Weeds: Nah... "Since your picture shows 'Temp Hold', the unit is in Temporary Hold. If you press ^ or v to change the temperature from the program, this is a Temporary Hold. This only lasts for 2 hours and then it reverts back to the program temperature. I'm betting this is what is going on: the program is running and at 8am it switches to 62. After a while, you feel chilly and look at the display and think "how did this get changed?", you push ^ to raise the temp to 72 and the unit goes into Temp Hold. Two hours later it reverts back to 62, you get chilly and the cycle repeats. " I've long "felt" the two-hour default reset. This isn't what's going on. I have the thing programmed, and the display at least still reads that I still have it programmed, to go to 67 at 5:45a, 60 at 7:45a, 68 at 5pm, 62 at 9:15pm . If I override it at 10am from, say, 67-deg to 69-deg it will do what I say. But if I override it from, say, 67-deg to 70-deg at 10pm, it will not do what I say. It will reach 70-deg and then keep going, it will not stop. During the day it will reach the temp I tell it to hold at and it will hold the temp there. At night it will ignore the upper maximum. I cannot understand it, but this seems to be empirically what's going on. If you say somehow the factory default is being reverted to, what I cannot understand is why the thermostat override seems to work in the am but not in the pm. If, as I think you are saying, it is not my thermostat that is actually controlling things, but the default furnaces', then why is it seemingly "feeling" the override in the morning only? OK, let me try to unprogram the thermostat altogether ... I wanted to wipe the program clean rather than reprogram it to "nothing". But I'll try this instead...

Do you have the manual for your Honeywell thermostat? If yes, what is the B terminal? Normally it is the heat pump control. The B terminal on the thermostat is connected to a black wire. The the B terminal on the control board is blue. Have you figured that out? I looked at XV80 documentation I found on line. I see a terminal on the control board labeled B/C. The note says it is the common connection. You should be able to find the the product data document if you search the model number. You may be able to use the B wire for the C connection. You need to be careful and not fry your new thermostat. The R and Rc (normally tied together) is the 24 V supply. The C is the ground. The WiFi radio draws most of the power. If there is no ground then the 24 V circuit is not complete. The Nest will then power itself with the internal lithium battery which lasts about a day.

For me the nest never felt very smart. I wanted the option of using smart features like running the furnace fan to balance temperatures between zones. There is no option of doing this on the nest. It couldn't figure out the schedule of when we were home, away to keep it comfortable. It was better than a programable thermostat but only because of geofencing. I'm saving electricity by only running things on my system when it's required and almost every zone in my home has a consistent temperature. Customizability of the Ecobee is just way better. Smart things with Samsung helps for sure. Does it have improvements to be made, yes, geofencing could be better between different users, but I have figured out a way to have it do everything I want.

Hey folks. Maybe I can explain this a little better. The transformer in the Taco SR503 is rated at 24VAC at 15 VA which translates to about 0.625A. This has to power all the relay coils (3 of them) plus the LEDs. Taco is saying the transformer is only providing enough power for when all three relays are on (calling for heat), plus the 4 LEDs. Assuming standard engineering practice of providing up to 50% more power than continuously required, the transformer may be able to provide the additional 150 mA (3.6 vA @24VAC). That is only an assumption. I looked up the 24VAC LY2 Omron relay specifications and it consumes upto 1.2VA when actuated. Since there are 3, that's a minimum of 3.6VA power required when all zone relays are on. So for those who say "wire it up and try it", it could work using a total of 7 or 8VA or maybe a little more with the resistors and LEDs on the board, which is still under the transformer's 15VA rating.. The transformer will run a little hotter, but I doubt the 1A fuse will blow. The fuse is a fast blow and over time, as it runs hotter than designed, it may fail and knock out all heat. Just hope it doesn't happen in the dead of winter. If you plan to test it, make sure you turn on all zone thermostats for a good long while to draw max current. If you're skilled enough, put your multi meter into ammeter mode and put the probes in place of the fuse to see how much AC current is actually being drawn when all zones are firing. (should be mAmps). If you exceed 660 mA, your transformer will run hot because it is rated only for that much continuous power max. (This would be bad.) Since I'm in the same boat, I plan to measure it when one zone is calling and multiply it by 3 for total load when all three zones are calling. If I have 300 mA to spare, I'll use the Taco to supply my C-wire, thus ensuring an adequate power budget from the 15VA transformer. I'm no expert, but I hope this helps more than confuses...