EMT is a thin-wall metal raceway that is not permitted to be threaded, EMT is also referred to in the trade as thinwall. The specifications for the Commercial Building in this text permit the use of EMT for all branch-circuit wiring. NEC Article 358 should be consulted for exact installation requirements
Electrical metallic tubing is a nonthreaded, thinwall raceway. Because EMT is not permitted to be
threaded, sections are joined together and connected to boxes, other fittings, or cabinets by couplings and connectors. EMT fittings available include the setscrew, compression and indenter styles.
Set-screw. When used with this type of fitting, the EMT is pushed into the coupling or connector
to the stop and is secured in place by tightening the set-screws This type of fitting is classified as concrete-tight but is not raintight. Some fittings may be concrete-tight only when wrapped with tape. If so, the carton containing the fitting is marked “Concrete-tight when taped.”
Compression. EMT is secured in these fittings by tightening the compression nuts with a wrench or pliers, These fittings are classified as raintight and concrete-tight types.
When installing EMT outdoors where exposed to rain, or in any other wet location, compression EMT fittings must be listed for this use. Check the carton for wording that indicates the suitability of
these fittings for use in wet locations.
Indenter. The indenter (crimp) type of fitting is a thing of the past, although an Underwriters Laboratories standard continues to have such a listing available. A special crimping tool was used to
secure the fitting to the EMT. The tool places an indentation in both the fitting and the EMT. It was a
standard wiring practice to make two sets of indentations at each connection, approximately 90° apart. This type of fitting is classified as concrete-tight.
Installation of EMT
Due to numerous failures of EMT in underground installations, many electrical inspection authorities will not permit EMT to be installed underground or in concrete slabs that are on or below grade. It is
also common for electrical consulting engineers to require the use of PVC conduits in these and other corrosive locations. Be sure to consult the authority having jurisdiction as well as the project specifications before beginning the electrical installation.
The efficient installation of EMT requires the use of a bender, Figure 6-9. This tool is commonly
available in hand-operated models for EMT in trade sizes 1⁄2, 3⁄4, and 1 and in power-operated models for EMT larger than trade size 1
Several kinds of bends can be made with the use of the bending tool. The stub bend, the back-to-back bend, and the angle bend are shown in Figure 6-10. Other types of bends include offset, saddles and kicks. The manufacturer’s instructions that accompany each bender indicate the method for making each type of bend.