The subject of cords came up in another thread, so as long as cords are a topic as of late..........

How do you guys feel about the practice of hooking up machinery in industrial settings with cords drop from the overhead? For a hypothetical instance a machine bolted to the floor, say 10 feet long, leveled to within thousandths of an inch, maybe 5 or 10 horsepower. It's never intended to be moved.
A connector body on the end of a cord that drops from a box above, and a cord and plug are field connected on the machine.

What are your thoughts?



[This message has been edited by electure (edited 09-25-2006).]

I hate cord drops.

In some industrial locations I think they have a place as many times the equipment is only in place for a relatively short time.

However I do see them used in many locations just because it's easier with the excuse given 'vibration'

'Cord' drops, as you described are NG.
400.7 Allowed uses does not fit your description.

That said, IF the unit has a cord and male cap, and said cord reaches the twistlock receptacle mounted on the ceiling, that's another story.

As you stated, this is a much debated subject.

John

Bob:
The vibration 'lemme get away with it this time' excuse does not fly here.

As you said, under the right circumstances; equipment that has to be 'moved' for cleaning (FDA & Health Dept), truly "portable" equipment, etc.

John

John, just for the point of discussion, what is the difference between a receptactle in a box, and a female plug on a cord?

Where is there a hazzard, and what if the cord drop was intended to be shared between 2 different pieces of equipment?

Dnk, one would be that when the machine is removed, there isn't 20' or so of cord left attached to the building, which will usually be coiled up and left hanging from the overhead to rot for eternity.

I like cord drops. That's all there is to it.

First of all, anything that gets the wiring out of the way gets my vote. I've seen way too much damage from trips, getting bumped into, etc.

Even when the machine is never going to be moved, is absolutely without vibration, etc... quite often covers are removed, raw material is transported, etc. A cord has some "give," and a plug will come out before damage occurs (usually). Much preferablt to having a poor forklift maneuver result in sparking, non-continuous pipe.

There is also the issue that pipe that drops down from a 20 ft ceiling is in no way properly supported- not in my book. And my supplier is fresh out of skyhooks. I'd rather see a properly strain-relieved length of S drop directly to the machine.

Agree with John 100%. Spent a lot of time when I first got into the trade in a very large machine shop. We used mostly SJ drops due to machines getting moved even when they were supposed to be permament and saw a lot of conduit damage from fork lifts ETC. The SJ being flexable held up better. We'd pipe to directly over the machine, add a box and then make an SJ drop.

What bothers me was seeing SJ tie wrapped to trusses and in places down low subject to physical damage.

So get off your rear and properly support it.

Double strut, steel tubing etc.

Would the same "flexibility theory" apply to all surface wiring within reach of a forklift? There is often conduit run all over machinery, and I've seen plenty of fork holes through walls.

Do you disagree that a drop to a permanent installation does not meet Code?

[This message has been edited by electure (edited 09-25-2006).]

Please excuse my ignorance, but I thought the NEC applied to the building wiring?

If we have a "plain vanilla" industrial rental unit, and I install a Bridgeport vertical mill, does the NEC care whether I use a properly sized and installed cord drop or EMT? Personally, I have been involved with enough remodels and moves to realize that nothing, including the building, is permanently installed.

Seperately, do you have to use the designed "Drop cable" with the multiple bundles of ground wires or could any service cable rated cable (SO, SJO, SOOW, etc.) be used?




[This message has been edited by LarryC (edited 09-25-2006).]

OK, I still stand by Article 400 and the previous comments.

YES, I used to install "cord drops", as everyone else probably has over the past 30 years; BUT not anymore.

Cord has it's place, twistlock at ceiling, for a male t/l on a cord (1-piece) directly to the device is acceptable, IMHO

John

PS: As we said, this is a big debatable subject

Most anything can be misused. The lazy, ill equipped, and incompetent are also quite clever in justifying their actions.

I don't like square boxes with double duplexes hanging from cords. I surely don't like cords looping over the equipment, through the lights, and across the machinery. And, even a proper cord drop that is directly connected to the machine causes me concern.

As I see it, a cord drop ought to drop straight down and end at a cord cap, for a single plug, with very few exceptions. If it's there for general convenience, it probably ought to come from a retracting reel.

We have to protect our stuff from mechanical damage. HOW we do that is a design issue. I agree that a 'hard-wired' cord offers no advantage over flex or EMT.
Yet, this forum has several pics of damaged pipe, even RMC. Cord and plug connections can be a better solution, 'giving' rather than 'breaking.'

I disagree about the plug belonging on the ceiling, though. Usually that is out of reach- so much for a disconnect meand. The entire weight of the cord is held by the plug- and a twist-lock isn't so likely to pull free when you want. I prefer the cord to end at a cap (female plug) just above head level, in a straight blade pattern.

As for "immobile" equipment, it is surprising just how often those machines have major parts (like dies) removed for product runs. Cranes, forks, hoists.... swinging panels, etc.... sometimes that ever-loving drop can't avoid being in the way.

