Thermostat Installation for DIY Dummies

Thermostat wiring

Unless the situation is pretty dire, we suspect most of you wouldn't go next door and ask a neighbor to stop mowing his lawn and take out your kid's appendix; ditto with writing you a new will. Doctors and lawyers go through extensive training for a reason – and, for that matter, so do professional plumbers and electricians. If and when we do attempt home repairs, we certainly want advice and instructions from an experienced person (preferably professional) instead of someone who... well, someone who's obviously never done the job. You know, someone like Sally Odum, who we caught pretending to know "How to install a new thermostat" at the site called Catalogs.com (formerly WhoWhatWhenWhereWhyHowWhatever or something like that).

We get the definite impression Sally's never installed a new thermostat herself (at best, perhaps she was around while her "hubby"¹ installed one) based on some of her dumber misinformation. She begins by informing her readers that,

"If you have an existing thermostat that is connected to an electrical box, or runs off 120-volt current, you should not try to install a new one by yourself."

First, thermostats wired to the electrical system are pretty rare (none of our DIY staff has ever seen one, even in 100-year-old houses) and second, why should replacing one be any different from working on any electrical wiring? Odum, however, soldiers on, explaining that the first thing you must do is

"Cut off the power going to the unit by removing the appropriate fuse to that area [emphasis ours], or turning off the circuit breaker..."

...which is a common misconception among those who've never actually done any electrical work: the thermostat isn't on a fuse (or circuit breaker) for "an area," a low-voltage thermostat is wired directly into the HVAC system. If you gotta cut the power, you power down whatever the thermostat controls, not the "area" where your thermostat is mounted on the wall. Sally goes on to blather about taking apart the old thermostat. This moron says to "Write down all information from your old thermostat so you can pick out the new one properly. You may even want to take the cover off the old thermostat to the store with you so you can compare it to others."

Odum, you ignorant fool, you don't need "information from your old thermostat" to choose a new one -- you need to know what kind of heating system you have, whether it controls separate heating-cooling system or a heat pump, and other facts. Not just the model number of the old thermostat -- that's probably damned near useless!

Once she's gotten that misinformation out of the way, Sally moves on to wiring up a new thermostat:

"Your new thermostat will most likely have some sticky labels included in the package. These are labeled 'A', 'B', 'C,' [sic] etc. They are for the wires. Before you disconnect the wires on the old thermostat, label them to correspond to the new thermostat. This will become clear when you look at it. You want the 'A' wire to go to the 'A' on the new thermostat, etc."

Two things, dumbass: first, newer HVAC systems use color-coded wires, and you match the yellow wire to the "Y" terminal, the orange to the "O" terminal, etc. (see image above). Second, if you have even half a brain you'll label the individual wires BEFORE you take them off the old thermostat, especially if they aren't color-coded! Oh, and if you have a whole brain, you'll take a picture so you can catch any jumpers like the black one in the image above.
No, as usual, this is the sort of how-to written by someone who actually dithers over "Find[ing] a screwdriver to match [the] screws"! Instead of shared experience, this rubbish is nothing more than someone else's instructions, reworded and with any bits the writer didn't understand omitted. That's probably the chief criterion for awarding a freelancer the Dumbass of the Day. Go, Sally, go.

¹ for the record, we at the Antisocial Network detest the word "hubby"

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