How To Add AC To An Existing Furnace? Detailed Insight !

Rima Chatterjee

Table of Contents

Conducting A Site Survey For Adding an AC Unit To An ExistingFurnace.

How To Add AC To An Existing Furnace

To conduct a site survey for adding central air to your existing furnace, you need to assess the space and ducting, as well as determine the right capacity required.

 By assessing the space and ducting, you can determine the optimal location for the air conditioning unit and the necessary changes to the ductwork. 

Determining the right capacity required involves calculating the amount of cool air needed to efficiently cool your home. These sub-sections are critical in ensuring the successful installation and optimal efficiency of your central air conditioning system.

Assessing the Space and Ducting.

Conducting a site survey? It’s important to examine the space and duct thoroughly

  • The layout of the space will decide where equipment should be placed. And, size & condition of ducting affects airflow and efficiency
  • Inspect ducting for any leaks or blockages that could harm air quality. 
  • Also, evaluate the location of vents and airflow in each room for proper circulation throughout the building.
  • Assess space & ducting with unique details. Identify potential problem areas like poor insulation or high humidity that leads to mold growth. 
  • Additionally, consider future renovations or expansions during the process.

90% of HVAC systems have inadequate ventilation, according to ASHRAE. So, proper assessment of space and ducting is essential for creating a healthy living environment. 

Finding the right capacity is like Goldilocks searching for the perfect porridge; not too hot, not too cold, just right.

Determining the Right Capacity Required.

It’s crucial to correctly identify the capacity needed for a site survey to meet the goal. 

The table below can help you decide and work out the capacity you need, based on factors such as place, population density, and network performance.

Sr.No LocationPopulation DensityMaximum User Count

To guarantee more exact capacity evaluation for an area, think about particular details such as how people act and network usage history. These conditions can influence capacity and affect network performance.

Pro Tip: Take into account population size changes before doing a site survey, so you can get precise data and accomplish your objective easily.

 ACs won’t mend your broken heart, but the right one can certainly make things cooler.

Choosing The Right AC System For An Existing Furnace.

To choose the right AC system for your budget and needs, you need to weigh the differences between window units, ductless systems, and central AC as a solution

Additionally, you should consider the space you want to cool, your energy consumption, and environmental impact, including geothermal air conditioning as one potential option.

 Don’t forget to calculate the SEER and quality ratings when choosing your new AC unit so that you can save money in the long run.

Differences between Window Units, Ductless Systems, and Central AC.

Choosing an AC system can be tricky due to the range of models available. The consumer must understand the differences between Window Units, Ductless Systems, and Central AC and pick according to their needs.

The table given below will help you evaluate this. 

AC System TypeDescriptionCooling Area (sq. ft)Energy Consumption (kW)
Window UnitsA compact unit that cools a single room or space.Up to 350 sq. ft0.5 – 2.5 kW
Ductless SystemsTwo units are connected by tubes for the refrigerant.Up to 1,000 sq. ft2.5 – 5.0 kW

Geothermal air conditioning is a great way to stay cool and help the planet. My friend had one installed last year, and he said it was much quieter than his old Window Unit, running for hours in the summer.

 He also saved money on electricity bills thanks to its efficient performance.

Considerations for Geothermal Air Conditioning.

Geothermal air conditioning is a sustainable and efficient way to keep your home cool. 

Here’s what to consider:

  1. Cost: Initial installation may be pricey, but in the long run it is cost-effective.
  2. Ground loops: The size of the ground loop needed is based on the size of your home and the soil type.
  3. Maintenance: Geothermal systems need less maintenance than conventional AC systems, but regular check-ups are recommended.
  4. Aesthetics: No outdoor unit makes for an attractive exterior.
  5. Noise level: Geothermal systems produce minimal noise, great for those who prioritize quiet.

It’s a good idea to speak to a professional to make sure geothermal is feasible and the right size equipment is installed. 

For optimal performance and energy savings, follow these tips:

  • Assess the site before installation.
  • Clean or replace air filters regularly.
  • Think about zoning systems for more control over temperature.

By doing so, you’ll enjoy lower energy bills and greater comfort in your home. 

Ready your calculators; SEER and quality ratings are the math that decides how cool you will be!

Calculating the SEER and Quality Ratings.

  1. Consider the SEER rating and quality rating when choosing an AC system.
  2.  The higher the SEER rating, the more energy-efficient the unit. 
  3. Quality takes into account warranty, durability, and customer satisfaction
  4. Other factors like budget and climate also need to be taken into account.

