How do you wire a switch when the power comes in the fixture first?

Question

How do you wire a switch when the power comes in the fixture first?

Answer 1

At the fixture you will have two cables plus the fixture wires.  In US the colors should be black, white and bare copper wire (or green) in each cable.  On the source wire (from the breaker box) connect the white wire to the white wire of the fixture.  Connect the source Black wire to the switch Black wire.  Connect the switch White wire to the Black wire of the fixture and wrap some black tape around the switch white wire to indicate it is hot.  Connect all the grounds together (bare wire to green wire of the fixture).  At the switch, connect the black wire to one of the switch terminals and the white wire to the other switch terminal.  The bare copper wire should connect to the ground connection on the switch and to the switch box if it is metal.

Answer 2

Hire an electrician. Better safe than sorry.

Answer 3

All of the previous answers have assumed you are dealing with a Type NM Cable premises wiring system; as that is the most common system used in the US. All are basically correct, although the terms used are "street" terms, and not "Code Language"; which is what should be used when you do not know what part of the country the other party is in. Various locations have their own street terms, the Code language and designators remain unchanged, there are no "regional" editions of the NEC. Using the correct Code terms is important to avoid any confusion due to regional differences in terms.

If your house wiring is installed in a raceway (conduit system), the wiring scheme is basically as described for NM Cable when RNC (Rigid Non-metallic Conduit) or ENT (Electrical Non-metallic Tubing, or “Smurf Tube”) is installed. When an EMT (Electrical Metallic Tubing, or “Thin-Wall”) raceway system is installed, the Equipment Grounding Conductor is generally the raceway itself. A bonding jumper must still be installed between the ground terminal on the switch (if there is one) and the metal box. The same goes for the fixture. The connection to the box must be by means of an approved, listed, and identified fitting (a GREEN colored 10-32 ground s***w, or a GREEN colored grounding clip); NEVER use a sheet metal s***w.

When installing a cable assembly system, the same rules apply. You CANNOT use the clamp screws or the device ring screws on the metallic box to bond your device to the box. This is a sign of a bad installation, done by an installer not familiar with Code and listing requirements.

The question did not mention whether or not the light being switched was previously controlled from a remote switch, or if a switch was being added to a location previously controlled by a pull-chain type switch. If that is the case, a new set of switching conductors must be installed. With a cable assembly, you must re-identify the neutral conductor where it is used as the switch leg. This is generally done using phase tape of any color but gray or orange. If the ungrounded (“hot”) conductor in the assembly is black, you will also want to avoid using that color tape. The tape must be placed around the insulation at any point that it is accessible (in any box that it passes through or is spliced in, and the box where it terminates at either end). Remember, all splices MUST be made in a box using listed connectors. The box must be closed with a listed and approved cover, and ALL boxes MUST REMAIN ACCESSIBLE without removing any of the finished surface material.

All Cable Assemblies recognized by the NEC (the Types typically used in home construction) may be fished through wall or ceiling construction, but must enter any boxes using only listed and approved box connectors.

Answer 4

the hot (black) goes to one pole on the switch and the black from light goes to the other pole on the switch, the two whites are connected and the grounds connected

http://www.indepthinfo.com/wire-switch/s...

Answer 5

connecting the black wire from the "source" to the black wire in "switch leg" as wired suggest would not meet the standards of NFPA 70.

Answer 6

The hot(black) is wired to the white of the switch leg and the returning black is the switched hot that feeds the fixture's black lead. The neutral(white) at the ceiling box is connected to the white lead of the fixture.  Better that you hire someone who knows what they are doing.  If you need to ask you need to not do it yourself.

Answer 7

You should have a cable from the light to where the switching is done.  Two wires are needed.  You will have a black and a white (and of course a bare ground).  The rules of black and white go out the window where switch legs are concerned.  Your switch just hooks to the black and the white in the switch box.  In the light box it is a little tricky.  First turn off power to the light at the breaker box.  Next identify the power input lines. Take the hot wire from the panel to the white wire of the switch leg. Take the black wire of the switch leg to the black wire of the light.  The white wire in from the panel to the white wire of the light.  If there are other wires in the light box, then hook the white wire to the white wire from the panel and white wire from light.  Take the black wire from the other cable and hook it to the black from the panel and white from switch.  The tricky part is just make sure you keep your switch and your panel wiring ID'd.  If you mix it up you could trip a breaker.