Smart Switches

Bored During the Pandemic

So I decided to spend some of my "shelter-in-place" time upgrading the old light switches in my house to "smart switches".  I document some of my adventures here in hopes that it will be useful for someone else trying to do the same thing.

Smart Switches

I wanted to buy a switch that was compatible with Apple HomeKit (Siri) and Amazon Alexa.  I have just decided that's what I'm going to use for home automation.  I want to be able to say "Alexa, turn on the kitchen lights".  Your mileage may vary depending on what kind of setup you want.  I bought my Meross switches off Amazon.  This blog post will be largely centered around these switches, and like I said earlier, your mileage may vary depending on what kind of switches you get.

Turn Off the Breaker

The most important part of changing a light switch is making sure you've turned off the power to the light switch before doing anything with it.  You can find this in the breaker panel.  There is one inside the house (mine is in the laundry room) and one outside the house.  The one on the outside of the house has a breaker in it called "sub-panel" which refers to the breaker panel inside the house (i.e. the main breaker panel is outside).

When the breaker switch is all the way to the middle, the switch is ON, if it's away from the middle, the switch is OFF.  I have started labelling the switches because sometimes "Bedroom #5" is not always obvious which bedroom it refers to :-).

The breaker switches, up close, look like this:

The top and bottom switches in the picture are "ON" (i.e. towards the middle), and the switch in the middle is "OFF".  If you go to turn the switch from OFF to ON and it bounces back to the middle, you probably have a short somewhere (like 99.9% chance).  I went on a whole adventure where I thought the breaker was bad, and I'll document that later if I have time, but the most likely scenario when the switch won't turn all the way on is that you've got two wires connected somewhere that shouldn't be (i.e. you have a short).

You should always verify that the power to your switch is off.  You can do this in two ways (and my paranoid self always does both ways).  The first way is you just try flipping the switch.  If it works, then the correct breaker is off.  If it doesn't, then you've got the wrong breaker.  The second way is to check with a volt-detector thingy (official name :-)).  You can get these off Amazon for pretty cheap.  You basically turn it on and put it near a wire - if it lights up, it's "hot", if not, it's not.

Like I said earlier, I usually check both ways, I'm just paranoid in that way.  Also, if you're wearing an Apple Watch, I would suggest you take it off before working with electricity.  It can be quite startling if you get haptic feedback in the middle of being around wires with electricity! :-) :-). Also, get used to going back and forth to the breaker panel and toggling the breaker.  If it's up a flight of stairs, just think of it like going to the gym and running the stair climber for a while. :-)

Single Pole Switches

The easiest light switch to change is the single pole switch.  This is one switch controls one light.  First, turn off the breaker to the switch.  Then remove the cover and remove the switch.  When you pull the old switch out, there can be multiple wires to it.  I'll document the configurations I have seen.

In the first configuration, there is one "ground" wire (the ground wire is either "green" or bare).  In the switch shown below, there are two black wires.  I really wish every wire had a unique color, but it just doesn't seem to work out that way.  The trick is to know which black wire is which.  One is Lin (which stands for Load-in), and the other is Lout (which stands for Load-out).  You can find out which wire is which by turning on the power to the switch (at the breaker) and turning off the switch at the switch.  Then using the voltage-detector against each black wire.  The one that's "hot" is the Lin wire -- there are stickers in most smart switches that will help you identify the wires - you don't have to use all of them, but I use enough of them to disambiguate which wire is which.

Once you've identified the wires on the legacy switch, you can just match them up to the smart switch and connect them.  In my smart switch, smart switch green wires goes to old switch bare ground wire, smart switch Lin goes to old switch Lin (black), smart switch Lout goes to old switch Lout (the other black wire) and the N (neutral wire) goes to the white wire in the box.  So this is kinda interesting.  There are four wires on the smart switch, and only three wires on the old switch.  The white wire connects to wires that are capped off inside the junction box.  You'll have to dig it out and unscrew the cap to get at it and screw in the smart switch white wire to it.

When you're done wiring everything up, it should look like this:

I usually test the switch before shoving it back into the junction box, because getting all the wires with the caps on them back into the junction box is a chore, and not something you want to be doing multiple times.  Once I verify the smart switch is working, I shove all the wires back in the box and screw everything back in place except the face plate.  Like I said, getting all the wires and caps back into the junction box is a chore.  I start with the thickest bunches of wires first and put them as far back as I can, and then finagle the other wires back into the box.  When you're done it should look something like this (not sure why the picture is titled slightly, but it's actually level):

Don't forget to clean up your mess :-).

Three Way Switches

Three way switches are when two light switches control the same light.  The way this "should" work is that you should be able to toggle the state of the light (on or off) at either switch.  Sometimes, when people screw this up (even lazy electricians do this from time to time), one light switch has to be "on" for the other light switch to work.  I've had this in my house, and it was absolutely maddening.  You want to be able to toggle the light from either switch -- i.e. no matter what position the "other" light switch is in.

Here is a picture my brother drew for me to help understand how three way light switches (that can toggle from either switch) works.

Ignore the neutral wire for a moment and convince yourself that the way the two switches work in the picture that you can toggle the state of the light from either switch.  Try to complete the path (where current flows) as you toggle the switches.

The black and red lines with two arrows on them are called "travelling wires" (because they travel between the two switches) and that will be important later, but just remember that for now.

The smart switch I bought has five wires connected to it.  The green wire is "ground", the red and black wires (labelled T1 and T2) are the travelling wires.  The white wire is the N for neutral wire.  The other black wire is the "load" (or L) wire.  This is the wire that is hot.  Be careful with this one.  For the life of me, I cannot figure out why they didn't give every single wire a unique color - it would have made things a lot simpler and easier.

The legacy (or old) wire that's in the junction box, typically looks like this:

There are usually four wires associated with these three way (older, non-smart) switches.  The green screen is connect to the bare wire.  This is the ground wire and needs to be connect to the green wire in the smart switch.  The two gold screws are connected to the travelling wires, and you can connect red to red and black to black.  The final screw is the "L" wire (or the Load wire).  This connects to the "other" black wire on the smart switch.  Then you just have to connect all the wires.  There is one final wire on the smart switch - the "white" or "neutral" wire.  Usually, inside the junction box, you will find a bunch of white wires twisted together.  You have to uncap them and connect this wire to that bunch.  When you're done, it should look something like this:

When you have everything connected all up, and before you shove it back into the junction box, and screw everything back in, I usually go to the breaker box, turn the breaker back on and test everything.  Trust me, once you get all the wires and caps back into the junction box, you're not going to want to have to pull it back out and do it again.  Once you verify everything is working, you can go turn the breaker back off and shove all the wires back into the junction box screw everything back and turn the breaker back on.  Sometimes when I'm feeling lucky (or lazy), I'll put on some light work gloves and shove the wires back into the junction box to avoid another trip to the breaker box.