In the domain of electrical installations, Electrical Metallic Tubing (EMT) plays asignificant role. EMT has diverse applications, being commonly used in commercial buildings to route electricity among numerous rooms and devices. It'scrucial to be aware of both its permitted and not permitted uses to ensure safeand compliant installations. Let's take a closer look at the various scenarios where EMT can be utilized.
EMT is a versatile option as it ispermitted for both exposed and concealed work. In exposed installations, EMT can be a great choice for industrial or commercial settings where access for maintenance or upgrades might be necessary. It can be neatly mounted on walls or ceilings, providing an organized way to route electrical wires. For concealed work, EMT can be hidden within the building structure, such as walls,floors, or ceilings. This not only gives a clean look but also protects the wiring from accidental damage, making it suitable for various construction projects, whether new or renovation.
Ferrous or non ferrous EMT, along with its elbows, couplings, and fittings, has specific rules regarding installation incorrosive environments. It can be installed in concrete, in direct contact with the earth, or in areas with severe corrosive influences, but only when protected by appropriate corrosion protection measures and deemed suitable forthe conditions. This shows that in harsh environments like those near salt wateror in industrial areas with high pollution levels, proper corrosion protectionis essential. It ensures the long term integrity of the EMT system and reducesthe risk of electrical faults due to corrosion related damage.
In wet locations, all supports, bolts,straps, screws, etc., must be of corrosion resistant materials or protected against corrosion by corrosion resistant materials. The Fine Print Note (FPN)directs us to section 300.6 for more details on corrosion protection. This emphasizes the importance of using the right materials to prevent corrosion inareas where moisture is present, ensuring the safety and durability of the EMT installation.
This is a crucial safety consideration asdamaged EMT could lead to electrical hazards. For example, in areas with hightraffic machinery or where there is a risk of accidental impact, EMT might notbe the appropriate choice.
When it comes to corrosion protection, EMTshould not be used where it is protected from corrosion solely by enamel.Enamel might not provide sufficient protection in certain environments, and relying on it alone could lead to premature corrosion of the EMT, which in turncould affect the electrical system's integrity.
In cinder concrete or cinder fill wheresubject to permanent moisture, EMT has restrictions. Unless it is protected onall sides by a layer of non cinder concrete at least 50 mm (2 in.) thick orunless the tubing is at least 450 mm (18 in.) under the fill, EMT should not beused. This is to prevent potential damage or corrosion caused by the cinderenvironment.
EMT is generally not allowed in any hazardous (classified) location, except as permitted by other articles in thecode. Hazardous locations have unique safety requirements, and EMT might notmeet those requirements without specific exceptions.
EMT should not be used for the support of luminaires or other equipment, except for conduit bodies no larger than thelargest trade size of the tubing. This is to ensure that the equipment is properly supported and that the EMT is used for its intended purpose of electrical wire routing.
Where practicable, dissimilar metals incontact anywhere in the system shall be avoided to eliminate the possibility ofgalvanic action. Galvanic action can cause corrosion and other issues in theEMT system, so this precaution is necessary to maintain the integrity of the electrical installation.
