Si18-201 System control
Main Functions 143
3.25 Fan Control
Purpose of the
Function
This function changes the fan rotation speed or stop the fan operation according to the
operating condition in order to prevent abnormal system operation (overload operation) and
ensure compressor reliability.
3.25.1 Fan Control under Normal Condition
Outline The following fan control functions are provided in normal operation.
1. Stop mode fan control.
2. Fan OFF function when the number of heating room units decreases.
3. Low-noise fan control when nighttime low-noise command is issued.
4. Fan control in Powerful operation mode.
5. Fan control in low-noise mode.
6. Fan control in normal cooling mode.
7. Fan control in normal heating mode.
The fan control functions are listed in the priority order.
(The priority order is for the above functions only, and there are fan control functions that take
precedence over these.)
→
Refer to the section regarding fan relay control.
Details Cooling stop/heating stop/stop fan control
The outdoor fans are turned off when the outdoor unit operating mode is in the stop, cooling
stop and heating stop modes.
Fan OFF function when the number of heating room units decreases
The outdoor unit fans are turned off for 30 seconds if outside temperature DOA is 10°C or
higher when the number of heating room units decreases (includes change of operating room
units that results in the same number of operating room units).
(When the number of operating room units decreases again during the operation of the 30-
second counter, the timer is reset and restarted.)
Fan control in Powerful operation mode
1. Control start conditions
Powerful command received from BP unit (even by one room unit).
Room unit receiving Powerful command is not in thermostat OFF status.
No nighttime low-noise command.
When conditions , and are met, the Powerful operation mode is activated, and the fan
rotation speed is increased 50 rpm from the rotation speed in normal operation.
Fan control in low-noise mode
Refer to the section regarding low-noise fan control on page 139.
Fan control in normal cooling mode
Due to outside air temperature DOA and output frequency FOUT, conditions and or
conditions and listed below are met, the silent mode is activated and sets the fan rotation
speed to FANLC.
DOA < 37°C
FOUT < FFAN
DOA < 8°C
FFAN
≤
FOUT
≤
FHP
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