Smart 3 phase contactor

Looking for hardware advice:

We have hourly tariffs which tend to fluctuate 30x over the day, I would like to tune my electricity spend. The most immediate target is my water heater (not for house heating, purely tap water). The family tend to take baths and showers when tariffs are high, and although the water is far more than sufficient, the dumb heater happily starts to consume 3kW immediately, rather than waiting for better tariffs within the next ~6 hours. It runs on two phases connected with 3-phases from the normcentral.


  • The thermostat is set to 60C. This is good against bacteria, but it should be ok to drop for a few hours.
  • Switching on/off does not harm my relatively new but dumb Nibe heater. It should however be done using hardware cutting 2 (or 3 including the non operational) phase simultaneously, typicall solved using a contactor.
  • If I get on/off switch into HA, I’ll be able to program it so that it uses the tariff pricing which is already available in the HA
  • My house is wifi only, and the HA has bluetooth, Zigbee and Wifi connections
  • Fiddling with the heater is potentially bad investment, since it may need to be replaced which is already set for hazzle/costs since it involved big hardware delivery, plumber and electrician. Therefor it is more sensible to install smartness in my normbox, DIN-mounted hardware
  • Heater is crucial. Intelligence can fail, and so it will, in particular wireless. So I should have a fallback with manual switch, involving minimal equipment between the switch and contactor/relay

So… my thought lead me towards DIN mounted wireless switch controlling a contactor which also has a physical button. Ideally there would be a smart contactor with integrated button. I thought Shelly would have something like this but it seems they do not.

The configuration with a three phase contactor in the pictures of

seem close to perfect. Possibly as close as I’d get.

My questions are:

  • Do you think I am reasoning inadequately?
  • Is there a better solution?
  • Is there a better supplier for the sames solution?
  • Does anyone know anything about Kincony? I do not know anything about them, haven’t even found where I can order the hardware the linked page promotes (maybe it is released too recently).

Additional background: I am located in Sweden so it is 240V / 400V, requiring CE approval and I need to convince an electrician to install a brand he might be new to. And being in Sweden also means that the electricity prices are extremely volatile do to some irresponsible political governance over the last 30 years :slight_smile:

Any advice would be highly appreciated!

FYI it actually only needs a thorough 60°C heating of the entire tank (right down to the bottom) once a week to tackle legionella bacteria according to the standards we use in Australia.

You can do what you want using any smart switch module and a dumb three phase contactor. The smart switch module will have more than enough power handling capability to energise the dumb contactor coil. And it can be controlled by a toggle or push-button switch.

You just won’t be able to measure power of the load.

If power measurement is important the Shelly EM has two phase measurement (50A or 120A current clamps) and a switch output that could drive your contactor.

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Easiest way is to buy a stupid 3 phase contactor then a smart switch to turn the contactor on and off. I am going to do this in the weekend using a snonoff switch and 3 phase contactor. I use sonoff because I already have sonoff devices and HA.
I have no idea about price control but Im sure someonw has figured that out and there is a code somewhere.
Aliexpress sells wifi 3 phase contactors but I wont dare put that in my home.

Hey, how’d this go and how’d you find out code around installing a contactor? I’m in the same boat (well pump) and can’t figure out the code requirements for installing a contactor relay regarding enclosure, using a switch powered from a separate circuit, etc.


you do not a code as everything can be done in the UI if you use a smart switch to turn on and off the 3 phase contactor. My setting is like this: 3 phase contactor that is turned on and off by a sonoff switch, the switch does not take any load it is just there to close and open the circuit. Then there are threads of how to automate this settings according to energy price for example if you wanna use it for the water heater. for your well, I do not know how your system looks like but for my well it is complicated because there is a relay that speaks to the 3 phase contactor, the relay measure the water pressure in the pipe and turns the contactor on or off accordingly.

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Thanks! This is great. I went with a pool pump timer that will probably work. I think it will take some time to get linked up though. Thanks for the details!

Hi, can you tell me what contactor you used? I’m going for the same setup. I’m thinking of buying this one: EMAT magneetschakelaar 230/400V 25A 3 maak en 1 verbreek (85010014) | Elektramat icm with a zigbee module like this Sonoff slimme schakelaar kopen? | We ❤️ Smart! | ROBBshop. Will that work? I will use it to shut down my car charger based on the energy tariffs.