My elderly parents recently moved into a new house. I'm converting their old thermostats to ones they can control with their voice. The most affordable option through their power company was Nest Thermostat Es. I'm having some trouble discerning if these will work with their system. Here is what's currently in place. [u][b]MAIN[/b][/u] Thermostat: [url=https://www.honeywellhome.com/us/en/products/air/thermostats/wifi-thermostats/visionpro-multistage-thermostat-humidity-setting-th8321r1001-u/]Honeywell Vision Pro 8000 (TH8321R1001)[/url] Furnace: [url=https://www.lennoxpros.com/docs/Technical/210575.pdf]Lennox SL280UHV Gas Furnace[/url] A/C: [url=https://www.lennoxpros.com/docs/Technical/210742.pdf]Lennox Elite Series XC14[/url] Wiring at main thermostat: Wiring at main furnace: [u][b]UPSTAIRS[/b][/u] Thermostat: [url=https://www.honeywellhome.com/us/en/products/air/thermostats/wifi-thermostats/visionpro-multistage-thermostat-humidity-setting-th8321r1001-u/]Honeywell Vision Pro 8000 (TH8321R1001)[/url] Furnace: [url=https://www.lennoxpros.com/docs/Technical/210575.pdf]Lennox SL280UHV Gas Furnace[/url] A/C: [url=https://www.lennoxpros.com/docs/Technical/210832.pdf]Lennox 14ACX[/url] Wiring at upstairs thermostat: Wiring at upstairs furnace: [u][b]Some other observations[/b][/u] [list] [*]-Both furnaces have variable speed fans which I've [url=https://support.google.com/googlenest/answer/9259652?hl=en]read[/url] do not work with Nest. However, I'm not sure the current system is even utilizing the variable speed. [*]-Under the setting "FAN CONTROL IN HEAT" both thermostats have "equip controls fan" instead of "tstat controls fan." [*]-Both current thermostats have "DEHUM EQUIPMENT" enabled in settings. The downstairs has "A/C with high fan" while the upstairs has "A/C with low fan". [*]-The upstairs system has a U1 wire which seems to be wired up for the dehumidifier setting of "A/C with low fan." [/list] [u][b]Some questions[/b][/u] [list=1] [*]1. Can I use the Nest thermostats with a variable fan system? I'm assuming I just lose the variable fan functionality (which may not even be in use already)? If not, do I need to look into other options, like the EcoBee? [*]2. The main level seems to be a pretty basic configuration. The lack of a C wire seems to create problems with smart thermostats. The nest supposedly works, but it will sap some volts from R (I think). I do have two terminated cables on both ends though (yellow and brown). Can I repurpose one of these as a C wire? [*]3. Given the minimal wiring of the main thermostat is there anything special about the "A/C with high fan" dehumidification. Is that setting actually controlling specialized hardware or is it just turning on the A/C when the thermostat senses humidity above a certain level? If it's the latter, then I think the Nest can do the same thing, right? [*]4. The upstairs unit seems to have specialized hardware for dehumidification (via U1). Is it possible to adapt this to work with the Nest? [*]5. The main isn't wired with U1, but it's the same furnace. Should this be wired up or do I really only need one unit dehumidifying? [/list] I know this is a lot. I tried to include as much information as possible. Please let me know if I forgot anything! Any help here would be appreciated!

I was overjoyed when i saw the same current thermostat that someone wanting to add an Ecobee-3. But those posts were a few years old and now we have the ecobee-5 on the market. More joy...as you know the Edge is a 2-wire communicating thermoStat And previously I only saw 4 wires going into it...tonight I actually pulled the wire out and it is indeed a 5-wire (with the blue wire!!!!). Background: Recently had solar panels installed and we need a new thermostat. Our HVAC is a Carrier heat pump setup (58CTA110-12), with gas furnace, aprilaire700. There is an Equipment control module (ecm) mounted next to the furnace, i guess to integrate the humidifier, and outdoor temp sensor. does anyone know what the small device is below the ECM’s function is? I hope all the pictures will post here. Question..Will I now be able to do this myself now that i found the cable has a C wire? it looks like there is a red and white wire going to the aprilaire700 that i will need to deal with. so essentially, i will be disconnecting from the ECM and routing everything to amd from the furnace’s board... since the Ecobee-5 will be connected to wifi, i wont need the temp sensor to the outside. I am getting ahead of myself....