IEC309 Plug/Receptacle on load side of Motor Starter

[Codemaster]

I would like to install a 480V, 3ph, 60A, 40hp rated IEC receptacle on the load side of a 100A CB, IEC 60A contactor, and 23-75A adjustable electronic overload for a 30hp motor. I have used receptacles many times to feed portable motor loads that have a portable motor starter on them, but this is the first time that the motor starter is fixed and the motor is portable. I didn't see anything in the NEC that specifically prohibited this practice. My concern is that someone could accidently plug in a non-motor load or even a smaller portable motor. The overloads set at 40A for a 30hp motor would trip faster than a 60A circuit breaker would, but of course it still might not meet NEC. I am not certain if 1999 210-21(b)(1) or Table 210-24 applies in this circumstance. I don't see much is 430 regarding receptacles. Any comments?

 

[jbartos]

Suggestion: The current electrical code is NFPA 70-2002. The
The following table applies:
Table 210.24 "Summary of Branch-Circuit Requirements" applies.
Section 210-21(B)(1) Single Receptacle on an Individual Branch Circuit.
A single receptacle installed on an individual branch circuit
shall have an ampere rating not less than that of the branch
circuit.
Exception No. 1: A receptacle installed in accordance with
430.81(C). (This is not applicable since the motor is bigger than 1/3 HP or less portable motor.)

When it comes to a smaller load, it should have a smaller rated receptacle not possible to insert into 60A receptactle. If the smaller load has the 60A receptacle, it is at risk by the violation of the receptacle rating.

 

[Codemaster]

jbartos

Based upon your reply, my comments are then:
1) Is having the 100A circuit breaker (albeit with adjustable overloads) protecting a 60A receptacle in violation of 210-21(b)(1)?
2) A 20hp or 25hp load could be connected with a 60A plug to the setup that I described and this would be adjusted only for a 30hp motor (although the overloads could easily be adjusted for the smaller load).
3)I just finally ordered my 2002 code handbook so I wasn't sure if the code references were the same. Most jurisdictions are one or sometimes two code cycles behind the latest code (although designing to the latest code usually is fine, the rules usually don't get less restrictive).

 

[jbartos]

Suggestion to Codemaster (Electrical) Nov 13, 2002 marked ///\\jbartos
Based upon your reply, my comments are then:
1) Is having the 100A circuit breaker (albeit with adjustable overloads) protecting a 60A receptacle in violation of 210-21(b)(1)?
///Yes, since the following is from the NEC: (B) Receptacles.
(1) Single Receptacle on an Individual Branch Circuit.
A single receptacle installed on an individual branch circuit
shall have an ampere rating not less than that of the branch
circuit.
Exception No. 1: A receptacle installed in accordance with
430.81(C).
Exception No. 2: A receptacle installed exclusively for the
use of a cord-and-plug-connected arc welder shall be permitted to have an ampere rating not less than the minimum
branch-circuit conductor ampacity determined by
630.11(A) for arc welders.
\\2) A 20hp or 25hp load could be connected with a 60A plug to the setup that I described and this would be adjusted only for a 30hp motor (although the overloads could easily be adjusted for the smaller load).
///Assuming that 20hp motor draws 27A (NEC Table 430.150) and 25HP motor draws 34A (NEC Table 430-150), the 100A circuit breaker rating violates NEC Table 430.152 inverse time breaker maximum setting.\\3)I just finally ordered my 2002 code handbook so I wasn't sure if the code references were the same. Most jurisdictions are one or sometimes two code cycles behind the latest code (although designing to the latest code usually is fine, the rules usually don't get less restrictive).
///Those were those good old times when the next NEC issue had a couple of changes only. Nowadays, it is different.\\\

 

[Codemaster]

I would like to modify my question above.

Given the above IEC 309 receptacles, is it against the NEC to have some 30A and/or 60A receptacles that would be energized by motor starters and others of the same exact pin configuration that are always energized by feeder circuit breakers all in the same industrial facility? The receptacles energized by motor starters would be automatically controlled by PLC's and would be intended to be attached to a specific machine.

The closest mention that I could find to this interchangeability issue was 410-56(i), however this only refers to voltage and current rating, not method of energization or type of use. Obviously having these two uses for the same receptacle could cause confusion by operators in the plant, especially if the receptacles (and the plug) was not labeled properly for the intended use.

 

[busbar]

Manufacturers like Crouse-Hinds make specially keyed pin-and-sleeve plugs and receptacles that would be applicable to such a need. Careful "end user" [id est, production employees] supervision should not lapse, or they will surely try to use the sharp end of a forklift to try a get them to mate.

 

[peebee]

Why not just provide 100A wiring and receptacle?

 

[jbartos]

Suggestion: It appears that the simplest solution could be mechanical, namely, use a padlock at the receptacle and key attached to the cord for the appropriate machine to plug to the appropriate receptacle.