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How do thermostats work?

Updated: May 17, 2023

As part of the modern world, all of us have dealt with, or received benefits from, a thermostat of one kind or another. Besides being found in a home’s heating and cooling system, a thermostat can be found in things such as an oven, a drier, or even a heat cable system.

Thermostats are a part of our daily lives, but how exactly do they work? Keep reading to find out the answer to that question from a few of our readers.

Regulates Your Home's Temperature

What is a thermostat? A thermostat is essentially a control device that regulates your home's temperature by turning off or on your boiler or air conditioning system based on the settings you have set. There are two types of modern thermostats that we'll talk about: digital and mechanical.

Digital Thermostats A digital thermostat has built-in components that allow it to provide you with accurate data on the current room temperature. These electronic sensors can constantly fine-tune your temperature. Digital thermostats are much more accurate than mechanical ones due to the newer sensor technology.

Mechanical Thermostats A little more complicated than digital thermostats, a mechanical thermostat utilizes a bimetallic strip, which is two pieces of metal bolted together. These two pieces of metal will bend and move depending on the temperature of the home.

If the house warms up, one of the metals will start to expand and eventually bend over the other piece. This bend causes the circuit to open and switch off or cut off the heat, allowing the house to cool down.

When the house cools down, the metals slowly return to their original form allowing the circuit to close again and turn back on the heat.

Which is more accurate? The notable downside to mechanical thermostats is that they are not as accurate as digital ones as they rely on the bimetallic strip.

Digital thermostats are usually accurate to within one Celsius. Mechanical thermostats have an accuracy of about five Celsius.

Why is it crucial where you place your thermostat? Since your thermostat requires direct contact with the air in your home, placing it where there is a flow of fresh air but not affected by external factors like sunlight, stovetops, and humidity from bathrooms is crucial to get an accurate reading.

The Expanding and Contracting of Metal Strips

It is pretty simple to understand how a thermostat works. If something warms up, it expands, and if it cools down, it contracts. An electrical circuit is switched on and off by thermal expansion, which is what mechanical thermostats use. In most thermostats, bimetallic strips and gas-filled bellows can be found.

Bimetallic strips are pieces of two different metals that have been bolted together. Your home's heating system is controlled by an electrical circuit that includes a bimetallic strip.

There will be electricity flowing throughout the circuit when this bridge is down, and the heating will be on. The strip will begin to bend as one metal expands more than the other, as one of the metals warms up more than the other. As the bridge bends enough, it will eventually open the circuit, that power will be switched off, and the heat will be cut, cooling the room.

The strip will start to cool again and soon snap back into place, enabling the heating system to operate again. The circuit will switch itself on and off based on the temperature set by the temperature dial. To keep your home at the desired temperature, turn up the thermostat. It simply tells your heating and cooling systems when to kick in. Max Shak, Founder of Craig Campbell, is an Automotive Repair Expert, Founder & CEO at Auto Parts Guideline.

Ambient Temperature Sensor

Thermostats are devices that help regulate the temperature. By sensing the ambient temperature, they can turn on or off heating or cooling devices to maintain the desired temperature. There are many different thermostats available on the market, but they all work using similar principles.

The most basic thermostats simply turn the heating or cooling device on or off based on a set temperature. However, more advanced thermostats can take into account factors such as humidity and solar radiation to more accurately maintain the desired temperature.

Some thermostats can be controlled remotely, using a smartphone or other internet-connected device.

Thermal Expansion Technology

A thermostat is a device that uses thermal expansion technology in which things expand when they heat up and contract when they cool down. In layman's terms, a thermostat helps regulate the temperature of your air conditioner or heater in your homes and offices.

With thermostats, a bimetallic strip is the thing inside it that expands and contracts according to the temperature. A bimetallic strip is essentially two strips of metal that have been fused; one of the metallic pieces is fitted to expand when the temperature rises, while the other metallic piece does the opposite and contracts when the temperature drops. Kriti Mawji, Marketing Manager at belledorm. Leonard Ang, CEO, iPropertyManagement.

A Thermometer and a Switch

At the basic level, thermostats work with a thermometer and a switch. The thermometer registers the temperature in the space. The switch activates the heating or cooling system when the temperature gets above or below a certain.

Traditionally, the mechanism inside thermostats was a strip of two different types of metal stuck together. Because different metals expand or contract at different rates in response to temperature changes, this strip would bend in different directions as it heated or cooled. When it bent enough, it would trip the circuit to activate the heating or cooling.

Modern one's work with digital thermometers and simple programming.

Sensors or Metal Strips

There are a few different types of thermostats, but the most common ones these days are digital and electromechanical. Both can control and change the temperature of your central heating system by monitoring the ambient temperature in the home.

Digital thermostats use sensors to determine whether your home is at the desired temperature. They often have programmable settings and Wi-Fi capabilities that allow you to control the temperature of your home while you’re out.

Electromechanical thermostats contain a metal coil or strip. When the temperature changes, the metal will expand or shrink, causing a vial of mercury to tip to one side. When the mercury flows to one end of the vial, a signal is sent to the central heating system that adjusts the temperature accordingly. Nick, Gas Manager at Toasti.


This is a crowdsourced article. Contributors are not necessarily affiliated with this website and their statements do not necessarily reflect the opinion of this website, other people, businesses, or other contributors.

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