Instead of keeping your home at one temperature throughout, a zoned forced-air furnace and air conditioner allows you to control how hot or cold it gets in specific areas. This system provides homeowners with individualized comfort, and it may even lower utility bills. In this article, we’ll explain how to zone a forced-air furnace and air conditioner. In the video above, Ask This Old House plumbing and heating expert Richard Trethewey demonstrates how to divide a home’s heating and AC system into different zones.
How HVAC Zoning Works
An HVAC technician installs motorized dampers in the ductwork, which controls the airflow to different areas within your home. The dampers are connected to a central control panel and individual thermostats in each zone. When you turn up the heat or AC in an individual room, the dampers open to allow airflow to that area while closing off other zones.
HVAC Zoning Benefits
Before we dive into the how-to, we’ll cover some of the advantages of HVAC zoning. Zoning your forced-air furnace and air conditioner offers several benefits, including the following:
- Cost savings: By lowering a room’s heat or AC when you aren’t using it, you reduce energy consumption and lower utility bills.
- Energy efficiency: Since you’re lowering your energy consumption, your home becomes more energy-efficient and eco-friendly.
- Extended equipment life: By controlling the temperatures in individual spaces, you reduce the wear and tear on your HVAC system.
- Improved comfort: You can adjust different zones according to comfort level and temperature preferences.
Zoning a Forced-Air Furnace and AC Unit
If you’re ready to take the leap to HVAC zoning, consult with a professional HVAC expert. While DIYers may want to tackle this project themselves, it requires a lot of plumbing and electrical experience.
Whether you choose to take the DIY approach or hire someone to help, it’s helpful to understand the installation process. Below are the steps to zone a forced-air furnace and AC unit.
1. Assess Your Current HVAC System
Before beginning the zoning process, evaluate your existing HVAC system to make sure it’s zoning-compatible. This assessment will help you identify any potential challenges, such as outdated equipment or inadequate ductwork. Here are a few things to look for:
- Age and condition of your furnace and air conditioner: Ensure that your equipment is up-to-date and in good working order to avoid complications during zoning.
- Capacity of your current system: Verify that your system can handle the additional demand from zoning without overloading.
- Layout of your existing ductwork: Check if your ductwork is designed to accommodate zoning or if modifications are needed.
- Size and layout of your home: Consider whether your home’s layout supports zoning and whether the space is suitable for effective temperature control.
2. Plan Your Zones
Now that you’ve determined the system is ready for zoning, you need to figure out how you’d like to divide your home. Effective zone planning takes into account certain factors, such as the number of occupants, their daily routines, and specific comfort needs. Common zoning strategies include the following:
- By floor (e.g., upstairs and downstairs)
- By room usage (e.g., living areas and bedrooms)
- By sun exposure (e.g., north-facing and south-facing rooms)
3. Install Motorized Zone Dampers
The next step is to install motorized zone dampers in your ductwork. In the video, Trethewey demonstrates this process. Here are the steps to take:
- Cut into each flexible branch duct.
- Insert the motorized zone damper.
- Secure the damper to the duct using nylon cable ties.
4. Wire the Zone Dampers
After you’ve installed the dampers, wire them to the control panel. Trethewey shows how to daisy-chain the dampers together using telephone jack connections. This makes the wiring process straightforward and efficient.
5. Install the Control Panel
The control panel is the brain of your zoned HVAC system. It communicates with the thermostats, zone dampers, and your furnace or air conditioner. When you’re ready to install the control panel, place it near your HVAC equipment and connect all the wires.
6. Install Zone Thermostats
Each zone needs its own thermostat. In the video, Trethewey installs wireless thermostats, which are convenient because you place them anywhere in the zone without the need for complex wiring. Position thermostats away from direct sunlight and heating registers to get accurate temperature readings.
7. Install a Bypass Damper
A weighted bypass damper will maintain proper air pressure within your system. This damper redirects excess airflow when some zones are closed, which can prevent a noisy system and potential damage to your furnace or AC.
Here’s how to install the bypass damper in the supply and return trunks:
- Cut one hole in the supply and another in the trunk. These holes must be the same diameter as the bypass damper.
- Attach the damper with screws.
- Seal all the duct joints with mastic or foil-faced duct tape.
- Adjust the weights on the bypass damper so that you get the proper airflow to all registers.
8. Seal and Insulate Ductwork
Once you’ve installed the damper and sealed it with mastic or foil-faced duct tape, seal the rest of the joints and connections in the ductwork. This will help to minimize air leaks and keep temperatures consistent across all your zones.
9. Test and Adjust the System
Now that you’ve installed everything, it’s time to test the system. Adjust the weights on the bypass damper so that you have proper airflow to all the registers. You may need to fine-tune the system over time if you notice it isn’t functioning at peak performance.
Benefits of Professional Furnace and Air Conditioner Installation
As stated above, you may want to consider professional installation. The benefits of hiring an HVAC technician include the following:
- Code compliance: Professionals know local building codes and regulations.
- Expertise: HVAC professionals have the knowledge and experience to design an effective zoning system.
- Proper sizing: A technician can evaluate your existing HVAC system to make sure it can handle the demands of zoning.
- Warranty protection: DIY installation may void your HVAC system’s warranty.
Maximizing the Efficiency of Your Zoned HVAC System
We have a few tips to help you get the most out of your newly zoned HVAC system:
- Adjust zones seasonally: You can change your zoning strategy based on the weather patterns.
- Program your thermostats: Set different temperatures for each zone based on how you use the space.
- Regular maintenance: Schedule annual HVAC tune-ups so that your system continues to run smoothly.
- Use smart thermostats: Advanced technology can learn your preferences and adjust temperatures automatically.
Common Challenges and Solutions With HVAC Zoning
While HVAC zoning offers many benefits, you may encounter some challenges. We’ve listed some common problems and troubleshooting tips below.
- Uneven airflow: If you notice uneven airflow after zoning, it may be due to improperly sized dampers, incorrect duct sizing, or malfunctioning zone controls. Ask an HVAC technician to assess your system and make adjustments.
- System short-cycling: Short-cycling occurs when your HVAC system turns on and off frequently. This could happen if the zones are too small or if the system is too big for the reduced load. To fix this issue, you can combine smaller zones or install a variable-speed HVAC system.
- Higher initial costs: You might find the initial installation for your zoned system is expensive. Consider the long-term energy savings and improved comfort as you evaluate your budget.
- Balancing air pressure: When your system isn’t balancing the air pressure properly, it might be noisy and you may notice inefficient airflow. Regularly check and adjust dampers and consult with a professional for precise tuning.
