How Does a Thermostat Work?

February 10, 2020


The thermostat is at the heart of every heating and cooling system. It’s the component that triggers the equipment to turn itself on and off automatically. There are several types of thermostats, and each has a specific way of sensing temperature changes in the home.

Electronic Thermostats

If you own a home built in the last several decades, you probably have an electronic thermostat. This type of control is also called a digital thermostat. These devices contain an electronic sensor that determines the temperature and responds by turning the system on or off. Most electronic controls are programmable and enabled for Wi-Fi. This means their operation can happen automatically based upon the settings provided by the homeowner.

Electromechanical Thermostats

There was a time when heating and cooling equipment was managed using an electromechanical thermostat. Many older homes may still have these devices connected to their heaters or air conditioners. Changes in room temperature are tracked using a bimetallic coil. As temperatures rise and fall, the coil expands or contracts, causing a mercury-filled glass vial connected to the coil to tip. The tipped vial triggers the unit on or off. Perhaps it sounds like something you’d find in a mad scientist’s laboratory, but it absolutely works.

If you want to replace one of these thermostats or you need help repairing a digital model, Scott-Lee Heating Company can handle it for you. We’re the thermostat experts to call in St. Louis.

Thermostat Problems

Electromechanical thermostats can’t respond quickly to temperature changes. It takes time for the bimetallic coil to heat up or cool down. The heater or air conditioner won’t turn off or on until the vial triggers the relay to the equipment. In very cold or hot climates this can create uncomfortable indoor environments. Digital thermostats respond quickly to indoor temperatures and setting changes.

Scott-Lee Heating Company has been serving St. Louis residents since 1978. We offer a full range of commercial and residential heating, cooling and air quality services, including installation, maintenance and repairs. Call us today to speak with a professional about your HVAC system.