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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, direct gas, evaporative cooling and
packaged or split DX cooling. All setpoints, lockouts
and delays are user adjustable via the integral keypad
display, remote display, or web user interface.
General 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 remote start input is in the off position.
• The shutdown input is in the shutdown position.
• A system shutdown alarm was activated.
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 schedule. When a start
command becomes active the following steps occur:
• Factory mounted and wired dampers are powered
(Outside air, and recirculation air dampers, if equipped)
• Exhaust 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. Damper
power is cut 30 sec. after the fans. This allows
the fans to slow down prior to spring closing the
dampers.
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
®
Sequence of Operation
• 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.
OCCUPANCY: The microprocessor controller offers
five modes of determining occupancy: digital input,
occupancy schedule, BMS, always occupied, or always
unoccupied. When in the unoccupied mode, the unit can
be configured to shut down, or cycle on to maintain the
unoccupied space setpoints. The unit can be temporarily
overridden to the occupied mode via a digital input,
keypad display, or space thermostat, if equipped.
• Occupied Mode:
-
Damper Control (refer to Outside Air and
Recirculated Air section), if equipped
-
Exhaust on, if equipped
-
Supply fan on
-
Tempering operations begin
• Unoccupied Mode:
-
Unit Off: Unit remains off when in unoccupied
mode.
Normal operation with unoccupied setpoints:
-
Unoccupied mode will operate as if in occupied
mode but will utilize adjustable unoccupied
setpoints.
º Damper Control (refer to Outside Air and
º Exhaust on, if equipped
º Supply fan on
º Tempering operations begin
-
Recirculation with unoccupied setpoints:
Unoccupied mode will operate using adjustable
unoccupied set points when a recirculation
damper is available.
º Supply fan on
º Recirculation air damper open
º OA damper opens to unoccupied minimum
º Tempering operations begin
Night Setback: Unoccupied mode when there
-
is space temperature and/or humidity sensor(s)
connected to the controller. The unit will cycle on
to maintain unoccupied space setpoints if there is
a call for unoccupied heating, or cooling.
º Exhaust off, if equipped
º Recirculation air damper open
º OA damper opens to unoccupied minimum
º Supply fan on
º Tempering operations begin
Recirculated Air section), if equipped
position
position
Microprocessor Controller for MUA
3
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