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my single pole dimmer has a hot (black), white (neutral) and green ground. The new dimmer appears to require a hot, neutral, ground and load.... why, don't get it?

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    You're going to want to tell us more about your dimmer. Please revise to add information. Are you sure it's not one designed for either two- or three-way use? What makes you think there's a "load" wire? Did you read the literature?
    – isherwood
    Mar 13 '20 at 16:29
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    Either you are wrong about the old dimmer, or you are misinterpreting the "white" wire as being neutral. If you connected to hot and neutral on the old dimmer, it would just be a controlled (through the dimmer) short circuit! There is ALWAYS a load connection; the load is the light! The thing that might be different about your new dimmer is that it has internal electronics, so it might need the neutral connection to power itself up, whereas your old one had no need for the neutral so there was no connection for it. Post a picture if you want confirmation.
    – JRaef
    Mar 13 '20 at 16:35
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    3-way dimmers are starting to be the default choice of stock for big box stores. Anyways, a picture would be immensely useful.
    – MonkeyZeus
    Mar 13 '20 at 16:48
  • why don't you follow the installation instructions?
    – jsotola
    Mar 13 '20 at 18:04
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Your old dimmer had neutral, eh? Now think that through.

Let's see. We've got safety ground; then always-hot as supply; then neutral to power the device -- Wait, aren't we missing something? How does it power the light???

The answer is, that wire you have identified as neutral, is not neutral at all. It is surely switched/dimmed hot to the light. The old dimmer does not need neutral to power itself; it's designed to get power by leaking it through an incandescent bulb. This is the old way of doing things, and it does not play well with LED.

Now, I seriously doubt the old dimmer had a white output wire. What I suspect is the wire in the wall is white. That's bad news: it means your wiring the is an old-style switch loop which is using white as a hot wire. That style of wiring does not have neutral. You cannot use that smart switch here, unless you want to pull a /3 cable into the wall and wire it as a new-style switch loop.

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I believe that JRaef provided the answer that smart switches need power even when 'off' and therefore need a complete circuit which is provided via the additional connection

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