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The microprocessor controller can be configured for
air handler, energy recovery, and dedicated outdoor air
systems. Each application utilizes similar technologies
for heating and cooling: chilled water, hot water, indirect
gas, electric heat, packaged DX cooling, and packaged
DX cooling with digital and inverter scrolls. All setpoints,
lockouts and delays are user adjustable via the integral
keypad display, remote display, or web user interface.
General Operation
UNIT START COMMAND: The microprocessor
controller requires a digital input to enable operation.
The unit can then be commanded on or off by this
digital input, keypad, the BMS or internal time clock.
When a start command becomes active the following
steps occur:
• Energy recovery wheel starts, if equipped
• Factory mounted and wired dampers are powered
(Outdoor air, exhaust air, and recirculation air
dampers, if equipped)
• Exhaust fan, if equipped, starts after adjustable delay
• Supply fan starts after adjustable delay
• Tempering operation starts after adjustable delay
UNIT STOP COMMAND: A shutdown occurs when
there is not an occupied or unoccupied start command.
The following shutdown methods can occur.
Hard shutdown occurs under the following conditions:
• A user or the BMS disables the system, and the
supply temperature is less than the soft shutdown
enable setpoint.
• Occupancy is commanded to unoccupied while there
is no unoccupied start command, and the supply
temperature is less than the soft shutdown enable
setpoint.
When a hard shutdown occurs:
• The unit shuts down immediately.
• Dampers spring-return to their off position.
Soft shutdown occurs under the following conditions:
• A user or the BMS disables the system, and the
supply temperature is greater than or equal to the
soft shutdown enable setpoint.
• There is no unoccupied or occupied start command
and the supply temperature is greater than or equal
to the soft shutdown enable setpoint.
The following occurs during a soft shutdown:
• Tempering outputs immediately revert back to their
off value; while
• Dampers remain open and fans continue to run; until
–
The supply air temperature falls below the soft
shutdown enable setpoint minus 5.0°F; or
–
The soft shutdown delay timer has expired.
®
Sequence of Operation
UNIT/SYSTEM DISABLED COMMAND:
The unit becomes disabled due to the following:
• The unit was disabled from the controller's Unit
Enable screen.
• The unit was disabled from the BMS.
• The shutdown input is in the shutdown position.
• A shutdown alarm was activated.
When disabled the following actions occur:
• The unit shuts down immediately; and
• Dampers spring-return to their off position.
OCCUPIED/UNOCCUPIED MODES: The
microprocessor controller offers three modes of
determining occupancy: digital input, the internal time
clock or the BMS. When in the unoccupied mode, the
unit can be configured to shut down, or cycle on to
maintain the unoccupied room setpoints. The unit can
be temporarily overridden to the occupied mode via
a digital input, keypad display, or room thermostat, if
equipped.
The controller can be configured with morning warm-
up and cool down to bring the space to the occupied
setpoint prior to occupancy.
• Occupied Mode:
-
Exhaust fan on, if equipped
-
Supply fan on
-
Heating (refer to Heating section)
-
Cooling (refer to Cooling section)
-
Energy Recovery Wheel Control (refer to
Energy Recovery Wheel section), if equipped
-
Damper Control (refer to Outdoor Air and
Recirculated Air section), if equipped
• Unoccupied Mode (Unit Off): Unit remains off when
in unoccupied mode.
• Normal Operation with Unoccupied Setpoints:
Optional unoccupied mode will operate as if in
occupied mode but will utilize adjustable unoccupied
setpoints.
-
Exhaust fan on, if equipped
-
Supply fan on
-
Heating (refer to Heating section)
-
Cooling (refer to Cooling section)
-
Energy Recovery Wheel Control (refer to Energy
Recovery Wheel section), if equipped
-
Damper Control (refer to Outdoor Air and
Recirculated Air section), if equipped
• Recirculation with Unoccupied Setpoints: Optional
unoccupied mode when there is an unoccupied
recirculation damper. The unit will continue to run,
but in full recirculation.
-
Supply fan on
-
Recirculation air damper open
-
OA damper closed
-
Tempering operations begin
Microprocessor Controller for DOAS
3
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