Honeywell TC500A WiFi with BACnet Thermostat


Active Member
I've been on the search for a WiFi thermostat that works without a cloud connection.  I've seen the Venstar thermostats, which do have a local API. However I'm not a fan of their styling. I recently found the Honeywell TC500A commercial thermostat. The catch is Home Assistant doesn't have a BACnet integration. I also haven't found an open source BACnet to MQTT bridge. I did find a BACnet support package for NodeRED package node-red-contrib-bacnet.
Since this is a commercial BACnet thermostat it is designed to integrate with building management systems like Tridium Niagara 4. On this thermostat BACnet allows remote configuration of basically all settings and the ability to override the local temp and humidity sensors. For example you can feed in points like:
Network Outside Humidity
Network Outside Temperature Value
Network Space RH
Network Space Temperature
Network Occupancy Sensor
Smoke Detector Network Input
This opens the door to using NodeRED to do things like:
- Set the space temp from an average from multiple sensors
- Set the outdoor temp; no need for a separate sensor
- Set occupancy based on alarm arm state or sensors
- Set smoke to shutdown the system on fire alarm
Additionally it has multiple outputs that can be used for things like humidifier and dehumidifier control among other features.
I've been thinking about replacing my OmniStat 2 thermostats with these. It would require me to either create a NodeRED flow to map the setpoints, etc into MQTT for Home Assistant climate or write a BACnet to MQTT bridge. I'm wondering if anyone has seen/used this thermostat before or has any thoughts?