A:AnswerI'm not an expert but this is how I understand it: These smart thermostats need 24V AC to operate. You will need a 'common' wire (usually referred to as a 'C' wire). 4-wire systems often do not provide the voltage loop required. The fan wire sometimes can used as a common but then you lose the option to control your fan. Not a great option.
In my system I have a 'C' wire which is connected to ground. I get 24V AC from my 'R' wire (Rh or Rc). I have a 5-wire system.
>>>There are ways to add a 'C' wire. Check out Venstar's add-a-wire for example. https://venstar.com/thermostats/accessories/add-a-wire/ Honeywell might have a similar option. Contact Honeywell's tech support. I find they are very responsive.
A:AnswerNot sure how long it will keep those settings. If you have a Honeywell account those setting will be held and you can just push them back tot he thermostat when it is operational again. I did take mine off the wall after setting it up to check it on another mount downstairs (that one wasn't working (blown fuse at the furnace) so I was testing) then when I brought it back upstairs it was still set the way I had it and I didn't' have to do anything. It was only disconnected a short time though! Good Luck!
A:AnswerThe Honeywell Home Smart Room Sensors work with the T9 and T10 smart thermostats. The Honeywell Smart Color Thermostat does not have the ability to connect to the Smart Room Sensors.
A:AnswerNot unless you have a generator to power up your system. In the event of a power loss, the thermostat will retain its settings and will even reconnect to WiFi once everything is back up.
A:AnswerI haven't had that problem with unit since I've installed it in Sep '18. So assuming everything is wired properly, do you have the latest firmware? If yes, you may have a bad unit.
