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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, cooling or
dehumidification.
º Recirculation air damper open
º OA damper opens to unoccupied minimum
position (0% adj.)
º Supply fan on
º Tempering operations begin
º Exhaust fan off, if equipped
º Energy Recovery off, if equipped
• Morning Warm-Up/Cool Down: At the request
to occupy the space, the unit will run using the
warm-up or cool down sequence until the occupied
setpoint is achieved. The heating or cooling mode
must not be locked out and the space temperature
is below or above setpoint by the unoccupied
hysteresis (5°F, adj). This optional sequence requires
a space temperature sensor and is field-enabled.
The following steps occur during a morning warm-
up/cool down:
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The dampers would be in full recirc if the
damper actuators are not powered (adj) during
unoccupied mode. Otherwise the following is
true:
• Outside air damper is open to unoccupied
minimum OAD position.
• Recirculation air damper is open at 100% minus
OAD position.
-
Supply Fan is on at 100%.
-
Exhaust fan is off
-
In heating, controls to maintain the maximum
supply setpoint (90ºF).
-
In cooling, controls to the minimum supply
setpoint (50ºF).
-
Reheat off
-
Energy recovery wheel off
Setpoint Control (Continuous)
When the unit is running continuously, the supply air
temperature setpoint can be configured as a constant
value or reset by either outside air temperature,
space temperature, or return temperature. Supply air
temperature reset modes can be set for both occupied
and unoccupied operation in the controller. If equipped
with BMS communications, the BMS system can also
directly command the temperature setpoint.
• Outside Air Temperature Reset: The controller will
adjust the supply air temperature setpoint based
on the OA temperature between the min (55°F) and
max (70°F). The min and max setpoints can be
locally adjusted at the microprocessor for the outside
temperatures and the supply air temperature min and
max.
4
Microprocessor Controller for DOAS
Sequence of Operation
• Space Temperature Reset: The controller will
adjust the supply air temperature setpoint between
the min (55°F) and max (90°F) to satisfy the desired
occupied or unoccupied space temperature setpoints
with a valid space temperature reading. The space
temperature setpoint for occupied and unoccupied
mode can be adjusted locally at the microprocessor
or the BMS. Occupied temperature setpoints can be
adjusted at the space thermostat.
• Return Temperature Reset: The controller will
adjust the supply air temperature setpoint between
the min (55°F) and max (90°F) to satisfy the desired
occupied or unoccupied return temperature
setpoint with a valid return temperature reading.
The return temperature setpoint can be adjusted
locally at the microprocessor or the BMS.
Setpoint Control (Night Setback)
When the unit is set to cycle on space temperature
in night setback, the supply air temperature is
automatically set using the following strategy:
• Heating: The unit is enabled when the space
temperature is less than the unoccupied heating
setpoint (60°F). The unit cycles off when the space
temperature increases above the unoccupied heating
setpoint by the hysteresis amount (5°F). During this
time, the supply air temperature setpoint is set to the
supply max reset limit (90°F).
• Cooling: The unit is enabled when the space
temperature is greater than the unoccupied cooling
setpoint (80°F). The unit cycles off when the space
temperature decreases below the unoccupied cooling
setpoint by the hysteresis amount (5°F). During this
time, the supply air temperature setpoint is set to the
supply min reset limit (55°F).
• Dehumidifying: The unit is enabled when the space
relative humidity exceeds the unoccupied space
relative humidity setpoint (60%). The unit cycles
off when the space humidity decreases by the
unoccupied dehumidification hysteresis amount
(5%). The supply air temperature setpoint will be
set to the equivalent occupied supply setpoint. This
sequence requires a valid space humidity reading
and is field enabled. Alternatively, the unoccupied
dehumidification control can be triggered by space
dewpoint, space dewpoint or relative humidity or
space dewpoint and relative humidity.
Heating
The heating is controlled to maintain the supply
temperature setpoint. The heating will be locked out
when the outside air temperature is above the heating
lockout (80°F adj).
• Indirect Gas Furnace: Microprocessor controller will
modulate the indirect gas furnace to maintain the
supply temperature setpoint.
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