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What's Wrong Here?

Aug 13, 2007 2:01 PM, By Joe Tedesco, NEC Columnist

I think it’s fair to say that this setup was probably installed before 1930. The service lateral is run from an underground manhole on Hanover Street in the North End of Boston, and has been in this condition for a very long time. I believe that this type of corrosion is typical, especially near the seashore, and has gone unnoticed for some time.

What's my beef with the arrangement? I think the electric utility really needs to pay careful attention to these types of old cruddy and corroded installations, and fix them before a catastrophe happens. Although the electric utility may not be required to adhere to NEC rules, I don’t think we should have to live with this type of power supply, do you? I’m also fairly certain the load side of this installation is in bad shape. The only way to rectify the situation is to change the service out entirely.

The corroded conduit reminds us why we have the following NEC rules:

• [300.6] Protection Against Corrosion and Deterioration. Raceways, cable trays, cable bus, auxiliary gutters, cable armor, boxes, cable sheathing, cabinets, elbows, couplings, fittings, supports, and support hardware shall be of materials suitable for the environment in which they are to be installed.
• [300.6(A)] Ferrous Metal Equipment. Ferrous metal raceways, cable trays, cable bus, auxiliary gutters, cable armor, boxes, cable sheathing, cabinets, metal elbows, couplings, nipples, fittings, supports, and support hardware shall be suitably protected against corrosion inside and outside (except threads at joints) by a coating of approved corrosion-resistant material. Where corrosion protection is necessary and the conduit is threaded in the field, the threads shall be coated with an approved electrically conductive, corrosion-resistant compound. Exception: Stainless steel shall not be required to have protective coatings.
• [300.6(A)(1) Protected from Corrosion Solely by Enamel. Where protected from corrosion solely by enamel, ferrous metal raceways, cable trays, cable bus, auxiliary gutters, cable armor, boxes, cable sheathing, cabinets, metal elbows, couplings, nipples, fittings, supports, and support hardware shall not be used outdoors or in wet locations as described in 300.6(D).
• [300.6(A)(2) Organic Coatings on Boxes or Cabinets. Where boxes or cabinets have an approved system of organic coatings and are marked “Raintight,” “Rainproof,” or “Outdoor Type,” they shall be permitted outdoors.
• [300.6(A)(3) In Concrete or in Direct Contact with the Earth. Ferrous metal raceways, cable armor, boxes, cable sheathing, cabinets, elbows, couplings, nipples, fittings, supports, and support hardware shall be permitted to be installed in concrete or in direct contact with the earth, or in areas subject to severe corrosive influences where made of material approved for the condition, or where provided with corrosion protection approved for the condition.
• [300.6(B)] Non-Ferrous Metal Equipment. Non-ferrous raceways, cable trays, cable bus, 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 shall be provided with supplementary corrosion protection.
• [300.6(C)] Nonmetallic Equipment. Nonmetallic raceways, cable trays, cable bus, auxiliary gutters, boxes, cables with a nonmetallic outer jacket and internal metal armor or jacket, cable sheathing, cabinets, elbows, couplings, nipples, fittings, supports, and support hardware shall be made of material approved for the condition and shall comply with (C)(1) and (C)(2) as applicable to the specific installation.
• [300.6(C)(1)] Exposed to Sunlight. Where exposed to sunlight, the materials shall be listed as sunlight resistant or shall be identified as sunlight resistant.
• [300.6(C)(2)] Chemical Exposure. Where subject to exposure to chemical solvents, vapors, splashing, or immersion, materials or coatings shall either be inherently resistant to chemicals based on its listing or be identified for the specific chemical reagent.

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