The project I am doing was visited by the Electrical Engineer today and he stated that I need bonding bushings on ALL concentric / eccentric knockouts regardless of voltage. He says this is code, I can only find where they are required over 250 volts to ground. I also have 6 transformers on the project. I ran Emt to within aprox. 4 feet then changed over to greenfield using a 90 degree fitting into the side of the transformer. He says that this no longer allowed that I am supposed to pipe them in hard.( Emt right into the transformer) I have always used a short run of flex ,due to vibratation. Been doing it this way this for 23 years. There is a room where there will be oxygen bottles stored and attached to a distribution manifold. He has speced out standard receptacles , light switches, and surface mounted strip lights. I asked him if this room should be class 1 division 2 ? His response ... a blank stare then he said no it's no problem.
What do you guys think ?

I'm only going to comment on the Classified Area part of your question, I'll leave the rest to others.

The presence of oxygen does not create a classified area. You may have gotten the blank stare because oxygen is not a flammable gas... it is an "oxidizer." Meaning that it would support or contribute to a fire in the presence of a flammable/combustible mixture (gas/vapor/dust).

[Edited to remove confusing reference see later post for more information]

That's the short answer to this part of your question, let me know if you want the long answer.

[This message has been edited by safetygem (edited 01-28-2005).]

What? General purpose equipment in Class 1 Div2?


501-12. Receptacles and Attachment Plugs, Class I, Divisions 1 and 2
Receptacles and attachment plugs shall be of the type providing for connection to the grounding conductor of a flexible cord and shall be approved for the location.

(b) Class I, Division 2. Switches, circuit breakers, motor controllers, and fuses in Class I, Division 2 locations shall comply with the following:
(1) Type Required. Circuit breakers, motor controllers, and switches intended to interrupt current in the normal performance of the function for which they are installed shall be provided with enclosures approved for Class I, Division 1 locations in accordance with Section 501-3(a), unless general-purpose enclosures are provided and
a. The interruption of current occurs within a chamber hermetically sealed against the entrance of gases and vapors, or
b. The current make-and-break contacts are oil-immersed and of the general-purpose type having a 2-in. (50.8-mm) minimum immersion for power contacts and a 1-in. (25.4-mm) minimum immersion for control contacts, or
c. The interruption of current occurs within a factory-sealed explosionproof chamber approved for the location, or
d. The device is a solid state, switching control without contacts, where the surface temperature does not exceed 80 percent of the ignition temperature in degrees Celsius of the gas or vapor involved.

........Just to name a couple

(250.96) if knockouts loose and not making a good bonding connection. If knockouts in good shape I;d say not under 250 volts. Over 250 volts (250.97). In classified areas then 501.19a applies.

Sorry its 501.16a in last post not 501.19 slip of the finger on the keyboard.

Before I go on, there may be other reasons for the engineers approach that we can not see, that make the way described the best and only proper way. Ask.

Or it could be in the project specs and miss-communication has us hear the word "code" not the intended wored "specs". You should check the specs to see if they require things done this way. If you did not receive any specs, check with the general to make sure they just did not pass them on.

Lastly (Heaven Forbid!) we engineers can get stuck, due to lack of field experience and training, thinking that because we were taught by our mentor that things are this way (and they never mention that it is the way they like it and call for it in some other project specs) and we never bother to go to code or the specs to check it out. (Look into the story about the wife who always cut off the ends off the roast before cooking.)

P.S. Next time you are in a code class look around, there will probably be one of us engineer types learning along with you. And personally, I am very impressed with engineering types that are at this site and hope that in 14 years (I am half way to retirement) that I can have the knowledge level that they show.

Shane P.E.

Shane - trust me I have nothing but respect for the engineers. I have read my specs for this project, that is one of the first things I do. Then I make a list of anything that is out of the " norm" to keep in the office trailor. The main thing that I question would be the oxygen room and the transformer connections. I really try and do it right the first time and hate to re-do things.This is my concern for thge room, I do not want to have to redo it after pulling wire and installing everything. We only make money the first time we do it. I can never figure out why guys try and cheat in the name of time. Why is there always enough time to do it right the second time ?

After some thought...I did read this post when it first came out....I can only conclude that your "engineer" is (to put it nicely) out of his depth, and uninformed. I'd look to the project manager, inspector, etc. to rein this college boy in!

That said, I would suggest that the presence of oxygen MIGHT lead to a very hot fire, so his concern ought to be on sealing penetrations.

Finally, you might very well be in a position where you, not he, is the defined expert. That is a matter of local contracting law.....can he pull a permit, sign off on electrical prints, etc? Does he belong to the NFPA, IAEI, etc? Has he passed any competency exams (and I DON'T mean the PE test)? Just where, pray tell, did he get his code expertise?
At the minimum, call him on his assertions, and have him show you where the requirements come from. If it's just something he "wants," well, that's what change orders are for!

electure wrote:

I apologize for potentially creating some confusion. I just want to clarify my position. (This time you get the long version... yet still incomplete version.)

