Class 1 Division 1 - Would this work

[phsfrog]

I have taken all make or break contacts (including two automotive relays, a PLC, a fuse and a 12 volt PMDC motor) and mounted them in a box. This box is then turned on its head and placed in another box. The outer box is filled with commercial motor oil to seal the perimitter of the box containing the circuit. The only thing leaving this box are some wire leads to inert devices and 3 magnetic reed switches. This device is a self contained and self propelled and goes through a spray booth where solvents will be sprayed.

Will this oil seal, with it ability to separate the two environments, work for Class 1 Division 1 locations?

 

[rbalex]

While I believe this would even be suspect as a case for "Oil Immersion" (See the definition in 500.2), it is not a recognized Protection Technique for Division 1. See 500.7(I).

 

[phsfrog]

Bob:
Thats what I thought...Do you have any knowledge of why this would not be sufficient? No vapors can enter the container with Make or break contacts! Is there any way the spray booth can be classified as class 1 div 2? The spray booths are open on three of the four sides and the forth side is the power ventalation system. This is a high end product the explosive vapor levels I feel are minimal.

 

[petersonra]

why not just pressurize the box?

perfectly safe and simple technique for reducing the classsification of the volume inside an enclosed space.

 

[rbalex]

A Type X purge, as would be necessary in this case, is not very simple. See NFPA 496, Chapter 5 in general and Section 5.5 in particular.

As to whether the assembly described in the OP ?would work? ? I have no idea. An end-user made assembly of that type isn?t in the scope of the NEC.

Basically the NEC applies to field installations of electrical equipment and material recognized as suitable for the various installations listed in Section 90.2. Approved is a defined term, as are listed, labeled and identified. I?m noting this because I believe the key to the OP and the follow-up question may be in Section 501.115(A).

All installations must be approved. See Sections 110.2 and 90.4.

In Section 501.115(A) the assembly must simply be identified. Note from the definitions that identified does not necessarily require listing or labeling, although it is strongly implied in FPN. This was a big deal during the 1999 and 2002 cycles. The problem, of course, is that generally AHJs do not have the ability to ?recognize? unlisted or unlabeled equipment as suitable for Classified locations.

Bluntly, I?m not qualified in this case and I have no intention of ?blessing? the assembly described in the OP. However; several NRTLs are qualified to evaluate it. If the assembly will be constructed for many installations, it could well be worth the evaluation fee. If it is ?one-of-a-kind? it may still be. I don?t know the economics of the system.

 

[phsfrog]

Bob:
The system is on its way to New York for a second evaluation at a NRTL. I feel the system is completely safe for its application.

Are there many products that get listed that deviate from the standard that you know of? Thanks Scott

 

[rbalex]

...Are there many products that get listed that deviate from the standard that you know of? Thanks Scott

Actually - Yes. Technically you are dealing with ?Product Standards? rather than the NEC. Product standards are promulgated by many more organizations than the NFPA. (IEEE, NEMA, UL, etc.) While I am familiar with some of them, I?m certainly not an expert. (If you read my ?moderator? profile, you?ll see I?m a simple design engineer by trade and training) The NRTLs may evaluate products with any standard they believe is appropriate for the assembly. I?ve seen them get creative a few times. Remember they WANT you to be able to use your product.

 

[Rockyd]

Is there any possibility of building something OUTSIDE of the classified space, thus only having wires within the space? Couple of seal-offs, pipe,additional conductor length, and added time, could be cheap, in comparison to get a listing on your assembly.

500.7(I) doesn't look to help your efforts either. I'm not seeing oil immersion offered as a method of protection for C1D1.

Don't let the 25% fill, at a seal-off bite you.

 

[phsfrog]

Rockyd - what do you mean by the 25% fill, at a seal off? I am not familiar with this. Scott

 

[kameele]

Rockyd - what do you mean by the 25% fill, at a seal off? I am not familiar with this. Scott

maximum allowable fill at a normal seal is 25% (501.15(C) (6)) but you can also get 40% rated seals. (EYSX series, for instance)

Also, the use of motor oil seems like a bad idea, seems if it might be acceptable, it should be something like transformer oil. A second point is that 501.115 says that the contacts themselves be immersed in the oil, not the shole box they're in.

 

[petersonra]

A Type X purge, as would be necessary in this case, is not very simple. See NFPA 496, Chapter 5 in general and Section 5.5 in particular.

Its pretty simple if you buy a kit, UL listed and everything.

 

[rbalex]

Its pretty simple if you buy a kit, UL listed and everything.

Do you know what the requirements for a Type X purge are? If you did, I don't beleive you would make this statement.

 

[petersonra]

Do you know what the requirements for a Type X purge are? If you did, I don't beleive you would make this statement.

As a matter of fact, off the top of my head I do not. But the venders that put the kits together do. They have worked out all the details, and supply all the little parts needed, even the signs. It is much simpler to buy this kind of thing than to try and assemble it yourself.

It does not get much simpler than placing a P.O.

 

[rbalex]

As I said, if you knew the reruirements you wouldn't likely be making this statement. It takes a good bit more than a kit to be compliant.