• Direct conditioned air proportionately based on the needs of
each zone, so that the zone(s) with the greatest demand receive
relatively more conditioned air.
• Keep the sound produced by the system low enough that
residents will not find it objectionable.
• Conveniently interface with and protect the home’s heating and
cooling equipment.
• Maintain at least the minimum airflow necessary to keep
heating and cooling equipment running efficiently.
B. Is a Zoning System Right for This Job?
When designing a zoning system, it is important to keep in mind
what a zoning system can and cannot do. A zoning system is only
part of a complete heating and cooling system for a residence. A
home’s heating and cooling system has a limited heating and
cooling capacity. A zoning system cannot increase that capac-
ity.
A zoning system reduces the effective size of the air distribution
system as dampers are adjusted and closed to meet the needs of
zones. The primary challenge when designing a zoning system is
to make sure that the air distribution system cannot become so
effectively small that the reduction in airflow causes one of the
following problems:
• Air noise becomes excessive.
• The heating or cooling equipment is shut down because
temperature limits are exceeded.
• The life of the equipment is reduced because of stresses related
to excess temperatures.
The addition of a zoning system will not correct existing duct
problems. A zoning system will compensate for oversized ducts,
but might make a bad situation worse in the case of undersized
ducts. There are many ways to make a marginal duct system
perform better. Most of these approaches involve changing ducts,
registers, and/or heating or cooling equipment.
ZONE PERFECT
PLUS
FEATURES
This section briefly describes features that are new in the Zone
Perfect Plus system and that distinguish this system from both
Zone Perfect and other residential zoning systems.
Zone Perfect Plus’s innovative features include:
• Humidification control
• Dehumidification control
• Sophisticated damper control scheme
• OUT zones
• Bryant Access Home Zoning Software
• Eight-zone capacity
• Improved ease of installation and installer testing.
A. Humidification Control
If a humidifier is included in the heating and cooling system, Zone
Perfect Plus can directly control it. A solid-state humidity sensor
is built into the User Interface to monitor and control humidity in
the home. The Equipment Controller’s HUM output controls any
humidifier with a 24-vac input.
The homeowner can set a humidify set point to any value between
10 percent and 45 percent relative humidity, or can turn off the
humidify feature. When the humidity drops 2 percent below the set
point in the heating mode, the system activates the HUM output to
turn on the humidifier. When the humidity rises 2 percent above
the set point in the heating mode, the system turns off the HUM
output. Humidification is provided only in the heating mode.
If the system includes an outdoor temperature (ODT) sensor, the
installer or homeowner can select an automatic humidity level
adjustment. This selection provides a 1 percent reduction in the
humidify set point for every 2°F reduction in outdoor temperature.
The homeowner can change the system’s humidify set point at any
time, and the system automatically adjusts the set point in response
to the outdoor temperature. This feature helps prevent sweating of
windows in very cold weather while allowing higher humidity
levels in warmer weather.
The system can be set to provide humidification only when there
is a humidify demand and any heat output (heat pump, furnace, or
auxiliary heat) is on. Alternatively, the system can be set to turn on
the HUM output and the blower when there is a humidify demand.
This selection allows humidification when there is no heat de-
mand.
B. Dehumidification Control
The Equipment Controller’s dehumidify output can be used to
control any 24-vac device that decreases humidity when its control
signal is removed. Zone Perfect Plus includes an extensive set of
features for enhancing and controlling dehumidification, particu-
larly when used with a variable-speed (ICM) blower.
The homeowner can set a dehumidify set point, separate from the
humidify set point, between 50 percent and 90 percent relative
humidity, or can turn off the dehumidify feature. When the
humidity rises 2 percent above the set point in the cooling mode,
the system turns off the dehumidify output. When the humidity
falls 2 percent below the set point in the cooling mode, the system
turns on the dehumidify output, supplying 24vac. Dehumidifica-
tion is provided only in the cooling mode.
Zone Perfect Plus provides the following modes of humidification
control:
• Mode 1: When an ICM blower with a dehumidify input is used
with the system, the Equipment Controller’s dehumidify output
can be connected to it. This connection provides reduced
cooling airflow while dehumidification is needed, yielding
better moisture removal from cooling air.
• Mode 2: If the system has a 2-speed compressor and a PSC
blower, a dehumidify demand makes the compressor operate at
high speed only for any cooling demand. High-speed operation
provides better water removal than low-speed operation under
these circumstances.
• Mode 3: In a standard system with a PSC blower, Zone Perfect
Plus lowers the cooling set point up to 3°F in response to
dehumidify demand. This feature increases the equipment’s run
time and lowers the evaporator coil temperature.
• Mode 4: The vacation mode optional feature provides humidity
control by operating the cooling system when cooling is not
required. If the humidity rises above the dehumidify set point,
the system executes a special dehumidification routine. As long
as zone temperatures are not less than 70°F, a dehumidify
demand turns on the cooling equipment, limiting its ON time to
no more than 7 minutes at a time.
C. Damper Control Scheme
Up to 3 dampers can be wired in parallel and connected to 1 zone
output. A multi-damper enabler is not needed.
Using the set points and temperatures for each zone within the
system. Zone Perfect Plus determines whether active heating or
cooling is required, the zoning system:
1. Fully opens 1 or more dampers and positions others so that
all zones will be conditioned back to their set points at the
same time. Based on experience, the system learns the best
damper positions for meeting the home’s current demand
for heating and cooling and starts from these positions when
it determines that heating or cooling is required.
2. Turns on the necessary heating or cooling equipment.
3. While the equipment is on, once every 2 minutes makes
small adjustments in damper positions so that all zones
converge on their set points at the same time.
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