Multi conductor MC cable terminations in classified locations

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eglaude

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Hello all,

The more I re-read the section of 501.15, the more confusing it becomes. Any help here to clear up the requirements is greatly appreciated.

If we have a motor starter that is in an unclassified location that controls a motor in a Class 1 Div 2 area via a MC-HL multiconductor cable, does it require a seal fitting on the cable at the motor lead box, the starter enclosure (i.e. outside rack mounted type), or both? Control cable is similar and are separate from the power cable to a start/stop in the same location.

Would TMC, or TMCX, terminations at both ends be code compliant? This cable is a direct burial application that stubs up to the motor.

Thanks for your advice, great forum. :confused:
 
In Class I, seals generally deal with two issues: explosionproof enclosure integrity and potential migration of flammable materials.

Since we are talking Division 2, we are talking 501.15(E). The confusion is probably caused by 501.15(E)(1). It seems to deal with several issues, when in fact, it only deals with what to do with seals at terminations. (Don’t take the text out of context.)

In your application, the issue 501.15(E)(1) addresses is whether the motor terminal box is required to be explosionproof. It usually isn’t, but could be if it is a single-phase motor. Assuming it isn’t required to be explosionproof, then no integrity seal is required and the rest of the Subsection is moot.

Subsection 501.15(E)(2) is also moot since there is no NRTL test for “Cables That Do Not Transmit Gases or Vapors” and no cable manufacturer would warrant that feature anyway.

You may as well assume the cables can transmit gases through the cable core. However, the UL White Book tells us that Type MC-HL does have“…a gas/vaportight continuous sheath.” In that case, Subsection 501.15(E)(3) applies and, for your application, no seals are required unless they were already required by Subsection 501.15(E)(1).

Edit add: The contol circuit may need a seal at the hand station. It will depend on whether it is a factory sealed or not.
 
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TMC at the starter. It's in the safe area.
TMCX at the motor. It's in the haz area.
MC-HL cable is considered non-transmitting W/R/T flammable gasses.
 
rbalex said:
In Class I, seals generally deal with two issues: explosionproof enclosure integrity and potential migration of flammable materials.

Since we are talking Division 2, we are talking 501.15(E). The confusion is probably caused by 501.15(E)(1). It seems to deal with several issues, when in fact, it only deals with what to do with seals at terminations. (Don?t take the text out of context.)

In your application, the issue 501.15(E)(1) addresses is whether the motor terminal box is required to be explosionproof. It usually isn?t, but could be if it is a single-phase motor. Assuming it isn?t required to be explosionproof, then no integrity seal is required and the rest of the Subsection is moot.

Subsection 501.15(E)(2) is also moot since there is no NRTL test for ?Cables That Do Not Transmit Gases or Vapors? and no cable manufacturer would warrant that feature anyway.

You may as well assume the cables can transmit gases through the cable core. However, the UL White Book tells us that Type MC-HL does have??a gas/vaportight continuous sheath.? In that case, Subsection 501.15(E)(3) applies and, for your application, no seals are required unless they were already required by Subsection 501.15(E)(1).

Edit add: The contol circuit may need a seal at the hand station. It will depend on whether it is a factory sealed or not.
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Couple of points.

At one point some cable manufacturers would provide potential gas transmisson rate capabilities of their product under certain pressure differential and length restrictions/limits.

If you have control station approved for Cl. I, Div. 2 area, no seal iis required. If you use control stations aprpoved fro Cl. I, Div. 1, then Bob's "Edit add:" aplies.
 
weressl said:
Some companies refuse to use non-explosionproof motors in Div. 2 areas, ...
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I'm sure that's true, although I've never run into one in over 40 years of Classified Location design. For curiosity's sake, do you know if they have the motor terminal boxes sealed?
 
rbalex said:
Is the motor terminal box required to be explosionproof in Division 2?
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I don't believe so...as long as there are hard terminals or connection posts within. With NEMA motors they are Ex-Proof tho...from what I've seen.

rbalex said:
Who says? Certainly not UL; there's no test for it.
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Look at the construction of the cable. It's completely filled. It can't transmit gasses. It's not RMC with open cavities.
 
zeus87gn said:
I don't believe so...as long as there are hard terminals or connection posts within. With NEMA motors they are Ex-Proof tho...from what I've seen.
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Where did the idea of "...hard terminals or connection posts within" come from? Not the NEC - or NEMA. There are plenty of NEMA motors in Division 2 that aren't explosionproof; in fact, most are plain old TEFC with standard connectors. Hard terminals or connection posts would certainly be acceptable, but not required in a standard TEFC motor in Class I, Division 2. If a NEMA three-phase induction motor in Division 2 is explosionproof, it is usually a design choice - not a requirement.
zeus87gn said:
Look at the construction of the cable. It's completely filled. It can't transmit gasses. It's not RMC with open cavities.
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A little history - what would become Type MC-HL (1996 NEC, Section 501.4 Ex 2) was proposed to the NEC by the API Subcommittee on Electrical Equipment (SOEE) and I was the SOEE member that sold the rest of the subcommittee on the idea.

At the time, I was trying to scuttle "Zones" not because they are bad but because most folks didn't (and still don't) understand them properly. The problem was that most Zone advocates were trying to sell ?Ex? as a safety improvement (which it wasn?t), when what they really wanted was cheap (which it wasn?t necessarily). If it does the job necessary, I have no problem with cheap as a matter of fact and ?Ex? works just fine when it is properly applied ? but the room for misapplication was (and still is) so great at the time that I didn?t believe it was warranted, especially with the haphazard way they wanted to include it directly into Articles 500 and 501 in earlier attempts to get Zone installations recognized. While Article 505 was also initially Proposed in 1996, it was still poorly written and it wasn't until 1999 that I endorsed it.

There was, however, one group of ?Ex? advocates that had a legitimate need: offshore rigs. They were still looking for inexpensive, but as a function of weight. Every ounce of weight removed from an offshore rig improves both cost and safety when a lighter structure has the same strength.

Offshore rigs are one of the few types of Classified location installations, where there is as much or more Division 1 as Division 2 since there are many closed or sealed compartments with potential accumulations of ignitable materials. Type MC was already accepted in Division 2 and I suggested it be extended to Division 1. Those familiar with Type TECK know it is already accepted in Canada for Division 1 applications. It is essentially a glorified metal-tape, type MC. The SOEE wasn?t comfortable with metal-tape type armor, but bought into continuously corrugated and sealed terminations.

You can also thank me for the ?-HL.? (kinda:roll:) When UL first circulated Standard 2225 for comment, the amount of markings they wanted to place on a cable would have required a minimum of 10? to get it all. They wanted to list every possible combination of Class, Division, Zone and Group (both Art 500 and 505) you could think of - including "Group IIB+Hydrogen." Since, in reality, there were no actual application restrictions, I suggested simply marking it ?for Hazardous Locations? and after the comments were circulated another colleague said ?Why not ?-HL?.?

As you can see, I?m fairly familiar with the construction of ?-HL? ? It isn?t ?completely filled? and it can possibly transmit gasses under the right conditions.
 
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