Conduit Fill Question

Discussion in 'Electrical Forum discussion & Blog' started by arfeller, Feb 20, 2008.

  1. kd

    kd New Member

    Messages:
    207
    Note to jwelectric: "Exception: Cables with entirely nonmetallic sheaths shall be permitted to enter the top of a surface-mounted enclosure.... "(using 18 inch to 10 ft pieces of conduit, sealed and under certain other conditions )
    This is an exception to the cable clamping rule above it. It tells us we are permitted to build under a certain conditions. It does not PROHIBIT all other installations.
    Obviously NM cables installed within a conduit system can enter the side and bottom of the box as long as all appropriate Code rules are followed.
    Therefore, if you install a junction box at the bottom end of the 2" PVC then you will be converting to a conduit with wire(or cable) in it wiring system. This will make your installation not subject to the cable clamping rule. And not subject to the "top of cabinet" exception to the cable clamping rule.
    Boxes with conduits entering top bottom sides and back are not breaking the rules, unless they are short, open ended pieces of conduit with NM installed.
    Last edited by a moderator: Mar 4, 2008
  2. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

    Messages:
    2,718
    Location:
    Central Florida
    Certainly not all of them, but probably most of them. There's a 6-lane divided highway near me with a 35mph speed limit posted. If you want to have some fun, drive it at 35mph.

    "Right" is not always defined by laws or codes, which were not all written by people with an adequate command of knowledge, reason, logic, or English.
  3. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,540
    Location:
    North Carolina
    Help me to understand just what you are saying here, please.

    Are you saying that just because someone is driving over the posted speed limit it gives everyone else the right to do the same thing?

    Should this type of thinking be used when raising children? A bunch of kids at school is picking on my kid so I just tell my kid that it is alright because one group of kids over rule the feelings of one.

    Come on now Mikey stand up for the laws that we tax payers have spent so much money to have enacted. Don’t join the crowd of misfits just so you can fit in but instead set an example for those who look up to you and do as out leaders say we are to do and drive at the posted speed.
  4. kd

    kd New Member

    Messages:
    207
    This traffic analogy is going overboard. Obviously, traffic rules are often broken in emergencies and to promote safety. These are one-time instances. Also, if a speed limit is too low or too high for safety, have your city council change it.
    We are building mechanical systems that will last for 50 or more years. This is why the rules are important.
    Generally, the electrical Code is carefully written. Our problem with the conduit and cable section is that we are not reading carefully or are out of context.
    See my solution above. The real arguments are about local AHJs interpretations of the Code.
  5. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,540
    Location:
    North Carolina

    In ***.10 and .12 of all the cable articles outlines the uses permitted and uses not permitted for the installation. Article 334 mandates the rules for the installation of NM cable.

    ***.22 of raceway articles will mandate the installation of conductors in that raceway. Let’s use PVC for an example;
    352.22 Number of Conductors.
    The number of conductors shall not exceed that permitted by the percentage fill specified in Table 1, Chapter 9.
    Cables shall be permitted to be installed where such use is not prohibited by the respective cable articles. The number of cables shall not exceed the allowable percentage fill specified in Table 1, Chapter 9.

    When dealing with junction or outlet boxes 314.17 mandates the installation of cables and the requirement to secure the cable to the box. 314.17(B) the rule to allow the installation of a cable to be installed in a raceway for protection is allowed as outlined in 300.15(C).
    These rules will allow the raceway and cable to come into the box from any and all directions.

    BUT

    Article 312 regulates the installation of conductors in enclosures such as panels. 312.5(C) is the rule for installing NM to a panel. When installed in a conduit the exception allows the installation as long as the installation follows ALL of the criteria outlined in the exception.

    I agree that this rule is not enforced as it should be but it is still the rule.
    When installed either in a raceway or as an open cable in ALL installations the sheath of the cable MUST enter the enclosure no less than ¼ inch.
  6. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

    Messages:
    2,718
    Location:
    Central Florida
    Actually, I do drive at the posted speed, which I've found to be a foolproof way of avoiding speeding tickets. I've only been rear-ended once while doing so, which I think is a miracle. People have been killed in our area by stopping for red lights.

    As for all the money we've spent to get these laws enacted, I think we've gotten a lousy deal. At least I don't live in any of the states where their learned legislatures actively considered changing the value of pi to something else, either easier to use, or based on biblical text.

    Having said all that, I agree with Winston Churchill, who is alleged to have said that democracy is the worst form of government except all the others that have been tried.
  7. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

    Messages:
    2,718
    Location:
    Central Florida
    Good luck.
  8. arfeller

    arfeller New Member

    Messages:
    77
    Location:
    Port Angeles, WA
    Crap.

    From this point forward i'm sticking to yes and no questions :D

    Thank you all for the input. Some real good suggestions here and now i have a good path forward.

    Thank you.
  9. Lakee911

    Lakee911 I&C Engineer (mostly WWTP)

    Messages:
    1,328
    Location:
    Columbus, OH
    Ok. I stand corrected.

    Jason
  10. Kiril

    Kiril New Member

    Messages:
    87
    Location:
    Sacramento, CA
    Somewhat related question, do the same fill restrictions apply to low volt?

    Also, are there any restrictions with regard to what type of conduit that can be used to run low voltage cables?
  11. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,540
    Location:
    North Carolina
    What kind of low voltage as there several different types of cables and different uses for low voltage
  12. Kiril

    Kiril New Member

    Messages:
    87
    Location:
    Sacramento, CA
    Primarily Cat and Coax. No low voltage lighting cables to share conduit used for media/comm applications.
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