I call it a design issue.

I've found that generally the same people that tout the "quality" benefits of cord drops seem to switch to conduit drops as soon as they reach the "magic" 30Amp limit of inexpensive connector bodies. Larger than that, cord,plug,& connector assemblies cost $$.
I guess larger machines don't vibrate or something
Sure does reinforce the idea to me that they are done because they're cheap and easy.

Like Hotline, YES I've put them in, and sure, there are some applications where they really belong. That's why the NEC allows them under the limited circumstances it does.

Larry C, once the cord is attached to the building, it is a part of the building wiring, just the same as a piece of conduit would be, and yes, the NEC does care.

Reno:
When you put a female cap on the end of a cord, it then becomes an extension cord, no??

Or, you start at a box, hard wire cord from that box, & put a female cap on the other end; that's using cord for permanent wiring??

Cord cannot be used for permanent wiring.

Some of US may not like or agree with Article 400, but, like I tell EC's; it's the Code, I didn't write it, I have to enforce it.

John

[This message has been edited by HotLine1 (edited 09-26-2006).]

How about this
210.50 General.
Receptacle outlets shall be installed as specified in 210.52 through 210.63.
(A) Cord Pendants. A cord connector that is supplied by a permanently connected cord pendant shall be considered a receptacle outlet.

Why can't a receptacle outlet serve a fixed in place machine?

Hot Line, you are correct...as is Electure... when you say that cords are not to be a substitute for proper methods.

Yet, cord does have a place in permanent wiring. Sometimes the reasons may not be immediately obvious though, so I would not want to be hasty in saying something was "wrong".

I suppose ther are two points to consider:

First, we are hired for our judgement, as much as anything else. Then, in order for our judgement to be any good, we need to know the nature of the place, as well as the "nameplate" information.

[This message has been edited by renosteinke (edited 09-27-2006).]

Gentlemen:
As I said above, this is and will remain a much debated item.

Yes, judgement has to come into the decisions, by ALL parties.

Also, a 4x4 box with a duplex recept does not qualify as a pendant.

John

How about a 4x4 box with two duplex recepts? Those are very common in labs and cleanrooms around here.

[This message has been edited by SolarPowered (edited 09-27-2006).]

A pendant box on a cord must have thread hubs, 314.23(H)(1).

If flexible cord pendants are so bad why do so many places in the code allow them?
210.50(A)
314.23(H)(1)
314.25(C)
336.10(7)
368.56(B)
400.7(A)(1)
400.8(4) exception

This discussion sounds too much like "I don't want to see it done that way, so I will look only at my favorite article and not the entire code book".

I believe the only listed for the purpose boxes can be found in the following links (warning, PDF's):
http://www.woodhead.com/data/current1488/multiple%20outlet%20boxes%20902.pdf http://www.woodhead.com/data/current3054/multitap%20902.pdf

I have seen FS boxes w/ kellem grips used as well, but I am not sure if they are listed for this.

The "threaded hub" in 314.23(H)(1) is only a suggestion, not a requirement. The requirement is that the conductors be protected against strain. If a connection to a KO accomplishes that, then it is also permitted.

As a note, I have never seen even one pendant around here that uses a box with a hub. I see four-square boxes all over the place.

I doubt I would take a 4" square box hanging on a regular connector as a pendant. How do you keep the lock nut tight?
I'm sure there is a 110.3(B) in there somewhere if common sense isn't enough.

Stamped steel boxes (4S, 5S, Handy Box, etc) w/ KO's are not for "portable" use. That means you can't make quadboxes, splitters, portable GFCI's etc out of them . The main reason for this is that the KO's bend inward and may touch the device screws, leading to problems. I believe their UL listing covers this...maybe somebody can post this?

I've always wondered why they were called knockouts instead of knockins
JBD,
My original Q dealt with fastened in place large machinery. I think it is addressed in Article 400. I'm not trying to look at one part of the NEC and not another. Sure I've got my opinion, but I'm trying to understand where I might be missing something. After all, that's what this forum's for.
336.10(7) doesn't seem to have anything to do with cord pendants.

Electure:
I fail to see where in Art 400 you may find a good 'argument' to use cord to connect large machinery.

edit

I just re-read your opening post; OK, you said 'non-movable', so why not RMC/IMC?. Or, as you described it, why not lengthen the 'field installed..." to go 'up' to a suitable twistlock recept?? Or, RGC/IMC down to a suitable box; nipple to floor flange on floor, then a TL in the box?

The usual debate (EC to AHJ) 'physical damage'; the load on the OH crane could hit the RGC; (me) but it can't hit the cord??
9ec) 'vibration'; (me) OK, use sealtite for the final conn.

As I said above, been there, done it.

John

John

[This message has been edited by HotLine1 (edited 09-28-2006).]

My point is that there are several places in the NEC that allow cords to fixed equipment.

400.7(A) only requires cord connectors for 3 of its 10 possible situations. So it is clear that cords can be used from one utilization device to another.

