This morning I pulled out the basic thermostat on the second floor and started installing the Aprilaire 8870 communicating thermostat. I found the Cat-5 wires behind the existing thermostat wires, figured out where they're connected in the patch panel, and hooked them all up to the 8870 base. It was about then, that I remembered I still need to purchase an Aprilaire 8027 transformer for the Aprilaire 8818 Distribution Panel to supply power to the thermostats. Ugh.

So I patched the old thermostat back on top of the 8870 base as a temporary solution until I get an 8027. Then I went online and ordered an 8027 (along with a few more Simply Automated switches) from StartHomeUSA.com.