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Thermostats: How Do They Work?

Thermostats are an essential part of every modern heating and cooling system. It keeps indoor temperatures comfortable without having to crank the HVAC system up. In addition to being convenient, it also helps make your HVAC system more efficient.

Thermostats: How Do They Work?

Have you ever wondered how thermostats work, though? Birdwell Heating & Cooling Inc gives you an in-depth look.

How Thermostats Work

While a thermostat detects temperature, it does not have a thermometer built in. Rather, it relies on thermal expansion, where most substances expand when exposed to heat and shrink when they cool down. The most common thermostat features a bimetallic strip, which is made of two layers of different metals fused together, usually steel and copper. Since these metals have different expansion rates, the strip bends when the room temperature increases.

The strip triggers a switch that turns on the air conditioner. It gets turned back off when the strip relaxes as the temperature returns to the desired temperature. The knob at the front panel adjusts the strip tension and the optimal room temperature. Some thermostats can be set to reverse so the relaxed state turns the heating on instead.

Kinds of Thermostats

There are several kinds of thermostats that operate on a similar principle:

  1. Bimetal – The aforementioned bimetal thermostat, while fairly effective, takes several minutes for the thermostat to “detect” the temperature change and turn itself off.

  2. Gas-Filled Bellows – This features a circular bellows-like assembly filled with gas that’s sensitive to temperature changes. As the gas expands, the bellows trigger a microswitch, turning on the HVAC. a similar thermostat is used for cooling vehicle engines.

  3. Smart Thermostats – Thermostats with digital readouts use a thermometer or temperature sensor that’s either built-in or installed somewhere else in the room. Newer models can be operated remotely using an app even if you’re not at home. Other models can even “learn” the use of your HVAC system and automatically apply such changes in the future.

To learn more about AC repair, service and maintenance, call Birdwell Heating & Cooling Inc today at (256) 229-3009. You can also fill out our contact form to schedule an appointment. We serve Rogersville, AL, and nearby areas.