Danfoss VLT Inverter Scroll CDS 801, Operating Instructions Manual, Page: 39 / 56

PI Σ
2
.
09 P 2 T P 0 Tc set FanMotor
Condensing
Unit
P 2 T Pc Tc
175ZB109.10
Illustration 6.7 AC Mode
Delta T Control
In Delta T mode, the fan speed control attempts to maintain a temperature difference of Delta T to ambient temperature,
see
Illustration 6.8 .
In AC mode, the fan speed control attempts to maintain condensing temperature Delta T above ambient temperature.
To run Delta T mode:
Set THERMO_IN_FAN_MODE = 1
The temperature difference Delta T is set through the register THERMO_SETUP_DELTA_TEMP.
PI
Σ
Tamb + Delta T FanMotor
Condensing
Unit
P 2 T Pc Tc
175ZB110.10
Illustration 6.8 Delta T Control
Open Loop/External Speed Control
In external speed control, the fan speed is set externally
from the OEM controller through the Modbus. The speed
can be overruled by the fan protection functions like min
and max condensing pressure derating, see
Illustration 6.9 .
To set the fan speed control in to external speed control:
Set THERMO_IN_FAN_MODE = 2
The external speed % is set in the
THERMO_IN_FAN_EXTERNAL_SPEED_PCT register.
175ZB130.10
FanMotor
Condensing
Unit
External
speed setpoint
P
Fan
Protection
c
Illustration 6.9 Open Loop/External Speed Control
Bypass fan speed control
In Bypass speed control, the fan speed is set externally
from the OEM controller through the Modbus. In the
bypass mode the external speed is bypassing the fan
protection functions, and will never be overruled by
functions like min and max condensing pressure derating,
see
Illustration 6.10 . To set the fan speed control in to
bypass:
Set THERMO_IN_FAN_MODE = 3
The external speed % is set in the
THERMO_IN_FAN_EXTERNAL_SPEED_PCT register.
FanMotor
Condensing
Unit
External
speed command
Pc
175ZB111.10
Illustration 6.10 Bypass Fan Speed Control
Embedded Application Contro...
VLT
®
Inverter Scroll CDS 801 Operating Instructions
MG10V402 - VLT
®
is a registered Danfoss trademark 37
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