The importance of grounding and bonding of electrical appliances
BY JEFFREY SARGENT
Connecting a household electric range may be viewed by some as requiring little more than simply “connecting the dots.” However, just because it works doesn’t mean it’s working safely. A recent accident highlights this important point and demonstrates the potentially lethal consequences of an improper installation.
While browsing the online version of a local newspaper recently, a headline—“Fatal accident in Portsmouth condo building under investigation”—piqued my curiosity. The story’s first sentence indicated that a death had occurred “from apparent electrocution.” Reading further, the victim was identified as a 52-year-old man from a neighboring town and that he was “in the process of installing a dishwasher” when the incident occurred. The story elaborated that the actual task being performed “may have involved replacement of an outlet.”
A follow-up story the next day provided additional detail. The victim was a self-employed plumber who was in the process of running the copper water supply line to the dishwasher—he was not performing any electrical work, as was suggested in the first report. The story went on to say that it appeared the electrocution involved the plumber coming in contact with an electric range that “was not installed per the manufacturer’s recommended instructions.”
Soon after the accident, the city electrical inspector shared the initial findings at a local electrical inspectors’ meeting. Based on his description, it appears that, due to improper installation practices, the frame of the range became electrically energized. It took an unfortunate set of circumstances for this condition to be discovered.
The first problem he described was the lack of a proper strain relief connector for the range supply cord. This connector protects the cord against abrasion and sharp metal edges as it passes through the opening of the range terminal box. The range was discovered to have been nicked severely enough—likely caused by moving it into place—that one of the “hot” conductors had come into electrical contact with the range, energizing the exposed conductive surfaces. The safety net for this condition is proper grounding and bonding of the range’s noncurrent carrying metal parts. Because this was an older installation, one predating today’s requirement to install an equipment grounding conductor in the branch circuit to the range, it was necessary to connect the neutral conductor supply terminal in the range to the frame of the range using a “bonding jumper” provided by the range manufacturer. When properly installed, the bonding connection creates a circuit for ground fault current to trip the circuit breaker or blow the fuse protecting the range supply circuit, de-energizing the range. Without this safety feature in place, the exposed metal surfaces of the range were energized at 120 volts to ground.
The range worked, but in an unsafe operating condition. As the plumber contorted himself to work in the close confines beneath the kitchen sink, it appears that an exposed portion of his leg came in contact with the range as he held the grounded copper piping in his hands, completing an electrical circuit through his body. It is likely that the current pulsating through his body made it impossible for him to let go of the piping. Presumably no one reported him as not returning home from work that evening. His body was discovered by a cleaning person the following morning.
It is apparent that improper installation practices created an unsafe condition that resulted in the range becoming a shock hazard. The range worked, but the unsuspecting plumber could not have known that it was an accident waiting to happen. Some may question why we have requirements for connectors and grounding and bonding if the appliance works without them. Unfortunately, there is now a statistic to illustrate why these easy-to-install safety features are so vitally important.