Interpretation of NEC Code for Conduit Seals in Div 2 areas 1

[Bloozntooz7868]

Sorry for the lengthy write up on a comparatively simple issue, but I want to provide all the info up front. I have tried to find this answered in other threads but found none that address this precise question.

As a European, I need a little advice on the interpretation of the NEC code for conduit installations on explosionproof equipment installed in Class 1 Division 2 areas:

NEC 501.15(B) states the following:
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(B) Conduit Seals, Class I, Division 2 locations, conduit seals shall be located in accordance with 501.15(B)(1) and (B)(2).
(1) Entering Enclosures. For connections to enclosures that are required to be explosionproof, a conduit seal shall be provided in accordance with 501.15(A)(1)(1) and (A)(3). All portions of the conduit run or nipple between the seal and such enclosure shall comply with 501.10(A).

In Class I, Division 2 locations, a seal is required in each conduit entering an enclosure that is required to be explosionproof, in order to complete the explosionproof enclosure.
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Now it is this part about "...connections to enclosures that are required to be explosionproof..." that I am unsure about, as the ramifications are pretty huge for the site I am working on.

I am thinking there are 2 ways of approaching this:

1) If I am using a certified explosionproof box then this automatically means that it "requires to be explosionproof" otherwise why would I be using it?

or

2) There is only a requirement that it is explosionproof if there are arcing/sparking/hot surfaces (ignition sources) that are used in it.

The latter one is what is stated in NEC Code 501.15(A) for the more onerous Div 1 areas, but the same explicitness used in the Div 2 narrative. Depending on the outcome, there may be hundreds of locations (certified field pushbutton stations / switches etc) that require retrofitting with seals, so it's something I need to be sure about before elevating this issue.

Can anyone provide clear guidance?
Thanks.

 

[rbalex]

1) In Division 2, simply using an explosionproof enclosure does not necessarily require it to be one. Seals are not necessary if the equipment isn't required to be explosionproof.

2) This is correct conceptually, but is more based on whether equipment described in Article 501, Part III (Sections 501.100 and following) are required to be. Note, not all equipment described in the Division 2, parts of those sections require explosionproof enclosures.

 

[Bloozntooz7868]

Thank you rbalex,

Having read 501 Part III I am still not convinced that this has answered what I was after. It appears to only be concerned with how the various equipment should be housed (either in a CL1 Div1 marked enclosure or in a general purpose enclosure if the ignition elements are individually certified), and not how they should be connected to other equipment.

I have, typically, the same equipment as shown in picture 'exhibit 501.17' on the same page - Appleton pushbutton or isolation switches. These are factory CL1 Div1 certified enclosures with an ignition source inside (i.e. the switch/pushbutton), and the conduits run from it to lighting fixtures and Panelboards etc, without any seals.

With regards to this being a Div2 area, are seals required?

Thanks again.

 

[rbalex]

I don't want to confuse the issue more, but I don't know what the reference to "'exhibit 501.17' on the same page" refers to. I couldn't find an antecedent reference in your previous or current posts.

By the way, I am citing the 2011 NEC.

This may seem convoluted, but we may as well begin as close to the beginning as we can:

1. Division 1. Baring installations covered by Article 504, all enclosures in Division 1 are required to be "approved for Class I, Division 1". [Section 501.10(A)] For all practical purposes within the scopes of equipment you have mentioned so far, this means explosionproof. However, not all explosionproof enclosures in Division 1 are required to be sealed. [Section 501.15(A)(1)(2)] That is, where the conduit entry is less than 2" OR only contains "terminals, splices, or taps", the enclosure is NOT required to be sealed, even though it is explosionproof.

NB: Unlike IEC/EN/CENELEC, "terminals, splices, or taps" are not considered to be arcing in the NEC, nor are they required to be effectively "Ex e" - no matter what type of enclose they are in.

2. Division 2. Not all enclosures are required to be explosionproof [Section 501.15(B)(4)]; however, those that are, are required to be sealed - just as if they were in Division 1. [Section 501.15(B)(1) which cross references back to 501.15(A)(1)(1)]

Now, Section 501.15(A)(1)(1) Exception also applies to Division 2 enclosures by virtue of the cross-reference in Section 501.10(B)(1).

So, with respect to the switch/pushbuttons, Section 501.15(A)(1)(1) Exception (3) may apply depending on whether the units are "factory sealed" or not. If they are "factory sealed", no additional seal is required for that specific enclose.

I referred to Article 501, Part III because it describes various types of Division 2 enclosures that may be required to be explosionproof. The general format is Section 501.1xx (B) for Division 2 applications. Section 501.105(B)(1) would generally be applicable to switch/pushbuttons. Again note the cross reference back to 501.15(A)(1)(1) Exception via the cross reference to 501.15(A).

 

[rbalex]

My interpretation of Section 501.15(A)(1)(2) may be misleading. I should have said something like IF 501.15(A)(1)(1) doesn't already apply THEN where the conduit entry is less than 2" OR only contains "terminals, splices, or taps", the enclosure is NOT required to be sealed, even though it is explosionproof.

Some enclosures may be nothing but pull points. They must still be explosionproof but unless the conduit entry is 2" or greater AND contains "terminals, splices, or taps", the enclosure is NOT required to be sealed,

 

[Bloozntooz7868]

You haven't confused anything rbalex - you have provided me with the path to enlightenment!

Although I was reading the exception rule it (obviously) hadn't sunk in with me. I have done a sweep of the site and found that although corroded, the pushbutton stations etc are all marked 'Factory Sealed' except for a few locations where there are definitely issues with the installation. Article 501.15 (A)(1)(1) point 3 is applicable.

Thank you very much for your time and detailed explanations - it got me on the right track and averted a personal embarrassment if I had raised the issue up as a general code violation.

Thanks again.