Danfoss VLT HVAC Drive Instruction Manual page 33

1. Press the Auto On button on the LCP.
2. Turn ON switch DIN3/27 on the control box to release the Coast command.
3. With the remaining switches off, the display status reads Auto Remote Standby.
4. Start the drive by turning ON switch DIN1/18 and modulate the feedback on Analog Input
54 above and below the set‐point. The drive should respond to the change in feedback.
When the feedback falls below the set‐point, the drive should speed up to compensate.
When the feedback goes above the set‐point, the drive should slow down. When the
feedback and set‐point match, the drive runs at a constant speed. Notice that when the
feedback is above the set‐point, the drive will only slow to 15Hz. This is because the
minimum speed is set to 15Hz in P 4‐12.
5. The Red LED on the switch box should light up when the drive is within 2% (+/‐ 0.1 in WG)
of set point.
6. Change P 20‐81 to [1] Inverse. Does the drive now speed up when feedback is higher than
the set point?
The function below is intended for applications where pressure can hold, like pumping applications
and may not be applicable to fan applications.
You noticed earlier that the drive would not slow down below 15Hz when running. The only
reason it slows to the programmed minimum speed is because the feedback is above the set‐
point. Imagine that this were a pumping application. A good example of where this might happen
is at an apartment building. During nighttime when all the water faucets are turned off, the
pressure would begin to climb, and the drive would slow down in order to stop creating excessive
pressure. It would not be desirable for the drive to continue to run at 15Hz all night long. Enter the
parameters below to allow the drive to Sleep when the pressure holds and there is no demand.
Use the Info button when you are at these parameters to gain an understanding of what they do.
Parameter
P 22‐22 [1] Enabled
P 22‐23 [1] Sleep Mode
P 22‐24 10 s
P 22‐40 10 s
P 22‐41 10 s
P 22‐44 10%
7. Adjust Analog Input 54 above the set‐point. When the drive reaches 15 Hz, count down 10
seconds and the drive should enter Sleep Mode.
8. Wait 10 seconds and then slowly decrease the feedback until it drops 10% (P 22‐44) below
the set‐point. The drive should wake up and start modulating again.
Verifying Operation
Setup Enhancement
Value
Low Speed Detection
No‐Flow Function
No‐Flow Delay
Minimum Run Time
Minimum Sleep Time
Wake‐up Ref./FB Difference
Description
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