Switching new dimmer for old dimmer

Question

My new dimmer for LED lighting has four wires: one black, one red, one red/white and a green ground. The old dimmer only has three wires: a single red, single black and green ground. This is also going to be a three way. How do I install?

manassehkatz-Moving 2 Codidact · Answer

Assuming the dimmer is similar to the Lutron dimmer in this question:
The new dimmer can be used as a regular switch or a 3-way switch.
For a regular switch, which it sounds like the way your old dimmer was connected:

Black - Hot
Red - Switched Hot
Green - Ground
Red/White - Not used - cap with a wire nut

For a 3-way switch:

Black - Hot
Red - Switched Hot/Traveler 1
Red/White - Switched Hot/Traveler 2
Green - Ground

The second switch for a 3-way setup should be a regular switch, not another dimmer.
Wiring a 3-way switch can be a bit confusing. Search for other information on that (plenty on DIY StackExchange, or Google it) and then just treat the dimmer as one of the 3-way switches.

Switching new dimmer for old dimmer

One Answer

For a regular switch, which it sounds like the way your old dimmer was connected:

For a 3-way switch:

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