Timely response by worker averts electrical incident

Blue arrow on the left indicates the location of the incident. Green arrow on the right shows the connection point to the supply authority’s conductors.

An alert worker’s timely response averted disaster at a Coquitlam residence. The incident took place when the worker was washing the area around a non-compliant electrical junction box located on the exterior soffit of the building.

The worker was using a 2000 psi power washer on a dry sunny day from a boom lift. Although water was not directed at the metal junction box, witnesses reported seeing multiple flashes of sparks and blue and white flames that were shooting out approximately 2 – 3 feet.

Acting instinctively, the worker turned off the power washer and immediately came down from the boom lift. As the arcing event continued to happen, emergency services were alerted and power was disconnected.

Technical Safety BC’s safety officer investigated the incident and found that the overhead electrical consumer service raceways and conductors were spliced and extended, possibly to relocate the point of attachment for the utility supply conductors from the left corner of the building to the right corner.

When the electrical service was extended, a metal junction box that was rated for indoors-use only was installed to splice the conductors. The splices in the junction box were made with bare copper split bolts taped with a layer of vinyl electrical tape, which had deteriorated over time.

The arc event and equipment damage were likely caused by deteriorating vinyl electrical tape that was used to insulate the copper split bolt splices made to extend the consumer service conductors. 

The water from the power washing or the vibrations from the power washer spray may have caused one phase of the system to come in contact with the bonded metal junction box, creating an electrical fault to ground and subsequent arc event and damage to the electrical service.

The incident alerts owners and contractors of the consequences of installing a non-compliant metal junction box that was a major factor leading to the failure.

See the detailed investigation report: Compromised insulation damages outdoor electrical junction box here.

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