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When it comes to HVAC systems, chances are you'll interact mostly with the thermostat.

As such, understanding how the thermostat controls the temperatures and the rest of the HVAC system can help you optimize efficiency and learn to troubleshoot any issues. 

So keep reading to learn more about this handy device. 

What is a Thermostat?

A thermostat is a device, typically mounted on a wall, that enables you to control the temperature in your house. 

It uses temperature sensors to sense the indoor temperature of your home (and in some models, the outside temperature as well) and then operates the HVAC system accordingly to raise/drop the temperature to the required levels. 

It's the main point of control for the entire HVAC system and has mechanical or digital interfaces which you can use to adjust the temperature and other settings.

Differences Between a Thermostat and a Thermometer

While both thermostats and thermometers are involved with temperature, they serve separate purposes.

A thermometer simply measures the temperature, whereas a thermostat measures the temperature while also actively controlling and managing the temperature of your home.

Basic Working Principle

The basic working principle of a thermostat revolves around temperature regulation within your home.

  • You first set your preferred temperature using the thermostat's buttons, display, or a compatible phone app.
  • With this set, the thermostat then gauges the room's current temperature with its built-in sensor or additional sensors.
  • Once it detects a deviation from the set temperature, it activates your home's heating or cooling system to achieve the desired level.
  • When you increase the heat, the thermostat communicates with the boiler, furnace, or heat pump, instructing them to increase hot water flow or push more hot air through vents, subsequently warming your house.
  • Conversely, when you request cooler air, the thermostat switches off the heating equipment or activates the heat pump in reverse to produce cooler air.
  • Additionally, it can switch on your air conditioning unit to cool the area as needed.

This continuous regulation ensures your home maintains a comfortable, consistent temperature.

Types of Sensors

Various thermostats utilize different sensor types, such as bimetallic, electronic, or infrared sensors, to accurately measure temperature and maintain a comfortable indoor climate.

So let’s talk a bit about the different mechanisms that most popular thermostats use to measure the temperature.

Mercury Thermostats

Mercury thermostats measure and control the temperature in the house through the use of mercury. 

The way it works is that mercury is responsive to temperatures, so changes in the temperature lead to the mercury, inside the thermostat, contracting or expanding. 

When that happens, it activates a switch that signals the HVAC system to either turn the heat up or down. 

A mercury thermostat has a good degree of accuracy and has a number of switches, depending on the number of heating or cooling systems you’re working with.

Mercury thermostat
Mercury thermostats are one of the oldest versions of thermostats

Bi-metallic Mechanical Thermostats

Bi-metallic mechanical thermostats use two combined metal strips to sense and respond to temperature changes.

These strips are made of metals that have different rates of expansion when subjected to heat.

When the temperature rises, one metal expands more rapidly, causing the strip to bend and trigger the thermostat.

Conversely, as the temperature decreases, the metals contract at different rates, which also alters the shape of the strip and engages the HVAC system.

This design allows the bi-metallic thermostat to efficiently initiate heating or cooling, making it a simple yet effective solution for maintaining a comfortable temperature.

Metallic Disc Thermostats

Bi-metallic disc thermostats utilize two bonded metals that respond to temperature changes by expanding and contracting.

Unlike strip-based designs, these thermostats feature a round, thin shape.

This shape allows the metal disc to quickly change its form in response to varying temperatures.

By snapping from one shape to another as it cools or heats, the disc either completes or breaks an electrical circuit, ultimately controlling the temperature within the space.

These precise and swift adjustments make bi-metallic disc thermostats an equally reliable option for maintaining ideal temperature settings.

Modern Electronic Sensors

Modern electronic thermostats leverage advanced digital sensors, such as thermistors, to accurately gauge a room's temperature.

These thermistors are highly sensitive, transforming temperature fluctuations into varying voltage signals.

The thermostat processes this data and compares it against your desired temperature setting.

