OESC 250.118 Types of Equipment Grounding Conductors.

Adding a wire type equipment grounding conductor inside a metal raceway ensures that the equipment grounding path is maintained in the event that extreme weather or abuse causes an exposed rooftop raceway fitting to become loose.
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Adding a wire type equipment grounding conductor inside a metal raceway ensures that the equipment grounding path is maintained in the event that extreme weather or abuse causes an exposed rooftop raceway fitting to become loose.

NEC Section 250.118(A) describes all things that can be used as an equipment grounding conductor. Most metal raceways like EMT, IMC and RMC are suitable to serve as an equipment grounding conductor as long as listed fittings and connectors are used and made up wrench-tight. Oregon has amended Section 250.118(A) with additional requirements for metal conduit installed on rooftops.

In Oregon, 250.118(A)(14) was modified to say “Where metallic conduit is installed on roof tops, an equipment grounding conductor shall be provided within the raceway and sized per 250.122”. The addition of a wire type equipment grounding conductor inside a metal raceway ensures that the equipment grounding path is maintained in the event that extreme weather or abuse causes an exposed rooftop raceway fitting to become loose.

Oregon amendments to the 2023 NEC® are located in “Table 1-E” of the Oregon Electrical Specialty Code (OESC) which can be seen using the following link or the OESC PDF file located near the bottom of the screen: 2023 OESC

  Click here to view the OESC  

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OESC 250.118 Types of Equipment Grounding Conductors.

Below is a Real Question from our Electrical Continuing Education Courses for Electrical License Renewal:

Which of the following is true of a length of rigid metal conduit installed on a rooftop to supply power to an HVAC unit?

A: The raceway itself qualifies as an equipment grounding conductor as long as all fittings are made up wrench-tight.
B: An additional wire-type equipment grounding conductor must be installed in the raceway and sized based on NEC 250.122.
C: Expansion fittings are required regardless of conduit length.
D: Only threaded fittings are permitted to be used with the rigid metal conduit.
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