WiFi Control for 6 kW / 240V Sauna Heater

Hardware
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#1

Hi all, I have an older Polar Sauna HMR 60 heater with built-in mechanical dials for temperature control and timer/shot off. It takes over an hour to heat the sauna to the right temperature. So after 20 years, I finally decided to automate turning the heater on and off.

I’m looking for advice on hardware configuration to set up WiFi control and how to integrate it with the current circuit. The temperature dial stays on maximum all the time. I have a 220V line on a 50A breaker going to the sauna.

Thank you for the heads up.

#2

For this use case you must no drive the sauna directly with an automation device, since none of them will be able to handle this load.

You must drive it with a relay, there’s domestic relay for boilers.

Depending on the country you live you will have different available hardware, if you cannot find something for domestic usage you can also take an industrial relay.

When you have the right command circuit you may choose any device to power the relay because it will only need to power a coil and will not support the heavy load

A random exemple of a 50amp contractor

#3

That is what I suspected. I’m wondering if I could use the existing heater relay and bypass the mechanical dial with a WiFi switch. Please see the attached diagram for the heater.
So if it works, what type of WiFi switch should I get, and where would I install it?

sauna heater
sauna heater1920×2485 236 KB

#4

Indeed looking at the diagram the thermostat will power two contractor and is wired in parallel to the load so it might be replaced by a micromodule.

You will need to just disconnect the thermostat and plug wires on your micromodule contact and wire its power directly to the poles of your power input

As I never used any WiFi micromodule I cannot really help but those are on budget and should do the job

I used the ZigBee equivalent to control a boiler

#5

Here is the timer switch that is currently installed in the heater. I assume the micromodule can be installed in parallel to the timer. The question is whether it will handle 190 degrees of heat and the moisture from pouring water on the heater. I sent their tech support a question about it. I doubt it would.
I can install the microunit outside the sauna, but it will require me to run additional wires and drill a hole in the wall.
So maybe I’d go back to the idea of installing an external contactor and a control unit next to the 240V wall plug. I would then need to close the internal timer switch.
My ideal scenario is to keep the internal timer switch operational, add an external wireless switch with a timer on the outside of the sauna, and have the ability to control it from the phone or Alexa.
Thx for your ideas.

#6

You can wire the timer to the micromodule input and set it to follow the the state of the timer (not sure it’s your intended behaviour, neither if you can set it that way, the input is intended for wall switches)

If you’re concerned about humidity you can put the micromodule in an IP67 enclosure if there’s enough space in your control panel, after all I guess that there should be a protective enclosure for the electronic circuit

#7

It appears that there is plenty of room to put the enclosure. The other parts are not enclosed, and the WiFi switch is relatively inexpensive to try it w/o IP67.

So, is this the correct wiring I’m thinking of? (I assume N on the diagram is the neutral, and 10 /11 is the line). That way, I would be able to turn on the sauna remotely or with the mechanical switch.

Heater diagram with smart switch
Heater diagram with smart switch2213×1429 267 KB

I assume I will be able to program timer in the application not to exceed 1.5 hour of heating time. There is also a high temp limit switch for additional safety measure.

Thank you for the advise

#8

At first glance this wiring should work but I never used this kind of controller who have only 4 poles

I use the one with switch input and ideally a separated power and contractor lines

#9

I ended up putting in a din rail wi-fi switch in parallel with the mechanical timer switch. It works as desired, i.e., I have both functionalities. The wi-fi switch is rated for 65 amps, so I assume it is more heat resistant than regular 10 amp inline switches.
Thank you for help

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