As I said in my post I was giving the short answer, but, it seems that the short answer may have given an incomplete understanding of the code requirements.

Luckyshadow specifically you were asking about a room with an oxygen cascade and your concern that it may be a Class I Division 2 area. You did not give us any information concerning the occupancy of the building or the presence of other hazards, so, we are left with applying very generalized requirements.

Actually this is three questions in one:
1. Does the presence of oxygen create a classified area?
2. If it does create a classified area, what Classification category is applied to the area?
3. If this is a Class I Division 2 area, is general purpose equipment appropriate for installation? Your examples of concern include receptacles, light switches, and surface mounted lights.

Before I answer the question it is important to explain a basic ground rule for the use of the NEC in classified areas. The NEC is not a classification document. You apply the NEC after consulting other documents that classify areas. Once you determine the type of area based on the appropriate standard or recommended practice, the NEC is used to determine the installation method and equipment that is appropriate for the area.

In order to apply another document (standard or practice) and actually determine the classification, you need to know the occupancy of the structure and what NFPA documents may apply. Or, you follow the general guidelines in the FPN that is at the beginning of Article 500.

A few other documents that need to be consulted include:
NFPA 30, Flammable and Combustible Liquids Code
NFPA 30A, Code for Motor Fuel Dispensing Facilities and Repair Garages
NFPA 32, Standard for Drycleaning Plants
NFPA 33, Standard for Spray Application Using Flammable or Combustible Materials
NFPA 34, Standard for Dipping and Coating Processes Using Flammable or Combustible Liquids
NFPA 35, Standard for the Manufacture of Organic Coatings
NFPA 36, Standard for Solvent Extraction Plants
NFPA 45, Standard on Fire Protection for Laboratories Using Chemicals
NFPA 50A, Standard for Gaseous Hydrogen Systems at Consumer Sites
NFPA 50B, Standard for Liquefied Hydrogen Systems at Consumer Sites
NFPA 51, Standard for the Design and Installation of Oxygen-Fuel Gas Systems for Welding, Cutting, and Allied Processes
NFPA 51A, Standard for Acetylene Cylinder Charging Plants
NFPA 52, Compressed Natural Gas (CNG) Vehicular Fuel Systems Code
NFPA 54, Natural Fuel Gas Code
NFPA 58, Liquefied Petroleum Gas Code
NFPA 59, Utility LP-Gas Plant Code
NFPA 59A, Standard for the Production, Storage, and Handling of Liquefied Natural Gas (LNG)
NFPA 61, Standard for the Prevention of Fires and Dust Explosions in Agricultural and Food Products Facilities
NFPA 85, Boiler and Combustion Systems Hazards Code
NFPA 88A, Standard for Parking Structures
NFPA 88B, Standard for Repair Garages
NFPA 99, Standard for Health Care Facilities
NFPA 407, Standard for Aircraft Fuel Servicing
NFPA 409, Standard on Aircraft Hangars
NFPA 480, Standard for the Storage, Handling, and Processing of Magnesium Solids and Powders
NFPA 481, Standard for the Production, Processing, Handling, and Storage of Titanium
NFPA 495, Explosive Materials Code
NFPA 496, Standard for Purged and Pressurized Enclosures for Electrical Equipment
NFPA 497, Recommended Practice for the Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas
NFPA 499, Recommended Practice for the Classification of Combustible Dusts and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas
NFPA 651, Standard for the Machining and Finishing of Aluminum and the Production and Handling of Aluminum Powders
NFPA 654, Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids
NFPA 655, Standard for Prevention of Sulfur Fires and Explosions
NFPA 820, Standard for Fire Protection in Wastewater Treatment and Collection Facilities

Based on the limited information given, here are some additional points concerning my post. Again, this is a summary, we don't have time or space for a complete discussion on the classification of spaces, that's part of a five day course offered by NFPA.

Question #1
Does the presence of oxygen create a classified area?
Answer
No. Oxygen is a non-flammable gas. While it may increase the chances for an explosion or fire in the presence of a flammmable or combustible vapor/gas/dust mixture, the presence of oxygen in an area does not itself require explosion proof electrical wiring methods. (Article 500.6) bold added
The NEC Handbook offers guidance on the hazards of oxygen.

So... unless there are other materials present or expected in the future at this project. The area with oxygen is not classified.

Question #2
If it does create a classified area, what Classification category is applied to the area?
Answer
This point is moot based on my answer to question one.

