Sonoff, Temperature, Humidity, Touch Panels

Heating a Cold Room with a “Smart” Block Heater

Creating a smart heater using an electric fireplaceWe all have that that space in our house that just doesn’t get warm enough on the coldest days or doesn’t get enough heat from our furnace. In my house that’s my basement which has been converted to living space, but which wasn’t well ducted when it was converted. Enter the “Smart Temperature Outlet”.

Rather than spending a great deal of time and money redoing the heating system when I plan to do a major home renovation in the near future, the easy solution is to put in a small block heater. In my case we chose an electric fireplace heater which provides some style along with enough heat for the space.

The only problem I have is that I hate “self-managing” the temperature downstairs and I don’t want to have a crazy hydro bill just because I want the room warm.

My solution was to turn my basic “dumb” fireplace heater into a smart appliance with a simple temperature monitoring solution – a smart temperature outlet. One thing you should consider is that you need to choose a fireplace or block heater that doesn’t have electric controls or a remote control. Since you are adding “smarts” to the device you need something with physical switches that can be left on.

Creating a Smart Fireplace Heater by building a Smart Temperature Outlet

This project can be done in less than an hour but it does require some patience when doing the wiring into the smart controller because of the small space you’ll be working in. You should be comfortable working with wiring and stripping wires. If you’re not comfortable working with electricity you can always contact us and we can assemble and ship you a completed version of this project.

What You Need


  • Phillips Head Screwdriver
  • Wire cutters and strippers


  • Sonoff TH16 Smart Switch
  • Sonoff Si7021 Temperature and Humidity Sensor
  • 12-gauge Power Wire
  • Three prong plug and receptacle

Buy The Full Smart Temperature Outlet Product Bundle

Smart Temperature OutletWe have assembled all of the products you need to build this Smart Thermostat Plug / Smart Temperature Outlet together in our Amazon powered store. Click “View Products” to order everything you need right now.

You can use any wire and plugs that you might have around as well, but make sure that you choose something that is at least 12-gauge wire for safety because most block heaters will draw 15 amps or more power.


The Sonoff TH16 is rated for up to 16 amps and is very simple to set up. Inside the box you will find the wiring diagram which provides the overview of the setup:

Sonoff TH16 Wiring Diagram

While they don’t use proper notation, the N leads are your white power lead (the notched end of your plug for neutral), the L leads are the black power lead (load), and E is the earth or ground line for your plug. While the E line is optional, I recommend using a three prong plug and outlet for this implementation.

For ease of working I recommend removing the cover from your Sonoff TH16 as in the diagram, otherwise you will definitely need a pair of needle nose pliers to clip the wires into the unit.

Take two short lengths of your wire and strip the outer cover about 1/2-3/4″ from one end, then strip the wires themselves about 1/4″ from the end. The length of wire you need will depend a bit on where you are putting the unit. I placed it directly at the wall outlet so I could minimize the amount of wire needed.

Pop off the plastic wire clamps from the TH16 unit and feed the two wires into the top cover through the wire opening. To connect them simply connect the two white wires from the two wire lengths to the “N” openings on the TH16 and push down the plastic clamps, then repeat that process for both the “L” (black) leads and “E” (ground) leads.

Once you are comfortable that all your connections are secure, pop the cover back on the TH16 unit and screw in the cable cover clamp plate making sure that you are clamped on the outer wire covering to provide some stress relief on the cables.

To add the plug and receptacle ends to your lead wires, strip approximately 1″ of the outer cover and approximately 1/4″ from each wire end. Undo the screw on your plug or receptacle connector and connect the wires to the leads inside. Remember to connect the white to the larger plug/outlet blade and the black to the smaller one and ground to the third prong connector in all cases. You should wind up with something that looks like this.

Wiring Completed - Sonoff TH16 Switch

Now you’re ready to connect your heater, the temperature sensor, and get your software set up.

First take out your temperature and humidity sensor (Si7021) and plug it into the small plug on the side of the TH16 switch. The temperature sensor has a small mounting hole that will allow you to mount it to the wall with a small screw and I highly recommend doing that to keep things neat and tidy and keep the temperature sensor at a good level to get good measurements.

Now you can plug your new switch into the wall and mount your temperature sensor to the wall. Hold off for now on connecting your fireplace to the device until you have set up the software.

You will need to download and install the EWeLink software from your app store by searching for it in either Google Play or the Apple App store. Once you download it you will need to register for an account to get yourself set up.

Once you are logged in, the device will prompt you to add your first device to the package and you’re ready to get pairing. First make sure that your new TH16 has a rapidly flashing light which will indicate that it is in pairing mode. If it is not flashing, push and hold the button on the top of the unit until it starts to flash (up to 10 seconds).

On your phone or tablet in the EWeLink software you will go through the following screens:

EWeLink Add Device Screens

Make sure you enter the correct WiFi network and password and you should finish this process with the device being connected.

In the app you can rename the device to something that is meaningful to you and then you are able to configure your switch settings:

EWeLink Sonoff TH16 Device Screen

You can easily see the current temperature and humidity from your sensor and you can toggle the switch from Manual  to Auto mode depending on how you want to control the device.

When you flip the device to “Auto” mode you will be prompted to enter your low and high temperature or humidity settings and what you want the device to do at those points. In my case I want my basement to stay between 20-21 degrees Celcius, so I set the low temperature to 20 for the device to turn on and the high temperature to 21 (to turn off).

You will want to make sure you verify the switch settings on the right side as mine generally default to turning on at the “Higher than” setting and off at the “Lower than” setting which doesn’t work in the case of a heater.

Now you can plug the heater into your new smart switch and turn it on at the heater and enjoy your newly managed “smart” heat!

Added Bonus – Also a Smart Air Conditioner

If you don’t have central air conditioning and rely on a window air conditioning unit, you can use your new “smart temperature switch” all year round! Just plug your air conditioner into your new TH16 smart plug and reset your auto temperature settings in the app, and this plug can keep you cool in the summer too!

Enjoy your new Smart Temperature Outlet!

Tim Empringham

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