At Caledonian Mechanical Inc., we’ve worked on homes and businesses across Fresno and Clovis, and one topic that comes up often is zoning systems. These systems can be a fantastic way to save energy and increase comfort—but only if they’re designed and installed correctly. We’ve seen the good, the bad, and the ugly. Here’s our take on what actually works, what doesn’t, and what homeowners should know before investing in a zone system.
What Is a Zoning System?
A zoning system allows you to divide your home into separate areas (or “zones”) with independent temperature control. Instead of heating or cooling the entire house at once, you can run your HVAC system to condition only the spaces you’re actually using—like bedrooms at night, or living areas during the day.
This is done with zone dampers inside your ductwork and a zone control board that tells your equipment when to open or close each zone. Paired with multiple thermostats, it gives you more control and can cut down on unnecessary energy use.
Our Preferred Setup
There are many zone damper systems on the market, but through our experience, we’ve found the Honeywell HZ322 Zone Controller paired with ARD 24V dampers to be one of the most reliable options for standard residential gas/electric systems (2 heat / 2 cool).
- Controller Board: The Honeywell HZ322 is simple, proven, and easy to troubleshoot.
- Dampers: The ARD10TZ motorized dampers are dependable and widely available.
- Result: When installed in the right application, this system balances comfort and efficiency with less wear on your HVAC equipment.
The Pros of Zoning
- Lower Utility Costs: If designed right, zoning means you only heat/cool the areas you’re using, reducing KW per hour usage.
- Improved Comfort: Bedrooms can be set cooler at night while living spaces stay warmer, giving you flexibility.
- Long-Term Efficiency: Less runtime overall when used properly, which can extend the life of your HVAC system.
The Cons (and Common Pitfalls)
- Ductwork Design Matters: If ductwork isn’t designed for zoning, static pressure (air pressure backing up in the ducts) can climb too high. This stresses the compressor and may cause refrigerant to slug back into it, leading to long-term damage.
- Bypass Damper Needed: Without a bypass relief damper, static pressure can exceed safe levels (above 0.5” WC), causing short cycling and inefficiency.
- Undersized Systems: We see this often in new builds—installers undersize the equipment, assuming only one floor or one side of the house will run at a time. That works in mild weather, but in 100+ degree Fresno summers, undersized units run constantly and never catch up.
- Improper Commissioning: A zone system must be tested with one zone at a time, two zones, and all zones open. Refrigerant charge, airflow, and amp draw must be correct in every scenario. Skipping this step guarantees future issues.
Key Design Rules to Follow
- Correct Load Sizing: Equipment must be sized for the home’s full heating/cooling demand, not just one zone at a time.
- Duct Balance: Ducts must be evenly distributed and sized to prevent bottlenecks and high pressure.
- Bypass Damper Installation: Keeps static pressure within safe ranges.
- Proper Insulation: Walls and attics should be well insulated to keep conditioned air inside. Poor insulation can cause short cycling (system turns on and off too often).
- Full Commissioning: Refrigerant charge, electrical readings, and airflow should be verified under different zone conditions.
Our Bottom Line
When done correctly, zoning systems are fantastic tools for controlling comfort and saving energy. But when done wrong, they create more problems than they solve—shorter equipment life, higher bills, and frustrated homeowners.
At Caledonian Mechanical, we design every zoning project with proper ductwork evaluation, static pressure relief, and load sizing in mind. That way, you can enjoy the benefits—without the headaches.
👉 If you’re considering a zoning system for your home or business, reach out to us. We’ll walk you through the options and make sure the system is designed for both comfort and longevity.