Classified locations and wiring methods

[DavidA]

I have just found out that I need to get educated about classified locations and associated wiring methods in a hurry. Does anyone have any suggestions for education materials?

 

[qcroanoke]

I would start here:

http://forums.mikeholt.com/forumdisplay.php?f=73
What class an division do you need to get familiar with? Class I division1?
Class II division 1?
Chapter 5 Special Occupancies covers (classified) hazardous locations

 

[kwired]

If you have a place covered by 511 - 516 you can rely a little more on NEC - especially the handbook.

These places as well as others you need to familiarize yourself with 500-506 regardless, but should also find other documentation to help you. Do not classify the area yourself, have someone else classify it and install wiring accordingly to the classification. That someone else could be the AHJ, fire inspector, owners insurance underwriters, the engineer that made your plans, etc.

 

[DavidA]

It's industrial work in a food processing Mill. The classification is II, div 1 and 2. Up to this point in my career, I've never had to work in an area requiring classification so I'm completely unfamiliar with the wiring methods associated with these locations.

 

[rbalex]

If the location has already been classified, the acceptable wiring methods in Class II are listed in Section 502.10 for both Divisions 1 and 2. Read and understand Section 502.5 too.

For some instrumentation and controls, Article 505(oops) may apply as well. Be sure you have a control drawing if it applies.

Sealing isn't quite the same issue as it is in Class I (502.15); that is, you are trying to keep dust out rather than containing an explosion.

Grounding and bonding is critical (502.30).

 

[kwired]

It's industrial work in a food processing Mill. The classification is II, div 1 and 2. Up to this point in my career, I've never had to work in an area requiring classification so I'm completely unfamiliar with the wiring methods associated with these locations.

If it is food processing area it is likely washed frequently. That may be enough to keep it from being classified, really depends some on the dust. I would not be the one that classifies it. The owner, owners insurance, fire inspector, or someone else will need to determine if this is a classified location.

You could easily have more trouble with sources of ignition in mechanical equipment than from electrical. Hot bearing = potential ignition source if dust accumulates on surfaces that will be hot.

 

[rbalex]

Good housekeeping indeed makes a significant difference in classifying a Class II (or III) location. My personal experience in food milling processes, especially sugars, can reach “hazardous” fairly quickly while the process is active. Mechanical sources of ignition also need attention, but tha tis where the health department usually keeps active tabs on cleanliness, often to the point where the equipment isn’t permitted to be directly exposed to the product.

My impression from subsequent responses of the OP is that the act of classifying the location has already occurred and he was seeking information on suitable installation techniques.

 

[DavidA]

For me it looks like the biggest change will be using type MI cable for motor terminations rather than LTMF. As I don't think a 3 phase 480v motor qualifies as being nonincendive.

 

[rbalex]

Not that there is anything wrong with using MI, but how did you arrive at the conclusion that it is required for motor terminations? "Nonincendive" has nothing to do with it.

MI may be required for certain food processing locations, but it isn't an NEC issue.

 

[DavidA]

Well, I just spotted the reference to flexible connections and zeroed in on that (2008) 502.10(B)(2). As I'm sure I mentioned somewhere in here I am completely ignorant of wiring methods in classified locations and am just making a shot in the dark as I read through the code. I didn't see LTMF as one of the approved wiring methods but saw MI under flexible connections. I am completely open to suggestion on this one as to methods of getting from RMC to a motor. I see that type TC is listed as an approved wiring method but I don't know if I can use that (with the appropriate connectors of course) in place of MI.

Okay, I'm begging now. What would be some other approved methods for connecting motors in a Class 2 Div. II area?

 

[rbalex]

Well, I just spotted the reference to flexible connections and zeroed in on that (2008) 502.10(B)(2). As I'm sure I mentioned somewhere in here I am completely ignorant of wiring methods in classified locations and am just making a shot in the dark as I read through the code. I didn't see LTMF as one of the approved wiring methods but saw MI under flexible connections. I am completely open to suggestion on this one as to methods of getting from RMC to a motor. I see that type TC is listed as an approved wiring method but I don't know if I can use that (with the appropriate connectors of course) in place of MI.

Okay, I'm begging now. What would be some other approved methods for connecting motors in a Class 2 Div. II area?

How about LFMC? [Section 502.10(A)(2)(2) as referenced in 502.10(B)(1)(1) and 502.10(B)(2)]

 

[DavidA]

Which is just part of why I can't stand wading through the depths of the NEC. Thank you for opening my eyes...to the referenced section 3" away from the part that had me losing my mind.

 

[Strathead]

OP. One of the pitfalls of the NEC is that it does not generally tell you how to do something. It just give you parameters of a safe and hopefully functional installation and allows you to decide what materials methods and means are best suited for your exacgt situation. If you want to make informed decisions and sound like you know what you are talking about, start by understanding the classifications and how they are developed. Then the constraints of installation. Along with the first five sections of Article 500 in the NEC, I have found Crouse Hinds to have some of the more comprehensive information. I did a quick Google search and found this PDF, that has explanations and a quick diagram of a typical installation for different classified areas. Don't get hung up on this though. Learn the main reasons that each wiring method is used and if you think a wiring method will work and suits your installation, then research it and find out. Sealed cables that protect the conductors, but do not allow gas and/or solids to pass through are usually acceptable wiring methods for example. http://www.coopercrouse-hinds.eu/download/1/Crouse-Hinds_Code_Digest_2011.pdf

 

[renosteinke]

Class II? Dust? Piece of cake.

The main concern is that nothing get hot enough to ignite the dust that's piles atop it. Most TEFC motors are rated for such use.

You'll probably encounter more problems with this being a 'food' site. USDA has all manner of concerns. In practical terms, it means everything is mounted somewhat off the wall (for cleaning and to prevent goop from accumulating), and that it be able to withstand the rather harsh chemicals used for cleaning and sanitizing. Again, in practical terms, that means using Noalox on your threads- and NO aluminum.

 

[kwired]

OP. One of the pitfalls of the NEC is that it does not generally tell you how to do something. It just give you parameters of a safe and hopefully functional installation and allows you to decide what materials methods and means are best suited for your exacgt situation.

Some may call that a pitfall, others see that as a way of having more options. What if NEC told you exactly how to do things - you think you would have many options of how to do things?

Class II? Dust? Piece of cake.

The main concern is that nothing get hot enough to ignite the dust that's piles atop it. Most TEFC motors are rated for such use.

You'll probably encounter more problems with this being a 'food' site. USDA has all manner of concerns. In practical terms, it means everything is mounted somewhat off the wall (for cleaning and to prevent goop from accumulating), and that it be able to withstand the rather harsh chemicals used for cleaning and sanitizing. Again, in practical terms, that means using Noalox on your threads- and NO aluminum.

Could also mean use PVC, PVC coated rigid, or stainless rigid. Frequent washing may change things from Class II to non classified.

 

[Strathead]

Some may call that a pitfall, others see that as a way of having more options. What if NEC told you exactly how to do things - you think you would have many options of how to do things?

I would actually classify as both, depending on the section and the application