Let me start this off by saying that I have successfully installed 4 Nest Leaning Thermostats. Two in my previous and two in my current home. Thats not to say that you learn something new every time you install something, even if it is the same product you have done time and time again.
Most recent lesson…Always cut the power to something that you are working on yourself.
Go to the breaker box yourself and make sure that the unit is off. The correct unit!
…or you could be making a late night trip to try and find someone who is open that may carry a replacement.
Now in everyones defense I have never seen a panel box that did not have a shut off for 1 of the 2 units but this was the case. To be more safe I recommend having a non-contact voltage tester like This sold by Home Depot laying around to make sure you don’t make the same mistake.
Nevertheless all was made good and the final product is up a running with a minimal snag along the way.