How do I seal a multiconductor at the boundary? C1/D2 - TC-ER Cable on Cable Tray

ibarrola

Member
Location
Houston
Hi guys,
I'm looking at the code in order to run TC-ER cable on top of cable tray. This will be running from a non classified area to a class 1 div 2 area in order to terminate on a motor (controlled by a VFD).

The VFD cable I'm looking at the moment is a 3/C with a ground wire per phase, type TC-ER for VFDs. Now, this does not have a gas/vapor tight sheath but it is rated for C1/D2.
Looking at the 2017 code 510.15(E)(4) where it mentions that a cable without this sheath needs to sealed at the boundary between unclassified and c1/d2.

(4) Cables Without Gas/Vaportight Sheath. Cables that do
not have a gas/vaportight continuous sheath shall be sealed at
the boundary of the Division 2 and unclassified location in such
a manner as to minimize the passage of gases or vapors into an
unclassified location.



How do I do this with a multiconductor cable or even a single conductor cable on a cable tray?
Thanks
 

rbalex

Moderator
Staff member
Location
Mission Viejo, CA
Occupation
Professional Electrical Engineer
TC-ER, in fact, does have a gas/vaportight sheath and is a Section 501.15(E)(3) application. (All Type TC forms do)

BTW, depending on the application, you probably won't have to seal at the terminations either. [Section 501.15(E)(1)]
 
Last edited:

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
TC-ER, in fact, does have a gas/vaportight sheath and is a Section 501.15(E)(3) application. (All Type TC forms do)

BTW, depending on the application, you probably won't have to seal at the terminations either. [Section 501.15(E)(1)]
I have never quite understood how the "vaportight sheath" designation comes about. It seems to me that just about anycable with an overall plastic or rubber sheath is all but guaranteed to be vaportight. How would vapors penetrate such a sheath?
 

ibarrola

Member
Location
Houston
TC-ER, in fact, does have a gas/vaportight sheath and is a Section 501.15(E)(3) application. (All Type TC forms do)

BTW, depending on the application, you probably won't have to seal at the terminations either. [Section 501.15(E)(1)]
Thanks RBalex, I asked southwire expert on the matter and he mention that his cable did not have a gas/tight sheath.

Hopefully it is ok to post the link to the cable?
http://industrial.southwire.com/en/tile/1/spec/45451/?country=US

I looked at article 336 for TC cable and did not see it mention gas/vapor tight sheath.
Thanks,
 

rbalex

Moderator
Staff member
Location
Mission Viejo, CA
Occupation
Professional Electrical Engineer
Thanks RBalex, I asked southwire expert on the matter and he mention that his cable did not have a gas/tight sheath.

Hopefully it is ok to post the link to the cable?
http://industrial.southwire.com/en/tile/1/spec/45451/?country=US

I looked at article 336 for TC cable and did not see it mention gas/vapor tight sheath.
Thanks,
It's too bad the Southwire "expert" doesn't know his own product that well.

From the UL White Book [2017]:

POWER AND CONTROL TRAY CABLE

(QPOR)

GENERAL



This category covers Type TC power and control tray cable intended for

use in accordance with Article 336 of ANSI/NFPA 70, ‘‘National Electrical

Code’’ (NEC). The cable consists of one or more pairs of thermocouple

extension wires or two or more insulated conductors, with or without one

or more grounding conductors, with or without one or more optical fiber

members and covered with a nonmetallic jacket. A single grounding conductor

may be insulated or bare and may be sectioned. Any additional

grounding conductor is fully insulated and has a distinctive surface marking.

The cable is rated 600 or 2000 V.

The cable is certified in conductor sizes 18 AWG to 1000 kcmil copper or

12 AWG to 1000 kcmil aluminum or copper-clad aluminum. Conductor sizes

within a cable may be mixed. Thermocouple extension conductors are certified

in sizes 24 to 12 AWG.
...
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.
It's too bad UL no longer publishes it's White Book. You can get the same info from the UL website but it is now a struggle - just like getting NEC info directly from NFPA.

In any case, any Type TC form (-ER, -ER-HL, etc.) is nevertheless Type TC and has a "gas/vaportight sheath". FWIW I'm an expert too - I helped write the original Section 501.15(E) in its initial format. It's been wordsmithed a bit since then.

BTW Section 501.15(E)(2) is basically useless; no cable has "...been investigated for transmission of gases or vapors through its core."
 
Last edited:

rbalex

Moderator
Staff member
Location
Mission Viejo, CA
Occupation
Professional Electrical Engineer
I have never quite understood how the "vaportight sheath" designation comes about. It seems to me that just about anycable with an overall plastic or rubber sheath is all but guaranteed to be vaportight. How would vapors penetrate such a sheath?
It goes back to the "horrors" of Section 501.15 IN. No. 2. Thankfully, most inspectors/AHJs are ignorant of its existence; especially in Division 2 where no gases or vapors should commonly exist anyway.

In Section 501.15(E), we tried to cover each reasonable cable construction conceived of at the time. A "Gas Blocked" cable was being considered by some manufactures. It never took off but it's left in Section 501.15(E)(2), "just-in-case". Technically, Type MI does meet the requirement but it has its own specific installation requirements anyway.

As I mentioned above, Section 501.15(E)(2) is basically useless for the reason stated. Section 501.15(E)(4) would only basically apply to unjacketed, interlocked armored Type MC. Section 501.15(E)(3) is the only one with a common practical application.
 

ibarrola

Member
Location
Houston
It's too bad the Southwire "expert" doesn't know his own product that well.

From the UL White Book [2017]:

It's too bad UL no longer publishes it's White Book. You can get the same info from the UL website but it is now a struggle - just like getting NEC info directly from NFPA.

In any case, any Type TC form (-ER, -ER-HL, etc.) is nevertheless Type TC and has a "gas/vaportight sheath". FWIW I'm an expert too - I helped write the original Section 501.15(E) in its initial format. It's been wordsmithed a bit since then.

BTW Section 501.15(E)(2) is basically useless; no cable has "...been investigated for transmission of gases or vapors through its core."
Hahha, well the company's website had a button that said "Talk to an Expert". I was actually a bit annoyed because I asked a straight up question and it took several back and forth emails until he finally answered and said no. One of there TC cables had gas/vapor tight on their description, but the other one didn't.

I appreciate the help and your reference to UL, I actually do have a copy :)
Thanks again!
 
Top