What Your Thermostat Actually Does - Meridian HVAC

It sits quietly on your hallway wall, and you probably check it every morning and every night. But how much do you really know about your thermostat?

Is it just a thermometer? Is it a computer?

At Meridian HVAC & Refrigeration, we consider the thermostat the "brain" of your heating and cooling system. Even the most expensive furnace can't do its job if the thermostat isn't telling it what to do.

Here is a look at what that little box is actually doing and how to use it correctly to save money.

The Basic Concept: It's a Temperature-Controlled Switch

At its simplest level, a thermostat is just an ON/OFF switch that reacts to temperature.

Sensing: It constantly measures the ambient temperature of the air around it.
Comparing: It compares that reading to the "Set Point" (the temperature you asked for).
Commanding:
- If the room is 68°F and you set it to 72°F, it closes a circuit (flick the switch ON) to start the furnace.
- Once the room hits 72°F, it opens the circuit (flicks the switch OFF).

The "Accelerator" Myth (Read This!)

This is the most common misconception we see.

Myth:

"If I set the thermostat to 90°F, the house will heat up faster than if I set it to 72°F."

Fact:

Your furnace only has one speed: ON. It produces the same amount of heat whether you ask for 70 degrees or 100 degrees. Setting the temperature higher simply tells the furnace to run for a longer period of time, not to run hotter or faster.

Tip:

Set it to the temperature you actually want. Turning it up higher won't warm you up any faster; it will just overheat the house and waste gas.

Why Location Matters

Because the thermostat measures the air right next to it, its location is critical.

The Kitchen Problem: If your thermostat is near the stove, it will think the whole house is hot while you are cooking and shut off the heat to the bedrooms.
The Window Problem: Direct sunlight hitting the thermostat will give "ghost readings," causing the AC to run constantly in the summer.
The Draft Problem: If it's near a drafty front door, it will think the house is freezing and run the furnace unnecessarily.

From Mercury to Wi-Fi: Types of Thermostats

1. Mechanical (The Old Round Dial)

These used a drop of mercury or a bi-metal coil physically moving to make electrical contact. They are durable but not very accurate (often swinging 3–5 degrees).

2. Digital Non-Programmable

Simple push-button screens. They are more accurate than mechanical ones but still require you to manually change the temp when you leave or go to bed.

3. Smart / Wi-Fi Thermostats (Nest, Ecobee, etc.)

These are the new standard. They connect to your phone, allowing you to change the temp from bed or from work.

Learning: Some learn your schedule and automatically turn down the heat when you leave.
Alerts: They can email you if your home gets dangerously cold (preventing frozen pipes) or if your furnace is acting up.
Zone Sensing: In two story homes a simple zone sensor can be installed and programmed to prioritize the temperature at different times of the day.
Indoor air quality: Some smart thermostats monitor the quality of your air and can alert you or even turn on mechanical ventilation (If available).

Is It Time for a Brain Transplant?

If you are still using an old manual slider or dial thermostat, you are may be wasting money on overheating or overcooling your home.

Upgrading to a modern thermostat is one of the cheapest, fastest ways to improve your home's efficiency.

Need help installing a new smart thermostat? We can wire it up correctly and teach you how to use the app.

More Than Just a Dial: What Your Thermostat Actually Does