Living Efficiently With Tom: Installing a Programmable Thermostat

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May 25, 2010 – Programmable thermostats are an extremely effective way to save serious money on your heating and cooling costs. So replacing our house's old manual model was a top priority soon after we moved in. And while it may look tricky at first, it's actually a fairly straight forward project. Just make sure it's actually programmed.

The Alliance has some background information on programmable thermostats, explaining the benefits and how automatically reducing your heating and cooling can save you energy and money.

Going Shopping

Step one is, of course, to acquire a shiny new programmable thermostat. You may still be able to select one with an ENERGY STAR label, though that label has been suspended as of December 31, 2009; those that did qualify for the label are minimally capable of having separate weekday and weekend programs, and four settings per day.

Regardless, those are the sort of capabilities you should look for. Whether you need one that can handle different programs for different days of the week (often labeled '7-day') or one that just does weekdays and weekends (often labeled something like '5-2' or '5-1-1') is up to you. You can save some cash with a 5-2. Since my wife often works from home, I went for a seven-day model so that we could program her schedule into the thermostat.

Assuming you don't have any particularly exotic heating and cooling system, most any available thermostat will work. For example, I've got forced air heat and a standard split AC system.

If you've got a geothermal heat exchanger or a chilled water cooling system, I can tell you that a) you're probably too advanced for this blog, and b) you will need to look more closely at specifications before you buy to ensure compatibility.

Removing Your Old Thermostat (Be Careful!)

For me, the trickiest part of the project was removing the old thermostat from the wall.

Not to scare you, readers, but be extremely careful as it's likely your old thermostat contains mercury, a potent toxin. If you break anything containing mercury, evacuate your house and call the fire department.

Bear in mind: it's likely that throwing the old thermostat in the trash is illegal in your area. You will probably have to take it to a hazardous waste facility; check with your county or city public works department.

While the thermostat wiring operates at low voltage, it's good practice to turn off circuit breakers or fuses when you're working with electrical wiring.

Once you've removed the cover or body of the old thermostat, be sure to note which wires are connected to which contact points. If your thermostat isn't too ancient, its contact points ought to have letters printed on or adjacent to them. My new thermostat included small stickers for labeling the wires with the appropriate letters, and the wiring itself was in common-sense coloring (yellow for 'Y,' etc.).

Alternatively, you could use a bit of masking tape and a ballpoint pen.

As you detach the wires from the old thermostat, make sure they don't fall back into the wall cavity. If they aren't stiff enough to stay up on their own, consider taping them to the wall while you work.

Installing the Your New Programmable Thermostat

From this point on, follow the instructions that came with your new thermostat. Mine began with screwing a base plate (to which the wires were connected) into the wall. Since I'd already labeled all the wires according to the old thermostat, connecting them up to the appropriate contacts was simple. The body of the thermostat then snapped onto this base plate.

Programming Your Programmable Thermostat

Again, this will vary by model, so follow the directions. Ideally, your thermostat will come with a default energy-saving program that will operate automatically, but you should set it according to your schedule.

And though the ENERGY STAR website has a table of recommended settings, your own needs will undoubtedly vary. For example, if you've got kids that get home at 4 p.m., you'll need different settings from those of a home that remains unoccupied until 7 p.m. Maybe you work on weekends and are off midweek. Maybe you spend weekend at home, or perhaps you tend to be out and about on those days.

Whatever the case, just make sure your thermostat is actually programmed. And remember, you can manually bump the temperature up and down as you need to. Your thermostat should return to its program after some pre-set time, unless you specifically set it not to.

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