The Realities of Smart Home Wiring
- Douglas Roberson
Smart home wiring is easy. Your home's wiring is hard. Whether you have a 1950s home without neutral in the wall box or just purchased a 10-year-old home whose prior owner thought he was the World's Greatest Electrician™, more often than not, your home is your greatest enemy in getting the automation and energy management that you want.
Yesterday, I updated two relays to Gen4 versions so that I can become familiar with Matter and get some real-life experience with how it works for Shelly consumers.
This reminded me of an important example of “old house wiring” headaches I ran into a couple of years ago and how I solved it.
Shelly 1PM – whether Plus, Gen3, or Gen4 – has really simplified this headache thanks to its terminal design. That’s one main reason why I am constantly pushing this as the go-to product for Shelly enthusiasts.
You don’t need wire nuts with this product. You can use it in places where any other product would work. Example:
This wall box is vintage 1978 design, 1 ¼ inches deep, surface mounted on the cement wall of my garage workshop, originally with a metal wall plate. Its original configuration would never allow anything behind the switch or outlet.
The switch controls a light for my back landing, which I use when taking out the garbage or taking the cans to the curb two nights a week. The outlet is one of the most important in my home, as we have a refrigerator freezer and a stand-up freezer in the garage, plugged in here.
Today, it’s sporting a ¾ inch extender plate, allowing me to use a plastic wall plate for improved RF performance, but it is still an incredibly tight fit. Worse, I want to use Shelly with both the outlet and the switch.
To make it a little more complicated, the light circuit and outlet share wiring, with the hot line split between the two.
I’m normally the guy who tells everybody else to turn off the damned lights, but this is my kryptonite, because I never remember to turn this off. I originally had Shelly 1PM handling the light and could barely get everything buttoned up with Wago connectors. There was no way it would have worked with wire nuts.
When Shelly Plus Mini PM came out, I knew I needed it on the outlet. Around that time, the old refrigerator was letting food go bad. I’d cleaned the coil, and put in Shelly HT to track the temperature, as well as a door/window sensor to keep track of when the door was left open. What I REALLY needed, though, was measurement of power consumption over time, so I could see if the equipment was failing.
The day before I planned to install Mini PM, the fridge died, so while waiting for the replacement’s delivery, I decided to get the new one installed for tracking and it was a train wreck trying to get it wired in with the existing Shelly 1PM (first gen).
I am never a fan of taking out a working product. It’s wasteful of material and time, so there has to be a strong argument for me to do it. In this case, I reached for Shelly Plus 1PM. Intellectually, I knew that the terminal layout should make things easier, but I hadn’t really experienced this for myself yet.
What happened was the best possible example – I connected 1PM to hot and neutral, jumpered hot from 1PM to the bottom pole of the light switch and to Mini PM, jumpered neutral to a Wago three connector (for the outlet and Mini PM), and then wired in the switch and fixture. While everything was open, I quickly wired Mini PM to the outlet.
I was able to trim a little bit of the wire down (still within code, it just had extra that wasn’t needed) and then fit everything back in the box without even shoving it hard. I was amazed at how well it all worked.
We’ve kept the same terminal layout for both Gen3 and Gen4, which, when combined with the electrical safety protections, along with Zigbee for Gen4 and Matter for both, Shelly 1PM is a home automation powerhouse.
When we have a gen4 version of Mini PM, I’ll probably swap out the current install and take that opportunity to install a decorator form factor switch and matching outlet. This is one of two locations in my home that still have old style switches and outlets and I’m ready to get rid of them both.
Here are pictures showing the setup when I switched to the Gen4 relay, including a Mini 1PM, which contrasts the wiring on 1PM Gen4.
