Smart House: Why? How?

I want some simple functions for the H33 house:

  • Energy monitoring: easy with Phisaver at the switchboard
  • House off: turn off all lights (and maybe A/C, vent, etc) with a single switch
  • Ventilation: run the ventilation if CO2 levels are too high
  • Aircon: run aircon for x hours, via a simple push-button or similar

So, do I need a all-singing-and-dancing smart hub with tri-colour lights and internet fridge? No, because:

  • Light switches are fine. I don’t need or want internet-connected lights.
  • Internet fridge is a solution without a problem
  • Smart-house software/hardware appears immature and likely possible point of failure

So, I think I’m looking for:

  • Requirements
    • Fail-safe design: house still works if software explodes
    • Prefer open source, non-vendor-specific to avoid lock-in
    • Wireless control (z-wave, wifi, bluetooth LE, etc.) of ”leaf” hardware.
    • Power to “leaf” hardware from 240v (avoid seperate 5v DC transformer and usb)
  • Software
    • Basic ‘hub’ if required
    • Maybe if “leaf” devices are wifi, no hub is required and communicate with each device via wifi-connected app.
  • Hardware
    • A handful of relays to turn three lighting circuits on/off. Sits in switchboard. Could be DIN mount. Control via a simple wall mounted on/off “soft”switch.
    • A device capable of sending low-voltage signals to air-con. We can’t just hard-power-switch the aircon. The low-voltage signal turns air-con on and off. Control via soft wall-mounted push-button (one press = run aircon for one hour).
    • Heat exchanger could be hard-power-switch (relay) or low-voltage signal. Control via CO2 sensor (maybe custom made). Override via similiar ‘soft’ button to air-con.

And The Winners Are…

Shelly. This seems a winner. Other options are Sonoff (cheaper, less flexible, less safe?) and millions of others. Shelly checklist:

  • Lots of safety stuff and certification
  • Ok ecosystem and seems to be around for a while
  • Wifi so no hub required
  • Good integration (MQTT, REST) for developers
  • DIN mount options (“pro series”)
  • I think: can do low-voltage signal for aircon
  • “Plus” series based on Esp32 which I’m familiar with

Design Sketch with Shelly


DIN mounted (new) 2 channel relay – one for each lighting circuit – in switchboard.

Control: A Shelly i3 or 2.5 which have AC inputs, housed in a “Wall Switch”. This is the “master off”


Maybe a Shelly Uni (2 inputs, two potential-free outputs) at condenser? or each controller? On the indoor units is a “CN32 Remote Stop Adaptor”

Control via master off button (A/C all off on exit)

Heat Exchangers

Shelly 1* at each heat exchanger to close contacts and soft power down. See next paragragh. Note hard power down is not recommended in manual. Control via seperate CO2 sensor/s and master switch.

The manual of the heat exchanger shows you can control operation via TM2 with unchanged contacts. Says “Fan runs at speed 4 in auto-vent mode”. (Bypass operation is unclear but could just ignore.)**

**(CN17 can be used to control fan speed (details vague). Also fan speed can be control via 0-10VDC signal. Bypass can be controlled too? )

*(Only Shelly 1 has dry contacts. Shelly 1P, 2P, etc have live (240v) contacts. Shelly Uni has low voltage outputs have requires a 12-30V AC/DC power supply. It might be possible to insert the uni into the HX box, and power from PCB but Shelly 1 simpler?)

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