Daikin MicroTech III Operation Manuals page 101

Heating
When the unit is operating in the Heating state, the energy
recovery wheel is stopped due to capacity limiting whenever
all heating is OFF and the discharge air temperature (DAT)
is above the discharge heating setpoint by more than ½ the
discharge air heating deadband . The wheel is re-started when
the DAT falls back to or below the discharge heating setpoint
plus ½ the discharge air heating deadband .
Cooling
When the unit is operating in the Cooling state, the energy
recovery wheel is stopped due to capacity limiting whenever
the energy recovery wheel leaving air temperature (ER LAT)
is above the discharge cooling setpoint by more than ½ the
discharge air cooling deadband . The wheel is re-started
when the ER LAT falls back to or below the discharge cooling
setpoint plus ½ the discharge air cooling deadband .
Variable Speed Wheel
When the enthalpy wheel is variable speed and the Variable
Effectiveness Control PI_Loop is active the ER LAT is
controlled to the current effective discharge temperature
setpoint .
Exhaust Fan
A variable speed exhaust fan controlled by a VFD is provided
for all Economizer units with either constant volume or VAV
supply fans and on 100% Outside Air units with VAV supply
fans . Either a constant volume exhaust fan or a variable speed
exhaust fan controlled by a VFD may be provided on 100%
Outside Air units with constant volume supply fans .
The exhaust fan is turned ON when any of the following sets of
conditions is true:
All four of the following are true:
• The Exhaust Fan is controlled by a VFD
• The OA Dampers are at least open to the Minimum OA
Position
• The Minimum OA Position is greater than 0%
• The building static pressure is above the building static
pressure setpoint by more than the deadband for longer
than the Minimum Exhaust Fan Start Time (Default =
120 seconds)
www .DaikinApplied .com
All four of the following are true:
• The exhaust fan is controlled by a VFD
• The OA Dampers are at least open to the Minimum OA
Position
• The Minimum OA Position is greater than 0%
• The exhaust fan capacity is commanded to a value above
the minimum value (Default = 5%) by a BAS for longer
than the Minimum Exhaust Fan Start Time (Default = 120
seconds)
Both of the following are true:
• The exhaust fan is constant volume
• The supply fan has been commanded on for at least 4
seconds
The exhaust fan is turned OFF when any of the following sets
of conditions is true:
All three of the following are true:
• The exhaust fan is controlled by a VFD
• The building static pressure is below the building static
pressure setpoint by more than the deadband
• The exhaust fan capacity is at or below its minimum value
(Default = 5%) for longer than the Min Exhaust Fan Stop
Time (Default = 120 seconds)
Both of the following are true:
• The exhaust fan is controlled by a VFD
• The exhaust fan capacity is commanded to less than or
equal to its minimum value (Default = 5%) by the BAS for
longer than the Minimum Exhaust Fan Stop Time (Default
= 120 seconds)
The exhaust fan is OFF when the supply fan is OFF
Whenever a variable speed exhaust fan is ON, its capacity will
be modulated using a VFD . The speed of the fan will be either
(1) modulated to maintain the building static pressure at a
desired value or (2) set at a fixed speed provided by a Building
Automation System via a network .
101 OM 920-6 • MICROTECH UNIT CONTROLLER
o ' g
peraTor s uIde