NST fault code stands for a Freewheel stop. MacroAir uses this fault code for communications.
If a drive displays NST, this means that communication has not been established between the VFD and the control source (touchscreen controller or AirLynk). Note that this differs from an SLF1 fault code in that SLF1 means that communication was established and lost, whereas NST means communication has never been established since the drive has powered on. Since the touchscreen cannot communicate with the drive to obtain a fault code, the touchscreen will display COMM ERROR.
The possible causes of an NST fault code are numerous. You will need to use your best judgment when troubleshooting to determine what happened. Below are some examples of common reasons for an NST code.
1. Insufficient or damaged CAT5. CAT5 must be CAT5E shielded stranded at a minimum. A 568B pinout configuration is required.
2. Incorrect CAT5 lengths. CAT5 length is limited to 200' to a standard touchscreen remote and a total of 4000' on networks from the control source (network controller) to the last fan in line. The CAT5 length from the screen to the first fan or between fans does not matter as long as the total length does not exceed 4000', with the exception of a Controller 4, which must be within 200' of the first fan. A list of CAT5 requirements can be found here.
3. Incorrect CAT5 wiring. Cat5 wiring must be daisy chained between control panels. There must be a single beginning and end to a network. Splicing of CAT5 is not recommended other than to tie in an AirEffect sensor.
4. Noise/Electrical interference. The communication signal can degrade if the CAT5 is ran too close to the fan's incoming power or other high voltage (120VAC and up) wiring. Ensure that the CAT5 wiring is ran at least 6" away from any power wires. The further away, the better. Never run CAT5 and power wiring in the same conduit. Cat5 cannot be coiled and any excess must be cut or ran in a method that eliminates any coils.
5. The controller is not plugged in or powered on. Ensure that the controller has power and is properly plugged into the CAT5. Ensure the dial on the back of the controller is pointed to 0. There should be 10-24VDC on the brown pair depending on fan model. Confirm that you are getting the same voltage readings both on the VFD output terminals and the terminal block on the back of the touchscreen.
6. The controller is not compatible with the fan. Call MacroAir Technical Support with the software version of the controller or AirLynk to ensure it is compatible with the model of fan you are working on.
7. The VFD is not properly grounded. Check all wiring between the VFD and the breaker to ensure that the system is grounded properly.
8. There is a bad VFD on the network affecting other VFDs. Isolate fans on a network and test them individually to ensure that the VFDs can communicate properly with the diagnostic touchscreen. Add fans back to the network one at a time to identify where the communication breakdown is occurring.
9. Communication parameters on the drive may have changed. Contact MacroAir Technical Support so that they can assist in verifying the VFD programming.
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