Martin's corner on the web

Upgrading my fan coil thermostats

We use a DIY air-to-water heat pump for climate control (heating/cooling) of our house with a combination of water underfloor heating and fan coils in the rooms. The fan coils are equipped with basic thermostats that allow for heat/cool mode setting, desired temperature and fan speed. We never use fan speed setting other than lowest, as higher fan speeds introduce slight fan noise. I can outline the following issues with that setup:

  • The fan coil temperature sensor is a wired one, it is not convenient to extend it to where I need the room temperature to be measured. The rooms are pretty large and measuring the temperature near the fan coil resulted in uneven room temperatures as the fan coil would switch off too early, leaving the far end of the room still cold.
  • The thermostats we used do not have a weekly schedule, so we have to walk around the rooms when leaving for/back from work and manually start/stop as needed.
  • There is no custom hysteresis control
  • The thermostats are not internet-connected, I cannot control/monitor room temperature from my phone.

These shortcomings mean we are wasting energy and could use some improvement in usability. I decided to add BBoilRF thermostats to the fan coils and address the above-mentioned issues.  The installation was trivial, there was plenty of room to install the BBoilRF inside the fan coils. I installed a wired temperature sensor to monitor the heating fluid temperature, and a remote battery operated wireless temperature sensor for the room temperature controls. I also use the wireless keyfob project to control the fan coil without the need for a mobile device or internet connection.