What is a Multizone unit

Don’t confuse multizone units with newer VRF systems. Seasons 4 manufactures custom, traditional multizone units, both new and as replacements.

A multizone unit is a single piece of equipment designed to serve multiple zones. It has zone dampers and multiple supply outlets. Typically, it has a hot deck with a gas furnace, electric heater, steam, or hot water coil, and a cold deck with a chilled water coil or DX coil. Most multizone units are rooftop package DX units, but some are DX split systems or chilled water units.

Each zone served by a multizone unit has its own thermostat, allowing for independent temperature control. You can also equip these thermostats with occupancy sensors and night setback overrides for added convenience.

People like multizone units because:

  • They provide comfortable space temperatures.
  • All equipment is on the roof.
  • There are no VAV boxes in the building.
  • Maintenance technicians don’t need to be in the hall or in the way.
  • Installation costs are lower.
  • There are no reheat boxes to power and control.
  • The unit has a single power source at the rooftop.
  • Control wiring is simpler.
  • Installation time is shorter.
  • You have a single source of responsibility.

Damper Configurations

Our multizone units have either 2-deck or 3-deck dampers. With 2-deck constant volume dampers, the cold and hot deck blades are fixed 90 degrees apart. The damper blends air from both decks as needed. Our units have an ambient lockout to prevent heating or cooling when the temperature is outside a certain range to comply with ASHRAE 90.1.

For simultaneous heating and cooling, you can equip the unit with hot gas reheat. This provides first-stage heating during off-peak seasons without violating 90.1.

Seasons 4 also manufactures 3-deck units where hot deck blades aren’t fixed at 90 degrees from the cold deck blades. The units consist of a cold deck, a bypass deck, and a heating deck. This allows for simultaneous heating and cooling without mixing the heated and cooled air. Our 3-deck units can be constant volume or VAV. The VAV version has a balancing damper in the bypass deck that creates a blockage. This helps maintain a set plenum pressure, saving fan energy.