It wasn’t so long ago that homeowners shouldered round-the-clock responsibility for monitoring the hearth fire; letting it go out would make the house uncomfortably cold or (during extremely cold weather) even deadly. Today we take for granted the central heating systems and thermostats that relieved us of fire-tending duties. But as energy costs continue to climb, comfortable temperatures come with an ever-increasing price tag. The good news is that technological advances in thermostats enable us to bask in comfort and maximize energy efficiency — without ever having to adjust a dial.
Most everyone knows how to operate a mechanical thermostat: Point the needle to the desired setting and your home will remain that temperature until you change the setting. These elegantly simple devices rely on two primary components: a coiled bimetallic strip thermometer and a mercury switch. The coil expands or contracts with temperature changes, tipping the mercury switch that activates the heating or cooling system. Mechanical thermostats often also feature a second switch that controls the fan.
During the past 15 years electronic or digital thermostats have replaced mechanical thermostats as the prevailing choice for homeowners. Electronic thermostats use a component called a thermistor instead of a coil thermometer to measure temperature changes and a tiny computer called a microcontroller to determine specific temperature readings. More important, the microcontroller makes digital thermometers programmable — a feature that can save as much as 35 percent of annual heating and cooling costs. In general, you can save about 1 percent for every degree you lower (during the winter) or raise (during the summer) the thermostat setting for an eight-hour period. Exact savings depends on your climate, your home’s construction and proper installation and operation of the thermostat.
Manufacturers typically estimate a 10-year life expectancy for thermostats, but plenty of 30-year-old mechanical models still operate perfectly. So if you’re home all the time and rarely change your mechanical thermostat’s setting, you probably don’t need to replace it. When it fails, you can install an easier-to-read electronic version for $15 to $30. But if you regularly spend hours away from home and don’t mind a less comfortable setting while you sleep, a programmable thermostat ($30 to $100 for DIY-installed models) can quickly pay off in lower energy costs.
Basic programming
The primary function of a programmable thermostat is to consistently adjust the temperature of the house from comfortable temperature settings when you are moving about the house to lower or higher temperatures when you are away or asleep. Additional features most programmable thermostats offer include digital displays, fan-operation controls and reminders to change the furnace filter.
Programming is typically based on four time periods that are assigned names such as “wake,” “day” (or “leave”), “evening” (or “return”) and “sleep.” You assign each time period a temperature and the thermostat makes sure that the heating or cooling system adjusts to the temperature at the assigned time (called recovery). Look for thermometers that feature a modified or adaptive recovery system, often labeled “smart” or “intelligent” by the manufacturer. These thermostats monitor the time it takes to reach each assigned temperature (this takes about a week to determine) and then adjust to gradually recover to the next temperature on schedule, resulting in more efficient operation.
Programmable thermostats feature at least two-day schedule combinations. A basic 5-2 combination lets you set two daily schedules: one for weekdays and one for weekends. A 5-1-1 combination enables you to set three daily schedules: one for weekdays, one for Saturday and one for Sunday. If you have an irregular personal schedule or your home has multiple occupants with different schedules, you will most likely want seven-day programming that lets you set a different schedule for each day of the week.
Don’t be afraid of being locked into a specific setting; you can override the programming with a temporary temperature setting at any time. Most models will maintain the temporary setting until the next scheduled period starts. If you want to maintain a temporary setting for more than one day, you simply enter it as a “hold” setting. For example, if you were leaving for a week and wanted to maintain a lower setting while you were away, you would set the temperature as a “hold” setting. (Some manufacturers also offer specific vacation setting options.)
Advanced features
Like most digital devices, programmable thermostats are constantly evolving to include more advanced features. New models are compatible with multistage furnaces, operate multizone systems, monitor outdoor temperatures and indoor humidity levels and control whole-house humidifiers and dehumidifiers.
The latest advances are targeted at making thermostats easier to use and program. Features such as touchscreens, voice activation and intuitive menus let you program a thermostat without a manual, and remote access lets you control the thermostat via phone and the Internet. For example, the Bryant Evolution thermostat offers remote access so that homeowners can monitor and adjust their systems and their designated dealer can diagnose some system problems and pull parts before a service worker leaves the shop. Like alarm and lighting systems, thermostats are often standard components of home-automation systems.
If you want the most advanced features available, you’ll have to invest in a professionally installed model. But features such as touchscreens, intuitive menus and multistage furnace compatibility are already filtering down to DIY models.
Before you go shopping for a new thermostat, you must know what type of system you have: a conventional (forced-air or hot-water) unit or a heat pump. Select a thermostat that is compatible with your system, including any specific operating features such as multistage heating or cooling functions. This information will be listed on the thermostat package.
Installation takes about an hour. If you’re replacing a mechanical thermostat, keep in mind that the switch contains a small amount of mercury, so you shouldn’t just throw it in the trash. Instead, check with your local waste-management service for disposal instructions.
Considering the ease of installation, replacing your old thermostat is a worthwhile project. Whether you choose top-of-the-line technology or a less-expensive basic model, you’ll save money while you sleep and wake up to a toasty home. It sure beats dragging yourself out of bed at 3 a.m. to stoke the fire.
INSTALLING A THERMOSTAT
Step 1: Shut off the power to your furnace. Remove the old thermostat’s cover plate to expose the wiring. Disconnect and label each wire with the corresponding terminal letter designation and then remove the old thermostat wall plate.
Step 2: Fit the wires through the opening in the new thermostat wall plate, being careful to not to let them fall into the wall. Mark the wall-plate screw-hole locations, drill holes for wall anchors and attach the thermostat to the wall.
Step 3: Follow the manufacturer’s instructions to securely connect each wire to the new thermostat connection terminals. In most cases the letter designations will match the old thermostat terminal designations.
Step 4: Install batteries and attach the faceplate to the wall plate, being careful to align the connection pins when pushing the plates together. Next, follow the manufacturer’s programming directions.