Indoor Air Fan Operation; Auto Mode; Manual Fan Mode; Occupied, Standby, And Bypass Operation - Daikin MicroTech Operation And Maintenance

Indoor Air Fan Operation

The UVC supports a variable speed, or three-speed indoor
air fan (IAF); low, medium, and high. The UVC calculates the
effective fan speed and operation based on the unit mode, the
occupancy mode, and the values of several network variables.
Figure 21: Fan Only State Diagram
Enter from: OFF
LUI Input Mode
Network Input (State 9)

Auto Mode

The UVC is provided with a user selectable auto fan mode
feature. When in auto fan mode, the UVC uses the space
temperature PI loop to automatically adjust the fan speed as
needed to maintain space temperature. This ensures that the
UVC maintains the lowest and quietest fan speeds whenever
possible. When in auto fan mode, a maximum of six fan speed
changes per hour is allowed (by default). This prevents frequent
automatic fan speed changes from disturbing room occupants.
The number of fan changes per hour can be configured through
the LUI keypad or ServiceTools software.

Manual Fan Mode

The indoor fan may be manually set locally to Low, Medium or
High speed through the LUI keypad or using the ServiceTools
software. When the fan speed is selected this way, the setting
is not affected by a unit power cycle.
A remote wall sensor with fan speed switch may be used to
locally change the fan speed.
Figure 22: Fan Control - 3-Speed Fixed/Adjustable
Staging
Up
OA Damper at 25% Open –
IA Fan Medium Speed –
SatHi
SatLo
Staging
Down
OA Damper at 30% Open –
IA Fan Low Speed –
Satisfied
OM 1280-2 • MICROTECH UNIT CONTROLLER
No
EMERGENCY
Is SpaceTemp
Yes
< EHS
OA Damper at 20% Open –
IA Fan High Speed –
Secondary
Cooling
Capacity
Degrees from
Setpoint and Time
Control Temperature

Occupied, Standby, and Bypass Operation

During Occupied Standby and Bypass modes, the IAF, by
default, remains On. The IAF can optionally be field configured
to cycle off when there's no call for heating or cooling through
the LUI keypad or ServiceTools software.

Unoccupied Operation

During unoccupied mode, the IAF typically remains Off and
HEAT
Mode
cycles with calls for heating and cooling. The IAF can optionally
be field configured to run at low speed in unoccupied mode
when there's no call for heating or cooling through the LUI
keypad or ServiceTools software.

Cycle Fan

The UVC is provided with a Fan Cycling Configuration
variable that can be used to force the IAF to cycle with calls for
heating and cooling during the occupied, standby, and bypass
occupancy modes. When the fan is off, the OA damper is
closed. Daikin recommends using this feature only when it is
acceptable that normal ventilation is not required.
When the IAF is set to cycle, the UVC is configured to continue
fan operation for a time period after heating or cooling is complete.

Off Delay

When the UVC is placed into Off mode or Shutdown mode, the
UVC is configured to continue fan operation for a short time
period and then shutdown.

Fan Control

The UVC is factory configured to control a fan in one of three
ways depending on the type of fan the unit has

3-Speed Fixed

The UVC uses three binary outputs to control a fan 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 will be calculated using a PI loop
comparing the control temperature and effective setpoint. The
fan speed increases when the capacity percentage required
is greater than or equal to the break point + the break point
differential defined in Table 16 on page 35.
The fan speed decreases when the capacity percentage
required is less than the break point.
If the UVC is configured for continuous fan operation, the fan
remains at low speed when no capacity is required.
34
Description of Operation
(Figure
www.DaikinApplied.com
21).