Support on type TC-ER cable

[Electrobe]

Section 336.10(7)(c) states the following for type TC-ER cable:
The cable is continuously supported and protected against physical damage using mechanical protection such as struts, angles, or channels.

What is the definition of "Continuously supported"? Can this cable be attached to a ceiling or wall and secured every 9" or so?
Just trying to determine best way to install this cable or if a different type cable should be used.

Thanks in advance.

 

[jaggedben]

We are talking about 'tray cable' so I think it stands to reason that the intended meaning is that is to be laid down into or onto a (more or less horizontal) tray, or strut, angle, or channel. I don't think that strapping to a ceiling or wall is intended to be a permitted use.

With that said, take a close look at the exception and the 6ft unsupported limit 'where not subject to physical damage'.

 

[Electrobe]

From my understating, the "ER" rating is "exposed run" which means this cable can run from the tray to the equipment without conduit and does not need to be supported for the first 6' out of the tray but needs to be supported continuously after that and secured every 6' (I do not see a length restriction in the code). Is this correct or am I interpreting this incorrectly?

Thanks

 

[Smart $]

From my understating, the "ER" rating is "exposed run" which means this cable can run from the tray to the equipment without conduit and does not need to be supported for the first 6' out of the tray but needs to be supported continuously after that and secured every 6' (I do not see a length restriction in the code). Is this correct or am I interpreting this incorrectly?

Thanks

No.

If more than six feet out of the tray, it needs to be supported the entire length of the out-of-tray run.

 

[MasterTheNEC]

Agree with Smart $...and as long as you understand the permission to leave the cable tray is for connection to utilization equipment or devices and not being subject to physical damage.

Of course if I had my way all the misunderstood limitations on Type TC-ER-JP would be eliminated......but that's for another time (2020...

Comments based on the 2017 National Electrical Code.

 

[Electrobe]

The code seems very unclear on the installation of -ER "expose run" cable after it leaves the tray. I have been searching everywhere and can not find any best practice guidelines. I would assume it would need to be installed similar to type MC cable but am not sure. For example, does it need to be secured within 6" of a box or others rules? Any other thoughts, I am trying to write a short procedure on installing this type of cable.

Thanks

 

[jaggedben]

The way I read it, you're simply not supposed to run TC-ER more than 6ft out of the tray (or other continuous support). That is, unless you're invoking one of the other allowances in article 336.

FWIW, we run it all the time on solar arrays supported every 2ft or less. But it is per the manufacturer's instructions on a cable with specialty connectors. (Enphase).

 

[Electrobe]

The way I read it, you're simply not supposed to run TC-ER more than 6ft out of the tray (or other continuous support). That is, unless you're invoking one of the other allowances in article 336.

For the normal type TC cable this is true but for the TC-ER "EXPOSED RUN" cable it is allowed to exit a cable tray (50Ft+) in industrial applications as long as it has adequate protection and support.

NEC section 336 seems to be very unclear about the installation outside of the cable tray other than it must be secured every 6'. Are there any other guidelines? Can we install similar to type MC cable?

Thanks Much

 

[jaggedben]

For the normal type TC cable this is true but for the TC-ER "EXPOSED RUN" cable it is allowed to exit a cable tray (50Ft+) in industrial applications as long as it has adequate protection and support.

...

Where does the NEC say that? I mean, I see that it says you can support it with means other than a cable tray in industrial applications. But I don't see where it says 50ft. And the other options for means of support are proscribed.

Mind you, I'm just reading the code wording, I have no experience running TC-ER in industrial applications, only what I mentioned above. Then again, lots of common practices aren't exactly code compliant.

 

[Electrobe]

Where does the NEC say that? I mean, I see that it says you can support it with means other than a cable tray in industrial applications. But I don't see where it says 50ft. And the other options for means of support are proscribed.

Mind you, I'm just reading the code wording, I have no experience running TC-ER in industrial applications, only what I mentioned above. Then again, lots of common practices aren't exactly code compliant.

I agree, based on this code section it if very hard to determine the rules. I just know the whole purpose behind the -ER rating was so that you could run the cable outside the tray. 336.10(7) is what allows it to be used outside the tray but it does not restrict the length or provide any other rules on how it should be installed outside the tray (Other than secured every 6').

