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Thermostats: Why They Can Sometimes Fail

Probably one of the best home inventions today is the thermostat. According to the Department of Energy, turning it between 7 and 10 degrees Fahrenheit for eight hours daily from its normal setting could save Americans as much as 10 percent of energy bills a year.

But to appreciate the device more, it helps to understand how it works. Learning what causes it to malfunction can also prevent paying more for electricity.

How Does a Thermostat Work?

How Stuff Works provides an in-depth explanation of how this nifty unit functions. But first, what is a thermostat?

It is a device connected to the home’s air-conditioning and heating systems. It contains parts that can detect fluctuations in ambient temperature, so it could adjust heaters, furnaces, and air conditioners accordingly.

One of the oldest types of thermostats was the manual mercury switches. Some historians say that these had been around for at least 200 years!

They were called as such since they contained mercury, a liquid metal that conducts electricity. The vial that held the metal also included three wires, which would be in contact permanently or temporarily with mercury depending on where the vial would tilt.

Meanwhile, the system also used bimetallic strips, which also served as thermometers of the non-digital thermostats. These strips were actually two different metals laminated together. They expanded or contracted as they were cooled and heated. These movements would trigger the mercury switch, allowing it to turn on boilers and ACs.

Although effective, mercury thermostats turned out to be dangerous if the vial would break, and humans would be exposed to the liquid. Thus, many states banned their production and use. Their gradual disappearance then led to the popularity of digital thermostats.

How Digital Thermostats Function

These thermostats are equipped with a thermistor, a resistor that uses electrical resistance to determine changes in temperature. A microcontroller then reads the resistance and then converts it to a figure that appears on the unit.

One of the primary reasons to use digital thermostats is convenience. One can program its settings to change depending on the time of day. Newer models can also work with smart or home automation and Internet of things (IoT) devices.

Homeowners, for example, can already adjust their thermostat remotely using their mobile app. These devices may also generate usage reports and even learn behaviors, so they could make good decisions on behalf of their users.

Further, in places where temperature needs vary (e.g., bedroom versus garage), homeowners can implement system zoning using several thermostats connected to a control panel. The entire system can be automated.

Why Thermostats Won’t Work

Current thermostats are so effective that they require less human intervention. But that doesn’t mean they run smoothly all the time. Homeowners may immediately suspect a problem if the digital device stops showing any display and that turning the furnace and AC on and off won’t change anything.

The thermostat may also be in trouble when the reading doesn’t seem accurate. It may display a high temperature, but the surroundings feel cold. The AC, moreover, may be running constantly and won’t shut down.

What causes these problems? There are a few.

  1. The Issue Might Be Heating or Air Conditioning

A problematic thermostat might suggest a furnace tune-up or air-conditioning inspection and cleaning. Dirty heating and cooling systems can affect the readings of the thermostat since all are interconnected.

Worse, they can offset the benefits of using a thermostat. When these appliances are not in optimal condition, they may be forced to work even harder. The temperature-controlling device might not turn them off. In other words, they can lead to a significant electricity cost.

  1. The Thermostat Is Already Old

No device lasts forever. Thermostats are usually good for ten years, after which they may need replacement. Around this time, their primary components are already old or even outdated. Their wires may be showing signs of wear and tear (which could also be dangerous for the house).

If the thermostat is old but hasn’t reached a decade yet, one may want to check the insides. More likely, they have already accumulated dust and debris, which could lead to faulty or erratic readings.

  1. They Are Not Connected to the Power Source

One saying goes that the simplest answer to a problem is the best one. The thermostat might not be working simply because it is not connected to the power source. Homeowners can forget to plug the device again after cleaning it, or the circuit breaker connected to it may have tripped. The batteries may also need changing.

Thermostats are an effective way to minimize energy expenses at home, but they also need some loving by monitoring problems that may make them less efficient.