Intrinsically Safe Wiring Entering C1D1 XP Enclosure

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schwarz633

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I have an XP enclosure on a machine in a C1D1 area. There are Turck isolating switching amplifiers with IS inputs in the XP enclosure for the guard door switches. The plan is to run a common M12 (4) conductor sensor cable (blue) from each door switch into the XP enclosure. I'm hoping to pass multiple cables through a single sealing fitting without removing the jacket from the cables. Inside the XP enclosure the jackets will be removed and each cable will be sealed with a 3" piece of adhesive lined heat shrink tubing. I'm hoping this will comply with the exception listed under NEC 501.15 (D) (2):

Exception: Multiconductor cables with a gas/vaportight continuous sheath capable of transmitting gases or vapors through the cable core shall be permitted to be considered as a single conductor by sealing the cable in the conduit within 450 mm (18 in.) of the enclosure and the cable end within the enclosure by an approved means to minimize the entrance of gases or vapors and prevent the propagation of flame into the cable core, or by other approved methods. For shielded cables and twisted pair cables, it shall not be required to remove the shielding material or separate the twisted pair.

Any opinions on this?
 

rbalex

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Begin with Section 504.70. If you were not dealing with intrinsically safe circuits, what you were suggesting would not meet the requirements of Section 501.15(C). Fortunately, you are dealing with intrinsically safe circuits and the seal is not required to be explosionproof. [Section 501.(C) Exception]

Now, your only concern is whether or not you could sell your suggested “method” to an AHJ as a means identified to “…minimize the passage of gases, vapors, or dusts under normal operating conditions and shall be accessible.”

IMO, you could sell it to me.

Note: identifed does not necessarily mean listed or labeled.​
 

don_resqcapt19

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Begin with Section 504.70. If you were not dealing with intrinsically safe circuits, what you were suggesting would not meet the requirements of Section 501.15(C). Fortunately, you are dealing with intrinsically safe circuits and the seal is not required to be explosionproof. [Section 501.(C) Exception] ...
I see what the rule says, but if there is other equipment in the enclosure that requires the enclosure to be explosion proof, that rule makes no sense to me. Now we would have arc producing devices in an enclosure that would permit the hot gasses and flames to be emitted into the hazardous area if there was an explosion within the enclosure.
 

schwarz633

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WI
I see what the rule says, but if there is other equipment in the enclosure that requires the enclosure to be explosion proof, that rule makes no sense to me. Now we would have arc producing devices in an enclosure that would permit the hot gasses and flames to be emitted into the hazardous area if there was an explosion within the enclosure.

OP here, I was thinking the same. Just to confirm, there are non-rated devices in the XP enclosure (VFD, power supply, transformer, relays, circuit breakers).
 

rbalex

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I see what the rule says, but if there is other equipment in the enclosure that requires the enclosure to be explosion proof, that rule makes no sense to me. Now we would have arc producing devices in an enclosure that would permit the hot gasses and flames to be emitted into the hazardous area if there was an explosion within the enclosure.
A point well taken Don. We didn't establish whether or not the enclosure was required to be explosionproof.

Assuming it wasn't, my original response stands, "as is".

Assuming it was, it still stands with respect to sealing the ends of the cable. However, the enclosure's seal would still need to be explosionproof although the cable outer jacket wouldn't need to be removed. That would still be an applicaton of Section 501.15 (D) (2), Exception.

Bob,

Thanks for the reply. I'm not sure what you mean by "[Section 501.(C) Exception]".
Did you read it? All of Section 501.15(C) applies to 501.15(D)(2) unless the noted Exception also applies. Section 501.15(C) wouldn't recognize 'a 3" piece of adhesive lined heat shrink tubing' as a valid seal. [Edit add: But I would in this particular application]
 

schwarz633

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Location
WI
Let's say the AHJ doesn't recognize 'a 3" piece of adhesive lined heat shrink tubing' as a valid seal, what would constitute a valid cable end seal?
 

schwarz633

Member
Location
WI
A type TMCX should be fine. But you would need one for each cable.

The smallest TMXC has a minimum cable OD of .45", my cables are .21". And they look expensive, plus the additional holes in the XP enclosure (I have 10 cables that I was going to run through (2) 1/2" sealing fittings). I guess I'll try to sell plan A.
 

rbalex

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Hazardous locations don't generally lend themselves to "inexpensive". If done properly, even intrinsically safe systems are not nearly as cost-effective as many believe; especially when they usually overlook NEC Sections 504.50 and 504.60 and ANSI/ISA RP12.06.01 (which is OSHA enforceable).

Edit add: I'm too lazy to do the calc, but I would check the fill on those half-inch seals. You are limited to 25% on standard seal fittings.
 
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