 

[jaggedben]

I did notice that they revised 336.10 in the 2017 NEC. I don't have it in front of me right now, so check the wording yourself. But there's something now about allowing it to be used per the rules for NM if it is 'identified' for that. So I guess what I would say is, use the NM rules for guidance, and see if the cable says something about that. An AHJ might still not allow it though if you're not on the 2017 NEC yet.

 

[Electrobe]

I did notice that they revised 336.10 in the 2017 NEC. I don't have it in front of me right now, so check the wording yourself. But there's something now about allowing it to be used per the rules for NM if it is 'identified' for that. So I guess what I would say is, use the NM rules for guidance, and see if the cable says something about that. An AHJ might still not allow it though if you're not on the 2017 NEC yet.

I Agree. I think I will follow both the NM and MC rules since its still a little grey.

Thanks for your help!

 

[rbalex]

I was one of the early advocates of what later became Type TC-ER.

Oddly enough it started as an Exception to "Uses Not Permitted" in the 1996 NEC.

The original intent was that, with the crush and impact requirements of Type MC, it would eventually be accepted as an "open wiring" method substitute for Type MC in many applications. Immediately and even before it was actually introduced to the NEC, it was saddled with so many restrictions that it gave the impression that it was somehow inferior to "standard" TC. This impression has lasted over 20 years. Any place Type TC is acceptable, Type TC-ER is too. Type TC-ER is Type TC.

The major opponents were MC manufactures and not entirely without reason. While it would potentially cut into the MC business there were legitimate concerns about the "crush and impact requirements". The applicable UL tests actually permitted a limited failure rate for the cables under test. Type MC never failed, but in the early days, some Type TC fell within the "acceptable" failure limits. Today's Type TC-ER rarely if ever fails. There was also a fear that it might become accepted in Class I, Division 1, locations. While process industries were generally in favor of what would eventually become TC-ER, there's no way it would make the NEC. Well, maybe Class I, Zone 1 someday, but that's a different story.

Transitions have never been a real issue. The fact is cables that are permitted in cable trays have always been permitted a 6' unsupported transition between the trays and between trays and the utilization equipment:

392.30 Securing and Supporting.
(A) Cable Trays. Cable trays shall be supported at intervals
in accordance with the installation instructions.
(B) Cables and Conductors. Cables and conductors shall
be secured to and supported by the cable tray system in
accordance with (l), (2) and (3) as applicable:
(1) In other than horizontal runs, the cables shall be fastened
securely to transverse members of the cable runs.
(2) Supports shall be provided to prevent stress on cables
where they enter raceways from cable tray systems.
(3) The system shall provide for the support of cables and
raceway wiring methods in accordance with their corresponding
articles. Where cable trays support individual
conductors and where the conductors pass from one cable
tray to another, or from a cable tray to raceway(s) or from
a cable tray to equipment where the conductors are terminated,
the distance between the cable trays or between the
cable tray and the raceway(s) or the equipment shall not
exceed 1.8 m (6 ft). The conductors shall be secured to the
cable tray(s) at the transition, and they shall be protected,
by guarding or by location, from physical damage.

The above if from the 2014 NEC. The formatting has changed throughout the years but the content/intent has pretty much been the same.

Type TC-ER's "History"

[1996 NEC]
340-5. Uses Not Permitted. Type TC tray cable shall not be
(1) installed where they will be exposed to physical damage; (2)
installed as open cable on brackets or cleats; (3) used where
exposed to direct rays of the sun, unless identified as sunlight
resistant; (4) direct buried, unless identified for such use.
Exception: In industrial establishments where the conditions of
maintenance and supervision ensure that only qualified persons will
service the installation, and where the cable is not subject to physical
damage, Type TC tray cable that complies with the crush and
impact requirements of Type MC cable and is identified for such
use shall be permitted as open wiring between the cable tray and the
utilization equipment in lengths not to exceed 50 ft (15.24 m). The
cable shall be supported and secured at intervals not exceeding 6 ft
(1.83 m). Equipment grounding between the cable tray and the utilization
equipment shall be provided by an equipment grounding
conductor within the cable

[1999 NEC]
340-4. Use Permitted. Type TC tray cable shall be permitted
to be used in the following.
…

(6) In industrial establishments where the conditions maintenance and supervision ensure that only qualified persons will service the installation, and where the cable is not subject to physical damage, Type TC tray cable that complies with the crush and impact requirements of Type MC cable and is identified for such use shall be permitted as open wiring in lengths not to exceed a total of 50 ft (15.24 m) between a cable tray and the utilization equipment or device

The cable shall be supported and secured at intervals not exceeding 6 ft (1.83 m).