Any discrepancies prompt the thermostat to send the appropriate signal to your heating or cooling system, increasing or decreasing the temperatures as desired.

In addition to enhanced precision, these devices come equipped with built-in clocks, allowing you to program schedules that match your everyday routine.

As a result, you can customize your thermostat's settings to maximize energy efficiency and comfort.

On top of that, modern electronic thermostats offer seamless integration with mobile applications, granting you full control over your home's temperature from anywhere, anytime.

SwitchBot Thermometer & Hygrometer
Thermostats or thermometers with electronic sensors are the most accurate and reliable right now

How to Pick a Thermostat?

When choosing a thermostat, right now you’ve got the option between a smart thermostat or a simpler, non-smart programmable option that better suits your needs and budget.

If cost isn’t an issue, and you’re hoping to make the HVAC system more efficient and versatile, I highly recommend going for a modern smart thermostat.

Modern Smart Thermostats

Modern smart thermostats are the latest and most advanced in the world of temperature control.

Just like traditional thermostats, they monitor the indoor climate and relay this information to your HVAC system.

However, with added innovative features, these devices go above and beyond their predecessors.

A couple of the most important smart abilities are mobile app integration and scheduling functions.

Mobile App Integration

One key feature of smart thermostats is the addition of mobile app integration.

This allows users to effortlessly control their home's temperature and energy usage from anywhere using their smartphone.

Beyond that, you get access to:

  • Alerts and notifications
  • More efficient scheduling functions such as geofencing
  • Vacation holds or low-power modes
  • Control several thermostats
  • Control them via your smart home hub or voice assistant
  • Incorporate them into your smart home routines
  • Intelligent functions that automatically control the system to be more energy-efficient
Bluetooth Thermostat Guide
Smart thermostats allow you to control it via your smartphone

Scheduling Function of Programmable Thermostats

Beyond these, one major advantage of smart thermostats is their ability to program time-based schedules. 

These are often one of the most underlooked features since they can help save a significant amount of money on your power bill while also making your home more comfortable.

You can customize schedules according to your preferences and override them anytime you want to change the temperatures yourself. 

Installing or Replacing a Thermostat

 If you're unsure about your skills or abilities with thermostats, we recommend seeking the help of a professional to avoid any potential hazards.

To install or replace a thermostat in your home, you must first have an HVAC system in place.

  • This typically involves hiring a professional HVAC company to determine the appropriate equipment and size of the system for your home.
  • Most homes utilize a split system, consisting of a furnace and an air conditioner.
  • However, based on your region's climate, you may only need an A/C or furnace system.
  • Once the HVAC system is set up, the installer runs thermostat wires from the furnace (or indoor unit) to the intended thermostat location, usually in a living space such as a common area or bedroom.
  • These wires connect to a wall mount where you (or your installer) can set up your thermostat.

An accurate installation ensures proper communication between the thermostat and your HVAC system for efficient temperature control.

How to Get the Best Use Out of Your Thermostat

Maximizing your thermostat's potential starts with proper placement and maintenance.

  • Avoid installing it near direct sunlight, drafty windows, or heat-producing appliances. This ensures accurate temperature readings and allows your HVAC system to function more effectively.
  • Regularly clean the thermostat's sensors, as dust accumulation can cause inaccurate readings and hinder its performance.
  • Make the most of your thermostat by understanding its range of features and tailoring them to your needs. For example, establishing schedules or temperature setbacks for different times of the day for when you're away can further optimize your energy usage and comfort levels without sacrificing convenience.
  • Gradually adjust thermostat settings over time, increasing the temperature in the summer and lowering it in the winter. This can save you up to 10% on your heating and cooling expenses.

The Verdict

A thermostat is one of the most important components in your home’s HVAC system. Without it, your heating and cooling are running blind or not running at all. 

So deciding on a thermostat and knowing where to place it is very important, especially since you need it to be more efficient and represent the actual temperature of your home. 

So make sure to read up on this article and drop us a comment if you have any questions.

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