V. DUCT TEMPERATURE OPTIMIZER (DTO)
FOR MONITORING LEAVING AIR TEMPERATURE
As Zone Perfect Two-Zone System operates through a heating or
cooling cycle, the zone demands will change. This changes the
actual load that is applied to the HVAC equipment. If the zone
airflow decreases, the cooling equipment will tend to lower
supply-air temperatures which could tend to exceed the LAT trip
limits. Conversely, the heating equipment will tend to raise
supply-air temperatures which could exceed high trip limits. In
cooling, when the LAT reaches the non-adjustable low tempera-
ture trip limit (50°F) the LAT algorithm begins operating, closed
dampers are initially opened 3 positions, then 1 position every 20
sec there after until full open. Zone Perfect Two-Zone will not shut
down second-stage cooling (if used); however, if temperature
continues to drop to 45°F, the zoning system will turn off both
stages of cooling. If the temperature improves, the system will stay
in the duct temperature optimizer mode until the LAT reaches
55°F or higher. At 55°F the LAT algorithm will reset and return
dampers to their original position. In the heating mode, Zone
Perfect Two-Zone will perform the same duct temperature opti-
mization. The trip limits will be determined by the jumper setting.
(See Fig. 12.) This will continue until the LAT problem is
corrected.
This control helps Zone Perfect Two-Zone System cope with
installations where the air conditioning system may suffer from
poor ductwork, improperly sized heating or cooling equipment,
and/or improper settings of the barometric bypass damper. This
control is especially useful in retrofit applications where the size
and routing of the ductwork may not be entirely known or
satisfactory.
The duct temperature optimizer works by controlling how cold or
hot the air inside the supply-air duct gets by monitoring the
temperature of the air inside the supply-air system.
Whenever Zone Perfect Two-Zone is providing heating or cooling,
the zone within the home that is asking for conditioned air will
always have its damper fully open. The other zone in the system
may or may not have an open damper depending upon its
particular needs. If the ductwork is too small (or the air
conditioner/heater is too large), then the zone requiring condi-
tioned air may not be able to take enough air to allow your
equipment to operate properly. Zone Perfect Two-Zone will detect
this, and open up the closed damper allowing the equipment to
continue to operate.
CAUTION: The duct temperature optimizer may be
disabled on the control center. A 10k resistor can be
installed in place of the duct sensor at the terminal block.
By disabling the duct temperature optimizer, the LAT
safety algorithm is removed from the system.
It is highly recommended that you use this control option. The
heating LAT is adjustable for the duct sensor. In this Installation
Instruction, you will find the section showing an adjustment for the
heating LAT. (See Fig. 12.) It is very important that this tempera-
ture is properly set. For gas or oil furnaces, the temperature limit
will be in the higher temperature range. For heat pumps the
temperature setting should always be in the lower temperature
range.
If you encounter a situation where 1 zone seems to have poor
ductwork, then the Zone Perfect Two-Zone system is capable of
reverting back to a fully open, constant-volume system. If this
condition persists, it should always be looked upon as an indication
of a HVAC problem, not a Zone Perfect Two-Zone problem.
VI. ELECTRONIC THERMOSTAT CONNECTION WITH
ZONE PERFECT TWO-ZONE CONTROL
Bryant electronic non-programmable and programmable thermo-
stats can be connected to the Zone Perfect Two-Zone. See pre-sale
literature for thermostat part numbers.
NOTE: The zone control board is only capable of 2-stage heat
and 2-stage cool operation. Fig. 13 and 14 will reflect these
applications only. Review and understand the following items
before installing.
A. Thermostat Setup
1. Thermostat will not operate unless both R and C are
connected to zone module input.
2. If selected thermostat is a heat pump (HP) or 2-speed (2S)
model, convert thermostat to air conditioning operation.
This will assure that Y signals are generated for cooling,
and W signals are generated for heating from thermostat to
zone module input. The thermostat O/W2 output will now
be the second-stage heat call. If installation is a heat pump
system, the zone control board will provide proper output
signal to heat pump.
3. Select "Zoning" option on thermostat. This will disable the
Timeguard and 4-cycle per hr (cph) protection built into
thermostat. Let zone control board perform the Timeguard
and cycle protection. Refer to thermostat Installation In-
struction under Zoning for more detail.
4. The zone 1 thermostat is the only thermostat that can
control continuous fan operation with zoning. Connect G
between zone 1 thermostat and zone 1 input on zone control
module.
5. Follow all safety and installation considerations outlined in
the thermostat Installation Instructions.
B. Zone Control Board Setup
1. Configure zone control board jumper for Tstat (thermostat)
Fnc option only. Do not use Tstat HP option. When Tstat
Fnc is selected this will setup control inputs to recognize Y1
and Y2 for first- and second-stage cooling, W1 and W2 for
first- and second-stage heating.
2. Configure zone control board for either Equipmt (equip-
ment), HP or Fnc. When a heat pump system is used,
Equipmt HP mode should be selected. The zone control
board will provide the proper output signal to the heat
pump. When a gas/electric furnace is used, Equipmt Fnc
mode should be selected for proper output signal.
3. Configure zone control board for either Fnc Ht, w/f (with
fan), or w/of (without fan). With Fan mode should be
selected when a heat pump is installed and fan is needed to
come on immediately with demand. Without Fan mode
should be selected when fan is controlled by gas/electric
furnace.
4. Configure zone control board for either DTO On or Off.
When DTO On is selected (Factory default) and if a LAT
trip occurs, closed dampers will begin opening to try and
keep equipment running by maintaining proper air tempera-
tures. However, if LAT temperatures exceed their limits,
equipment will start staging down. When DTO Off is
selected, equipment will stage down. Closed dampers will
not open on initial trip, however if LAT temperatures
exceed their limits, control will lock out and damper will
open.
NOTE: An HP temperature sensor must be used with a heat pump
application using electric strip heat. This is necessary in case the
DTO is set to the Off position.
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