Smart Thermostat Lite
for Central Heating (HVAC)

The concept of heating and cooling stages is fundamental to understanding how modern central HVAC systems operate, especially those using a heat pump.

A stage refers to a distinct heating or cooling source or capacity level within a system.
A thermostat that can control multiple stages is called a multistage thermostat.

How multistage systems work

In residential central HVAC systems, there are generally two main types of systems.

1. Single-stage system

This is the simplest type of system. It has only one operating speed and one heating or cooling source.

• Example: a conventional gas furnace.

  When the thermostat detects that the temperature is too low, it signals the furnace to run at 100% capacity until the desired temperature is reached.

  The operation is simple: either fully on or fully off.

2. Two-stage or multi-stage system

These systems are designed to provide greater comfort and improved energy efficiency.
They operate with two or more levels of heating or cooling capacity.

a) First stage (low capacity)

The first stage is the primary heating or cooling source and operates at reduced capacity (typically around 60%–70%).

Purpose:

• Maintain a consistent indoor temperature

• Improve comfort by reducing temperature swings

• Lower energy consumption

Under most weather conditions, the system will operate only at this first stage.

b) Second Stage (High Capacity or Auxiliary)

The second stage activates only when the first stage cannot maintain the desired temperature, typically when outdoor temperatures are very low.

Purpose:

• Provide additional heating or cooling capacity

• Activate a supplementary (auxiliary) heat source

Summary

To ensure that the thermostat is compatible with your current installation, you must first validate your system’s current connections and verify that they are compatible with the thermostat.

Click here to check your compatibility by using our online tool.