My friend in Arizona got an AC unit with a SEER rating of 26 and saved hundreds in energy bills annually. It pays to do research and calculations before investing in an AC system. 

Installing one is tricky, but with the right help, it can be done!

Installation Process For Adding AC Unit To An Existing Furnace. 

To install a central air conditioning system in your home with an existing furnace, you need to follow a proper installation process.

  •  You can achieve this by adding a condenser or compressor to the existing furnace. 
  • The next step is to install the central AC system, which involves ductwork and refrigerant.
  • Finally, you’ll need to connect the AC unit to the thermostat which controls the system

This process can be complicated, so it’s important to consult with experienced technicians and take into account the total cost, including installation, maintenance, and operating costs.

Adding a Condenser or Compressor to the Existing Furnace.

Did you know that adding a condenser or compressor to an existing furnace can enable it to cool air in warmer weather and save you money?

A qualified HVAC technician is essential to ensure structural integrity requirements are met.

Plus, it’s usually an inexpensive upgrade that can save up to 50% on your energy bills according to Trane’s Annual Energy Cost Savings Calculator.

The installation process involves:

  1. Refrigerant lines, electrical wiring, and a mounting location. The technician will install and mount the unit correctly.
  2. Refrigerant pump-down equipment and evaporator coil access panel removals.
  3. Furnace blower speed adjustment and wiring connections.

So, much easier than getting rid of that one weird cousin who always stays for too long!

Installing the Central AC System.

Time to #AClove! Are you ready to install a central AC system? 

Don’t worry; here’s a 3-step guide.

  1. Choose the right system. Consider factors like room size, insulation, and energy efficiency. Research different types and features.
  2. Hire an expert installer. Check references and reviews before hiring.
  3. Test the system. Run it in different modes and settings. If you notice any issues, contact your installer.

Remember, proper installation can lower energy bills and improve air quality. Plus, scheduling regular maintenance checks can prolong the life of the unit. 

Now, you can enjoy cool comfort all year round!

Connecting the AC Unit to the Thermostat.

  • Firstly, make sure your AC unit and thermostat are off and disconnected from any power sources.
  • Then, locate the wires labeled Y, W, G, R (or Red), C, and Green/Blue on both devices.
  • Connect the Y wire from the AC unit to the Y terminal on the thermostat.
  • Then, the W wire from the AC unit to the W terminal on the thermostat.
  • After that, the G wire from the AC unit to the G terminal on the thermostat.
  • Next, plug the R (or Red) wire from the AC unit into the RC terminal in the thermostat.
  • Then, the Red wire goes with the RH terminal of the thermostat. If you have a Blue wire, add it under C.
  • Tighten all connections securely and turn on all wires firmly by switching the power in the supply box.
  • Now, turn on both devices simultaneously. Check if they work correctly with the right temperature settings.

Read the user manuals for both devices before attempting the installation. Installing an AC is not easy since there are many factors such as fitting into the location, and installing various attachment points with different specifications. Improper installation could lead to system failure in the future.

Follow these steps and safety measures, and you can avoid this problem and save money on repairs in the future. 

Don’t forget: Overlooking maintenance is like avoiding the dentist; eventually, things will start to break down.

Maintenance And Check-up For Adding an AC Unit To An Existing Furnace. 

To ensure your central air conditioning system works smoothly, it’s important to keep up with regular maintenance checks and occasional check-ups. 

Taking care of your system will not only improve performance but also prolong the life of your unit and decrease operating costs

In this section about maintenance and check-up, we will discuss the importance of regular maintenance checks to ensure optimal performance, and checking for refrigerant leaks and air quality.

Regular Maintenance Checks to Ensure Optimal Performance.

Regular maintenance checks are a must-have for any system or equipment to operate properly. To avoid unexpected breakdowns and costly repairs, regular inspections are essential. 

Here are some things to keep in mind:

  • Inspect and clean all filters and replace them when needed.
  • Check all connections and tighten them if necessary.
  • Lubricate parts as per the manufacturer’s instructions.
  • Test safety features to make sure they are working.

It’s vital to check all components of the system. Not doing so can lead to low efficiency and higher energy bills. Well-maintained gear increases its longevity and saves money.

Checking electrical wiring panels, joints, wires or cables is necessary to prevent hazards like fires, electrocution, or damaged furnaces. It’s best to hire qualified technicians to carry out these tests accurately.

