Learn More About Thermostats
What is a thermostat?
A thermostat is a device that allows you to control the temperature inside your home by controlling the functions of a heating and / or cooling system. Today's electronic models are a vast departure from earlier mechanical styles. Microprocessors allow you to program your home temperatures to suit your lifestyle, so you can keep things comfortable while you're home and automatically set back your temperatures to save energy when you're away or sleeping.
How do thermostats work?
A typical thermostat turns on the heating device whenever the temperature falls below a certain temperature and turns it off whenever the temperature rises above another temperature. Those two temperatures are slightly separated so that the heating device doesn't turn on and off too rapidly, and are usually set within a couple degrees from the desired temperature (also called a set point). If, for example, you set your thermostat to 68°F, it does not maintain the temperature precisely at 68°F. The temperature will fluctuate between approximately 67°F - when the thermostat turns your heating device on, and 69°F - when it turns your heater off. More sophisticated models can also control cooling devices - like turning an air conditioner on to cool the room down faster and turning it off when the air reaches the desired temperature.
What are the different kinds of thermostats?
There are three main kinds of thermostats:
In a typical electromechanical thermostat, a coil made of two different metal strips sandwiched together tips a small mercury-filled glass bottle. As the temperature changes, the two metals expand differently and the coil winds or unwinds. As it does, it tips the glass bottle and the mercury rolls from one end of the bottle to the other. When the mercury falls to one end, it allows an electric current to flow between two wires and the furnace turns on. When the mercury falls to the other end of the bottle, the current stops flowing and the furnace turns off. So the winding and unwinding of the coil controls the furnace and the home temperature tends to hover at the point where the bottle of mercury is almost perfectly level.
These are the oldest kind of thermostats. Although newer digital models are quite popular these days, electromechanical thermostats are still widely spread because of their simplicity and cheap cost. Their main setback is that they are less accurate than digital ones and cannot support programming features.
Digital manual thermostats
Digital thermostats work in much the same way as older electromechanical thermostats did, except that the metal coil is replaced with an electronic temperature sensor. The microprocessor inside compares it's readings to the desired temperature you select. Then, it gives start and stop commands to the heating or cooling system to bring the temperature to a level that makes you comfortable.
While digital thermostats are more accurate than electromechanical ones, changes in their temperature settings still have to be done manually. Digital thermostats (both manual and programmable) also contain no mercury, making them more environmentally friendly.
Digital programmable thermostats
Programmable thermostats basically work the same way as the digital manual ones, but they are far more convenient. Once you program the thermostat to customize the system's operation to fit your lifestyle and schedule, all you have to do is relax and let it do all the work. To stay comfortable and save energy all season, you simply program into its memory the temperatures you need, at what time of the day. You only need to program your thermostat once - until the season or your lifestyle changes.
Depending on the model, a thermostat can be programmed in one of four ways:
- 1-day programming: The desired temperature can be set to change throughout the day
- 5-2-days programming: Like above, and you can have separate programs for weekdays and weekends
- 5-1-1-days programming: Like above, and you can have separate programs for weekdays, Saturday and Sunday
- 7-days programming: Like above, and you can have separate programs for each day of the week
What are the benefits of using a thermostat?
- Convenience. Instead of heading towards your furnace every time you need to tweak the temperature up or down, you can place a thermostat at a convenient spot.
- Energy savings. Instead of running your heater or furnace 24-7, a thermostat turns it on only when it is needed to maintain the desired temperature. If you have a programmable thermostat, you can program it to turn the heat down when you do not need it. Programming temperatures around 63°F on cold winter nights, when you're snuggled under blankets, can help you save as much as 30% on your heating costs. You can save even more by programming your system to "setback" the temperature when your family is away at work, at school, or on vacation.
Where should my thermostat be located?
For best results, the thermostat should be located where people spend the most time. It should be about 5 feet off the ground and at least 18 inches away from an outside wall. It is best to keep your thermostat away from any sources of heat other than the air in the room. It should be kept away from heaters, vents, windows, and hot-water pipes and out of direct sunlight. It also works best when not away from stairways or corners, because they can affect the circulation of air.
Installing a thermostat
Some thermostats are simple enough to be installed as a DIY project, while other require professional installation. In many cases, some wiring work may be required. Consider the following guidelines when installing your thermostat:
Go back to:
- Make sure you have the right thermostat for your system. A thermostat meant to be used with a heat pump may not fit any other heating system.
- The thermostat should be located away from the room's cooling or heating vents or device, yet exposed to general airflow from the room to be regulated. If the thermostat is too close to the air vent, the system will tend to "short cycle", with numerous starts and stops that can be annoying and in some cases shorten equipment life.
- Placing the thermostat in open hallway may be most appropriate for a single zone system, where several rooms are operated as a single zone. In this case, the doors to these rooms should be open when the system is in use.
- For a larger area, setting up multiple zones controlled by different thermostats can save considerable energy, allowing different rooms to vary in temperature, and turning the heat and / or cooling off completely where it is not needed.