together in this manner, but to the ground terminal on the switch. Each light will have a cable "entering" (from the switch) and "exiting" (away from the switch). At each light you'll connect the entering and exiting black wires together, as well as 1 terminal on the light. Do the same with the white wires. If there is a ground terminal on the light, do that as well, otherwise just connect the incoming and outgoing ground wires together. At the last light, just connect the incoming black wire to 1 terminal on the light, and then connect the white wire to the other one. This method is called wiring in parallel, so if one light blows, the current can still continue to the other lights to light them up.
Some other things to be aware of:
Most home wiring is either 12 or 14 gauge, corresponding to either a 20 amp or a 15 amp circuit, respectively. The maximum "design capacity" is 80% of that. Let's say you're using a 20 amp breaker with 12 gauge wire. This circuit should run at no more than 16 amps. Let's assume you're using 100 watt bulbs at 120 volts. Using watts/volts = amps, for 600 watts/120 volts = 5 amps. So this would work fine on a 15 amp breaker, depending on what else is on that circuit. http://www.thecircuitdetective.com/ is also a superb reference for novice electricians to get an idea of how things work.
Something like this is what you're looking for the end result to be:
Since your light is on a different circuit than the outlet, you'll need to run a switch loop from the light to the 2-gang box using 14/3 (yes 3) cable, with black as the hot, red as the switched hot, white as a spare neutral, and the bare or green wire as well, the ground (aka EGC) :)
In the light box, you'll take the black that currently goes to the fixture hot and connect it to the black of the switch loop instead; the fixture hot then gets wired to the red wire of the switch loop. The switch loop white and green wires get wired into the existing white and green wires coming into the box.
After transposing the existing GFCI from the old 1 gang box into the new 2 gang box, you'll want to leave it alone from here on out. To wire up the switch, you connect the brass screws to the black and red wires, the green screw to the EGC, and simply wirenut off (i.e. put a wirenut on the exposed end of) the neutral on the switch loop -- it's there for future use by say a motion sensor or lit switch as per 404.2(C) (neutrals are called 'grounded conductors' in the NEC, btw, if you're a Code newbie and scratching your head at this :):
C) Switches Controlling Lighting Loads. The grounded circuit conductor for the controlled lighting circuit shall be provided at the location where switches control lighting loads that are supplied by a grounded general- purpose branch circuit for other than the following:
(4) Where a switch does not serve a habitable room or bathroom
Best Answer
According to your diagram, yes it is possible.
You would connect it similar to your existing bathroom switch. Run a #14/2 ROMEX (or other appropriate cable) to the light fixture. The white wire would tie into the white wire on your diagram. The black would connect to one terminal of your switch, and you would connect the other terminal of the switch to the black wire in your diagram (the one on the bottom). Bond the ground wire to the other grounds in the box or the ground screw.
Alternatively, you could power the new light from the existing switch. With a 2 wire cable, connect the white to white. Connect the black of the new wire to the red existing wire along with a pigtail (a 6" or so short wire). Connect the pigtail to the top terminal of the switch. This will allow one switch to turn both lights on at the same time.