Danfoss VLT Inverter Scroll CDS 801, Operating Instructions Manual

Page: 37 / 56

6.3.3.1 Single Loop Room Temperature Control
In single temperature control, the Inverter Scroll CDS 801 system attempts to maintain a temperature, typically a room
temperature, see
Illustration 6.4 .
The reference and the room temperature are sent from the OEM controller.
The Thermo Control controller calculates the necessary compressor speed and condenser fan speed.
To set the compressor control to single temperature closed loop control:
Set THERMO_IN_COMPRESSOR_MODE = 0
The Thermo Control controller reads the reference from
THERMO_IN_ROOM_TEMPERATURE_SET_POINT
and the actual room temperature from
THERMO_IN_ROOM_TEMPERATURE.
PI
Drive
AC
/
HP
system
Compressor Room
Σ
Troom
Setpoint
175ZB107.10
Illustration 6.4 Single Loop Room Temperature Control
6.3.3.2 Open Loop/ External Speed Control
In external speed control (see Illustration 6.5 ), the compressor speed is set externally from the OEM controller through the
Modbus.
When in external speed mode, the compressor derating and safety envelope functions are still active and takes precedence
over the external speed signal.
To set the compressor speed control into external speed control:
Set THERMO_IN_COMPRESSOR_MODE = 2
The external speed % is set in the THERMO_IN_COMPRESSOR_EXTERNAL_SPEED_PCT register.
Drive
AC
/
HP
system
Compressor Room
External
speed command
Troom
175ZB108.10
Illustration 6.5 Open Loop/External Speed Control
0% Speed request = 0 Hz, and start will not be allowed until 60 s later. (control restart timer).
1% Speed request = 15 Hz
100% Speed request = 70 Hz, see
Illustration 6.6
Can be overruled by derating functions (explained in 6.3.5.5 Derating ).
Embedded Application Contro...
VLT
®
Inverter Scroll CDS 801 Operating Instructions
MG10V402 - VLT
®
is a registered Danfoss trademark 35
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