Danfoss VLT HVAC Drive Instruction Manual page 32

Note: The Live Zero function works as follows: If the analog signal on Analog Input 53 or 54
falls below 50% of the minimum scaling of that input (P 6‐10 or P 6‐20), the drive will start
to count down from the time set in P 6‐00. If the condition still exists after the timer
expires, the function set in P 6‐01 will be executed. These parameters are there to protect
you from losing an analog reference/feedback signal and running out of control. P 6‐00 & P
6‐01 apply to both Analog Inputs, but you can enable or disable the function for either
input individually using P 6‐17 & P 6‐27.
14. Enter the data shown below for PID functions.
Parameter
P 20‐21 1.500 in WG
P 20‐93 2.00
P 20‐94 10.00 s
P 20‐81 [0] Normal
P 20‐83 15.0 Hz
P 20‐84 2%
Note: For P 20‐81, choosing Normal allows the drive to build pressure UP to meet the set‐
point. Choose Inverse on a cooling tower to make the drive bring temperature DOWN to
meet the set‐point. For P 20‐84, the On Reference Bandwidth means that the feedback
signal is within 2% of the maximum feedback from the set point. 2% of 5 in WG = 0.1".
On Reference means feedback is between 1.4" and 1.6" in WG.
Why does it make sense to set P 20‐83 to at least the same value as P 4‐12?
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15. Enter the following data to set up the LCP display lines with relevant data.
Parameter
P 0‐20 [1601] Reference [Unit]
P 0‐22 [1652] Feedback [Unit]
P 0‐24 [1664] Analog Input 54
16. Press the Status button and view the top line. You should see the set‐point of 1.5 in WG in
the left, the voltage applied to Analog Input 54 in the bottom middle and the
corresponding feedback in inches of WG in the top right line of the display. Notice what
happens to the displayed set‐point when you adjust the potentiometer on Analog Input 53.
Because P 3‐15 still declares Analog Input 53 as a reference source, and because the closed
loop mode reference is your set point, any signal there will be added. Change P 3‐15 to
[0] No Operation to avoid this. Use the potentiometer to change the voltage on Analog
Input 54 and watch the feedback pressure change.
Approximately how many volts on Analog Input 54 represent 2.5 In WG?_______________
Value
Setpoint 1; Desired system set‐point to maintain
PID Proportional Gain; A higher gain is more aggressive
PID Integral Time; A higher number softens response
PID Normal/Inverse Control
PID Start Speed
On Reference Bandwidth
Value
Display Line 1.1 Small
Display Line 1.3 Small
Display Line 3 Large
Description
Description
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