So another question is "what is a pendant", as it pertains to 400.7(A)(1)? Is it any vertical riser? We know plugs and receptacles are not required, because 400.7(B) does not apply to it.

JBD:

You stated:
"My point is that there are several places in the NEC that allow cords to fixed equipment.
400.7(A) only requires cord connectors for 3 of its 10 possible situations. So it is clear that cords can be used from one utilization device to another.

So another question is "what is a pendant", as it pertains to 400.7(A)(1)? Is it any vertical riser? We know plugs and receptacles are not required, because 400.7(B) does not apply to it."

Your statement regarding 400.7 (A); I cannot understand what you mean!

There is no definition for "pendant" in Art. 100. I know of a 'pendant', as a control station, like for a rolling OH crane with various buttons or switches; in flex cord, into a strain relief connector.

There are probably 'pendant' receptacles, but, I have not seen any.

John

Look at the fryer behind the counter at a burger king. Every one I have seen in SW Florida was supplied by an IEC309 connector from an SO cord pendant.

Is any vertical drop of flexible cable a pendant and therefore allowed by 400.7(A)(1)? Or, do pendants need to be "free hanging" and only fixed in place on one end?

Greg:
As I said above, that equip has to be 'moved' to clean. Falls under Health Dept.
Same in FDA regulated mfg.

John

JBD:
"Pendant" is not in Article 100 defs.
To the best of my knowledge, it has to 'hang', like the control station for an OH crane.

John

I've wondered about the pendant thing for a long time (maybe 30 yrs). All I've ever been able to find has been references to pendant lighting, and like John says, crane controls.
Then you have Daniel Woodhead's products, clearly advertised as pendants.
I sure don't see how something secured at the bottom could be considered a pendant.

314.23(H)(2) makes reference to enclosure on conduit pendants that are not supported by other means. Does this mean that "pendants" can be supported on both ends?

JBD:
Your above reference deals with requiring a means of movement on a stem of conduit to prevent damage. Basically, a stem mounted exit unit in a whse that could be hit by a forklift.

I guess you could call that a 'pendant' as I called it a stem.

314.23 (h) (1) addresses cord pendant boxes.

John

Electure:
Ah, Daniel Woodhead, a pleasant memory.

Havn't seen any of them around here for quite some time.

As I said, this is a much debated subject (cords)

John

Just to throw another log on the fire:

What is the basis for the prohibition against using flexible cords as building wiring?

Clearly there are good historic reasons for doing so; cloth covered rubber insulated wires bundled in a cord have no comparison to conductors protected in raceway, or physically separated as in knob and tube.

But compare modern flexible cords to, for example, modern non-metallic cable types. The flexible cord has thicker insulation, and more finely stranded conductors. The insulation material is different, but has similar temperature rating. The insulation is softer, and probably more prone to damage, but the sheath is much thicker, and can 'absorb' small nicks and tears without exposing the inner conductors.

I see no reason _in principal_ that flexible cords could not be safe for permanent installation as building wiring. The cords would need to be suitably tested and listed for long term hidden stationary use as well as flexible use, so not all cord insulation would be suitable. The cords would probably need different support means, different clamps at junction boxes, and possibly different termination techniques to use with the finely stranded wire. The conductors would need to be sized to article 310 rather than article 400, and there are probably a number of other issues.

I bet that there are situations where it would be quite useful to have 'dual rated' cable that was both one of the 'SO' family of cords, and _also_ listed as a type NM cable.

-Jon

Jon, I'll see your bet and raise you one.

I can't think of anyplace it would be advantageous at all.

Just a personal observation, but most of the places I've seen rotten cord has been where it's NOT been flexed, has been in a stationery position for years, and when someone goes to flex it, the insulation crumbles off of the individual conductors.
--------------------------------------------

On different notes, pendant comes from the same word as pendulum, appendage, etc., which are free to swing, & attached on one end.
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(BTW) 400.8(7) Was added in the 2005 NEC to include "where subject to physical damage" as a use not permitted. The "better because it gives some if hit" argument is no good. Could this be just the reason it was added? to clarify the intent?

Electure:
You're bring back more now vivid memories.....

The petrified SO/SJ twirled around the jack chain, from the 3"round box, down to the 2-lamp40 industrial. 30 years, in place, serving the <100 watt load, exposed for all to see.

Or, how about the plastic item that provided 3 places to plug-in a 2 wire lamp cord, that was "wired' onto the baseboards? Heck, they even made them that you could 'feed thru' & go all the way around the room. That fine 18/2 zip cord, extending the sole 'receptacle' in the room to two or three other places. On a good day, you could feel the heat.

Of course, the zip cord was protected by the 30 amp edison fuse.

John

I also agree with John and Scott.

The majority of times I find rubber cords damaged is when they have been used ion permanent non moving installations.

I think it is similar to dry rot, it becomes brittle it cracks and will start flaking off.

[This message has been edited by iwire (edited 10-06-2006).]