I'm connecting a dimmer.

There are four wires coming from the wall. 2 black (one is HOT). 1 White. and 1 ground.

There are four wires on the dimmer switch I bought. 1 black. 1 red. 1 green (ground). and 1 red (for three way switch).

I've connected the black (hot) wire from the wall to the black wire on the dimmer and the other black wire from the wall to the red wire on the dimmer. However, when I try to push on/on on the switch nothing happens.

I've verified that there is power coming to the wire on the wall (hence I know it is HOT).

What could be the reason?

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  • The green wire on the dimmer should be connected to the bare copper ground wires in the box. There appear to be two red wires on the dimmer - what does the tag on the second red wire say? Were there any instructions with the dimmer?
    – Peter Bennett
    May 28, 2014 at 2:11
  • 1
    I answered, but on reflection, decided that I couldn't determine how this is supposed to be wired. Some reference drawings are here: cache.smarthome.com/images/2476dside3big.jpg and here cache.smarthome.com/images/2477dside2big.jpg. A dimmer can't work unless there's neutral ("cold") wire, and it's also essential not to interchange the Line in and Load wires. So for this dimmer, it's likely that green is supposed to be neutral (not ground). But it should have instructions that are definitive.
    – gwideman
    May 28, 2014 at 2:13
  • @Peter I've connected the green wire to the copper wire but still when I turn the button on/off it has no effect. However, I have noticed that when I do conenct the green to the copper then both wires coming from the wall become HOT (when dimmer is connected). Latest image: imgur.com/xjiQ1eX May 28, 2014 at 2:25
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    'A dimmer can't work unless there's neutral ("cold") wire' is not an accurate statement. It is possible to trickle current through the bulb itself to get enough current to run the dimmer's electronics. This is deprecated because of LED and fluorescent bulbs not working with this system, and new codes require there be an active neutral in each switch box. Green is NEVER neutral, it is reserved for ground alone. Do not connect the neutral side of any load to a ground conductor. I would recommend hiring a licensed electrician at this point.
    – mfarver
    May 28, 2014 at 2:48
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    Not relevant to your question, but I wanted to point out that you have too much insulation striped from the conductors. You only need about 3/8" stripped, and definitely no copper showing with the wire nut on. It's easy for one of the conductors to touch the bare ground wire or metal on a grounded receptacle when everything's bunched up in the box.
    – Edwin
    May 28, 2014 at 4:18

1 Answer 1

  • One red wire on your dimmer should be connected to the supply from the wall live
  • The other red should be connected to the load the one that switches the lamp on off
  • Black should be connected to your neutral
  • The Green should be connected to your bare conductors or earth (ground)

As mentioned previously you should have as physically minimal copper exposed as possible realistically none it should all be inside the connector the insulation should go right to the connector itself.

Test to find what you need?

  • Your earth or ground when tested to neutral should present 0v
  • When tested from your neutral to your live supply full voltage should be present
  • When tested from your neutral to your load the wire that goes to the lamp 0v should be present as this is only live once in your particular case has gone through the dimmer

Could you provide if possible a picture showing the model number and one of the front or alternatively if it is simply an open up dimmer case a picture showing the electronics on the inside. Usually you will have one red power in, one black power return path or neutral, one ground or earth and finally one power out to your load (lamp light)

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