MC cable and rigid conduit on same Junction Box

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lpena

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Can you have MC cable (s) from a cable tray go to a Junction Box that has rigid conduit. Is this acceptable by the NEC? This will be for an installation on a class 1 Div 2 location. Some field instruments' wiring will be connected to a junction box via MC cable / cable tray. On this same box other instrumentation wiring will be connected using rigid conduit. Can this be done. Thanks
 
To me the Code reference would be 501.10(B)(4)
Hmmm... that only covers requirement for box or fitting to be explosionproof.

I'd say the relevant Code reference is simply 501.10(B)(1) and/or (2) covering the permitted wiring methods.
 
I missed this one since it wasn't posted in the HAZLOC forum.

While the previous posts are both correct and relevant, what is more significant (and often overlooked) where sheet-metal boxes are used in Class I, Division 2 is Section 501.30.
 
I missed this one since it wasn't posted in the HAZLOC forum.

While the previous posts are both correct and relevant, what is more significant (and often overlooked) where sheet-metal boxes are used in Class I, Division 2 is Section 501.30.
Hmmm... my 501.30 is on grounding and bonding.

And there is no mention of sheet metal in 501... :?
 
Hmmm... my 501.30 is on grounding and bonding.

And there is no mention of sheet metal in 501... :?
How would you bond a sheet metal box with either a conduit or MC installation? It can certainly be done compliantly for either wiring method but most would use a double-locknut or a locknut bushing type bond on a sheet metal enclosure without a second thought when they understand explosionproof isn't required. CMP14 has been absolutely paranoid about bonding for many many Code cycles - even in Division 2 (all Classes and IS systems BTW). Don't know about now, but I don't see any current proposals to change that position.
 
How would you bond a sheet metal box with either a conduit or MC installation? It can certainly be done compliantly for either wiring method but most would use a double-locknut or a locknut bushing type bond on a sheet metal enclosure without a second thought when they understand explosionproof isn't required. CMP14 has been absolutely paranoid about bonding for many many Code cycles - even in Division 2 (all Classes and IS systems BTW). Don't know about now, but I don't see any current proposals to change that position.
I understand the concern, but see it as a consequential issue to the OP... meaning MC and rigid to the same box is not prohibited, but bonding the rigid and MC armor must be ensured as required by 501.30.

While we're on that subject, exactly what is a locknut-bushing?

Do you feel a [properly-installed] bonding locknut meets the requirement?

685038-ProductImageURL.jpg
 
I understand the concern, but see it as a consequential issue to the OP... meaning MC and rigid to the same box is not prohibited, but bonding the rigid and MC armor must be ensured as required by 501.30.
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That's correct. It's usually overlooked though when someone generally unfamiliar with Hazardous Location installations simply assumes that since Section 501.10(B) and other Sections permit many nonexplosionproof enclosures in Division 2 that grounding/bonding for what would otherwise be Article 250 compliant in an unclassified installation would also be suitable in Division 2.


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While we're on that subject, exactly what is a locknut-bushing?
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Basically a locknut on the outside and a treaded bushing on the inside of an enclosure.


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Do you feel a [properly-installed] bonding locknut meets the requirement? "Double locknut" would have a locknut both inside and out.

View attachment 11850
IMO, it would.

It is difficult to explain CMP14's paranoia. The Panel wants five fully engaged threads or another "approved method" to achieve bonding. [See Section 500.8(E)] The basic idea is that "circulating currents" may cause arcs at joints even in Division 2 or IS Systems.
 
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