Question #3
If this is a Class I Division 2 area, is general purpose equipment appropriate for installation? For example, receptacles, light switches, and surface mounted lights.
Answer
The basic question of classification has been answered for this circustance. But, let's go out on a limb here and assume that there is something else (other than oxygen) that would cause this are to be classified as Class I Division 2, can you use "general purpose" equipment in this type of area?

Yes (sometimes). I should have prefaced (but in the interest of brevity originally I left it out) that Class I Division 1 always requires explosion proof equipment... and/or adequate ventilation. Class I Division 2 may require explosion proof equipment, but, often you can use general purpose equipment. Particularly for boxes and fittings. For example, Article 500.8(A)(3) allows the use of general purpose equipment.
The NEC Handbook explanation of one of these circumstances:

A similar allowance to the above also exists for luminaries in 70-2005, 500.130(B)(1)
Which means... if you don't exceed 80% of the temperature of the gas/vapor in the area ((and we do not apparently have a flammable gas or vapor) then you can use general purpose lighting.

The 2002 NEC Handbook (soory don't have the new handbook yet) also provides the following explanation of the hazards involved with fuses and/or circuit breakers in a Class I Division 2 location:

Obviously, while on its face this post may seem to pose simple questions there are in fact no simple answers... especially without more information.

BTW, nobody (with the exception of Yoop) seemed to fully give their opinion on any of the other issues that were not related to the classification of the space. Let's step up and give the guy an opinion on let's say the use of the greenfield (FMC). I don't see anything that prohibits it, but, what do you guys think?

I'm not an engineer, but, let's not bash the comments of the engineer without more background. Maybe he's right... then again maybe he's wrong. We really don't know.

I do agree that you should always question something if it doesn't seem right... and make the person that is giving you the information back it up with documentation. If they can't or won't, then ignore them and move on...

Lucky... you seem conscientious and that's always commendable.

[This message has been edited by safetygem (edited 01-28-2005).]

Safetygem, now this is a guy that knows his O.

The only question I have on that great post, is the point of Oxygen being an accelerant?

I somehow remmember a fireman telling me one time that Oxygen was an accelerant.
If this is true, wouldn't that in considerable amounts be enough to reclassify some divisions or areas to another?
(mind the spelling on accelerant, prob wrong)

Once again, great response.


Dnk....

Just exactly what (how much)did you edit?
Do you really think any one will buy all of these NFPA documents?
Even if you're a member and can access them free, who but an attorney (with their support staff) would try to research every standard you provided?

I simply ask that answers be practical and somewhat (I know this can be relevant)concise


Roger

Dnkldorf
Thanks for the kind words. Let me take a stab at a “short” answer to your question about oxygen as an accelerant.
Oxygen is not technically an "accelerant." An accelerant is:
Typically, the use of the word catalyst in the above definition refers to a source of fuel. Oxygen is not a fuel. However, oxygen is required for a fire to happen. In fire engineering there is a concept called the "fire tetrahedron." This concept is used to explain that for any fire to occur there must be four elements present: Fuel, Heat, Oxygen, and an uncontrolled chain reaction. If you can remove (or control the presence) of one of these four elements, a fire will not occur or will be extinguished. The firefighter was probably simplifying this for purposes of explanation.

An Oxidizer for the record is:
So… oxygen must have a source of fuel to initiate or promote a fire. If there is a sufficient fuel source present or expected to be present then yes, it would be prudent to possibly classify the area. You have to have an adequate level of fuel present not just “some” fuel.

Ahh but my post is getting long again! Which brings me to Roger’s comments.

Roger
Not much, but, when you are trying to type everything in the teeny tiny box, it gets confusing. After posting and rereading, I decided the add everything starting with the BTW near the end of the post.
Sorry, I honestly didn’t expect the post to go on… and on… and on. It just kinda’ snowballed, hey it is winter here in the great state of OHIO.
I guess I was trying to make a point by including all of the document titles. I would expect an Electrical Engineer or other “design professional” to research the appropriate document. Since many (but not all) of people that visit this site are Electrical Contractors, I would expect that if you are doing design work… then yes… I would expect you to get the document… review it… apply it. If you are only working off of someone else’s specs or prints… heck, let them pay for the documents and the time doing the research.
Sorry, but, just being a member doesn’t get you “free” access to the standards.
However, members do get “free” access to the on-line version of the NEC.

Edited to correct two code errors.

[This message has been edited by safetygem (edited 01-29-2005).]

After reading such a fine response from safteygem, I was a bit surprised to see that response, let alone from a moderator. Maybe it was meant differently.

I think the point that was well made is that the EE is considering alot more things that just the NEC when he/she specifies something, and that's why they are a critical part of the process. Makes me glad I don't have to research it, and now I know the extent to which I am relieved.