Equipment grounding for the utilization equipment shall be provided by an equipment grounding conductor within the cable.

[2002 NEC]

336.10 Uses Permitted. Type TC tray cable shall be permitted
to be used in the following:
…

(6) In industrial establishments where the conditions of
maintenance and supervision ensure that only qualified
persons service the installation, and where the cable is
continuously supported and protected against physical
damage using mechanical protection, such as struts,
angles, or channel, Type TC tray cable that complies
with the crush and impact requirements of Type MC
cable and is identified for such use shall be permitted
between a cable tray and the utilization equipment or
device. The cable shall be secured at intervals not exceeding
1.8 m (6 ft). Equipment grounding for the utilization
equipment shall be provided by an equipment
grounding conductor within the cable.

[2005 NEC]

336.10 Uses Permitted. Type TC cable shall be permitted
to be used as follows:
…

(7) In industrial establishments where the conditions of
maintenance and supervision ensure that only qualified
persons service the installation, and where the cable is
continuously supported and protected against physical
damage using mechanical protection, such as struts,
angles, or channels, Type TC tray cable that complies
with the crush and impact requirements of Type MC
cable and is identified for such use with the marking
Type TC–ER shall be permitted between a cable tray
and the utilization equipment or device. The cable shall
be secured at intervals not exceeding 1.8 m (6 ft).
Equipment grounding for the utilization equipment
shall be provided by an equipment grounding conductor
within the cable. In cables containing conductors
sized 6 AWG or smaller, the equipment grounding conductor
shall be provided within the cable or, at the time
of installation, one or more insulated conductors shall
be permanently identified as an equipment grounding
conductor in accordance with 250.119(B).

[2008, 2011, 2014 NEC]

336.10 Uses Permitted. Type TC cable shall be permitted
to be used as follows:
…

(7) In industrial establishments where the conditions of
maintenance and supervision ensure that only qualified
persons service the installation, and where the cable is
continuously supported and protected against physical
damage using mechanical protection, such as struts,
angles, or channels, Type TC tray cable that complies
with the crush and impact requirements of Type MC
cable and is identified for such use with the marking
Type TC–ER shall be permitted between a cable tray
and the utilization equipment or device. The cable shall
be secured at intervals not exceeding 1.8 m (6 ft).
Equipment grounding for the utilization equipment
shall be provided by an equipment grounding conductor
within the cable. In cables containing conductors
sized 6 AWG or smaller, the equipment grounding conductor
shall be provided within the cable or, at the time
of installation, one or more insulated conductors shall
be permanently identified as an equipment grounding
conductor in accordance with 250.119(B).
Exception: Where not subject to physical damage, Type
TC-ER shall be permitted to transition between cable trays
and between cable trays and utilization equipment or devices
for a distance not to exceed 1.8 m (6 ft) without
continuous support. The cable shall be mechanically supported
where exiting the cable tray to ensure that the minimum
bending radius is not exceeded.


[2017 NEC]

336.10 Uses Permitted.
Type TC cable shall be permitted to be used as follows:
…

336.10(7) Between a cable tray and the utilization equipment or device(s), provided all of the following apply:

1. a. The cable is Type TC-ER.
2. b. The cable is installed in industrial establishments where the conditions of maintenance and supervision ensure that only qualified persons service the installation.
3. c. The cable is continuously supported and protected against physical damage using mechanical protection such as struts, angles, or channels.
4. d. The cable that complies with the crush and impact requirements of Type MC cable and is identified with the marking “TC–ER.”
5. e. The cable is secured at intervals not exceeding 1.8 m (6 ft).
6. f. Equipment grounding for the utilization equipment is provided by an equipment grounding conductor within the cable. In cables containing conductors sized 6 AWG or smaller, the equipment grounding conductor must be provided within the cable or, at the time of installation, one or more insulated conductors must be permanently identified as an equipment grounding conductor in accordance with 250.119(B).

