How to make a smart garage heater


On this article, I’ll present you ways to take a common 5000W electrical heater and switch it into a smart heater utilizing a low-cost WiFi smart change and a relay.

I lately insulated my indifferent garage and purchased an electrical heater to heat the house. I’m not in my garage daily, so it could be pointless and costly to preserve the house heated continuously. Due to this fact, on days once I need the garage heat, it can want to be heated from a pretty low temperature. Since it can take a couple of minutes to stand up to a comfy temperature, I need to have the ability to flip the warmth on/off from the consolation of my home.

Initially, I assumed it is perhaps good to use a line voltage smart thermostat. I have already got a Mysa thermostat related to an electrical baseboard heater in my kitchen. It seems good, it’s very dependable, and I’d fortunately buy one other for my garage. Nevertheless, the 5000W garage heater is past the capability of the Mysa and all different smart thermostats I discovered.

Another choice can be to purchase a heavy duty smart switch that may deal with the load ( the 21 Amps of the heater is an excessive amount of for any customary smart change). Nevertheless, all these heavy obligation switches include an enclosure. I choose to put all my elements contained in the heater enclosure. So for my functions, the included enclosure is an pointless added value.

In the end, I made a decision to go the DIY route. Right here’s how I did it:

Mission plan and wiring diagram

First, I’m going to join a common smart change to the coil of a contactor (principally a large relay). The contactor terminals will probably be related to the heater. When the smart change is turned on, the contactor switches will shut and the warmth will activate (see wiring diagram beneath).

If wiring diagrams aren’t your factor, don’t fear. I included step-by-step wiring directions beneath.

Second, I’d like to energy the smart change and the contactor from the identical energy supply because the heater. That method I solely want to plug one wire into the wall.

Third, I’d like to enclose the Sonoff and the contactor contained in the heater so the entire set up seems good and clear.

Three Main elements

Right here is an evidence of the necessities for the three main items of this construct:

Electrical Heater

Most electrical heaters will work for this. The primary factor is that you just want to have the ability to set the mechanical controls to the “on” place. That method, when the facility is turned on, the warmth comes on:

heater change in “on” place >>> energy utilized >>> warmth

You don’t need a digitally managed heater that requires you to press a button to begin the warmth:

energy utilized >>> display comes on >>> press begin >>> warmth

Additionally, my heater is 5000W, however you possibly can purchase one with extra energy if mandatory. You simply have to make certain that the contactor you purchase can deal with the facility (see beneath).


There are Three options to think about whenever you purchase your contactor:

Present ranking – The contactor will do the heavy-duty switching. Due to this fact, it wants to have the ability to deal with the total present of the heater. The heater is 5000W operating on a 240V outlet which implies I can anticipate the heater to draw about 21 Amps (5000W/240V). I’ve to make certain my contactor exceeds this, so I’ll select a 30A contactor.

Change kind – The contactor is DPST (double-pole single-throw). What which means is that it controls two circuits (double-pole), however can solely flip them both each on or each off (single-throw). Within the US, 240V electrical energy has two “scorching” wires (each 120V). It’s most popular to have a double-pole change as a way to change each “scorching” wires.

Coil voltage – The contactor coil must be 120VAC. This can enable you to join the smart change circuit to one “scorching” wire (120VAC).

Smart Change

I made a decision to use a Sonoff Primary for my smart change. I used it as a result of it’s what I’m acquainted with, and since I’ve spare ones laying round. You need to use any change you want, however think about the next:

Present ranking – You is perhaps pondering, “You’ll be able to’t use the Sonoff for that! It’s solely rated for 10A. You’re gonna blow up your Sonoff and burn down your garage!”

The Sonoff will not be related to the heater’s load. The Sonoff switches the coil for the contactor which solely requires a minimal present nowhere close to the capability of the Sonoff.

Any 120VAC smart change with a 10A ranking will probably be greater than sufficient to deal with this job.

Wi-fi protocol – I would love to have a WiFi smart change (Sonoff is WiFi) to management my heater. I’ve Z-Wave and Zigbee units (with a SmartThings hub) in the home, however the garage is simply too far for the sign to be dependable. Nevertheless, I used a powerline adapter to extend my WiFi to my garage in order that sign is robust.

DIY – The smart change ought to have simply accessible wire terminals. You don’t need a totally enclosed smart change that’s designed to be plugged into an outlet. The Sonoff is well disassembled. The circuit board will be simply accessed for attaching wires.

Record of instruments and supplies

Right here is a record of what you’ll want to full this venture:

Heater – I used a ProFusion 5000W heater from Menards, however there’s plenty of fashions that can work.

Sonoff Basic – The smart change for this construct will be bought by itself or with amount reductions.

30A DPST contactor w/120V coil – There are a lot of variations of contactors so both make sure of what you want, or purchase this one.

Wire Stripper and connectors – You are able to do this venture with out a wire stripper, however having one makes it simpler. In case you don’t have one, the equipment within the hyperlink is a nice deal. The included connectors on this equipment will probably be helpful for this construct.

10/3 wire– You have to about 1 foot of 10/Three wire (as well as to wire for the twine). I already had 15 ft of wire for the heater twine. The twine was loads lengthy so I simply reduce 1 foot from it.

