Interpretation of 501.15(E)(1) and 501.15(E)(3)

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I have a question regarding sealing multi-conductor tray cables in Class 1 Division 2 locations.

I believe that the multiconductor tray cable I am using contains a "gas/vaportight continuous sheath capable of transmitting gases or vapors through the cable core". One end of the multi-conductor tray cable terminates in an enclosure outside the Class 1 Division 2 area. The other end terminates in a junction box inside the Class 1 Division 2 area. Note: the junction box inside the C1D2 area is NOT explosion-proof.

NEC 501.15(E)(3) - seems to speak to "CABLES" and states "....shall NOT be required to be sealed except as required in 501.15(E)(1),...."

NEC 501.15(E)(1) - The first sentence of 501.15(E)(1) seems to address terminations in explosion-proof enclosures. The third sentence in 501.15(E)(1) speaks to "MULTICONDUCTOR CABLES with a gas/vaportight continuous sheath capable of transmitting gases or vapors through the cable core shall be sealed in a listed fitting in the division 2 location...."

Additionally, the NEC 2005 Handbook "Commentary Table 5.3" seems to indicate that cable seals in C1D2 areas ARE REQUIRED for "MULTICONDUCTOR CABLES with a continuous sheath capable of transmitting through the cable core", but are NOT required for "CABLES with a continuous sheath capable of transmitting through the cable core.

Is the distinction between tray CABLES and MULTICONDUCTOR tray cables intended?

Does the third sentance of NEC 501.15(E)(1) deal with terminations in explosionproof enclosures only or is it intended to be more broadly interpreted?

Would the multiconductor tray cable installed in the non-explosionproof junction box inside the C1D2 area require a cable seal?
 

rbalex

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This reply assumes the multiconductor cable is not also in a raceway as it enters the enclosure; otherwise, see the last sentence in 501.15(E)(1).

Note, UL specifically states in their Information Guide:
Regarding cable seals outlined in Article 501 of the NEC, Type TC cable has a sheath which is considered to be gas/vapor tight but the cable has not been investigated for transmission of gases or vapors through its core.
Assuming only a cable installation, 501.15(E)(3) does not require cables to be sealed in Class I, Division 2 unless they terminate in an enclosure that is required to be explosionproof or the cable is connected to the equipment in such a way that it may experience process pressures over 1500 Pascals.

For the second case, while the Section titles are a bit vague (it?s a historic issue, well overdue for a rewrite), the conditions in mind are generally for installations described in Section 501.15(F)(3).
 

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Please clarify the following:

It is your interpretation that 501.15(E)(3) applies to "multiconductor" tray cables as well as "cables"; therefore, a cable seal would not be required for a "multiconductor" tray cable unless terminating in an enclusure that is required to be explosionproof or if connected to equipment in such a way that the cable may experience process pressures over 1500 pascals.

You interpret the third sentence of 501.15(E)(1) to indicate that "multiconductor" cables require a cable seal ONLY if connected to enclosure that is required to be explosionproof or if connected to equipment in such a way that the multiconductor cable may experience process pressures over 1500 pascals.
 

rbalex

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Cable is a ?general? word and per the NFPA Manual of Style:
3.2.1.2 Spelling and definitions of general words and terms shall follow Webster?s Collegiate Dictionary, 10th edition.
which further defines cable as:
3 a : an assembly of electrical conductors insulated from each other but laid up together (as by being twisted around a central core)
Technically all electrical ?cables? are ?multiconductor cables.?

This is consistent with ICEA terms and further NEC usage also. (A single insulated conductor is a ?wire.?). While most would use the term multiconductor as an implication of a common overall jacket, this is not necessarily the case.

It is your interpretation that 501.15(E)(3) applies to "multiconductor" tray cables as well as "cables"; therefore, a cable seal would not be required for a "multiconductor" tray cable unless terminating in an enclusure that is required to be explosionproof or if connected to equipment in such a way that the cable may experience process pressures over 1500 pascals.
Yes

You interpret the third sentence of 501.15(E)(1) to indicate that "multiconductor" cables require a cable seal ONLY if connected to enclosure that is required to be explosionproof or if connected to equipment in such a way that the multiconductor cable may experience process pressures over 1500 pascals.
Not exactly. Section 501.15(E)(1) deals with the terminus at enclosures themselves regardless of the cable construction. The third sentence (last sentence of the main rule) deals with cables that also enter the enclosure through a raceway.

Edit correction: The Webster?s Collegiate Dictionary, 11th edition is now referenced in the 2004 Manual of Style.
 
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