Cable and plug types for stage jumpers

[STEVETERRY]

Originally Posted by gafftaper

Is SJ allowed on just the split end of the two-fer or is allowed on the single line side of the two-fer as well. That seems like a bad idea if it is. True it's only a couple feet of SJ, but it's only a matter of time until somebody's going to run 12 gauge lines 25 feet in opposite directions and try to burn the place down with a couple of 1000 watt fresnels.
Has someone cleaned up this thread and put it in the Wiki yet? There are at least three different topics that should be in there.

The reasons that SJ is now allowed in twofers is that the cable entry on a male plug will not accept the OD of two pieces of Type S. The wording of the applicable section is as follows (from 2005 NEC, copyright NFPA):

520.69 Adapters.

Adapters, two-fers, and other single- and multiple-circuit outlet devices shall comply with 520.69(A), (B), and (C).

(A) No Reduction in Current Rating. Each receptacle and its corresponding cable shall have the same current and voltage rating as the plug supplying it. It shall not be utilized in a stage circuit with a greater current rating.

(B) Connectors. All connectors shall be wired in accordance with 520.67.

(C) Conductor Type. Conductors for adapters and two-fers shall be listed, extra-hard usage or listed, hard usage (junior hard service) cord. Hard usage (junior hard service) cord shall be restricted in overall length to 1.0 m (3.3 ft).


So, if you are using a molded twofer using SJ (junior hard service cord), the overall length of the twofer from male to either female is restricted to 3.3'.
Frankly at the time we updated the code to allow SJ in twofers, molded twofers were not contemplated, so it's a bit clumsy for those devices.

ST

[Radman]

So adapters can be 1 m of junior hard service as well, it appears. I need to get the latest NEC, 2002 was a while ago now.

[STEVETERRY]

Correct.

But why use Junior Hard Service if Extra Hard Usage will fit?

ST

[Radman]

Originally Posted by STEVETERRY

Correct.

But why use Junior Hard Service if Extra Hard Usage will fit?

ST

Personally I wouldn't under normal circumstances. But say you need adapters and you have spare connectors and a bit left on a spool of SJOOW, like a certain theatre I used to work at, its nice to know you could make the necessary adapters under code with on-hand materials. Call me a Nazi but I like following rules set for my safety.

[ship]

Originally Posted by Sean

The three-foot limitation is from male connector to female connector. It doesn't matter if it's a "Y" style or a "V" style.
--Sean

"V" style twofers are also against code no matter what cable etc. Connector/plug as an interconnection device.

No matter what type of stage, edison or twist plug it is, it's not sized sufficiently in it's terminal to fit two of the conductors in it's maximum amperage rating wire size & the strain relief for the cable is not designed to properly strain relief two cables.

Possible theoretically with extra thick rubber coated single conductors inside a crimped Union plug - Design Lab in Chicago still has some of them, but not on the more modern Bates style plug or anything else.

Didn't see this mandate in the 2002 Handbook but do specifically remember it as with not being allowed to modify a plug. "V" style twofers, where the plug end is doing the splice in my opinion and in having seen very many hack and on show site attempts at doing them is a big wrong to attempt or have. Could be my memory on this concept goes back to 1996 and my study of it, and it's been taken out since - something I would be against.

[gafftapegreenia]

V style are against code...oh to think how many V style I've seen, used, rented....

[ship]

Impossible to fit 2x 12ga conductors within the terminal of a Bates plug, this much less two cables within the strain relief, and you are not allowed to modify a plug.


Ok, it's possible with a double wire ferrule but not something to be doing or the plug norm in the industry is designed to do. Normally what I see by way of two hack 12/3 type SJ cables shoved into one Bates style plug is a half rear type strain relief, no ferrule in use and a few strands of each cut away or sticking out so it sort of fits. Totally incorrect. Even seen one Bates plug that someone ground away extra area into the strain relief so as to fit two cables - again against code and "the sperit of the code." You are not to modify a plug or to use it as an interconnection device. Not designed for that purpose, nor rated for that purpose.

When I speak of what Design Lab has still in service from like 20 years ago, I mean a braided single conductor cable which has like 1/8" insulation over each conductor and they are using old style Union plugs which would accept six individual thick & braided conductors.

[STEVETERRY]

Originally Posted by ship

"V" style twofers are also against code no matter what cable etc. Connector/plug as an interconnection device.
No matter what type of stage, edison or twist plug it is, it's not sized sufficiently in it's terminal to fit two of the conductors in it's maximum amperage rating wire size & the strain relief for the cable is not designed to properly strain relief two cables.
Possible theoretically with extra thick rubber coated single conductors inside a crimped Union plug - Design Lab in Chicago still has some of them, but not on the more modern Bates style plug or anything else.
Didn't see this mandate in the 2002 Handbook but do specifically remember it as with not being allowed to modify a plug. "V" style twofers, where the plug end is doing the splice in my opinion and in having seen very many hack and on show site attempts at doing them is a big wrong to attempt or have. Could be my memory on this concept goes back to 1996 and my study of it, and it's been taken out since - something I would be against.

