01-16-2023 05:38 PM
I tried installing the Nest Thermostat but it says the wiring is incompatible, but upon searching in this community, it seems like others had success with a Honeywell TH4110D1007, so I'm wondering if there is something in my wiring (the letters in the picture) that is tripping this up. It's a relatively new house (2015) so think it would be odd if wiring was such that it wouldn't accomodate a modern thermostat. Thanks so much for all your help!
01-17-2023 04:52 PM
In the picture it is hard to see the letters for the terminals the wires are connected to. It looks like it is probably something like this:
W - White
Y - Yellow
G - Green
R - Red
Those are relatively normal connections and a Nest thermostat should be compatible. HOWEVER, there is not a C Common wire connected. Nest thermostats work best with a C "common" wire.
Use the Compatibility Checker to see if your Nest model is compatible.
Information about the C (common) wire. Here are some options:
You may not need C, but is it good to plan for it just in case.
01-18-2023 12:07 PM
Thanks! What is the benefit of having a C Common wire connected? What is the difference in performance/functionality when connected?
01-18-2023 12:22 PM
The common wire is dedicated to powering the thermostat. Without C the thermostat will try to "borrow" power from the other wires and/or use the battery. For some HVAC systems it works fine without C and for others it can be problematic.
01-18-2023 12:31 PM
Ah, so if I maintain working batteries, this would t be an issue (albeit this isn’t the most efficient solution)?
01-18-2023 01:10 PM
If you have the "Nest Thermostat" (opposed to E or Learning) it will not run on batteries alone for any length of time. It requires a source of power. The batteries are primarily used as backup during power outages or when the furnace is being maintained. It may get enough from the other wires, but if not, you would be replacing batteries frequently - possibly every few days.
My recommendation is always use C if at all possible. Given the age of the home there is probably an unused wire in the thermostat cable, and most likely there is a C connection on the furnace.
Read the documentation linked to in my first reply to find out more information.
01-26-2023 02:29 PM
Hello there,
I wanted to ensure that everything was covered here.
Thanks for sharing your expertise here, @sporfrog.
@davidjhoberman, I hope you've got the answer you're looking for. If you're still in need of assistance, feel free to let us know.
Regards,
Mark
01-30-2023 11:55 AM
Hello davidjhoberman.
I wanted to follow up and see if you are still in need of any help. Please let me know if you are still having any trouble from here, as I would be happy to take a closer look and assist you further.
Thanks,
Mark
01-30-2023 06:07 PM - edited 01-30-2023 06:09 PM
Thanks @sporfrog for the advice and @Markjosephp for following up. I'm a bit at a loss. There is a spare blue wire in my thermostat that isn't plugged into a slot and I was advised to plug that into 'C' in the thermostat and make a similar connection in my HVAC. Below are the pictures from my HVAC, the blue wire seems to be connected bunched in with the other wires (see below). I'm a little over my skis here, appreciate any advice. TIA!
01-30-2023 06:08 PM
01-31-2023 01:09 PM
Hey there,
Thanks so much for the help sporfrog.
I wanted to follow up. If you are in need of a Nest pro, you can follow the link here to learn more about that. Please let me know if you have any questions from here, as I would be happy to take a closer look and assist you further.
Best regards,
Jake
02-03-2023 10:56 AM
Hey there,
I wanted to check in and see if you had any questions from here. Please let me know, as I would be happy to assist, and answer any you may have.
Best regards,
Jake
02-05-2023 12:08 PM
Hello davidjhoberman,
It has been a few days since your last reply, and we're going to lock the thread within 24 hours. If you have any questions, please feel free to create a new post.
Thanks,
Mark
01-31-2023 11:32 AM
I suggest seeking out an HVAC professional. The images attached are not the thermostat cable and should not be altered or changed.
If you are still determined... there should be a cable with multiple wires in the cable. It will have the same outside jacket color - typically a shade of brown - as the cable at the thermostat. Inside it will have multiple wire colors that match those at the thermostat. The suggestion for using an extra blue wire applies to an unused wire in that cable NOT any blue wire in the furnace.
The wires in the thermostat cable will be connected to a wiring terminal typically on or near a circuit board.