Thanks for giving me the opportunity! Who doesn't love to blather on about their HA system eh?
Well, the two UMI-32 outputs are connected to the heat and AC request thermostat lines. Contact closures there make the circuit from the furnace 24V supply just like a thermostat would. My system doesn't have a low voltage blower output so I connected a 120V relay to the blower output and the other side of the relay to one of the contact closure sense inputs of the UMI-32. When my furnace blower activates, my central controller receives the signal from the UMI-32 and may activate two inline duct fans that supply the east side of my output plenum. This side feeds the primary living areas of the house. If "Master Bedroom Occupied (MBO)" is set (I press a switch at the bedside table which also does a "all lights off", closes the garage door if open, deactivates all motion sensors and activates the Intruder sensors) then the fans aren't activated. This increases pressure in the west side of the primary plenum which feeds the sleeping area of the house. If the system decides to activate the fans because MBO isn't set, then they are set to 80% if the system is in AC mode or 50% otherwise. Additionally, if the system is in AC mode then a 3 hour timer activates. This timer is cancelled by a 24V-0V transition from the thermostat AC request line which is wired through a low voltage sense input on my UMI-32. If the time limit expires then the system hasn't cooled the house down in 3 hours so the controller sets the inline fans to 100% for MAX AC mode to the home living areas.
I have a templinc in the master bedroom too. When MBO is set and the system is in AC mode, then the central controller uses templinc output to control the AC request side of my HVAC via the UMI-32. My templinc is set to 72 degrees. This essentially overrides the main thermostat and works to keep the sleeping areas cooler.
System AC mode is a flag that is set if the controller sees an AC request from the thermostat and the flag is in system heat mode. Conversely, system heat mode is set if the controller sees a heat request from the thermostat and its in system AC mode.
How's this wired on the UMI-32? Here the terminal map
1 AC control output
2 AC control output
3 Heat control output
4 Heat control output
5 Thermostat heat request voltage sense
6 Thermostat heat request voltage sense
8 Thermostat AC request voltage sense
9 Thermostat AC request voltage sense
15 Blower contact closure sense from relay
16 Blower contact closure sense from relay
I am thinking about changing this setup in the near future however and simply wire another thermostat into the bedroom and use the UMI to control which one is active by switching the common 24v supply between the two. This will free up the templinc for the following:
I am not currently using the heat-request outputs but plan on implementing this and the templinc as a low temperature fail-safe for when the house is in vacation mode. Logic here will SMS me when the failsafe heating system activates then SMS me a second time if the temperature doesn't reach the failsafe setpoint in 2 hours.