Cooling Tower Reset Procedure

by Rob Walker, June 1, 2005

ISAC I Cooling Tower VFD reset procedure:

If either of the cooling tower Variable Frequency Drives has tripped off due to a VFD fault condition, the VFD cannot be reset from the DDC workstation. All faults must be acknowledged using the Human Interface Module (HIM)  mounted at the top of the VFD. As long as the fault condition exists, the VFD will not be resettable, and you will not be able to clear the fault. Once the fault condition no longer exists, the VFD can be reset as follows:

1. Read and record the fault code displayed on the HIM.
2. Press ESC to acknowledge the fault. The fault information will be removed so you can use the HIM.
3. Press STOP or select "Clear Faults" on the HIM diagnostics menu.
4. The DDC system waits 20 seconds after you have cleared the fault before trying to run the VFD.
5. Press START.
6. The DDC control continuously checks the cooling tower leaving water temperature. If it is less than 20°C, the VFD will not start.
7. If the leaving water temperature is 20°C or more, the VFD will then start and the HIM will display the fan speed.