All references are based on the 2011 edition of the NEC
I discovered this buried aluminum box full of moisture when I removed its cover. The trapped moisture had caused severe corrosion to the box as well as the wiring, which arced and tripped the circuit breaker.
Section 314.15 requires boxes, conduit bodies, and fittings to “be placed or equipped so as to prevent moisture from entering or accumulating within the box, conduit body, or fitting.”Clearly, that did not happen here, and the result was a gooey mess of corrosion. In addition, the twist-on wire connectors used in this box were not specifically designed for use in a wet location. According to Sec. 300.5(B), “any connections or splices in an underground installation shall be approved for wet locations.”
Lastly, Sec. 300.6(B) requires installers to provide supplementary corrosion protection for “aluminum raceways, cable trays, cablebus, auxiliary gutters, cable armor, boxes, cable sheathing, cabinets, elbows, couplings, nipples, fittings, supports, and support hardware embedded or encased in concrete or in direct contact with the earth.”
The installer should have installed a small, nonmetallic handhole in place of the aluminum box and used wet location-rated twist-on wire connectors.
I found this surprise during an infrared thermal scan. Just as some people replace a blown Edison-based fuse with a copper penny, somebody replaced these fuses with copper plumbing pipe hangers. This created a very dangerous situation, since these wires were essentially left with no overcurrent protection.
Most of us know that a fuse or circuit breaker is required to be installed in series with each ungrounded conductor. In accordance with 240.21, “overcurrent protection shall be provided in each ungrounded circuit conductor and shall be located at the point where the conductors receive their supply except as specified in 240.21(A) through (H).” Nowhere in (A) through (H) is there any mention of copper strap pipe hangers being an approved overcurrent protective device.
Because this feeder was supplying power to two elevators, we could also make reference to Art. 620. In accordance with 620.61(C), “Motor feeder short circuit and ground fault protection shall be as required in Art. 430, Part V.” Sections 430.61 and 430.62 require that this feeder be provided with a protective device to protect against short circuits and ground faults. There are no exceptions that would ever allow the use of pipe hangers in place of fuses.