If you’re concerned about the high cost of cooling your home or have issues with parts of your home often being too hot, upgrading to a multi-zone cooling system is a great option. You can also add multi-zone heating to lower your heating costs and help your home stay consistently warm. To understand why multi-zone cooling is such a great choice, here is an overview of how it works and the benefits it will provide to your home.

Single-Zone vs. Multi-Zone Cooling

The majority of central air conditioning systems are single-zone systems that are controlled by one central thermostat. In a single-zone system, cool air always flows through the ducts and into every room. A multi-zone system splits the home and ductwork into multiple smaller areas or zones. This is done by installing metal dampers or gates in various ductwork parts. Each zone has a dedicated thermostat that controls the damper for that zone.

How Multi-Zone Cooling Works

With a multi-zone cooling system, you can set different temperatures for each zone instead of just having one temperature for the entire house. If you only have four zones that are similar in size, the thermostat in each zone can control the AC system independently and signal it to turn on and off as needed. If you have more than four zones or some zones that are much larger or smaller than the others, only some of the thermostats will control the system. However, every thermostat will still control the damper for its zone.

If any zone with a control thermostat is 1-3 degrees above your desired temperature for that zone, that thermostat will signal the AC to start running. If all of the other zones are still at the correct temperature, the dampers in those zones will remain shut. This means that all the cool air will only flow to the zone or zones warmer than the desired temperature.

There will be times when air flows to all zones at once. However, the thermostat in each zone will signal the damper to close as soon as it registers that the zone has reached the desired temperature. If any control zones are too warm, the AC will continue running until every control zone is at the correct temperature. If you have a smaller zone that isn’t a control zone, it will only receive cool air if the closest adjacent control zone it’s connected to is warmer and currently calling for cooling. This makes it essential that an HVAC technician design the system properly so that you don’t end up with a smaller zone that often stays warmer than you want.

What Type of AC Unit Do You Need for Multi-Zone Cooling?

Depending on how many zones the system has, it will require either a two-stage or variable-speed AC to work properly. If you tried to use a standard single-stage AC in a multi-zone system, it would constantly freeze when it wasn’t supplying air to every zone. This is because single-stage ACs always run at 100% capacity. If even one zone isn’t open, less warm air will come into the system, and the refrigerant won’t absorb enough heat to keep the evaporator coil from freezing.

Two-stage ACs can operate at either 100% or around 65% capacity. You could theoretically use a two-stage AC in a multi-zone system, but it would generally only work correctly if you only had two zones. Even then, it may have problems with freezing up and experience other issues if it supplies air to only one of the zones for too long.

Variable-speed ACs are always the best choice for a multi-zone system, as they can slow down to where they only run at around 25% of the total capacity. As long as the system supplies air to at least 25% of the home, it will never have any issues. This explains why you must have no more than four equal-sized zones, or not all thermostats will control the system. If you had a control zone that was less than a quarter of the total size of your home, it would end up causing many issues.

Depending on how many zones are currently calling for cooling, a variable-speed AC can speed up or slow down the cooling rate and how much air flows as needed. Even if every zone is open and calling for cooling, a variable-speed AC will typically not run at 100% power unless your home is much hotter than the desired temperature. Even then, it would quickly reduce its power and speed as soon as the temperature in some zones starts to decrease.

Benefits of Multi-Zone Cooling

The most significant benefit of a multi-zone cooling system is that it will greatly reduce how much it costs to cool your home. This is because you’ll rarely need to cool every zone at one time and also because a variable-speed AC will run at a much lower power setting most of the time.

A multi-zone system also gives you far greater control over the temperature in your home, which is vital for your family’s comfort. It will also make it much easier to ensure every part of the home always stays at the desired temperature to prevent issues with some parts being too hot or too cool.

Multi-zone systems are an especially good option for homes with multiple stories. If you have a two-level home, the lower level will generally stay much cooler than the upper floor. This is partly because heat rises. The other reason is that the upper floor will also be warmer in a single-zone system because the thermostat is located on the ground floor. Since the ground floor tends to be less hot, it will cool down faster than the upper floor. This means the thermostat will typically signal your air conditioning to shut off before the upper floor is entirely cool.

With a multi-zone system, you can create a separate zone for each level or even multiple zones on every level if some of the zones aren’t control zones. Since your ground floor will always stay colder, the system won’t have to cool it nearly as often as the upper floors. This will help ensure your ground floor is never too cold and reduce your air conditioning costs. A multi-zone system will also overcome issues with an upper floor staying too warm since it will keep running for however long it takes to cool that zone down to the desired temperature.

If you also have multi-zone heating, it will greatly help keep your lower floor warm enough in the winter and prevent the upper floor from being too hot. However, this will also require upgrading to a variable-speed furnace or heat pump. In this case, a heat pump will almost always be the best option since it works more energy efficiently than a furnace and provides heating and air conditioning.

Another significant advantage of a multi-zone system is that it will usually help extend your HVAC unit’s life. This is because your AC generally won’t ever have to run as often or work as hard, lessening the wear and tear it receives. Variable-speed ACs also tend to have a longer lifespan since the wear and tear is reduced when they aren’t running at full power.

If you’re ready to upgrade your current home to multi-zone cooling, you can trust the experts at Norman Air for help. We specialize in all types of HVAC installation, repairs, and maintenance, and we also offer expert plumbing and electrical services in Norman and throughout the OKC Metro area. For more information on your multi-zone cooling or heating options, call us today.

Meet the Author
Michelle Morrison
Michelle Morrison

Marketing Manager

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