TC without conduit

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ee_intern

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What I am trying to do is run cable in the low voltage class (120-240VAC) along a fence to power some remote electronics along the way. Price is a constraint I am working under and I was wondering if I am able to run TC (Tray Cable) along this fence without conduit. I have read Article 346 of the NEC, and I am not familiar with the mechanical exceptions (struts, angles, or channels) listed under 336.10(7) for the 2005 NEC version. Am I allowed to run TC rated at 300V, with PVC that has sunlight resistance per UL 1277, and passes flame tests? If not, is there another type of cable that does not need conduit or some cable that its outer coating constitutes conduit? Do I need conduit if I am in the low voltage category? Any references to the code would help aong with any answers to these questions. Thanks
 
Re: TC without conduit

This question was temporarily moved to an area accessible only to the Moderators. I took that action because it appeared to me that the poster was talking about doing installation work on his own property. I have been assured that this is a company project, and that the poster is not planning to perform the installation work himself.

I am now returning the question to the Forum. I hereby apologize to "ee_intern" for mis-interpreting his intentions, and extend to him a hearty "Welcome to the Forum."
 
Re: TC without conduit

Type TC is a wonderful cable and TC-ER is even better. There is a "gotcha" in 336.10(7) though-you gotta have a cable tray in there somewhere.

"...Type TC-ER shall be permitted between a cable tray and the utilization equipment or device..."

This is pure commercial protectionism in my opinion.

"TC rated at 300V" is a different animal. It is either PLTC or ITC, depending on the application. See Arts 725 and 727.

You may be looking for Type MC - see Art 330. But they screwed that one up too, they deleted the general "open wiring" provision.

As you can see I'm not too happy with CMP7 - and I have several good friends on it. I think to spite them I just might hang it on a messenger.
 
Re: TC without conduit

Bob thanks for the input. I will look into MC as an option. There has been discussion as using the horizontal bars on the fence as a possible way around this requirement. Or do you need certified conduit?
 
Re: TC without conduit

I'm afraid I don't quite picture what you're asking, but I don't see Type TC (or TC-ER) being installed in compliance by any method supported only by the fence. It too bad because (TC-ER) should be acceptable just about anywhere MC is.
 
Re: TC without conduit

I may have to backpedal on the "open wiring" comment in my original response. According to the original Proposal that deleted it, "exposed" incorporates "open wiring" as it applies to wiring methods.

From the NFPA 70 Report on Proposals ? May 2004 :
Recommendation:
7-58 Log #104 NEC-P07
(330-10(A)(4))
Revise (4) as follows:
"(4) [Where e - deleted ] Exposed or concealed".
Delete (8) in its entirety.
Renumber (9) through (13) as (8) through (12).
Substantiation:
This is one of a series of proposals to provide consistency throughout the code in the use of the terms "exposed", "open wiring", and "open runs" as applied to wiring methods.
"Exposed" is used 306 times throughout the code, "open runs" is used 7 times, and "open wiring" is used 29 times but only 10 of those instances do not refer to "open wiring on insulators".
Exposed is defined in Article 100 as shown below.
"Exposed (as applied to live parts). Capable of being inadvertently touched or approached nearer than a safe distance by a person. It is applied to parts that are not suitably guarded, isolated or insulated."
"Exposed (as applied to wiring methods). On or attached to the surface or behind panels designed to allow access."
Open wiring on insulators is defined in 398.2 as "An exposed wiring method using cleats, knobs, tubes, and flexible tubing for the protection and support of single insulated conductors run in or on buildings."
"Open runs" is not defined in the code.
This series of proposals will limit the term "open wiring" to open wiring on insulators (Article 398) and have the term "exposed" apply to "open runs" and open wiring not on insulators.
Wire and cable that must be continuously supported and protected will be specifically addressed in the applicable section.
Click to expand...
( Italics and Bold Italics mine - rbalex)

[ July 27, 2005, 01:08 PM: Message edited by: rbalex ]
 
Re: TC without conduit

Sorry for the vagueness. The question that has arisen is whether we can just suspend cable from a fence via a bracket or hangar of some sort to power our equipment that is being installed. Objections arose saying conduit would be needed around this cable. Price needs to be as low as possible, therefore if conduit is needed, it is going to cost an amount that is no longer useable. While brainstorming, the idea to feed the cable through the horizontal bars of a fence was brought up. The fence is a typical chain link steel fence you can find anywhere, with vertical bars every 10 feet or so, and horizontal bars between for added structure support. The reasoning for this is if these horizontal bars that are now enclosing the cable can be classified as conduit, we have a cheap solution. Or more specifally, does a material have to be built with the intent of being conduit or cable tray, such as those listed later in the 300's, and you cant use part of the fence as a conduit or cable tray. If this still isnt clear, let me know and I will try to clarify more
 
Re: TC without conduit

Originally posted by ee_intern:
Also, if we went with the messenger cable approach, isnt that violating 336.12(2)
Click to expand...
No, it's specifically permitted in [2005]336.10(4).
 
Re: TC without conduit

whats wrong with pvc conduit?

I don't see that it would violate any rules if one were to use electrical conduit as the runner at the top of the fence, but I suspect it would not be cost effective.
 
Re: TC without conduit

I think you could run PVC conduit and a few wires for about what TC would cost.

Clamp it to the runner on top of the fence for support along the way.
 
Re: TC without conduit

When I sent a spec sheet of what we were looking for to Anixter, they provided a cable that the UL specified as TC but still had the PVC coating. To correct an earlier mistake, it is rated at 600V, not 300V. If I were to do as you suggest, how would it differ from that cable Anixter could provide.


For reference, here is the cable Anixter 3H-1203
 
Re: TC without conduit

What would you classify that Anixter cable as then? It is looking like MC could be a realistic choice. In general, I would assume it is going to cost a little more then TC cable?
 
Re: TC without conduit

Or more specifally, does a material have to be built with the intent of being conduit or cable tray, such as those listed later in the 300's, and you cant use part of the fence as a conduit or cable tray.
Click to expand...
The key word in this sentence is " listed". Is steel chain link fence pipe "listed" for use as a wiring method? I would think that would be out for sure. How would you enter the pipe (listed connector for this purpose) or exit it? I would think RNC would be the cheapest and safest solution to your problem. "PVC" is cheap and so is THHN (relative) as previously stated. Don't forget expansion joints if needed.
 
Re: TC without conduit

ee-intern -- I think you are making this too complicated. If you are simply trying to feed 120/240V AC power along a fence line to some electronic equipment, then I agree with knickelj and the other posters regarding PVC conduit.

PVC (RNC) conduit properly clamped to the horizontal fence pipe bracing, containing THHN standard building wire, will be your most cost effective solution.

Just make sure it is installed per code, with expansion joints, J-Boxes, adequate straps, etc. as required. If you can't afford to do it this way, then you just don't have enough funding.

By the way, what are the magnitude of the loads involved and the distances involved and the actual voltage of the equipment to be powered?

You need to make sure that you compensate for voltage drop regardless of the wiring method employed, or your equipment may not work after you have gone to all of this trouble.

Vd is dependent on voltage, load and distance. What are those variables in this application?
 
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