You’re right, this could be a lot easier if we were to implement something along those lines, you can look forward to some new features soon. In the meantime, assuming you’re in bacnet protocol, you can refer to the stat by its instance number.
10 IF 123AI1 > 20 THEN START ACSTAGE1 <where 123 is the bacnet instance number for the stat and AI is the bacnet keyword for reading analog inputs.
If you’re in modbus protocol then refer to the thermostat by modbus ID and modbus register number.
10 IF 1.2.MB_REG121 > 20 THEN START ACSTAGE1 <where:
1 is the ethernet network ID of the T3 controller
2 is the RS485 subnet modbus ID of the thermostat.
121 is the modbus register for the internal temperature sensor of the thermostat.
You can get all the modbus registers from this spreadsheet and there’s a modbus register tool in the T3000 menu system you can also refer to.
Note: The names of the modbus registers aren’t currently showing up from the T3000 modbus tool properly, will be fixed this week.
Bacnet mode is considerably easier because the i/o and other parameters can all be read easily using the bacnet keywords rather than digging through the register list when working in modbus protocol.