16 gauge wire – The Sonoff terminals are too small for 10 gauge wire so I used 16 gauge wire for the contactor coil circuit. Hopefully you’ve some laying round since you don’t want a lot.

Wire clamp – Be certain to get the right dimension to your knockout.

Self-tapping screws – You’ll want one thing to mount the contactor and Sonoff to the heater.

Step-by-Step Directions

Alright, let’s get began!

1. Format

Open your heater and discover an acceptable place to mount your contactor and smart change.

Ensure that the screw holes for the elements will probably be in a protected place. You don’t need them to come by the opposite facet and injury one thing.

2. Take away knockouts

Your heater ought to have some round indentations (knockouts) on the case. These are designed to be detachable so as to enable wiring to move by. Discover the knockout that’s in probably the most handy place for environment friendly wiring and take away it.

My knockout didn’t come out simply. In truth, I almost destroyed the heater case and threw it out the window within the technique of eradicating it. Fortunately, a few selection phrases and a few targeted respiration prevented me from doing one thing I regretted.

Breathe, Eric. Chill out, and simply breathe…

I ended up needing a wire snips, a pliers, and a tiny little bit of persistence (in contrast to my regular quantity of zero) to get the job completed.

3. Set up wire clamp

The wire clamp will present a clear level of entry to your electrical wires and in addition maintain them in place.

Set up the clamp within the gap from the knockout you simply eliminated. Place the screws for the wire clamp on the within of the case. This can present a cleaner look. Additionally, make certain the screws face a course that’s accessible with a screwdriver.

To tightly fasten the wire clamp to the heater case, use a screwdriver and small hammer.

4. Fasten smart change and contactor to case

I used 1/2″ #6 self-tapping pan-head screws.

Once more, make certain when your screws poke by the opposite facet, they aren’t going to injury something vital.

NOTE: Earlier than fastening the elements make certain you’ll be able to simply entry all of the wire terminals. If not, it’s your decision to wait till the wiring is completed to completely fasten them.

5. Join your floor wire to GND on the heater

In case your heater doesn’t have a clearly labeled GND terminal, you’ll be able to drill your individual gap and connect the bottom wire anyplace on the metallic case.

6. Join L1 and L2 to contactor enter

Your L1 and L2 wires must be the black and purple wires. Trim the wires to the suitable size and strip about 1/4″ off the tip. Fasten the stripped ends utilizing the screw clamps of the contactor.

NOTE: L1 and L2 terminals on the contactor are arbitrary. If they aren’t labeled, simply assign one to be L1 and the opposite to be L2.

7. Join L1 and L2 of contactor output to L1 and L2 of heater

For every connection, measure the suitable size of 10 gauge wire. Strip about 1/4″ off every finish and fasten utilizing the screw clamps.

8. Join Sonoff L enter to L1 of contactor enter

Lower an acceptable size of 16 gauge wire. Strip each ends and insert one finish into the L enter terminal of the Sonoff. Connect a spade connector to the opposite finish of the wire. Plug it into the L1 spade terminal of the contactor.

9. Join Sonoff N enter to impartial

Lower an acceptable size of 16 gauge wire. Strip each ends. Insert one finish into the N enter terminal of the Sonoff. Join the alternative finish to the impartial wire (white) utilizing a wire nut.

10. Join Sonoff L output to contactor coil A

Lower an acceptable size of 16 gauge wire. Strip each ends. Join one finish to the L output terminal of the Sonoff. Join the opposite finish to a spade connector and plug it into the spade terminal of contactor coil A.

NOTE: The contactor coil terminals are situated on the facet of the contactor. They might not be labeled. If they aren’t labeled, simply assign one to be A and the alternative facet to be B. Polarity doesn’t matter.

11. Join Sonoff N output to contactor coil B

Lower an acceptable size of 16 gauge wire. Strip each ends. Join one finish to the N output terminal of the Sonoff. Join the opposite finish to a spade connector and plug it into the spade terminal of contactor coil B.

12. Plug in and arrange Sonoff

The wiring is completed! Now, plug the heater into the wall outlet in order that the Sonoff has energy. Use the cellular app (eWeLink) to setup your Sonoff. It’s your decision to depart the case open to enable for a higher wi-fi sign.

13. Shut heater and check sign

As soon as the Sonoff is setup, attempt closing the heater and see if the wi-fi sign nonetheless works. If it does, you’re good to go. If not, you’ll have to relocate the Sonoff to the surface of the heater case. It’s additionally attainable to add an antenna to the Sonoff, however I haven’t wanted to try this but.

14. Set heater to desired settings

Set the mechanical switches and dials to your required settings in order that the heater activates when the facility is utilized. My heater has a number of completely different warmth intensities in addition to a thermostat dial.

15. Add desired automation

Okay, the arduous half is completed. Now, the enjoyable half.

I use Alexa for nearly everything. Due to this fact, I named my Sonoff “garage warmth”. That method I can say, “Alexa, activate garage warmth.”

Remaining Ideas

I do know that is a pretty easy venture, nevertheless it’s one of the crucial helpful smart house initiatives I’ve completed. I hope you discover it helpful, too.

This works nice for an electrical heater, however there’s no purpose the identical technique couldn’t work for different heavy electrical load functions.

Be at liberty to counsel any modifications/enhancements within the remark part beneath. Thanks for studying!