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How Does a Thermostat Work?

The thermostat serves as the control panel for your air conditioning system, allowing you to set the temperature and cool your house. Older thermostats used mercury switches to function, while newer ones are almost exclusively digital: allowing them to add convenient features like automatic activation. You may wonder how exactly they work, especially in an area like Fresno where temperatures climb during our hot Central Valley summers. The specifics depend on the type of thermostat you have.

Older thermostats placed several wires in a small vial which contained a measure of mercury. One wire stays in contact with the mercury at all times. The other two sit on either side of the vial and are attached to thermometer coils on the ends. When you adjust the heat or the cooling controls, the thermostat tips the vial, putting the mercury in contact with one of these wires and activating the heating or cooling cycle. The coils unwind until they tip the vial again, moving the mercury and shutting the system off.

Digital thermometers are much more complex, utilizing electronic components to perform the same function as mercury thermometers. Specifically, they use a device called a thermistor, which permits shifts in electrical resistance when the temperature changes. A microcontroller can gauge the level of resistance in the thermistor and convert that to an actual number. When that number is hit, the system turns the heat or the cool air on and off as needed. That allows users greater control over the process. For instance, they can set the thermostat to automatically turn on at a specific time, then turn off again when the goal temperature is reached.

When thermostats break down, it pays to call on an air conditioning professional in Fresno to enact repairs. The mercury in older thermostats is hazardous and requires a qualified air conditioning technician to approach properly. Newer thermostats may utilize a number of different components, and still require the proper know-how to properly connect to your air conditioning system. If you are experiencing problems with your thermostat, or you’d like to replace an older model with something more up to date, contact Purl’s Sheet Metal & Air Conditioning. Our service technicians can travel to anywhere in the Fresno, CA area and can handle whatever air conditioning needs you may have.

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