A local hotel manager wants you to solve a problem with the outdoor hot tubs they had installed last fall. The tubs were closed for winter but put back into service a few weeks ago.
“It’s the strangest thing,” the hotel manager says, “Everything worked fine during the installer’s 90-day warranty period. But three pump motors failed in just the past few weeks.”
He goes on to tell you that some people complained of feeling “tingled” by the water and that’s why these are shut down again.
What are some first steps in solving this problem?
The tingling in the water is one clue that undesired current is circulating where it’s not wanted. All those motor failures are probably due to the same cause as the tingling: no equipment grounding conductor (EGC). Without a low-impedance path to the source, most undesired current will flow through other available paths, such as motor bearings and people in the water.
If the grounding terminals of the pool equipment panelboard are not connected to the service panel via an insulated EGC [680.25(B)], then you’ve found the problem. If a ground rod was driven in lieu of an EGC, then also bond it to the ground rod(s) at the service.