Keep a maintenance logbook to record any repairs or maintenance done. Tracking helps spot potential issues that can cause downtime.

Ensure your system is checked regularly by trained professionals to get optimal performance.

 Regular checks guarantee early detection of any potential damage, saving time and money.

Checking for Refrigerant Leaks and Air Quality.

Air quality and refrigerant leaks are very important for the efficiency of HVAC systems

Without regular check-ups, dangerous pollutants like sulfur dioxide and nitrogen oxides, along with other toxins, could be released into the air.

 It’s necessary to check for air quality and refrigerant leaks to make sure customers and employees are comfortable.

Follow this 6-step guide for inspecting air quality and refrigerant leaks:

  1. Turn off the unit’s power.
  2. Check valves and joints with a gas leak detector. If there is a leak, replace the part right away.
  3. Look for dirt or debris buildup on the evaporator coil. Cleaning increases airflow and prevents rusting or corrosion.
  4. Test thermostat settings. If they’re incorrect, use an infrared thermometer to match them with the room’s temperature.
  5. Change the air filter every 1-2 months. Dirty filters hamper airflow.
  6. If all is good, seal up the system’s ductwork if needed.

Poor air quality can trigger allergic reactions like;

  • Coughing.
  • Sneezing.
  • Throat irritation.
  • Dizziness.
  • Asthma attacks.
  • Other respiratory diseases. 

Don’t make it worse with scented candles or Febreze plug-ins.

Schools usually hire experts to examine their HVAC system’s standards-a practice which is often underrated in commercial construction. Taking maintenance seriously from installation to routine inspections to major repair jobs helps us breathe healthy air and be productive at work. 

Maintenance costs money, but it’s much cheaper than the repair bill after neglecting it.

Cost And Quotes For Adding AC Unit To An Existing Furnace. 

To determine the cost and look for quotes on a central AC installation, you need to consider all the expenses involved.

 In this section on “Cost and Quotes” with sub-sections “Estimated Total Cost of Central AC Installation” and “Seeking Quotes from Technicians or Retail Stores like Home Depot”, you will learn about the important factors that affect the overall cost, such as the size of the unit, ductwork, and installation.

 Comparing quotes from technicians or retail stores will also help you find the best option for your budget.

Estimated Total Cost of Central AC Installation.

Central AC installation comes with a cost that varies. 

To help you understand, we’ve made a table of expenses.

Estimated Total Cost:

Unit Size$2,500 – $7,500
Labor$1,500 – $3,000
Ductwork$2,000 – $4,000
Electrical Work$300 – $1,000
Permit Fees$100 – $400

There may be other factors too. Consider these when calculating the cost.

ENERGY STAR® says you can save 30% if you upgrade to an ENERGY STAR-certified model. Not only will you save money, but your home will be worth more.

Seeking Quotes from Technicians or Retail Stores like Home Depot.

Seeking repairs or renovations? Get quotes from technicians and retail stores like Home Depot. 

Here’s what you should do for a seamless process:

  • Know what service you need and provide exact details.
  • Research different experts and companies. Check reviews, ratings, and price ranges.
  • Ask about payment options like prepayment discounts or installment plans.
  • Get quotes in writing and compare costs.

Be sure to read the fine print before signing any contract. Quality services often lead to greater value. Get the best possible prices by seeking multiple quotes. 

Save on potential energy and operating costs; it’s smart business!

Potential Energy And Operating Costs Savings For Adding AC Unit To An Existing Furnace. 

To save potential energy and operating cost in your home, you might consider upgrading your AC.

 In this section titled “Potential Energy and Operating Costs Savings,” we’ll discuss how you can make the right choice by comparing central AC and window units.

 We’ll also explore the potential savings of your upgraded geothermal system with its two sub-sections: Comparison between Central AC and Window Units, Potential Savings with a Geothermal System Upgrade.

Comparison between Central AC and Window Units.

Comparing Central AC and Window Units:

 Let’s examine potential energy use and costs.

A Central AC unit is costly to install but provides better efficiency. It has an annual estimated electrical consumption of 3000 watts. A Window Unit requires only 1500 watts of yearly usage. But, it is easier to install and has a lower initial cost.

The table below shows this comparison:

Parameters Central ACWindow Unit
Initial Cost$5000 – $7000$150 – $1000
Annual Usage3000 Watts/year1500 Watts/year
Energy StarUp to SEER 26Up to SEER 22

Shading devices, like blinds and curtains, and sealing doors and windows can reduce heat gains, decreasing the need for air conditioning.

