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Step 5—Install Barometric Bypass Damper
NOTE: The barometric bypass damper is a critical part of the
WeatherMaker Two-Zone System for control of minimum airflow
and noise reduction. It is recommended that the bypass be
installed.
The bypass should be installed according to local codes and
SMACNA standards. Be sure the bypass is properly supported.
For proper installation, refer to the Installation Instructions pack-
aged with the barometric bypass.
Failure to properly install the bypass damper can cause
permanent damage to the HVAC equipment. For single-speed
furnace applications, the bypass air must never exceed 25
percent.
Step 6—Install Leaving Air Temperature Duct Sensor
Locate duct temperature sensor in main supply trunk after heating
and cooling coil and before the bypass damper and before the first
branch. The duct sensor must be radiant shielded to prevent heat
from affecting the correct air temperature.
1. Drill 1/4-in. hole at location in supply trunk where sensor will
be installed.
2. Insert sensor in hole and use as template to mark 2 mounting
holes.
3. Drill two 1/16-in. holes to accept No. 6 screws through
pre-drilled holes in duct temperature sensor back plate.
4. Use 2 No. 6 sheet metal screws to mount duct temperature
sensor to unit.
5. Connect sensor to 2-conductor wire using provided wire nuts.
(See Fig. 12 for connection to equipment controller.)
Step 7—Install Heat Pump (HP) Temperature Sensor
The HP temperature sensor is required in all heat pump/fan coil
installations. It is not used in dual fuel (heat pump/furnace
installation.) It measures the indoor coil temperature. The sensor is
to be installed downstream of the indoor coil, but before the
electric heaters. It can be installed through the wall of the fan coil
or may be located entirely inside the fan coil near the blower inlet.
Anchor firmly in place with cable ties so that it cannot interfere
with the blower wheel. To activate the HP temperature sensor,
remove factory supplied resistor from HP terminal block and
replace with sensor leads. When activated, the HP temperature
sensor has built in LAT set points of 50°F and 45°F in the cooling
mode, and 105°F and 110°F in the heating mode. This is
non-adjustable. (See Fig. 12 for connection to WeatherMaker
Two-Zone center.)
SEQUENCE OF OPERATION
Step 1—Sequence of Events for a Normal Heating or
Cooling Cycle
The thermostats will determine if active heating or cooling is
required. If so, the WeatherMaker Two-Zone System will perform
the following:
• Make sure all zone dampers are fully open.
• Energize HVAC equipment fan.
• Energize heating or cooling equipment. The equipment may be
a compressor, furnace, strip heater, etc.
• Set zone damper to the open or closed position based upon
individual zone demand.
• Energize additional stages of heating or cooling if the thermostat
demand warrants.
• Turn off heating or cooling equipment when all zones are
satisfied.
• Open all zone dampers when equipment is turned off (after 90
sec delay).
This is the basic sequence of operation for the WeatherMaker
Two-Zone System. The actual control of the dampers, HVAC
equipment, and system fan will change with the configuration of
the system. Depending upon the configuration, WeatherMaker
Two-Zone can control heat pumps, furnaces, and dual fuel
applications, (dual fuel will require a third party relay interface).
Step 2—Selection of a System Mode
The first step in any heating or cooling cycle requires Weather-
Maker Two-Zone to receive an input from any thermostat located
in a zone. WeatherMaker Two-Zone will then prepare to operate
the heating or cooling equipment as requested by the thermostat.
(See Fig. 12.)
Step 3—Pre-Positioning Dampers and Starting
System Fan
In order to minimize noise and enhance system operation, Weath-
erMaker Two-Zone maintains fully open zone dampers prior to
starting the system fan or the heating/cooling equipment. The
intent is to provide the HVAC equipment with unrestricted
ductwork and to reduce pressure surges. WeatherMaker Two-Zone
also fully opens the dampers whenever a heating or cooling cycle
is completed (this is done after a 90 sec delay). All zone dampers
will remain fully open until the next heating or cooling cycle.
The other reason for opening the dampers is to provide unrestricted
ductwork to other equipment which is not directly controlled by
WeatherMaker Two-Zone. One example may be a Heat Recovery
Ventilator. If WeatherMaker Two-Zone is not actively controlling
the HVAC system, then it must not impose any control influences
(such as closed zone dampers) on the system and prevent proper
operation of other devices.
Only the zone 1 thermostat controls continuous fan operation.
When the zone 1 thermostat has the fan selector switch in the
AUTO position, the fan will operate only when the heating and
cooling equipment is operating. When the zone 1 thermostat has
the fan selector switch in the ON position, the fan will operate
continuously. Zone 2 will not control this.
Step 4— HVAC Equipment Connections
The WeatherMaker Two-Zone relay outputs are shown in Table 1.
The Y1 and Y2 contacts are used for the compressor contactor
only. WeatherMaker Two-Zone operates the heat pump by ener-
gizing the compressor contactor and controlling the reversing
valve through the O relay output. The W1 and W2 contacts are
always used for heat sources. These are heating only units such as
furnaces, strip heaters, etc. The relay outputs for WeatherMaker
Two-Zone are shown in Table 1.
Table 1—Available Heating and Cooling Stages Versus System Type
TYPE OF HVAC
EQUIPMENT USED
COOLING STAGE 1 COOLING STAGE 2
REVERSING VALVE
O
HEAT STAGE 1 HEAT STAGE 2
REVERSING VALVE
O
Single-Stage Heat
Pump
Y1 — Energized Y1/W1 W2 De-energized
2-Stage Heat Pump Y1 Y2 Energized Y1/W1 W2 De-energized
Cooling Only, any
Heater Type
Y1 Y2 — W1 W2 —
4
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