Hello. For the Honeywell '9421 T-stat and '5421 EIM combo, what is gained by connecting a discharge air temperature sensor? I'd like to think it offers some dynamic heat-mode optimization, however in reviewing Honeywell docs, one states it does nothing but offer setup status while another indicates it can be used to prevent coil freeze in cool-mode. Thank you and regards!

Hello everyone, I am buying my parents a new programmable thermostat, and have run into an issue with compatibility. My parents have a zoned forced air system, which means the existing thermostat has the following wires: O B G Y R W The issue is that the O and B wires, which I guess control the zone damper, cannot be separately hooked up to O and B terminals on the new programmable thermostat. It only has an O/B connection. I have read varying bits of advice on this problem across the web but can't seem to get a clear answer. One solution I heard was to essentially connect and set up the thermostat as if it were a heat pump system, with the O connected to O/B terminal and B connected to C terminal. Unfortunately, the person on that post didn't follow up about whether this solution actually worked. Any advice would be greatly appreciated! Would love to make sure this thing can function before giving to my parents! Thanks in advance.