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Installing a new Thermostat

Recently I replaced my aging thermostat with a new, smart, Nest thermostat, and I thought I’d quick capture a how-to for anyone who wants to do the same but probably doesn’t have the skills to do so.

1. Remember your existing thermostat’s battery is dead.
2. Replace the battery.
3. Wonder why the new batteries refused to revive it. (Protip: You will never learn the answer.)
4. Try various “reset” techniques.
5. Decide you wanted a new smart thermostat anyway.
6. Check that the existing wires coming out of the thermostat hole support smart thermostats.
7. Realize they don’t.
8. Google “Nest thermostat without the right wires”
9. Learn about a “magical blue wire” that usually exists but is often hidden, tucked into the wall by lazy HVAC installers.
10. Check the wall, find the blue wire. (Hooray!)
11. Go to Target
12. Acquire Nest Thermostat.
13. Return home.
14. Follow the directions that came with the Nest Thermostat.
15. Wonder why it is also not working.
16. Realize it’s new-in-box batteries are also dead.
17. Ponder a future where batteries are no longer needed.
18. Replace the batteries.
19. Be thrilled it now works!
20. Find a warning light in the Nest’s settings that says the “magical blue wire” isn’t connected correctly.
21. Take the thermostat down.
22. Re-strip the wire.
23. Reconnect the wire.
24. Reboot the Nest.
25. Be taunted by the warning light’s continued presence.
26. Swear. (Not required, but recommended.)
27. Google “thermostat blue wire not working.”
28. Discover those same lazy HVAC installers also sometimes don’t connect the blue wire to the furnace.
29. Swear. (Again, not required. Still recommended.)
30. Go down to your basement or wherever you keep your furnace.
31. Search for the thermostat wires. (They are likely camouflaged with the other thousand wires in this part of your basement.)
32. Hit head on joist. (Swear, required.)
33. Find the blue wire, notice it is in fact dangling unconnected next to the furnace.
34. Google “what should the blue wire be connected to?”
35. Discover that the blue wire should be connected to the “common” port on the furnace’s control board.
36. Take apart the furnace to find at the control board.
37. Discover the control board already has a wire coming off the “common” port.
38. Follow the wire.
39. It goes to the Air Conditioner.
40. Google “can I wire a Nest into the common port on my furnace if it’s already connected to an air conditioner”
41. Discover a wiring diagram that says yes you can. (Hooray!)
42. Start to wire everything per the diagram.
43. Realize that the dangling blue wire is 4’ too short to reach the furnace’s common port.
44. Swear. (Louder this time, they should be able to hear you upstairs.)
45. Debate with yourself for an indeterminate amount of time the merits of going to the store to acquire “official thermostat wire.”
46. Decide not to, you probably have perfectly fine “wire” somewhere in the house.
47. Remember an old spool of unnecessarily heavy gauge wire that’s probably “good enough” and retrieve it from a disused toolbox.
48. Cut off 5’ of it.
49. Wire the dangling blue wire to the common port on the furnace using the new 5’ wire.
50. In a fit of unwarranted optimism, put the furnace back together.
51. Return upstairs to the thermostat.
52. Reboot it.
53. Make sure the warning light is gone. (It is!)

Congrats! You now have a smart thermostat.