house92

My HVAC is a few years old and I have the old-type thermostat with mercury in it. I was considering replacing it with a digital one. Is this an easy "do-it-yourself" project? That may seem like a "duh" question, but I know a lot of people who talk about getting a professional to replace their thermostat, so I wondered if there was something more complicated than matching wires like when installing a ceiling fan. Is it simple, or are there some special tips i need to know if I plan to do it myself? Thanks.

Wuzzat?

If you look at the varieties available, the packaging will state what type of HVAC equip. they are for, so what type furnace/AC you have is the first question to be answered.
The default choice is the simplest 'stat you can find.

Finding some online manuals may clue you in as to what you are up against. One sticking point may be your anticipator coil setting which your old one had and your new one will not have.

The good news is "nobody" dies from 24 vac. and I can't even the current flow resulting from this voltage.

For an improvement in comfort, some types have an outdoor sensor so they can adjust your indoor temperature to compensate for the radiant heating component your walls are providing depending on the outside temps.

If you don't get into trouble with it, the install might take less than one hour, excluding painting/drywall patch if necessary. To avoid this patching you might get one with a bigger 'footprint' than the old one.

house92

What is the average cost to have a professional replace it with a simple digital? I won't have any drywall issues. I live in an old house and the thermostat is on a wall with wood paneling, so the thermostat replacement will be the only work involved.

Wuzzat?

Where I am
http://zipskinny.com/
the median household income is ~$110K and this job would take an hour and would cost maybe $100 for labor.

Adjust this price for your area's median income.

A $7 thing in Austin costs $11 in Honolulu, IIRC.

keepinitcool

Go down to your local hardware store and pick up a 1 heat/1 cool single stage digital tstat. Shut power off to your furnace, rip that old one off the wall (might want to disconnect wires too, remembering what was connected to what of course). Now mount the base of the new one to the wall, pull the tstat wire through and connect to the new stat exactly how it was connected to the old one. Snap the tsat into the base on the wall and turn your power back on to your furnace. Test that bad boy out and enjoy. This is all assuming you have a simple system that only has single stages for heating and cooling of course. Cost will be between 25 to 50 bucks i would assume. Add 100 bucks to that for someone to come do it for you.

Wuzzat?

Label all wires so you can return to the original setup.

The colors are not standard but the terminal designations may be good enough.

With four wires, each being hot, heat, cool, fan
and a voltmeter
you can confirm the function of each wire.

Find a wire (probably red) that gives at least 24 vac to each of the other three wires. This is the hot lead. Each of the other three wires taken two at a time should not have voltage between them but should read a few ohms.
Jumpering this lead to each of the other wires should give heat, cool, or fan.

Almost all of the $100 is the cost to have someone else assume the risk in this project.