CID2 conduit to cable tray transition

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Jim1959

Senior Member
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Longmont, CO
It's common practice to adapt from CID2 rated tray cable in cable tray to tray cable in conduit but seems like the conduit should be sealed where this is done.
Help me understand how this open ended conduit in a hazardous area is acceptable.
 
See Section 501.15(B)(2) Ex No. 2. IF in the case both the conduit and tray are in the same Division 2 location (i.e., Ex No. 2 doesn't apply) THEN there is no boundary AND no seal is required for boundary purposes.
 
(2) Class I, Division 2 Boundary. A conduit seal shall be
required in each conduit run leaving a Class I, Division 2 location.
The sealing fitting shall be permitted to be installed on either
side of the boundary within 3.05 m (10 ft) of the boundary and
it shall be designed and installed to minimize the amount of gas
or vapor within the portion of the conduit installed in the Division
2 location that can be communicated beyond the seal.

I'm not referring to a boundary seal, but how it can be acceptable to have an open ended conduit at the cable tray transition within the CID2 area.
Seems like the same issue of vapor entering the conduit is valid.
 
If is isn’t a boundary seal, what you highlighted doesn’t apply. However, for practical purposes, what would a seal accomplish in an open transition since the seal would be bypassed in the first place?
 
Your thoughts are certainly reasonable and consistent with Section 501.15 IN No.1. The IN doesn’t speak to the philosophical differences between Divisions 1 and 2 though.

In Division 2 there shouldn’t be any gases to migrate in the first place AND should they appear a boundary seal won’t do much good in most cases since it would readily be bypassed in the open air. This is the reason there are so many Exceptions to Section 501.15(B)(2). The fact is, in most cases Division 2/Unclassified boundary seals are unnecessary. The places they are useful is where there is a significant positive pressure in the Division 2 location with respect to the unclassified location AND the unclassified location would be likely to collect the gases. Another example is where the gases are heavier than air and the conduit is a stub up at grade.

Not a big deal, since I don’t know what’s actually in it, but I’d question using an explosionproof “X” in Division 2. If it needed to be explosionproof is should also be sealed. [Section 501.15(B)(1)]

Filling the conduit ends with duct seal is probably an unnecessary response to the last sentence in Section 501.15(B)(2).
 
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