Motor rating in hazardous location

[Rhumb]

An interesting debate has gone on between me and one our electrical engineers, and I am hopeful someone can affirm either side.

Can a Class 1 Div1 group D motor be used without issue in a Class 1 Div 2 Group C+D rated environment? One point of view is that the Div. 1 requirement is more stringent, and therefore exceeds the Div 2 requirement, regardless of Group. My thought is that the group classification indeed is important, and we cannot simply infer that the Div 1 protections are sufficient for all gas groups. For example, I would have a really hard time putting a Div 1group D rated motor in a Div 2 group A rated environment.

Thank you for your thoughts-

 

[don_resqcapt19]

If the motor is a standard motor without heaters or arcing contacts there in no need of a special rating on the motor for a Class I, Divison 2 application.

501.125(B) ... In Class I, Division 2 locations, the installation of open or nonexplosionproof enclosed motors, such as squirrel-cage induction motors without brushes, switching mechanisms, or similar arc-producing devices that are not identified for use in a Class I, Division 2 location, shall be permitted.

 

[Rhumb]

Group effect-

Group effect-

Thanks very much Don for the response, it is very good information.

However, the discussion does center around motors with brushes, and particularly the way gas group protections are handled. Does the code specify that if an area is rated for example Class 1 Division 2 Group C and D that all electrical components must at least meet the Group C specification, regardless if the protections are more stringent for division 1 areas? Let me propose the following to see if it illustrates a misunderstanding-


Class 1 Div 1 Group D
Class 1 Div 2 Group A
Class 1 Div 2 Group B
Class 1 Div 2 Group C
Class 1 Div 2 Group D

Are these ordered in descending order of protections? No one would argue that a component rated for group A would be perfectly suitable in a Group D environment (although I am not sure the Code specifically indicates such). But does that hold true as the division rating changes to a 'stronger' protection than required by the classification of the area it is going into; but the group requirement of the area becomes stronger than the group rating of the component?

Thank you very much-

 

[rbalex]

Group is indeed important. See Subsection 500.8(A)(2). You might want to read all of Section 500.8 for that matter.

I'm curious; do you actually have a Class I, Division 1 motor that is only suitable for Group D?

 

[Rhumb]

Motor Class

Motor Class

Yes indeed - we ran into an issue due to having the motor only available as class 1 div 1 group D. I have found that this occurs more frequently with inverter duty motors. O[ne vender of a pump I was sourcing indicated that obtaining the C+D rating would be a special order and a 12 week lead time item.]

example, Baldor: pg. 21 of their XP catalog
http://www.baldor.com/pdf/literature/BR454_0506_WEB.pdf

I have seen this with Leeson as well, among others. It is a fun game to try to spin the wheel and get the right HP, motor mounting, voltage, hazardous area classification, and then try for the quinfecta of inverter duty. I am overstating the challenge a bit, but occasionally due to the requirements, these may not be stock motors.

Thank you for your comments, I will review the noted section of the code.

Best regards- CR P.E.