February 18th, 2008

How-To Tuesday: Install a Programmable Thermostat

Posted by Jason Pelletier, Low Impact Living

Installing a programmable thermostat is one of the most cost-effective ways to save energy and to cut your carbon footprint. In many parts of the country they can cut your energy bills by $100 or more a year, and as a result pay for themselves in your first heating or cooling season. They save on both heating and cooling, so there’s never a wrong time to consider an upgrade.

What are the benefits?

Programmable thermostats save energy and money in several ways. First, they automatically adjust your home’s temperature so that you aren’t over-heating (or cooling) when you’re away from home or asleep. The savings are greatest when there’s no-one home during the day and you can lower the temperature, but they’ll still save at night even if someone is at home. Second, certain models can operate your furnace in ways that maximize efficiency. Finally, some models notify you when your furnace filters need replacing, or when there are malfunctions with your furnace.

Can I Do It Myself?

First, before we get started, this is only a DIY project if you’re comfortable working with electrical wiring and can do so safely. If you have any concerns at all, it’s best to leave it to a professional!

To Do Before Buying a New Thermostat

Before you buy a thermostat, it’s important to know what type you’ll need. So, these quick tips will help you pick the right one.

1) Note what type of heating system you have (boiler, furnace, radiant heating, etc), and what the fuel is (natural gas, electricity, heating oil, etc).

2) Turn off the power to your thermostat at the circuit breaker.

3) Remove your existing thermostat, and investigate how many wires are connected to the back. There could be anywhere between 2 and 10. Don’t disconnect them yet! Also, most thermostats are low-voltage and will have small wires. If you have electric resistance heating (baseboard, for example), you might have a line voltage thermostat. This will have heavier wires attached, and the wires will likely be connected in an electrical box behind the thermostat using heavy wire nuts.

4) Purchase a thermostat that meets your needs:
  +  Low or line voltage?
  +  Right number of connecting wires?
  +  Works for heating, cooling or both?
  +  Can be programmed to fit your lifestyle - different program every day (7-day programming), weekday + two weekend day programming (5-1-1 programming) or weekday + weekend only (5-2 programming).

You can see a few versions that we recommend here.

Replacing your existing thermostat

1) Once again, MAKE SURE you’ve turned the breaker for the furnace circuit off at the electrical panel.

2) Unscrew the old thermostat from the wall, but don’t remove the wires yet.

3) Using either masking tape or the labels that come with your new thermostat, note the letter on the thermostat that the wire correponds to and place the tape or label around the wire. Make sure that the wires don’t fall into the wall when you remove them.

4) Most thermostats come in two parts, a wall plate that screws onto the wall and the main thermostat unit that plugs into the wall plate. Mount the wall plate to the electrical box that remains from the old thermostat. Pass the wires through the hole in the mounting plate.

5) Connect the wires to the terminals that correspond to the letters on the wires.

6) Install batteries in the new thermostat unit. If your model allows for it, program the date, time and scheduling (based on your model’s instructions) before attaching it to the wall. Otherwise, attach the unit as shown in the instructions and complete the programming. Programming may seem complex to begin with, so make sure you follow the directions closely. With a little practice, though, adjusting the programs will be a snap.

7) Turn the power to the furnace circuit back on at your electrical panel. Test the new thermostat and make sure it operates your HVAC equipment as expected.

That’s it - you’re now well on your way to lower energy bills, a smaller carbon footprint, and a more comfortable home!

I’ve actually found the websites of several big thermostat manufacturers to be very helpful. Honeywell has this entire section for do-it-yourself thermostats. Aube has information about thermostats organized by heating / cooling type. Click on the relevant model using the menu on the left side of the page, and then you can download the installation and operating instructions before you purchase.

Please let us know if you have any additional tips or tricks by leaving comments below.