Page 5 - Zone Control Product Guide

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5
What are the components of a Zoned
Comfort Control system?
The system is comprised of virtually any forced air
HVAC equipment, a control panel, dampers (usually one
for each zone, however, multiple dampers may be used),
thermostats (one for each zone) and the ductwork. In
addition, depending upon the system’s design, a bypass
damper may be required for pressure relief.
How does Zoned Comfort Control work?
Thermostats in each zone are wired to the Zoned Comfort Control panel. The control panel is then wired to
the HVAC equipment and to zone dampers located in the system’s ductwork. The control panel understands
each zone’s need for conditioning and operates the equipment (on/off) while controlling the position of the
dampers (open/closed) based upon the thermostat requirements. This assures that conditioned air is
directed where and when it’s needed.
When is the best time for a Zoned Comfort Control system to be installed?
It is least expensive and easiest to install in a new home. However, in most cases, Zoned Comfort Control
can be added to existing systems at any time. Zoning in existing homes can pose challenges, but Aprilaire
®
addresses these challenges with a full line of slip-in round dampers designed to be low in cost and easy to
install in existing systems.
Why is pressure relief an issue with Zoned Comfort Control systems?
It is important to design zone systems to account for the added system pressure that is caused when zone
dampers are closed. With Zoned Comfort Control, as dampers close to restrict airflow to non-calling areas,
the equipment will attempt to deliver its full capacity, although only a percentage of airflow is required.
Therefore, to avoid problems that are associated with restricting the airflow, (i.e., high limit, freezing of the
coil, air noise) some method of pressure relief is required. This may include over-sizing of the ductwork (all
zones capable of carrying 70% of the system’s airflow), using a bypass damper, or Aprilaire’s exclusive
Controlled Pressure Relief (CPR)’ method. The CPR method involves slightly over-sizing the system’s supply
ductwork while an engineered amount of bypass is allowed into a closed zone. This method eliminates the
need for a bypass damper, minimizing system cost while maximizing comfort. (For more information on
designing for pressure relief, see the Aprilaire Design Manual, Form #5001.)
Programmable
Thermostats
68
°F (20°C)
Joe’s Bedroom
70
°F (21°C)
Great Room
65
°F (18°C)
Dad’s Den
Zoned Comfort
Control System
Furnace
Automatic
Humidifier
Electronic
Air Cleaner
Energy Recovery
Ventilator