Ok, heres part of the article itself. Had to shorten because of the limit of characters here. sorry about the link, you have to register to see the whole article.
Plumber Electrocuted After Installing Unsafe Temporary Power Connection at New Construction Residential Housing Development
Mar 1, 2009 12:00 PM, By Chris Shiver, P.E., Cerny & Ivey Engineers, Inc.
When plumbers Jim and Dave arrived at a new residential development, their task at hand certainly seemed routine — performing trim-out work (installation of fixtures and appliances) in a partially completed house. Once on-site, however, they quickly hit a snag.
After realizing that the mostly finalized electrical system in the house was not connected to the electric utility, they questioned the general contractor (GC) on the availability of power for their tools. The GC promptly directed them to a temporary construction pole setup on the adjacent lot.
Not considered an out-of-the-ordinary request on a new construction residential project, this situation did not raise any red flags for the plumbers; however, the events that soon unfolded would quickly turn this typical job into tragedy.
As he approached the temporary power location, Jim found that an unconnected length of Type NM cable was lying loose on the ground between the temporary pole and meter base of the house they were working at, with the house end routed into (but not connected to) the meter base.
He recalled that a few days earlier he had seen an electrician using this NM cable to create a temporary service connection for the house — to enable testing of the wiring and fixtures. Apparently, the electrician had left it in that location, he thought to himself, possibly for follow-up testing/troubleshooting use. Based on this assumption, Jim recreated the connection (as he thought the electrician had done) and succeeded in energizing the house wiring, enabling the use of lighting and tools. Next, Jim and Dave began working on different levels in the house, with Dave in the basement installing a water heater.
Both plumbers worked separately for some time, with Jim occasionally coming down to the basement to check on the water heater installation. During at least one of those visits, Dave mentioned to Jim that he'd received a few electrical shocks while touching pipes or other bare metal. Because they'd experienced similar occurrences at other locations in the past without any ill effects, neither man was overly concerned.
Soon thereafter, Jim went outside to speak to another plumber (Mike), and then returned to the basement, only to find Dave sitting on the floor — slumped back against a furnace installed adjacent to the water heater. Assuming Dave was pulling a prank, Jim immediately scolded him. However, when Dave did not respond, Jim shook him and received an electric shock. Jim immediately ran outside to get help from Mike. The pair quickly called 911, moved Dave away from the metal-cased appliances, and administered CPR until emergency medical services arrived.
While watching the medical responders work on Dave in the basement, Mike touched the furnace casing, received a shock, and yelled for someone to shut off the power to the house to prevent further injury. Another contractor (Roger), who had responded to the incident, ran outside and disconnected the NM cable from the temporary power pole. Prior to making that disconnection, Roger noted the connection details at the temporary pole and also observed the connection details to the meter base on the house where the accident occurred (click here to see Figure). His account of those details proved crucial to determining fault in this case.
Unfortunately delayed by the lack of street names and map information for this new housing development, once on the scene medical responders were unable to revive Dave. As suspected, medical and forensic examination later indicated that Dave had died from electrocution with the fatal current probably passing from one arm to the other through his chest.
Because a fatality was involved, OSHA performed an inspection at the work site within a week of the accident. This investigation was followed by inspections of the involved electrical systems and hardware at the site by several engineers, including myself. I became involved in the case as the technical representative of the insurance carrier for a major electrical equipment manufacturer, which had provided some of the temporary electrical setup hardware.
Prior to the OSHA visit, the NM cable, which was originally lying loose on the ground before Jim reconnected it, reportedly was fully removed from its connection points at both ends (temporary pole and house). Therefore, Roger was the only person known to have a recollection of the connection details at the time of the accident (plumber Jim was unsure). As detailed in the Figure, Roger's recollection indicated that the NM cable was probably a 10/2 + ground configuration. The connections reportedly did include insertion of the two insulated conductor's previously stripped ends into the slots of a GFCI-type receptacle at the temporary pole, as diagrammed. However, they did not include the bare conductor in the cable. His description also indicated connection of the previously stripped opposite insulated conductor ends to one of the meter base hot leg lugs with the other conductor end connected to the neutral. (Note the polarity of these connections indicated in the diagram.)
Examination of the temporary power pole revealed it included four 120VAC GFCI-type duplex receptacles downstream of two 20A circuit breakers (two receptacles supplied from each circuit breaker). The components were mounted in an outdoor-type box with a damaged cover that would not properly close. The GFCI receptacle identified as the unit supplying temporary power through the NM cable was then removed for detailed laboratory examination (Photo 1). During this removal, proper supply connections within the temporary power pole assembly for that receptacle were confirmed, including bonding connection. It was verified that the neutral and ground were bonded together within the main service panelboard in the house — and that there was a bonding connection to the copper piping within the house from the panelboard grounding electrode connection point.
The diagrammed temporary terminations for the NM cable would have the effect of connecting the GFCI receptacle outlet hot leg with the service entry neutral in the house where the plumbers were working. This would have resulted in energization of any exposed bonded metal, including the furnace and water heater casings and metal piping, at voltage levels potentially up to 120VAC.
The GFCI receptacle was confirmed as a UL-listed 20A rated indoor-only-type assembly with front-mounted “test†and “reset†buttons. The receptacle exterior evidenced some age and weathering, including heavy corrosion of the screw heads that secured the plastic casing. Investigators also confirmed that when connected to a nominal 120VAC supply, the outlets were live — a condition that did not change when the GFCI test button was pushed. During disassembly, the receptacle internals evidenced significant contamination from dirt, insect remains/webs, and other debris. External corrosion from probable water intrusion also was apparent. The unit evidenced heavy overheating/burn damage to the circuit board (Photos 2a, 2b, and 2c). Provided information indicated this GFCI receptacle was probably at least five years old. Based on these findings, it's unlikely that the GFCI circuitry would have reacted to the expected ground leakage currents and shut off power, following connection of the outlet hot leg to the house grounded conductors as described above.
After its investigation, OSHA cited the plumbing company for “serious†violation of four federal health and safety regulations:
Failure to instruct each employee in the recognition and avoidance of unsafe conditions and hazards, as required by 29 CFR 1926.21(b)(2).
Failure to ensure that electrical equipment is free from recognized hazards likely to cause death or serious physical harm to employees, as required by 29 CFR 1926.403(b)(1).
The path to ground from circuits, equipment, or enclosures was not permanent and continuous, as required by 29 CFR 1926.404(f)(6).
A ground conductor was attached to a terminal or lead so as to reverse designated polarity in violation of 29 CFR 1926.404(a)(2).
Particularly noted was no evidence that any of the plumbing company employees had been provided with safety instructions regarding safe usage or connection to temporary construction site power sources, proper testing and usage of GFCI-protected circuits, or typical construction site electrical shock hazards.
At the time of this accident, the 1996 National Electrical Code (NFPA 70/NEC) was in effect at the accident location. Therefore, the references below come from that edition. Article 305 addressed Temporary Wiring, with 305-2(a) requiring that all permanent wiring provisions apply except where specifically modified in this Article, and 305-2(b) requiring approval for any temporary methods. Additionally, 305-4(a) requires installation of services in conformance with Art. 230, and Sec. 305-5 requires that all grounding conform to Art. 250. Section 305-6 requires ground fault protection for all personnel utilizing temporary wiring installations.
The NM cable feed used as a temporary service for the house where the accident occurred clearly did not meet numerous Art. 230 requirements, including ampacity/size (230-23), clearances (230-24), and attachment (230-26). Section 250-23(a) requires that a premises wiring system connected to a grounded service should have a connection between the grounded service conductor and the grounding electrode conductor.