22 Jul 2015
Several questions about the use of IMC have been asked at trade shows and other events over the last year and we realize that there are a many misconceptions concerning IMC. Here is some clarification:
One of the most common misconceptions of IMC (intermediate metal conduit) is that it is not as strong as GRC (Galvanized Rigid Conduit) and does not offer the same physical protection as GRC. The truth is that IMC is actually stronger than GRC. Although crush and impact tests are not required in the product standards, historically, we have done testing and have found the following exemplary mechanical properties:
Another misconception concerns the permitted uses of IMC in the National Electrical Code® (NEC®). There seems to be a misconception that IMC has limitations under the NEC that GRC does not. The fact is that IMC is allowed to be used under “All atmospheric conditions and occupancies” according to Article 342 of the NEC. This same statement is made under Article 344 of the NEC in reference to GRC. A simple rule to remember for using IMC would be: If you can use rigid steel conduit, you can use IMC! (Always check local code requirements as well).
Is IMC allowed to be used in wet locations? NEC section 342.10 (D) states IMC can be used in wet locations but all supports, bolts, straps, and screws should be of a corrosion resistant material. The same requirement applies to rigid metal conduit.
Can IMC be used for protection of service entry cables? Yes, IMC can also be used for physical protection of service entrance cables according to NEC section 230.50(1).
Can you install IMC in a hazardous location? Yes, NEC section 501.10(A)(1) allows threaded steel intermediate metal conduit(IMC) to be installed in Class I, Division 1 and Class I, Division 2 applications. Just like rigid steel conduit.
Have an installation in concrete or another corrosive environment? IMC can be installed in concrete, in direct contact with the earth, or in areas subject to severe corrosive influences where protected by corrosion protection and judged suitable for the condition. Just like rigid steel conduit.
Those are the answers to the most common questions we receive regarding IMC. We would also like to share some other facts about IMC that may be of interest during the selection, installation, or inspection of IMC.
If you still have questions or concerns about using IMC please contact Raymond Horner at (708) 915-1547 or firstname.lastname@example.org
The questions and answers in this article are based on the current edition of the NEC. However, local codes can differ, and your Authority Having Jurisdiction (AHJ) may have opinions that also differ. It is always important to verify your planned installation with the local AHJ.