Thanks for the great responses as to the oxygen question ! I have talked with the owners of the building ( state of maryland prison system ) , the general contractor, and am awaiting a reply from AHJ, and we are going with the engineers thought and if it needs correcting it will be on his time.
Safetygem - the room is in a new building at a maximum security female prison, it is located off a corridor the seperates medical/dental and security.
As to flex (FMC) into transformers - can't find anything about this in NEC so I'm keeping it the way I feel is best ( AHJ has approved this method )

Jps, I think you may indeed have taken it wrong.

But since we're here let me ask you this, would you take the time (I know you said you're glad you don't have to) to research all these standards for one specific item?

Now for my comment to the engineers request.

If he had not specifically called out for a method in his spec and only mentioned "Per the NEC and all applicable codes" in the opening of his spec, I would ask for a change order to provide anything above and beyond them.

Now, if this oxygen storage area has been deemed as a non classified room by an Architect under an AIA design, and the engineer based his design around it, all is probably fine.

I don't know about Luckyshadow's location, but in my area plan review would have questioned it also.

Roger



[This message has been edited by Roger (edited 01-30-2005).]

Lucky,
You may truly be "lucky" as to the transformer question.
I also learned, and as a habit also, to connect transtormers to conduit with some form of "flex." This was clearly taugh to me, when I was an apprentice, as a "trade practice," and not a code requirement.
Yet I have noticed, on the last few transformers I've installed, that the instructions referred to loosening some internal bolts...seems that the coils are mounted on rubber pads, that are compressed for shipment! So the flex is probably redundant.

It is that transformer comment of the engineer's that helped me decide that he has NO trade experience, is out of his depth, and needs to be reined in. I just don't believe the engineer is qualified! (Having three years, including time at one of the "premier" schools, I know all too well that engineers, including "electrical engineers," graduate without having the slightest educations in matters electrical!)
Not to denigrate engineers, but their trade is quite different that that of an electrician (just as a 'mechanical engineer' doesn't learn squat about fixing cars).

No Rodger, I wouldn’t take the time nor would I think it was part of my job description as an electrician. Had I thought that was what he was suggesting by the post, I suppose I too would have felt the response was impractical. I appreciate the list, however, as an example of the breadth and depth of issues involved in just determining how to properly classify an area. As an EC, even though I may have a slight edge on the EE in NEC, it’s a little humbling to see how much I don’t know about the given situation. There is a lot more to consider than just NEC, and now I know how much more.

FYI, many public libraries and most Fire Departments have current copies of the various NFPA codes, and (the FD's at least) will be happy to let you review them during "business hours" ie 0800-1900.

Just my $0.02

Hi,
I think he may be confusing that Grounding bushings are required on concentric/eccentric knockouts when used on a SERVICE.

I will have to dig up the article but I know a lot of inspectors who will not pass an inspection for this.

Look at 250.92 (B) last paragraphs.

I will see if I can find the reference in Stallcups Designing Electrical systems and the code...I know I saw that somewhere.

As far as the oxygen question, just consider this...how many places is oxygen bottles used? HUNDREDS IF NOT THOUSANDS. They are in bedrooms, cars, planes, trains, submarines, etc. Are there any classified equipment installed there?

Anytime this situation comes up just get up with the engineer with a code book in your hand. Say to him...” I was looking in my code book to see if I could find the reference you were making and was not able to find it...would you mind showing me where it is or getting me the article so I will know for future reference?"...

As far as flex to a transformer...that is first year apprentice stuff. Flex is used to feed small transformers for a couple reasons, one is to makes it easier to connect, disconnect, replace etc. I am not so sure I buy into the vibration theory. The transformer itself will be constructed of regular nuts and bolts for the most part.

Hard piping in a transformer is okay when you’re talking a big transformer but for a small one flex is the only way to go. If flex was not legal for connecting motors and transformers anymore it would have been heard like a shot around the world! Just think of the millions of connections that are already out there!

Just my 2 cents worth of bytes.

Regards

Greg

Common sense prevails a lot of times, not to knock any of the other responses.

There are specific ways to determine a classified location and NFPA 30 is a good place to start.

Regards

Greg


[This message has been edited by mustangelectric (edited 02-05-2005).]

luckyshadow ---

Oxygen is one of the most dangerous substances about.

Self-exstinguishing materials will burn or explode in just several pounds of additional oxygen pressure.

It is not my project so I will let you do what you wish.

Hi,
Here is another fact about oxygen.

The most abundant element in the earth's crust is oxygen (49.5%), and air contains about 21% oxygen.

Does that mean that everything around us is 70.5% OXYGEN? Oh and water has two molecules of it too.

I would say the biggest concern is securing the bottles and transport.

Regards

Greg



[This message has been edited by mustangelectric (edited 02-05-2005).]