Whether you're installing a regular or smart thermostat, don't forget to turn off the air conditioning and furnace units before making any changes. If electrical wiring systems stress you out, hire a home service pro instead to get the job done.
The temperature in my house was going down and it was winter. Need I say more. I found that at 5:30 in the morning Romaniuk Heating was open. I phoned them and spoke to a kind person...