What makes a thermostat work

Hence, when you require the temperature to change quickly, it will not happen. This is where bellows with gas and two metal discs come in. The metal discs have a wide surface area, allowing them to quickly heat. So, when an electric current passes through the circuit, the gas in the bellows heats and the bellows expand. This causes the two metal discs to separate, and the disc that is posterior in position is pushed towards a tiny switch located at the center of the thermostat.

This immediately interrupts the circuit, causing the heating or cooling to switch off. Then the gas in the bellows starts cooling down, causing the bellows to contract. This forces the metal discs back together, resulting in the inner disc moving away from the tiny switch. So, the circuit gets completed and the HVAC unit turns on again. Electronic Thermostats: Today, thanks to advances that technology has made, there are electronic thermostats that come with electronic heat sensors and circuits that can sense any change in the ambient temperature and automatically turn on the heating or cooling.

They are similar to a mini-computer and can be programmed. An electronic thermostat contains a device known as thermistor, which is responsible for measuring the ambient temperature. The thermistor is also a resistor that facilitates changes in the electrical resistance as that temperature changes. The thermistor generates heat when electrical current passes through it.

This heats the thermometer coil, which unwinds with heat, causing a microcontroller in the electronic thermostat to switch off. As a result, the heating or cooling shuts off. Once the thermistor and thermometer coil cool down, they go back to their original position, causing the HVAC unit to turn on.

A digital or electronic thermostat prevents wastage of energy. It allows you to program the heating and cooling of your home for different time periods, so that minimal energy is used when optimal cooling or heating is not required. To put it in simple words, a car thermostat works by responding to the changes in the temperature of the engine coolant. If the engine coolant is cold, then the thermostat maintains its closed position.

Once the engine coolant is hot enough, then the thermostat opens to allow the coolant to go to the radiator. It is a very simple yet very effective mechanism.

The thermostat contains a cylinder filled with wax. This cylinder lies on the engine side of the thermostat so that it maintains contact with the coolant circulating in the engine.

The cylinder also comes with a valve that connects to a rod. The rod presses into the wax at the center of the cylinder. As the engine temperature rises, so does the temperature of the coolant. This outward movement of the rod is what opens the valve of the cylinder. Coolant can now flow from the engine to the radiator through this opening in the cylinder. As such, when you start your engine early in the morning, the thermostat is still in its closed position.

This allows the engine to warm up and reach its operating temperatures a lot faster. As soon as the engine is warm enough, the engine coolant also rises in temperature. This melts the wax and creates an opening for the coolant to flow. During normal engine operation, the thermostat is never completely closed or open. Its state is dependent on the operating condition of the engine. Keep in mind that the thermostat serves like a gate valve controlling the flow of coolant from the engine to the radiator.

This helps the engine to operate at the best possible temperature. This can have substantial implications in engine performance. A well-functioning engine means the engine oil is able to lubricate all parts of the engine while also removing harmful deposits. This can also translate to a reduction in harmful emissions while also improving fuel economy.

Now we know what a car thermostat is and how it works. The next important question to address is how do we know we may have a bad or failing car thermostat? Here are some of the more common symptoms of a bad thermostat in your car. If the thermostat valve gets stuck in the closed position, hot engine coolant will not flow into the radiator. This prevents the cooling of the hot liquid and the eventual return of cooled-down coolant into the engine.

If you keep your engine running you run the risk of destroying it, quite literally. Of course, engine overheating can also be due to other reasons. It could be because of a low coolant level or a failing water pump. It is also possible that there are leaks in the cooling system. Many digital thermostats also are programmable, which allows a user to set different preferred temperatures for different times of the day or days of the week.

A mechanical thermostat uses physical means to gauge the air temperature and activate a switch that turns on a heating or cooling system on turns it off. There are several types of sensor technology that can be used in mechanical thermostats, such as bimetallic strips, wax pellets, bulbs filled with gas or tubes filled with air.

Each of these types of sensors will react to changes in temperature, such as by expanding or contracting, and will trigger the proper switch to raise or lower the temperature. Bulbs filled with mercury were once commonly used in thermostats, but its use has been discontinued or outlawed in many places because of the dangers of mercury.

The most common of these technologies in home thermostats is the bimetallic strip. This technology uses two thin strips of different metals — such as copper and iron, copper and steel and brass and steel — bonded together and rolled into a coil.

As the temperature changes, the different metals expand or contract at different rates, causing the strip to bend. When the strip bends enough to touch an electrical contact and complete an electrical circuit , it turns on the heating or cooling system. If the temperature changes enough to unbend the strip, contact is lost, and the system turns off.