Replacing - Installing a Thermostat

Replacing a Thermostat My thermostat died on me. It's a good five or six years old and it quit turning on the furnace via the programmable settings. I had a new furnace installed and the installer indicated that my thermostat was better than the one he would be putting in so I kept my thermostat. Six months later, it died on me. So if you get a new furnace, consider replacing your thermostat at the same time. You can save yourself some trouble later. Anyhow, this is a shot of the old thermostat. I can still turn on the furnace via the "hold" function. So if I want to hold the temperature at a certain setting, the furnace will come on. But I can't get it to kick on via the other functions. Begin by shutting off all power to the house. That way you know the furnace is off.

Replacing a Thermostat I've taken off the faceplate in this picture. So far so good. Everything is going smoothly. Next, I'll remove the batteries from the thermostat and the two screws that hold it on the wall. I'll wait to remove the wires from the thermostat until later. I want to secure them so that they don't fall back into the wall. That would be a real nightmare!

Replacing a Thermostat Ok, I've removed the back-plate of the old thermostat and secured the wires with a cord. There are probably better ways of securing your thermostat wires but this is what I came up with on the fly. The other end of the cord is tied to a combination lock. If these suckers go down into the wall, you are probably screwed big time.

Replacing a Thermostat Here's the new backing plate. After I got that on, I unsecured the wires. I probably should have moved it over just a tad to the right. Oh well, c'est la vie The directions indicated to label the wires beforehand, stating that the color of the wires is not always determinative of what they are. Since I had changed this thermostat once before and the wires worked out, I assumed that I was okay. In this case, the colors matched with the description.

Replacing a Thermostat Ok, she's wired in. I've got a four wire system so I left the jumper wire in place. I've got a blue wire that I did not attach during the first thermostat replacement. Of course, I've forgotten why I didn't. I know it wasn't necessary. I'll have to do some research. So the blue wire has been left unattached here as well. Here's a quick tip that will save you some time when wiring - Wires should be inserted behind the black terminal shields. If you do this, they will stay in. Basically, there are black terminal shields behind the screws.

Replacing a Thermostat Here's the finished product. This thermostat has an auto recovery feature (via a switch on the back of the faceplate) which allows the furnace to gradually recover from an energy saving setpoint temperature. This is basically so you don't blow your wad going from 60 to 70 degrees in 20 minutes or less. Mine was set in the auto recovery mode by default. My thermostat was also set by default for a gas furnace. There is a switch on the back of the faceplate for a gas or an electric furnace. This replacement thermostat is a Hunter Model 44110 that I picked up for $29. A couple other neat features include a filter replace reminder. When you replace your filter, hit a button and the thermostat will remind you to change it the next time. The thermostat also has a span cycle setting which allows you to adjust the systems cycle rate. By default it is set to 2 - which means the system kicks on when the temperature is within a degree of the desired temperature.