I am trying to find out why NEC limits us to 4" trade sizes for most conduits/raceways. Example: 5" LFMC is available, but NEC 350.20B says that 4" is the maximum allowed size. I have not been able to find an answer for why the NEC limits us to 4". 5" and 6" LFMC is listed. Why can we not use it? Why is anything larger than 4" considered "Utility" code?
Trade sizes
- Thread starter Publius
- Start date
- Status
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
That answer may need to come from trade association. Look at the CMP responsible for the LTFMC article and you will the trade association.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Who makes 5" and 6" LFMC?
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
Maybe it has to do with the 6th limitation on length, because at more than 4", you can't make a 90 degree bend in 6ft or less, so there would be little use for it. Just speculation though.
- Location
- Illinois
- Occupation
- retired electrician
350.6 requires the use of listed LFMC. The listing standard, UL 360, only provides for sizes up to 4".
Not sure what the 6" LFMC is listed as, but it should not be listed as LFMC per the scope of UL 360.
Not sure what the 6" LFMC is listed as, but it should not be listed as LFMC per the scope of UL 360.
Coppersmith
Senior Member
- Location
- Tampa, FL, USA
- Occupation
- Electrical Contractor
What are you trying to put in this 5" pipe?
- Status