Conduit Types Conduit Fittings and Electrical Boxes

Conduit Types

Unless otherwise specified on the contract drawings, all conduit shall be rigid galvanized steel (RMC). The following list is a description of the various conduit types that might be specified on the contract drawings:

Rigid Metal Conduit Type RMC (steel):

Conduit and conduit elbows, couplings, and similar fittings shall have an outer zinc protective coating and an inner protective coating of zinc, enamel, or an equivalent corrosion-resistant material.

Rigid Metal Conduit Type RMC (aluminum):

Conduit and conduit elbows, couplings, and similar fittings shall be a corrosion-resistant aluminum alloy containing not more than 0.4% copper.

Liquid-tight Flexible Metal Conduit Type LFMC:

Flexible conduit shall have a liquid-tight, PVC outer jacket over a flexible galvanized steel core. Flexible conduit shall be 105°C rated, type ATLA with integral ground wire up to 1-1/4″ and fully interlocking strip up to 4″. (No Substitution.) This conduit is suitable for use in Class 1, Division 2 hazardous areas as required by Article 501-30(b) of the NEC.

Electrical Metallic Tubing (EMT):

Tubing and fittings shall be steel or aluminum and shall have the same protective coatings or alloys as specified for rigid steel or aluminum conduit. Fittings shall be of the compression type. Note: The use of EMT conduit is limited to indoor, non-process area applications only (for example, offices, maintenance areas, electrical rooms, or control rooms).

Rigid Metal Conduit, Steel, Plastic Coated (RMC/PVC):

Conduit, elbows, couplings, and similar fittings shall have an outer and inner protective coating of zinc, as well as a 40 mil, polyvinyl chloride coating bonded to the outer surfaces.

Rigid Nonmetallic Conduit (RNC): Schedule 40, 90°C, wire-rated, heavy wall, rigid plastic conduit. Carlon PV-DUIT, or equivalent.

Electrical Boxes and Conduit Fittings

Pull boxes shall be standard gauge galvanized steel, aluminum, fiberglass, or stainless steel as indicated on the contract drawings, with captive stainless steel cover screws and a neoprene gasket attached to the cover. All pull boxes in wet or outdoor locations shall be weatherproof, NEMA type 4X as indicated on, or referenced through, the contract drawings.
Terminal boxes and equipment enclosures shall be NEMA-rated galvanized steel, aluminum, fiberglass, or stainless steel as indicated on the contract drawings with a hinged door and a removable mounting panel or terminal straps as specified. A 12 mm ½” stainless steel drain fitting Hubbell #DPE-30-29-S3 or equal shall be installed in the bottom of all outdoor enclosures. Enclosure rating shall be selected as follows:

NEMA 1 General indoor use

NEMA 4 Indoor use where frequent water hose-down of equipment occurs

NEMA 4X General outdoor use and corrosive areas

NEMA 7 Hazardous locations as required

NEMA 12 General indoor use

Receptacle, switch, and junction boxes for dry, indoor locations shall be standard gauge galvanized steel with captive screw-fastened covers. Cast boxes with threaded hubs and gasketed rain-tight covers (Crouse-Hinds or Appleton FD or FS) shall be used for wet or outdoor locations.
Conduit fittings for rigid galvanized steel conduit shall be Crouse-Hinds Form 8 with gasketed covers, retained cover screws, and threaded hubs or Appleton FM 8 Grayloy-iron with FG series cast cover and neoprene gasket. Conduit fittings for conduit systems containing 4/0 AWG (American Wire Gauge) conductors, or larger, and high voltage cables shall be Crouse-Hinds or Appleton “Mogul” series.

Conduit fittings for rigid aluminum conduit shall be Crouse-Hinds Mark 9 with gasketed covers, retained cover screws, and threaded hubs, or Appleton FM85 with cast cover and neoprene gasket. When aluminum fittings terminate on rigid galvanized steel conduit, threads shall be coated with zinc chromate to minimize galvanic reaction between the dissimilar metals.