How do you install a dimmer switch black wire black wire and green wire to some existing black white wires?

Answer 1

First let's consider the existing wiring in the wall box: A Red wire can be the first "Hot Leg" of a 240 volt supply.

A Black wire can be the second "Hot Leg" of a 240 volt supply or the "Hot" wire of a 120 Volt supply.

A white wire is normally the "Neutral" wire. It is common to both hot legs on a 240 Volt supply.

A Green wire (or bare wire with no insulation) is normally the local "Ground " wire. However, if, and ONLY if, there was an on/off switch for a 120 Volt lighting fixture installed onto that wall box before, it is possible that the red and black wires in this situation are:

a) the "hot" feed wire coming from the mains breaker panel to the switch and

b) the "switched hot" wire going to the lighting fixture.

BE VERY CAREFUL TO BE SURE HOW TO DO ANY OF WHAT FOLLOWS SAFELY BEFORE YOU TRY TO TEST ANYTHING WHICH MAY BE A HOT OR LIVE WIRE: Only someone who knows how to use a test lamp or voltmeter safely would be able to confirm whether the red wire in the wall box is a) and the black wire is b), or if they were actually wired the other way round meaning the black wire in the wall box is a) and the red wire is b).

If that is the case,

AND YOU ARE ABSOLUTELY CERTAIN THERE IS NO 240 VOLTS MAINS SUPPLY INVOLVED IN THIS JOB,

then all that is needed is to do the following: BE SURE TO SWITCH OFF THE MAINS SUPPLY AT THE MAIN BREAKER PANEL.

TEST THAT NO WIRING IN THE WALL BOX IS LIVE USING A PROPER TEST LAMP OR VOLTMETER.

Then connect one of the black wires on the dimmer to the red wire in the wall box and the other black wire on the dimmer to the black wire in the wall box - using proper insulated connectors of course.

The green wire on the dimmer must be connected to the existing Ground wire, a green or bare wire in the wall box. If there isn't an existing Ground wire then you must fit one or have an electrician fit one for you because the dimmer may be unsafe to use without it! After you have checked that all the screws holding the wires in the various terminals in the insulated connectors and the wall box are tight, screw the dimmer to the wall box using its fixing screws. You can then switch on the mains supply at the main breaker panel and check that the dimmer operates to dim the lamp in the lighting fixture. Please refer to the Related Questions shown below for more information, expecially the requirement to check whether what you want to do - to install a new dimmer - will comply with the wiring code in your locality. (Town/state/country). If you do this work yourself, always turn off the power

at the breaker box/fuse panel BEFORE you attempt to do any work AND

always use an electrician's test meter having metal-tipped probes

(not a simple proximity voltage indicator)

to insure the circuit is, in fact, de-energized.

Answer 2

Sounds like you are are installing a single pole switch (your load is controlled from one location only). If your existing switch is hooked up to a black and a white wire you are dealing with a switch loop and that white wire is being used as a hot wire. Make sure the circuit breaker is off of course, and hook up the black wires on your dimmer to the existing black and white wires on the original switch (polarity doesnt matter here) the green wire on the dimmer is a ground and should be hooked to a bare copper wire or green wire in the box if it is there.

Answer 3

Answer for USA, Canada and countries running a 60 Hz supply service.

If this is a replacement from an existing wall switch to a new dimmer switch to replace the old wall switch, this is what you need to do. The two wires that were connected to the switch are removed and reconnected to the new dimmer. Don't worry about the white wire as it is not a neutral in this occasion. The white wire is a switch leg and as such it should have been identified by a piece of black tape wrapped around it to identify it as a current carrying conductor. The green wire from the dimmer switch is a ground and is connected to the ground terminal in the switch box.

As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.

Before you do any work yourself,

on electrical circuits, equipment or appliances,

always use a test meter to ensure the circuit is, in fact, de-energized.

IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB

SAFELY AND COMPETENTLY

REFER THIS WORK TO QUALIFIED PROFESSIONALS.