How NOT to Bypass a VFD

During a recent client service visit to investigate a suspected VFD failure, our field engineers discovered a potentially deadly remedy that someone had put in place. Luckily no one was injured and no equipment was damaged. During our service visit, our field engineers had to remove an access panel to look at the equipment. As one engineer was removing the metal panel, the other engineer saw the hazard and immediately told the engineer removing the panel to Stop!

As you can see in the photos below, the motor leads were connected directly to the “hot” ( 480 VAC) leads utilizing romex connectors! They were not even taped up for safety or insulating purposes. I recognize the need to improvise in emergency situations, but not at the cost of safety. Romex connectors are designed to provide strain relief to a piece of romex (residential/house wiring) cable connected to a metal box. In this terrible example, they were used as substitutes for split bolts to splice two large cables together. However even when utilizing split bolts, the connections are then well insulated with several layers of different types of tape. Furthermore, the motor was running in the wrong direction so no air was flowing in the system.

The original VFD had failed quite spectacularly when water had leaked into the unit while running. The purpose of that “emergency repair” that was put in place by someone was to force the fan motor to continue to move air within the building. However several things were definitely overlooked. First, the absolute and complete disregard for safety. Secondly, the motor was running backwards, so no air was moving at all in the system. And last, but certainly not least, in some systems the duct work cannot withstand the high pressure produced when a fan is running at 100%, such as directly across the AC line voltage, and may rupture with catastrophic results.

Our solution to the multiple issues found at this location, was to relocate a new VFD away from the water intrusion, then be certain of the fan rotation and safely reconnect the wiring.

This is just a reminder to always work safely! Even when improvising and/or an emergency repair.

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About deltaautomation

President of Delta Automation, Inc. Working in industrial automation in excess of 30 years
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