Technical information

NOTE
If a feedback is not used, its source must be set to No
Function [0]. 20-20 Feedback Function determines how the
three possible feedbacks will be used by the PID
Controller.
20-01 Feedback 1 Conversion
Option: Function:
This parameter allows a conversion function
to be applied to Feedback 1.
[0]
*
Linear
Linear [0] has no effect on the feedback.
[1] Square root
Square root [1] is commonly used when a
pressure sensor is used to provide flow
feedback
(( flow ∝ pressure )).
[2] Pressure to
temperature
Pressure to temperature [2] is used in
compressor applications to provide
temperature feedback using a pressure sensor.
The temperature of the refrigerant is
calculated using the following formula:
Temperature =
A 2
(
ln
(
Pe + 1
)
− A 1
)
− A 3,
where A1, A2 and A3 are refrigerant-specific
constants. The refrigerant must be selected in
20-30 Refrigerant. 20-21 Setpoint 1 through
20-23 Setpoint 3 allow the values of A1, A2
and A3 to be entered for a refrigerant that is
not listed in 20-30 Refrigerant.
[3] Pressure to
flow
Pressure to flow is used in applications where
the air flow in a duct is to be controlled. The
feedback signal is represented by a dynamic
pressure measurement (pitot tube).
Flow = Duct Area × Dynamic Pressure
× Air Density Factor
See also 20-34 Duct 1 Area [m2] through
20-38 Air Density Factor [%] for setting of duct
area and air density.
[4] Velocity to
flow
Velocity to flow is used in applications where
the air flow in a duct is to be controlled. The
feedback signal is represented by an air
velocity measurement.
Flow = Duct Area × Air Velocity
See also 20-34 Duct 1 Area [m2] through
20-37 Duct 2 Area [in2] for setting of duct area.
20-02 Feedback 1 Source Unit
Option: Function:
This parameter determines the unit that is used
for this Feedback Source, prior to applying the
feedback conversion of 20-01 Feedback 1
Conversion. This unit is not used by the PID
Controller.
[0] * None
[1] %
20-02 Feedback 1 Source Unit
Option: Function:
[5] PPM
[10] 1/min
[11] RPM
[12] Pulse/s
[20] l/s
[21] l/min
[22] l/h
[23] m³/s
[24] m³/min
[25] m³/h
[30] kg/s
[31] kg/min
[32] kg/h
[33] t/min
[34] t/h
[40] m/s
[41] m/min
[45] m
[60] °C
[70] mbar
[71] bar
[72] Pa
[73] kPa
[74] m WG
[75] mm Hg
[80] kW
[120] GPM
[121] gal/s
[122] gal/min
[123] gal/h
[124] CFM
[125] ft³/s
[126] ft³/min
[127] ft³/h
[130] lb/s
[131] lb/min
[132] lb/h
[140] ft/s
[141] ft/min
[145] ft
[160] °F
[170] psi
[171] lb/in²
[172] in WG
[173] ft WG
[174] in Hg
[180] HP
Parameter Description
VLT
®
HVAC Drive Programming Guide
130 MG11CD02 - VLT
®
is a registered Danfoss trademark
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