Is this config too complicated for DIY? Replacing dual-zone thermostats for Nests.
Hello All,
We moved into a home last year with what appears to be dual zone (main floor, and second floor Honeywell 7-day thermostats) but we decided we wanted to look at Nest.
The compatibility checker isn't really going to help because it appears the system might be more complicated, so here is what I know:
- I know this system runs cool/heat/e. heat modes.
- The previous owner mentioned that Heat is the heat pump and e. heat is natural gas.
- Also this thermostat pulls the outdoor temp reading from somewhere. It is apparently supposed to know when to switch from heat pump to gas based on that reading, but I was never sure of that. When I knew it was too cold for the heat pump to be efficient I manually switched to e. heat and it worked exactly how it should (gas heat)
Anyway opening up the two thermostats to see the wiring definitely threw me a bit as they could not be more difference and I wanted to see if anyone knowledgeable can tell what is happening without tracing these wires back to the furnace (which is in a crawl space and not overly accessible)
Here is the main floor wiring and here is the 2nd floor wiring ... so, much to my chagrin, it does appear that I am going to be found wanting when I plug this into most HVAC wire compatibility checkers.
Now I know I have seen that the Nest can work with just about anything as long as you know what every wire is controlling - I just wanted to see if anyone was confident enough to tell me if I could replace these 2 thermostats for 2 nest thermostats and how the wiring would have to be mapped. While I would like to have nest/learning/wifi thermostats available I do not want to get an installer out at this time; I would rather just use what I currently have (which works well) for another year or so before taking the dive and having a professional come out. I just wanted to make sure that I turned over this rock and confirmed its too complicated for me to do on my own or not and figured that if a configuration like this was even relatively common I might still be able to install myself.
Thanks for any help or insight you can provide, it is always welcome!
5 comments · 100% upvoted · other discussions
Main floor looks fine. Follow the heat pump labels and should be an easy install.
2nd floor is proprietary wires and won't work with Nest or most other thermostats. You may be able to go to the other end (zone control or air handler) and see if standard terminals are available.
bobbybac [OP] 1 points · May 2019
thank you for that information this is very helpful information. When you say proprietary to you mean to the air handlers or to the thermostats? or "it depends"? Heck I guess it could also be "proprietary" to whatever company rigged all these up!
I ask because these are honeywell thermostats and if I don't end up forcing nest perhaps I could easily get the step up honeywell model that provides wifi? The models I have don't and I think that + basic scheduling will be good enough going forward. I will also do some research on this so don't feel obligated I just figured I would ask since you clearly know what you're talking about. thanks again
AStuf 1 points · May 2019 · Nest Thermostat Generation 3
Most of the time if there are enough wires in the wall the system can be converted to conventional wiring to use Nest and other standard thermostats.
If can't add wires then you can look at Honeywell's system - https://www.amazon.com/Honeywell-YTHX9421R5127WW-Prestige-Internet-Thermostat/dp/B00OZXEEG4/