How a Thermostat Works

The thermostat – that little device on your wall that controls the furnace and air conditioner – is an essential part of your HVAC system. Today’s thermostats are highly sophisticated, offering a variety of features that improve energy efficiency, like zoned heating and cooling which allows you to apply separate settings to different areas of your home.

What a Thermostat Does

Cornelius Drebbel, a Dutch man, invented the first thermostat in the 17th century by using a float inside a mercury thermometer connected to a damper cover on a furnace. When the mercury climbed to a certain level, the float closed the damper to stop the heat. Modern thermostats perform essentially the same function. Sensing the ambient temperature in your home, the thermostat automatically turns the furnace or air conditioner on or off to maintain the desired temperature by completing or interrupting an electrical circuit.

Types of Thermostats

There are essentially two types of thermostats, electromechanical and electronic.

Electromechanical Thermostats

This type of thermostat uses a bi-metal coil or strip and a small vial of mercury (which conducts electricity) to create an electrical circuit. The two different metals that comprise the coil expand and contract at different rates when the temperature changes, causing the coil to move and complete the circuit.

Electronic Thermostats

An electronic thermostat uses an electronic element and circuitry to sense temperature changes and turn the equipment on and off as needed. Electronic thermostats are programmable, allowing for automatic temperature adjustment based on the time of day. By aligning the temperature settings with your needs and lifestyle (e.g. when you are home versus when you are out) you can minimize wasted energy and cut your utility bills.

Programmable thermostats come in varying levels of sophistication and price. Keep in mind, however, that the more energy you conserve, the more money you save throughout the year.

The most basic models adjust only for day and night, and are the least expensive. More expensive models allow greater flexibility to match your specific needs. The most sophisticated (and priciest) thermostats connect to your Wi-Fi and actually learn your habits and adjust accordingly.

Your HVAC professional can help you determine which thermostat is appropriate for your needs and budget. IAQ recommends and installs a number of Honeywell Programmable Thermostats, including the Vision Pro IAQ system which offers several additional benefits:

• Maintains the desired humidity level of your home
• Signals you to change your air filter
• Alerts you to problems with your furnace or air conditioner

Learn more about the Vision Pro IAQ system and other Honeywell products. Contact IAQ today!