Installing 3 way smart switch for light that has three existing smart switches?

wjgrayson · Sep 26, 2023

I can't seem to find the right answer for a smart switch installation for a light that has THREE switches. There's conflicting information, and most of it is for two-switch installations and not three-switch installations. Do I need to install a three-way smart switch at each location, or can I just install one smart switch at the "master" location where the power comes in? How would this work if you have three locations?

Avo Mk8 · Sep 26, 2023

You don't need more that one smart switch in the chain of switches. The one will do the 'smart' job and the other physical ones give functionality where they are situated.
When you have three manual switches controlling one light, the switch "in the middle" is called (in the UK) an 'intermediate' switch, with a crossover switching function. They don't make smart switches with that functionality as far as I'm aware, as it's not really needed.
You need to buy the right sort of smart switch, known as 2-way in the UK and I think '3 way' in USA. Very confusing!

circuit below, the big thing is the smart switch, and the two little switches bottom right are your existing ones. Except one of those may currently be an intermediate type, so you may have to alter your wiring if you have three manual switches already!

[ElectriciansForums.net] Installing 3 way smart switch for light that has three existing smart switches?

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wjgrayson · Sep 30, 2023

Avo Mk8 said:
You don't need more that one smart switch in the chain of switches. The one will do the 'smart' job and the other physical ones give functionality where they are situated.
When you have three manual switches controlling one light, the switch "in the middle" is called (in the UK) an 'intermediate' switch, with a crossover switching function. They don't make smart switches with that functionality as far as I'm aware, as it's not really needed.
You need to buy the right sort of smart switch, known as 2-way in the UK and I think '3 way' in USA. Very confusing!

circuit below, the big thing is the smart switch, and the two little switches bottom right are your existing ones. Except one of those may currently be an intermediate type, so you may have to alter your wiring if you have three manual switches already!
View attachment 110754'

Hi. Thank you for responding earlier this week (I didn't get a notification there was a response.) This will be a smart switch placement in the U.S. Follow-up question: When you say "manual switch," do you mean a regular function switch that does NOT have a traveler wire? I'm trying to identify if either of the two other switch locations (your two little switches on the diagram) is an intermediate switch.

Avo Mk8 · Sep 30, 2023

wjgrayson said:
Hi. Thank you for responding earlier this week (I didn't get a notification there was a response.) This will be a smart switch placement in the U.S. Follow-up question: When you say "manual switch," do you mean a regular function switch that does NOT have a traveler wire? I'm trying to identify if either of the two other switch locations (your two little switches on the diagram) is an intermediate switch.

I do mean a regular function switch, which would be wired (at least in the uk!) as the diagram below.
The significant point is that it has four terminals! It's the one in the middle in the circuit diagram below.
Should be easy to spot!
Sorry I wasn't clearer In my post.

Edit: Imagine the circuit here is what you have, and you are going to replace the left hand switch with your smart switch (which has the necessary 3 wires). The middle and right hand switches in the diagram are how the rest of the circuit would remain. If you open up the box in the wall to fit the smart switch, and you find a switch with four terminals, I suggest that is not the right location to add your new switch! Choose another place to site it! Hope this helps