As of build 827 XTension supports the RS-485 serial communicating thermostats from RCS. RCS has been in the communicating thermostat business forever and make a terrific product. The also make versions that accept changes and setbacks for all the various powerline and wireless communication protocols from X10 to ZWave and UPB but by far the most reliable is the 485 serial model.
The RCS thermostats are also the easiest to retrofit. They come in 2 parts, the thermostat which connects via 4 of the existing thermostat wires up to the second part, a control box at the furnace. The serial wire is run to the control box at the furnace and not down to the stat itself so it’s much easier to get a wire in there than it is to get one into the middle of a finished wall usually. The connection to XTension is via any RS-485 half duplex adaptor. There are RS-232 to 485 adaptors available for under $20 if you have existing adaptors or want to use an ethernet to serial adaptor. They also work with the FTDI chipset USB/485 adaptors and also the 485 port on the Barix Barionet 50 boxes. 3 wires are required for the serial, the data +/- and a reference ground.
Xtension can control any reasonable number of stats on a single port, but it does expect to be the port master at address 0. It should be possible to setup as an observer on the network and piggyback off of an existing install with another master controller but I do not have this equipment to test with, if you’re in this situation please drop me an email and we can discuss some testing that will be necessary to make sure it will work.
Once you have a connected thermostat and have create a device in XTension pointing to it you can create the units that you need to control the device. You can name the units anything that makes sense to you, but the addresses that you use will link them to the device on the thermostat. The naming convention for the addresses is the name, i.e “TEMP” followed by the address of the thermostat. So if you have only one then you’ll address the current temp unit “TEMP1”
Xtension will regularly set the clock and date on the thermostat to keep them in sync. Additionally commands are available to set the setback mode and levels and the various offsets. These will all be implemented but if you wish to use them before I get to them please drop me a note and like the vent control I will add it sooner rather than later.
Make sure you’ve read the General Thermostat Notes