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Table of Contents

How Electronic Thermostats Work

How a Smart Thermostat Works

Switching To a Smart Thermostat

  1. Resource Center
  2. Repair

How Do Smart Thermostats Work?

5 min readUpdated Nov. 13, 2024Lyle WeischwillHVACAppliance 101
Title image for article "How Do Smart Thermostats Work?"

Smart HVAC thermostat connect to your smart phone or tablet through the WiFi signal in your home. Installing and connecting a smart thermostat enables you to monitor and control your HVAC system remotely. You can save money on energy bills and use less energy by installing a smart thermostat in your home.

KEY TAKEAWAYS

  • A smart HVAC thermostat is a sophisticated type of control device that can allow you to remotely control your heating and cooling system from a smart phone or tablet.
  • Multiple inputs and learning logic in a smart thermostat can help a smart thermostat control the climate inside your home efficiently to save energy and lower your energy bills.
  • Smart thermostats are relatively simple to install on most HVAC systems so you can easily switch to this new technology when you find that this control system is right for your home.

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How Electronic Thermostats Work

A smart thermostat is an enhanced version of an electronic thermostat.

Some homes still have a basic mechanical thermostat that simply has a dial or lever and a metal coil that senses temperature to cycle the unit.

Understanding the differences in how mechanical and electronic thermostats work will help you realize the advantages of upgrading your HVAC control system to a smart thermostat.

How Mechanical Thermostats Differ from Electronic Thermostats

One of the main differences between mechanical and electronic HVAC thermostats is the type of temperature sensor that they use.

A mechanical thermostat uses a bi-metal strip coiled up to detect temperature inside your home. Two different types of metal (copper and steel) are joined together and the thermostat physically moves a tab at the outer end of the coil to engage and disengage an electrical contact inside the thermostat to cycle the unit on and off and maintain the set temperature in your home.

An electronic thermostat uses a more accurate type of temperature sensor called a thermistor. A thermistor is an electrically conductive resistor. The electrical resistance of the thermistor changes proportionally with temperature. The control board in an electronic thermostat sends DC voltage through the thermistor and measures the voltage drop caused by the resistance to determine indoor temperature in your home. This method of sensing temperature is much more precise than the method that mechanical thermostats use. You can also position additional thermistors remotely in your home to provide an electronic thermostat more input about indoor temperatures throughout the house instead of just at the thermostat location.

Mechanical thermostats use a dial or lever to set desired temperature. The dial moves the sensor contact that turns on and off the HVAC unit so that the switch activates at the desired set temperature. When the bi-metal tab moves to the position that equates to the set temperature, the thermostat contact will engage the tab and turn on the unit. When indoor temperature rises above or below the set temperature, the bi-metal tab moves away from the contact and the thermostat shuts off the unit.

Although the mechanical thermostat is very reliable, it isn’t as efficient as an electronic thermostat. An electronic thermostat can use internal logic to run the circulation fan for longer after the contact shuts off the heat exchanger to use up every bit of cool or warm air in the system.

If your HVAC system still uses a mechanical thermostat, switching to an electronic thermostat will save energy and lower your heating and cooling costs.

Types of Electronic Thermostats

There are 3 types of electronic thermostats available for HVAC systems:

  • Basic electronic thermostat: Uses a digital display that allows you manually set desired temperature.
  • Programmable thermostat: Allows you to set up a daily schedule of automatic temperature setting changes.
  • Smart thermostat: Connects to your smart phone or tablet so you can remotely control thermostat setting and includes learning features that help improve the efficiency of climate control in your home.

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How a Smart Thermostat Works

A smart thermostat uses an electronic control board to connect to your home’s WiFi so you can monitor and control the settings remotely with your smart phone or tablet.

As an electronic thermostat, the smart thermostat uses a thermistor as discussed above to sense temperature. With many smart thermostats, you can add additional remote thermistor temperature sensors throughout your home to more precisely control indoor climate.

Smart thermostats use learning features and multiple inputs to more precisely control indoor climate and save energy.

  • Many smart thermostats have humidistats that sense humidity in your home and adjust settings to keep you comfortable.
  • They can also use outdoor temperature and conditions to help the thermostat operate your heating and cooling system efficiently.
  • A smart thermostat can sense when you’re home or away and adjust settings accordingly to save energy by automatically adjusting temperature settings and run times.
  • Smart thermostats can get input from your energy provider to run the system efficiently when electrical rates are lower and help put less strain on the electrical grid.
  • Sophisticated learning features of smart thermostats allow the device to observe your temperature adjustments over time, gradually building an efficient adjustment schedule based on your preferences, so it can automatically adjust temperature settings throughout the day based on when you're typically home, away, or asleep.
  • You can connect many smart thermostats to home automation hubs and controllers for easier and integrated control and efficiency.

Switching To a Smart Thermostat

Even if you have a mechanical thermostat, switching to a smart thermostat is relatively simple in most homes. You’ll need a smart phone or tablet and internet with WiFi to use the remote control features of a smart thermostat.

Wiring connections to connect a smart thermostat to your HVAC system are almost always compatible with your unit. The smart thermostat will have detailed instructions that allow you to install the thermostat yourself if you choose. You can also schedule HVAC service and we can send a Sears Home Services technician to your home to install a smart thermostat.

To get an idea of what’s involved when installing a smart thermostat, view this helpful video:

Understanding the advantages and features of smart thermostats will help you decide whether this device is right for your home. If you’re ready to switch to a smart thermostat, visit Sears.com to find the right one for your home.

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Glossary Terms

A humidifier is a device designed to increase humidity levels in a single room or an entire building, improving air quality and comfort.

Swamp cooling, also known as evaporative cooling, is a method that cools air through the natural process of water evaporation. It is energy-efficient and environmentally friendly, particularly effective in hot, dry climates.

Freon is a trade name for a group of chlorofluorocarbons (CFCs) used as refrigerants in air conditioning and refrigeration systems, known for its role in ozone depletion.

An inverter AC unit is an air conditioning system equipped with inverter technology that allows it to vary the compressor speed, enabling precise temperature control and increased energy efficiency.

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