Air-conditioning (AC) tech is electrocuted on roof of strip mall, after coming in contact with an energized sign that later proved to have no solid ground path
When an air-conditioning (A/C) installer, who worked for an HVAC contractor, was tasked with upgrading the A/C unit for a retail tenant in a local shopping center, he considered the job business as usual. For starters, he was a proficient technician with considerable experience in this type of work, which required replacing the original swamp cooler (evaporative cooler) with a new package. At the outset of the work, no unusual circumstances were present that could have warned him of the underlying problem that would ultimately lead to his electrocution.
Electrocutions and injuries resulting from electric shocks generally can be categorized into actions caused by an individual, an installation failure, or lack of maintenance. As will be revealed in the details of how this accident unfolded, the death of this young man (in his 20s) resulted in the culmination of someone else's sloppy workmanship, multiple Code violations, and the property owner's failure to supervise the property.
This fatality occurred while the decedent was installing an A/C unit for a retail tenant in a strip mall — the wood frame/stucco building of which dated back to the early '50s. The roof rafters served as the ceiling joists of the occupancies. The branch circuit wiring of the building was heavy wall steel flexible metallic conduit, which served as the equipment grounding conductor. The building was built in a large city jurisdiction whose electrical code preceded the general adoption of the National Electrical Code (NEC). As is always required, the local code was more restrictive than the NEC. Therefore, the applicable code at that time was similar to current editions of the NEC.
Each occupancy had a junction box installed in the fascia for a sign installation. In order to get a fascia for signage, the building's roof was elevated approximately 3 ft at a 40° angle near the front of the building (Photo 1). The roofing was of the hot mopped roll roofing variety, and the top edge of the incline was covered with a sheet metal cap. The building's service entrance was a factory-built switchgear consisting of a 120/240V single-phase service as well as 240V 3-phase service. The grounding conductor of these units had illegally cut strands to fit into the improperly sized ground clamp. The roof area, which was accessible via a permanent metal ladder, housed electrical work plagued by several Code violations that had existed for some time.
All of the signs for these stores measured 30 in. high and 10 ft wide. The lighting arrangement featured fluorescent lamps fed by a single ballast, which was controlled by a time clock. In this particular store's case, the dial trippers had been removed, leaving the sign energized at all times. Although the signs had disconnect switches, they lacked other Code-required items, such as a testing lab label and manufacturer's label, indicating the voltage and load amps.
While atop the roof working on cutting the hole required for the package, the A/C installer needed some additional materials. He called down to his helper, who was at ground level, for assistance. The helper prepared the sheet metal fitting needed and got ready to hand the item to the installer from a ladder that did not reach the roof. Subsequently, the installer placed himself on the sloped roofing in a lying position (with his chest resting on the sheet metal cap, as shown in Photo 1 on page 8) so he could reach the item being handed up to him.
When the installer reached over the roof to lift the material, he touched the store's sign, causing a current to flow from his hand to his chest. Evidently, when the installer was electrocuted, his body reaction caused him to roll off the elevated section of roofing, thereby breaking the circuit.
First on the scene, firefighters attempted to resuscitate the installer and transported him to a local trauma center, where he was pronounced dead. The autopsy sketch revealed a burn mark on the decedent's chest, and there were no indications that the installer had any life-threatening health history issues prior to the incident. Although the helper was not physically injured, his mental anguish led to his leaving the trade.
In addition to fire and rescue squads, the serving electric utility was also called to the scene. Based on a verbal statement by one of the utility representatives during this early investigation, the installer was probably exposed to as much as 515V. However, the source of that high of a voltage could not be confirmed in later testing and examination of the site.
I was retained within days of the accident by the law firm handling the wrongful death claim for the plaintiff (installer's widow).
The property owner's insurance company promptly dispatched an electrical expert to the scene, who tested areas the A/C installer was exposed to and found that the sign's ballast was the probable cause of the electrocution. Because the store manager wanted the sign to be lit at all times, the expert isolated the ballast on a piece of cardboard (Photo 2), reenergizing the sign circuit after his examination and isolation of the ballast. This apparently cleared the problem temporarily.
Investigation of the sign was conducted at the site by the experts representing the plaintiff and the defense. The sign's face was removed and immediately showed the lack of any type of equipment grounding conductor from the light fixture to the junction box in the face of the building (Photo 3).
Had there been a solid ground path, the fault would have tripped the branch circuit breaker, thus removing the hazard. The oversized opening in the sign case was not equipped with an approved insulator such as a bushing — a potential trouble spot. This was not the only place where the conductors were not adequately protected; note the conductors entering the wireway through the ½-in. conduit opening. In addition, a digital multimeter reading (41.4V) was taken from the metal roof cap to a grounded conduit. Further examination did not find any source for this unusual voltage reading.
The sign was relocated to a lab facility for further examination, where the methodology was to concentrate on the ballast and then the total sign. After being X-rayed in various positions, no visible problems were identified with the ballast. The connection diagram on the ballast was checked for the proper connections. Temporary connections were made in a number of variations to see if forensic investigators could replicate the 515V reading mentioned by the employees from the electric utility. None of the wiring arrangement produced such a reading. When the balance of the fixture was inspected, no salient problems were identified.
During the investigation of this wrongful death case, problems surfaced that ultimately derailed any meaningful theories of what had caused the electrocution. Although Cal OSHA was called to the scene, the service lacked any electrical field personnel in the immediate area. While Cal OSHA red tagged access to the roof as well as the panel in the effected store occupancy, it requested that the electrical inspection agency of the city follow up with a reinspection of the building. It also asked me to provide copies of my report for its use.
A further impediment to finding a specific fault was caused by the building owner's expert witness, who determined the cause of the electrocution was the ballast. Evidently, at the insistence of the store manager and the building owner to keep the sign illuminated, the expert isolated the ballast. This act removed the actual condition at the time of the accident from examination and led to spoliation of the evidence.
The lack of any specific failure of the ballast, fixture, and building wiring was, to say the least, frustrating. As a result of this accident, the property owner replaced all signs to meet current code requirements. In addition, other violations of code requirements noted at the building were corrected, such as non-conforming wiring on the roof and the area of the incoming service.
Although investigators were not able to duplicate the condition that electrocuted the young A/C installer, the defendants agreed to a settlement in favor of the plaintiff, avoiding a court battle that would have been more costly to all parties.
The basics of this case illustrate why anyone working on or near electrical components cannot make assumptions as to the quality of the installation or the safety of the work area. When substandard work is encountered, it should be pointed out to responsible parties so repairs or corrections can be made prior to any work being performed.
While there was never a specific cause of electrocution officially revealed, the absence of a grounding strap from the building's metallic wiring system to the sign enclosure would have tripped the circuit breaker, and de-energizing the circuit to the sign enclosure would have eliminated the hazard posed by the sign's case being energized.
David is a certified electrical inspector and owner of Liaicon, Long Beach, Calif. He can be reached at firstname.lastname@example.org.