www.DaikinApplied.com 35 OM 1280-2 • MICROTECH UNIT CONTROLLER
3-Speed Adjustable
to low, medium, or high speed. When fan control is in the
Auto mode, the UVC adjusts the fan speed up and down in
an attempt to maintain the control temperature setpoint. The
fan capacity percentage required is calculated using a PI loop
fan speed increases when the capacity percentage required
is greater than or equal to the break point + the break point
Table 16
.
Table 16: Fan Speed Break Points
Break Point Auto Low 5%
Break Point Auto Medium 77%
Break Point Auto High 95%
2%
The fan speed decreases when the capacity percentage
required is less than the break point.
The fan speed signal used for low, medium, and high speed
Table 17
keypad or ServiceTools software. The application ensures that
selection of a fan speed that is outside of the min/max range
for that fan setting.
remains at low speed when no capacity is required.
Table 17: Ranges For 3 Speed Adjustable Fan
Fan Speed Operating Range
50% - 80%
70% - 90%
80% - 100%
Variable Speed Fan
The UVC uses a variable PWM output to control the IAF.
When fan control is in the Auto mode, the UVC adjusts the
fan speed up and down in an attempt to maintain the control
temperature setpoint. The fan capacity percentage required is
calculated using a PI loop comparing the control temperature
Outdoor Air Damper Operation
proportional actuator. The OA damper actuator contains a
spring that ensures the OA damper is closed upon loss of
power. The proportional actuator is controlled by a single
typically is open to the current minimum position during the
occupied and bypass occupancy modes and closed during the
unoccupied and standby occupancy modes.
Minimum Position
amount of fresh air required to the space at each of the three
speed fan operation and no CO
2
, the OA damper minimum
position ramps linearly between the low speed minimum position
percent to the high speed minimum position percent as the
motor ramps linearly from minimum speed to maximum speed.
Table 18: Default OA Damper Minimum Positions
IAF speed Without CO
2
With CO
2
High 20% 5%
Medium 25% 5%
Low 30% 5%
NOTE: If the CO
2
Demand Controlled Ventilation (DCV)
option is used, the UVC only uses the IAF high
speed OA damper minimum position regardless
of fan speed. The DCV function adjusts the OA
damper above this minimum as needed to maintain
CO
2
setpoint.
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