Microprocessor Controller for MUA
4
®
Sequence of Operation
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 (65°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 (100°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).
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 (65°F adj).
•
Direct Gas Heating
: Microprocessor controller will
modulate the direct gas burner to maintain the supply
temperature setpoint.
•
Indirect Gas Furnace:
Microprocessor controller will
modulate the indirect gas furnace to maintain the
supply temperature setpoint.
•
Hot Water:
Microprocessor controller will modulate a
hot water valve (provided by others) to maintain the
supply temperature setpoint.
Coil freeze protection
must be provided by others in the field!
•
Electric Heater:
Microprocessor controller will
modulate an electric heater to maintain the supply
temperature setpoint.
Cooling
The cooling is controlled to maintain the supply
temperature setpoint. The cooling will be locked out
when the outside air temperature is below the cooling
lockout (80°F).
•
Chilled Water:
Microprocessor controller will
modulate a chilled water valve (provided by others) to
maintain supply air setpoint.
Coil freeze protection
must be provided by others in the field!
• 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:
- 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 is OFF.
- In heating, controls to maintain the maximum
supply setpoint (100°F).
-
In cooling, controls to the minimum supply
setpoint (50°F).
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.
• Space Temperature Reset:
The controller will adjust
the supply air temperature setpoint between the min
(55°F) and max (90°F clg/ 100°F htg) 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 clg/ 100°F htg) to satisfy the
desired occupied or unoccupied return temperature
