In 1975, I examined an electric clothes press on the premises of a laundry in Maryland that was patronized by the public for general clothes washing, cleaning, and pressing. A customer had been shocked while using the press. The purpose of my inspection was to determine why the accident had occurred.
The appliance was bolted to a table adjacent to the store’s front window, about 3 feet from a wall-mounted pay-telephone. The telephone receiver’s flexible cord was enclosed in a metal shield. The shield was at ground potential, as measured with respect to the store’s electrical feeder ground.
The press was a 120-volt AC, 1,550-watt unit, powered by a two-conductor black plastic- or rubber-covered power cord. The attachment plug cap of the power cord had been clipped off. The power cord was permanently connected to the power source, without a separate, readily accessible disconnect switch. No visible means of grounding the exposed non-current-carrying metal parts of the press was present.
After disassembling the press I noted that the internal conductors of the appliance, which were connected to the power cord by means of laminated plastic twist-type connectors, were in a general state of disrepair. Their insulation had been almost completely abraded off at points approximately 4 inches from the plastic connectors, to the extent that portions of the metal conductor strands were visible. The metal frame of the arm of the clothes press bore two sets of black marks along its raised ribs. These marks were discolorations caused by rubbing of the ribs against the conductor insulation, in several different locations. In addition, an area adjacent to one of the discolored areas on the right rib, as viewed from the operating position, bore a mark that appeared to be caused by a burn, rather than a non-heat related discoloration.
Upon further inquiry, it was established that the laundry store patron had received a severe electric shock while she was holding the telephone receiver, whose metal shield was grounded, while she was operating the ungrounded appliance. The shock was caused by energized conductor strands that were exposed because of abraded conductor insulation, which resulted from improper assembly or reassembly after servicing of the press. The ungrounded metal frame had become energized by the exposed metal conductor.
The design and construction of the appliance permitted improper initial placement, or resetting of the internal conductors after servicing the press. During reassembly after servicing, the internal conductors of the press had simply been pushed back manually into the arm cavity, with no fastenings, clamps, or positive channelization to hold them in place, before the cover was reset and fastened into the body of the press with bolts. This method of placing and securing internal wiring was not in conformance with many electrical standards. Section 422-1 of the 1971 National Electrical Code (NEC) stated that it applied to appliances. Section 110-4(b) was concerned with mechanical protection of parts. Section 384-3(a), although focused on switchboards and panelboards, required that conductors “be held firmly in place.”
International Electrotechnical Commission PUB 335-1, “Safety of Household and Similar Electrical Appliances” required in Section 23, “Internal Wiring,” protection of wires from contacts that might damage insulation, or that might be moved during servicing.
The metal frame of the clothes press had been energized for an unknown period of time, and presumably had been operated often without any shocks occurring, as long the store patrons were not grounded while operating the press. Compressing a wire not properly recessed between the cover and body of the press would immediately destroy the wire’s insulation and bring its exposed strands into contact with the metal frame. The photograph depicts wires with damaged electrical insulation. Thus the accident would not have occurred if the appliance had been grounded, since the branch circuit breaker would have tripped, or the voltage of the grounded frame of the press reduced to a harmless level. NEC Section 422-16 required that metal frames of all electrical appliances operating above 150 volts be grounded. It also recommended, but did not require, that all appliances, whether portable, fixed or stationary, be grounded. However Section 250-45(d) required grounding of exposed non-current carrying parts of cord- and plug-connected equipment in non-residential use. Since the appliance had an Underwriters Laboratory (UL) label, it was assumed that the labeling basis was solely for residential use of the clothes press.
Also, the accident would not have occurred if the appliance had been mounted at a location that prevented the user from simultaneously touching it and an electrical ground point. Sections 250-42(a) & (b) provided that fixed appliances should be so mounted, if not grounded. The clothes press was stationary, being bolted to the table.
The design and installation of the press did not conform to Section 110-11 in that special approval for operating the clothes press in a damp or wet environment had not been requested or obtained.
Instructions provided with the press were for use of a water sprayer, for spraying a fine water mist onto clothing being pressed. The presence of moisture could have contributed to the severity of the electric shock experienced by the patron.
Other NEC violations were present, i.e., employing a flexible power cord at a stationary electrical installation not requiring frequent servicing, and faulty reassembly and lack of testing after servicing at some unknown time in the past.
Sections 422.21(b) and 422.23(b) of the NEC are concerned with readily accessible means for disconnecting an appliance from a source of electrical power, which was not provided at this installation site. The manufacturer’s installation instructions were primarily devoted to mechanical aspects, but no electrical details were included.
Often, a single electrical defect, such as lack of grounding, does not result in an immediately dangerous condition. But when defects occur in deluges in a commercial installation, particularly when exposed metal parts become energized, this condition reflects a casual attitude during the appliance’s initial selection, installation, and maintenance toward well-thought-out electrical standards.
MAZER is a consulting electrical engineer specializing in electrical safety issues. His telephone number is (202) 338-0669, and his e-mail address is firstname.lastname@example.org.