Exception to (7): Where not subject to physical damage, Type TC-ER shall be permitted to transition between cable trays and between cable trays and utilization equipment or devices for a distance not to exceed 1.8 m (6 ft) without continuous support. The cable shall be mechanically supported where exiting the cable tray to ensure that the minimum bending radius is not exceeded.

Frankly, I would use the Type-MC rules [Section 330.30] and not look back.

 

[Smart $]

...
Frankly, I would use the Type-MC rules [Section 330.30] and not look back.

Frankly, with all the hoops one must jump through to use TC-ER in the not-more-than-6'-out-of-the-tray manner in an industrial environment, I'd just use regular TC installed as such and not look back.

 

[rbalex]

Frankly, with all the hoops one must jump through to use TC-ER in the not-more-than-6'-out-of-the-tray manner in an industrial environment, I'd just use regular TC installed as such and not look back.

You may be right. The raceway and Type MC manufacturers have been trying to kill Type TC-ER for years. Your position just might do it for them.

 

[Smart $]

You may be right. The raceway and Type MC manufacturers have been trying to kill Type TC-ER for years. Your position just might do it for them.

Killing the TC-ER market is not the intent of my position. My position is one of practicality (and I'm sure there are others with the same outlook)... but I'd still prefer the option remain available for those, let's do this one off using TC-ER. Perhaps the PV branch of the industry will help keep TC-ER alive.

 

[shortcircuit2]

I agree, based on this code section it if very hard to determine the rules. I just know the whole purpose behind the -ER rating was so that you could run the cable outside the tray. 336.10(7) is what allows it to be used outside the tray but it does not restrict the length or provide any other rules on how it should be installed outside the tray (Other than secured every 6').

But 336.7(C) requires continuous support of the cable out of the Tray.


Then we have the physical damage rules in 336.12(1)...so if you leave the tray without support IMO it would be exposed to physical damage.

 

[rbalex]

Killing the TC-ER market is not the intent of my position. My position is one of practicality (and I'm sure there are others with the same outlook)... but I'd still prefer the option remain available for those, let's do this one off using TC-ER. Perhaps the PV branch of the industry will help keep TC-ER alive.

Basically, once you combine the logical implications of Sections 336.10(2), 336.12(2), and 392.30(B), there's nothing standard Type TC can't do that Type TC-ER can. Originally Type TC(-ER) with the crush and impact requirements of Type MC was proposed to be an open wiring system. I cited that in my original post. [Section 340-5, Exception] While it was limited to 50' at the time, it was still fairly beneficial. There was a Proposal for 1999 to extend it to 100' but it was killed in the Comment stage (HEY -- this is only supposed to be tray cable. I'm serious essentially that was the argument) After that the restrictions were piled on.

I never actually had a dog in the fight so other than the ridiculous trade restrictions that have subsequently been imposed - I don't care.

 

[Smart $]

Basically, once you combine the logical implications of Sections 336.10(2), 336.12(2), and 392.30(B), there's nothing standard Type TC can't do that Type TC-ER can. Originally Type TC(-ER) with the crush and impact requirements of Type MC was proposed to be an open wiring system. I cited that in my original post. [Section 340-5, Exception] While it was limited to 50' at the time, it was still fairly beneficial. There was a Proposal for 1999 to extend it to 100' but it was killed in the Comment stage (HEY -- this is only supposed to be tray cable. I'm serious essentially that was the argument) After that the restrictions were piled on.

I never actually had a dog in the fight so other than the ridiculous trade restrictions that have subsequently been imposed - I don't care.

I'm certain there are many specifiers that would like to see TC-ER be used in a manner similar to Type MC. But I think, as you have pointed out, many will always say "HEY -- this is only supposed to be tray cable." Better off calling it some other approved cable type and dual listing it. :happyyes:

 

[Payoder]

So I don't get it.
How can we get 10' or 15' TC cord drops from the Cable Tray to small conveyors in a food processing environment?
I had assumed that the 6' rule was for going horizontal.