Xem thêm

A Comprehensive Guide to Installing Central Air Conditioning

CEO Khai Intela
Are you considering installing central air conditioning in your home? Whether you're building a new house, replacing an existing unit, or retrofitting an older home, understanding the process is essential. In this guide, we'll provide...

Are you considering installing central air conditioning in your home? Whether you're building a new house, replacing an existing unit, or retrofitting an older home, understanding the process is essential. In this guide, we'll provide valuable insights to help you navigate through the central air installation journey.

Understanding the Basics

Before we dive into the details, let's start with some key definitions. Central air conditioning refers to a system that cools the air in one location and then distributes it throughout the entire home using the air handling capabilities of the furnace. This distinguishes it from other cooling options, such as window or wall air conditioners or mini-split systems.

Now, let's explore the sizing and efficiency factors that are essential in central air conditioning.


When discussing air conditioners, "size" refers to the cooling power of the unit, not its physical dimensions. HVAC professionals use a measure called British thermal units (Btu) to determine the cooling capacity. The higher the Btu, the more cooling power the unit provides. For example, a 2.5-ton air conditioner is equivalent to 30,000 Btu.


Efficiency is measured using the seasonal energy efficiency ratio (SEER). Higher SEER units are more efficient, thanks to features like two-stage compressors and variable-speed blowers. These technologies allow the air conditioner to consume less energy when the temperature is lower.

team of HVAC installers repairing central air conditioning system outside of house Image: A team of HVAC installers repairing a central air conditioning system outside of a house.

Can You DIY a Central Air Installation?

While the DIY ethos is admirable, central air conditioning installation usually requires professional help due to its complexity and the specialized skills involved. Attempting the installation yourself without proper knowledge and experience can lead to costly mistakes and potential warranty issues.

That said, if you're determined to take on some tasks yourself, you can handle certain aspects of the installation. However, handling refrigerant requires a licensed professional, and in some places, only a licensed electrician can connect the electrical to the service panel.

Working with Professional HVAC Installers

When working with professional HVAC installers, it's essential to establish clear communication and ensure that your preferences are reflected in their estimate and the finished product.


Before starting the installation, spend time planning with your contractor. Discuss your priorities, such as energy efficiency and cost considerations. Additionally, decide on the location of the condenser unit and the type of thermostat you prefer.


Your HVAC installer will assist you in determining the appropriate size of the central air conditioner for your home. It's crucial to find the right balance between a unit that's too small, which will run constantly, and a unit that's too large, which cools the house too quickly and shuts down prematurely.

To estimate the size, multiply the square footage of your home's conditioned space by 25 to determine the required Btu. Then, divide it by 12,000 to get the tonnage. However, it's important to note that this rough estimate may vary based on factors such as ceiling height and the presence of large windows.


Always request written estimates from multiple vendors to compare prices and services. Clarify any questions and ask for detailed expense breakdowns, if possible. Open communication will ensure a smooth and transparent process.

two central air conditioning units outside of a house Image: Two central air conditioning units outside of a house.

The Central Air Installation Process

Now, let's walk through the main steps involved in the central air installation process:

  • Duct Work Installation or Modification: Existing furnaces or air conditioning systems typically require minimal duct work. However, if new ducts are needed, work with your contractor to find ways to conceal them to avoid extensive repairs.

  • Interior Unit: The evaporator coil fits inside the furnace plenum, which is the section of the furnace where air is brought in and sent back into the house.

  • Exterior Unit: The placement of the exterior unit depends on factors like the distance to the interior unit and electrical service panel, ground level, proximity to windows or doors, and code requirements.

  • Connect the Line Set: The evaporator and condenser units are connected by a pair of copper pipes called the line set. Ensure proper sealing to prevent water infiltration at the exterior penetration.

  • Connect the Electrical Supply: Installation involves an exterior shutoff for the condenser unit, electrical wiring from the condenser to the shutoff and the service panel, and a low-voltage wire connecting the condensing unit to the furnace for thermostat control.

  • Condensate Drain Line: All air conditioners produce condensation that needs to be drained. Depending on the location of the unit, the condensation can be piped outside or drained into a floor drain or evaporate using a drain pan.

  • Thermostat: If you're installing central air conditioning in a new build, you'll need to choose a thermostat. For existing homes, you may need to upgrade your thermostat to control cooling as well. This is an excellent opportunity for a DIY effort by purchasing a basic thermostat and upgrading to a programmable or smart version later.

Central Air Installation Costs

Central air installation costs vary depending on factors such as the local market and job specifications. On average, labor and materials for a split system central air installation using an existing furnace range from $3,000 to $5,500, with labor accounting for the majority of the cost. If you're replacing an existing system, expect additional charges for removing and disposing of the old unit.

While it's possible to purchase the AC system yourself and hire an HVAC professional for installation, keep in mind that you may not receive commercial discounts, and you'll be responsible for sizing and any equipment issues that arise.

In Conclusion

Installing central air conditioning is a significant investment that enhances your home's value and provides comfortable living conditions. Although the process may seem complex, this guide offers valuable insights to help you navigate the installation smoothly. Don't hesitate to ask questions and communicate openly with your installer to ensure a successful outcome.