Code Change Summary: Electrical Metallic Tubing (EMT) was added to column 3 of Table 300.5(A) for underground installations.

NEC Table 300.5(A) provides minimum cover requirements for direct-buried cables, conduits, or other raceways installed underground. There are 5 columns in Table 300.5(A); each of which specifies different burial depths that apply to the specific wiring methods named at the top of the column. In the 2023 NEC^®, Electrical Metallic Tubing was added to column 3 of Table 300.5(A).

NEC section 300.5 is all about underground installations. Section 300.5(D)(4) provides specific requirements for protecting underground enclosures and raceways that are subject to physical damage. In the 2014 NEC^®, Section 300.5(D)(4) required underground conductors that were subject to physical damage to be installed in rigid metal conduit, intermediate metal conduit, RTRC-XW, Schedule 80 PVC conduit, or equivalent. In the 2017 NEC^®, EMT was added to the list of suitable protection methods.

Adding EMT to the list of suitable protection methods in Section 300.5(D)(4) created controversy for many inspectors and electricians. Even though the 2017 NEC^® allowed EMT to be used to protect underground conductors from physical damage, there were many who felt and still feel strongly against installing EMT underground.

EMT has been allowed “in direct contact with the earth” for many code cycles in Article 358. Direct contact with the earth means touching the earth which is different than being buried in the earth.

In the 2023 NEC^®, Section 358.10(A)(1) was revised to specifically allow EMT in concrete, in direct contact with the earth, in direct burial applications with fittings identified for direct burial, or in areas subject to severe corrosive influences where installed in accordance with 358.10(B).

Some installers not familiar with the local soil conditions may still prefer to use nonmetallic wiring methods underground in order to avoid potential service calls from EMT corroding underground or where it emerges from grade.

During the 2023 NEC^® development process, justification to add EMT to column 3 of Table 300.5(A) and to modify Section 358.10(A)(1) was heavily reliant on the UL Guide Info for product category FJMX which covers EMT.

Both CMP-3 and CMP-8 made mention of the language in UL product category FJMX in their committee statements regarding the UL Directory recognizing the use of EMT for direct burial applications. Recognizing is different than approving. At the time of the code development process, the UL Guide Info for EMT didn’t actually specify that EMT is suitable for direct burial, it simply stated the following: “Where galvanized steel EMT without supplementary corrosion protection extends directly from concrete encasement to soil burial, severe corrosive effects are likely to occur on the metal in contact with the soil.