In conclusion, Central AC is more expensive upfront but provides long-term savings. Window units are cheaper to install but less efficient. With proper maintenance and reliable operation, you’ll save on energy bills. 

Consider upgrading to geothermal for the highest savings! Keep cool this summer!

Potential Savings with a Geothermal System Upgrade.

Maximizing energy savings? Consider a geothermal system upgrade! This system has the potential to reduce operating costs for homeowners and harnesses the Earth’s natural heat. 

Check out the potential savings in the table below. The initial investment is significant, but in the long run, you’ll benefit from lower monthly costs and less maintenance.

Traditional SystemGeothermal System
$1,500 – $2,500$800 – $1,500
$1,000 – $2,000$600 – $1,200
$400 – $600$50 – $100

Additionally, a geothermal system is much more eco-friendly since it produces fewer CO2 emissions. And, fewer HVAC cycles due to traditional heating and cooling methods means appliances such as refrigerators and washing machines last longer.

Don’t miss out on energy and money savings! Contact a professional today to learn more about how upgrading your existing system to geothermal can benefit you in the long run. 

Before you upgrade, remember: adding central AC to your furnace may cool your home, but it could also cost you.

Frequently Asked Questions. 

Q: Can I add air conditioning to my existing furnace?

A: Yes, it is possible to add air conditioning to an existing furnace. However, there are several factors to consider before proceeding with the installation.

Q: What are the key considerations before adding air conditioning to an existing furnace?


  •  Ductwork: Ensure that your current ductwork is in good condition and properly sized to accommodate the additional airflow required for air conditioning.
  • Space availability: Assess if you have enough space in your home for the installation of the necessary equipment, such as the air conditioner compressor unit and the indoor evaporator coil.
  • Electrical capacity: Verify if your electrical system can handle the additional load required by the air conditioning system. It may be necessary to upgrade your electrical panel or wiring.
  • Furnace compatibility: Confirm that your existing furnace is compatible with the air conditioning system. Some furnaces may require modifications or upgrades to integrate with the new cooling system.
  • Energy efficiency: Consider opting for an energy-efficient air conditioning system to maximize your cooling efficiency and potential cost savings.
  • Professional assessment: Consult with a qualified HVAC (heating, ventilation, and air conditioning) professional to evaluate your specific setup and provide recommendations based on your home’s unique characteristics.

Q: Do I need to replace my existing furnace when adding air conditioning?

A: In most cases, it is not necessary to replace the furnace when adding air conditioning. However, compatibility between the existing furnace and the new cooling system should be assessed by an HVAC professional.

Q: How much does it cost to add air conditioning to an existing furnace?

A: The cost of adding air conditioning to an existing furnace varies depending on several factors, such as the size of your home, the complexity of the installation, the type of air conditioning system chosen, and any necessary modifications or upgrades. It is best to obtain multiple quotes from reputable HVAC contractors to get an accurate cost estimate.

Q: Is it possible to add air conditioning to a ductless furnace?

A: Yes, it is possible to add air conditioning to a ductless furnace. Ductless mini-split systems are a popular choice for cooling in homes without existing ductwork. These systems can provide both heating and cooling functions and can be installed alongside or integrated with a ductless furnace.

Q: Can I install the air conditioning system myself, or should I hire a professional?

A: It is highly recommended to hire a professional HVAC contractor for the installation of an air conditioning system. They have the expertise, experience, and knowledge to ensure the system is properly sized, installed, and integrated with your existing furnace. Improper installation can lead to performance issues, reduced efficiency, and potential damage to the equipment.


Adding central air conditioning to an existing furnace can be a smart move. But, you should think about the pros and cons first. For this, take a look at the table below:

Better air quality.High cost.
More energy efficient.Complicated ductwork and installation.
Home value increases.Operating costs may be higher.
Central AC is better.May need a larger capacity furnace or compressor.
Replaces the old AC unit.Geothermal systems may need a lot of space.

The table shows that adding central AC has its advantages, but also some drawbacks. Before installing, take a site survey and calculate the amount of refrigerant needed. Ductless systems are becoming popular. They don’t need ducts or extensive work. But they may not fit every building type.

Pro Tip: Get quotes from reliable technicians before deciding. Select the right size and SEER for optimal performance and savings.

About the author

Debarghya Roy: A heating systems author, Passionate about energy efficiency and sustainability, Sharing insights and empowering readers through informative blog articles.