User Tag List

Page 1 of 2 1 2 LastLast
Results 1 to 10 of 12

Thread: Sizing loads to industrial machinery

  1. #1
    Join Date
    May 2019
    Location
    Rochester ny
    Posts
    3
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Sizing loads to industrial machinery

    We have in our factory a trim press machine with a nameplate FLA of 192 amps at 460 v 3 phase. No resistive load, just a control plc and 2 servo motors. Avg draw using a clamp on meter is 10 to 15 amps. It is fed from a 30 amp breaker with #10 wire and we have not had any problems for the 8 years this machine has been running, 3 shifts , five days a week. I need to relocate this machine within our factory. I’m stumped at finding a code allowace for under sizing a load, even though experience shows 30amps is more than enough. I hate to install a 200 amp service unnecessarily,but i dont want to be violating any codes at the same time. Any help would be greatly appreciated.

  2. #2
    Join Date
    Dec 2006
    Location
    Chapel Hill, NC
    Posts
    34,883
    Mentioned
    4 Post(s)
    Tagged
    0 Thread(s)
    I don't believe the nameplate is correct. What is the HP of the motor?
    They say I shot a man named Gray and took his wife to Italy
    She inherited a million bucks and when she died it came to me
    I can't help it if I'm lucky



  3. #3
    Join Date
    Dec 2014
    Location
    CO
    Posts
    118
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Mark1990 View Post
    We have in our factory a trim press machine with a nameplate FLA of 192 amps at 460 v 3 phase. No resistive load, just a control plc and 2 servo motors. Avg draw using a clamp on meter is 10 to 15 amps. It is fed from a 30 amp breaker with #10 wire and we have not had any problems for the 8 years this machine has been running, 3 shifts , five days a week. I need to relocate this machine within our factory. I’m stumped at finding a code allowace for under sizing a load, even though experience shows 30amps is more than enough. I hate to install a 200 amp service unnecessarily,but i dont want to be violating any codes at the same time. Any help would be greatly appreciated.
    Maybe the poster meant 19.2 amps?

  4. #4
    Join Date
    May 2019
    Location
    Rochester ny
    Posts
    3
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    A little more detail on the machine. The prints call out several options not installed, totaling 33hp. Motors that are utilized are 27.5 kw servo and a 7.2 kw servo, along with a 7.5 kva transformer, for some 120 v loads. Maybe the nameplate includes the never installed options? My main question is, does the code allow me to run a smaller feed than the nameplate calls for? I dont see this anywhere in article 670. Any help is appreciated . Thank you

  5. #5
    Join Date
    Feb 2016
    Location
    Illinois
    Posts
    1,463
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Sizing loads to industrial machinery

    I think if the conductors are properly protected, you’re fine code-wise.

    I have had similar experiences. We had machine tools that were never loaded anywhere near capacity. A vertical turret lathe with an integral 100 A breaker that never drew more than 15A the way it was used. Not uncommon.

    We never downsized the conductors, however. We never knew what kind of work it would be asked to do next month!

  6. #6
    Join Date
    May 2005
    Location
    Richmond, Virginia
    Posts
    25,757
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    With the history of operation you provided, I would just duplicate what you have, and sleep well.
    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
    Electrical Contractor
    Richmond, VA

  7. #7
    Join Date
    May 2019
    Location
    Rochester ny
    Posts
    3
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I agree that practically speaking as long as conductors are properly protected there is not a fire hazard etc. my main sticking point is if the job were to be audited by our fire insurance company or corporate for some reason I would like a code to reference that allowed a smaller than nameplate service. As everything I read in the code points to sizing the conductors and over current protection based on machine nameplate FLA.

  8. #8
    Join Date
    Jun 2004
    Location
    Cherry Valley NY, Seattle, WA
    Posts
    5,943
    Mentioned
    2 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by MrJLH View Post
    Maybe the poster meant 19.2 amps?
    Quote Originally Posted by Mark1990 View Post
    I agree that practically speaking as long as conductors are properly protected there is not a fire hazard etc. my main sticking point is if the job were to be audited by our fire insurance company or corporate for some reason I would like a code to reference that allowed a smaller than nameplate service. As everything I read in the code points to sizing the conductors and over current protection based on machine nameplate FLA.
    Got a letter/number punch set with a "." in it
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

  9. #9
    Join Date
    Feb 2003
    Location
    Wisconsin
    Posts
    10,349
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Mark1990 View Post
    As everything I read in the code points to sizing the conductors and over current protection based on machine nameplate FLA.
    I don't see a problem.

    NEC 2017
    670.3(A)(2) - nameplate must list the maximum possible overcurrent protective device.
    670.4(A) - The conductor sizing shall take into account the loads that will be connected at one time based on their duty cycle.670.4(C) the overcurrent device is sized to handle the full load current connected at one time.
    Just because you can, doesn't mean you should.

  10. #10
    Join Date
    Feb 2016
    Location
    Illinois
    Posts
    1,463
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by jim dungar View Post
    I don't see a problem.

    NEC 2017
    670.3(A)(2) - nameplate must list the maximum possible overcurrent protective device.
    670.4(A) - The conductor sizing shall take into account the loads that will be connected at one time based on their duty cycle.670.4(C) the overcurrent device is sized to handle the full load current connected at one time.
    And since it ran for 8 years without problems on a 30A ocpd, it will obviously handle the actual full load current.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •