Operating instructions

3.18.3 20-3* Feedback Adv. Conversion
In air conditioning compressor applications it is often useful to
control the system based on the temperature of the refriger-
ant. However, it is generally more convenient to directly
measure its pressure. This parameter group allows the
frequency converter’s PID Controller to convert refrigerant
pressure measurements into temperature values.
20-30 Refrigerant
Option: Function:
Select the refrigerant used in the compressor
application. This parameter must be specified
correctly for the pressure to temperature conversion
to be accurate. If the refrigerant used is not listed in
choices [0] through [6], select User defined [7]. Then,
use par. 20-31 User Defined Refrigerant A1,
par. 20-32 User Defined Refrigerant A2 and
par. 20-33 User Defined Refrigerant A3 to provide A1,
A2 and A3 for the equation below:
Temperature =
A 2
(
ln
(
Pe +1
)
− A 1
)
−
A 3
[0]
*
R22
[1] R134a
[2] R404A
[3] R407C
[4] R410A
[5] R502
[6] R744
[7] User
defined
20-31 User Defined Refrigerant A1
Range: Function:
10.0000 * [8.0000 -
12.0000 ]
Use this parameter to enter the value
of coefficient A1 when
par. 20-30 Refrigerant is set to User
defined [7].
20-32 User Defined Refrigerant A2
Range: Function:
-2250.00 * [-3000.00 -
-1500.00 ]
Use this parameter to enter the value
of coefficient A2 when
par. 20-30 Refrigerant is set to User
defined [7].
20-33 User Defined Refrigerant A3
Range: Function:
250.000 * [200.000 -
300.000 ]
Use this parameter to enter the value
of coefficient A3 when
par. 20-30 Refrigerant is set to User
defined [7].
20-34 Fan 1 Area [m2]
Range: Function:
Used for setting the area of the air ducts in
connection with feedback conversion
pressure/velocity to flow. The unit (m
2
) is
determined by the setting of par. 0-03 Region-
al Settings. Fan 1 is used with feedback 1. In
case of flow difference control, set
par. 20-20 Feedback Function to [1] Difference,
if flow fan 1 – flow fan 2 is to be controlled.
0.500
m2
*
[0.000 -
10.000
m2]
20-35 Fan 1 Area [in2]
Range: Function:
Used for setting the area of the air ducts in
connection with feedback conversion pressure/
velocity to flow. The unit (in
2
) is determined by
the setting of par. 0-03 Regional Settings. Fan 1
is used with feedback 1. In case of flow differ-
ence control, set par. 20-20 Feedback Function
to [1] Difference, if flow fan 1 – flow fan 2 is to
be controlled.
750
in2
*
[0 -
15000
in2]
20-36 Fan 2 Area [m2]
Range: Function:
Used for setting the area of the air ducts in
connection with feedback conversion
pressure/velocity to flow. The unit (m
2
) is
determined by the setting of par. 0-03 Region-
al Settings. Fan 2 is used with feedback 2. In
case of flow difference control, set
par. 20-20 Feedback Function to [1] Difference,
if flow fan 1 – flow fan 2 is to be controlled.
0.500
m2
*
[0.000 -
10.000
m2]
20-37 Fan 2 Area [in2]
Range: Function:
Used for setting the area of the air ducts in
connection with feedback conversion pressure/
velocity to flow. The unit (in
2
) is determined by
the setting of par. 0-03 Regional Settings. Fan 2
is used with feedback 2. In case of flow differ-
ence control, set par. 20-20 Feedback Function
to [1] Difference, if flow fan 1 – flow fan 2 is to
be controlled.
750
in2
*
[0 -
15000
in2]
Parameter Description
VLT
®
HVAC Drive Programming Guide
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®
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