I don't agree. The vast majority of the twofers in the world are "V" style, not molded "Y". Manufacturers like TMB make covers for their plugs that specifically alter the strain relief to accept two SJ cords. That is an NEC-accepted construction.

The reason that the code was altered to allow SJ on twofers was to promulgate use of at least hard service cord in this application. Previously, after the industry ceased using single conductor type AA asbestos for twofers, a wide variety of non-compliant single conductor wires were used. Allowance of SJ stopped this.

Molded twofers have never gained much acceptance in the professional theatre due to their size, the fact that they cannot dress flat on a pipe or truss, and the fact that they don't have enough reach.


ST

[ship]

PP2PGMCODB “Oversized for 2-fer-All Black”

Did not know this existed before, you can bet a E-Mail to Tommy will be in later tomorrow in me wanting a sample to look at.

One in the “Oversized” description can assume that this plug is not the standard stage pin plug and designed to fit two 12ga cables, nor is it in general any Edison or twist lock plug as in general with any other stage pin plug - defiantly not designed to be a twofer.

Vast majority of what’s sold for use as a twofer is “Y” style thus while your grasp on the current NEC is much better than mine, we thus agree to disagree. TMB is even my supplier for twofers in the “Y” style - I love the SO grade Woodhead twofer over all other types.

Understood the NEC - accepted construction in doing a "V" but more one in engineered product for that purpose is an exception and not to be conveyed as the general practice. Not also to say that I don’t have some stringers under my supervision and even plug modification that are not twofers which started out as stock plugs. I have my own modified plugs which are twofers in stock I actively would rather not have but accept given only that I wired them to the best possible and safe way possible. All others in stock are being removed from circulation and replaced. Highly not recommended to modify a plug and make it into a twofer - this only if absolute necessity and only an exception given technology available does not allow for what is consider safe and proper otherwise, than done in a professional way.

Be sure that A) were I a member of the code panel I would fight for any accepting of the V twofer = other than with specific exception for factory designed twofer plugs, and B) that as soon as the other ME and I get time to modify our vulcanizer that this stringer concept is top priority. Way too many people on a job site sticking two five foot cables into one male plug. Yep, it works - acceptable or ever completely safe - nope.

What’s the current ruling on the use of plugs as interconnection device and or modifying factory engineered products? As I said, in searching the 2002 Handbook, I couldn’t find the code rules and section numbers I was looking for but do remember specifically. Not persay challenging the change in your stating that it’s ok and proper by code - other than in my own view point of challenging it and saying it’s not, more very curious to learn what’s the current guideline and as with GFCI’s required as per 99' looking for it to get respecified in a more accurate way thus corrected.

Again I disagree not persay on professional theater - no longer driving the market, more on size, cannot dress flat etc. or reach. Stock twofers are 36". Longer than that you get into problems of what it is in not being a jumper cable it’s an adaptor or twofer. At 36" it is reasonable in length as a sort of disconnect and or in general what’s it’s purpose. Folding flat... you never seen a Y folded for the most part flat for a tour I suppose, they are used in the industry - touring/entertainment lighting industry, a few brands of them out there both SO and SJ and any number of them are folded flat sufficiently for a cable loom - the type SO last better than the SJT types in folding. I buy a few hundred a year for the largest in tours, conventions, churches and at times even theater uses. Not just me or if one clicked on any theater retailer, one would be able to find one if only a few that sell a plug based “V” twofer instead of a “Y” twofer as the industry standard. Times have changed, TMB’s plug the exception.

I agree to disagree in this a good debate of opposing sides - and neither of us having spite but in my opinion - and it’s that based upon my own experience, I’m correct. But on the other hand looking forward to learning from your own opinions as I did tonight about the TMB ProPin twofer plug - but a plug specifically designed for it. Definately not a Hubbell Edison plug with two 12/3 SJ or even SO cables attempting to come out of it.

[STEVETERRY]

The TMB plug is the same as a standard pin plug in all respects except for a larger cable entry hole.

Here's an important point: many safe things we do in the theatre are different from "normal" electrical practice. The NEC helps us with this. Chapters 1 through 4 of the Code are general requirements for all installations. Chapters 5 through 8 modify or extend those requirements for special occupancies or applications. A theatre is a special occupancy covered by Article 520.

Here's a clear example of how Art. 520 can change a "standard" requirement:


Here are a few sections from Chapter 4 relating to connectors:


400.10 Pull at Joints and Terminals.

Flexible cords and cables shall be connected to devices and to fittings so that tension is not transmitted to joints or terminals.

Exception: Listed portable single-pole devices that are intended to accommodate such tension at their terminals shall be permitted to be used with single-conductor flexible cable.

FPN: Some methods of preventing pull on a cord from being transmitted to joints or terminals are knotting the cord, winding with tape, and fittings designed for the purpose.


406.6 Attachment Plugs, Cord Connectors, and Flanged Surface Devices.

All attachment plugs, cord connectors, and flanged surface devices (inlets and outlets) shall be listed and marked with the manufacturer’s name or identification and voltage and ampere ratings.

(A) Construction of Attachment Plugs and Cord Connectors. Attachment plugs and cord connectors shall be constructed so that there are no exposed current-carrying parts except the prongs, blades, or pins. The cover for wire terminations shall be a part that is essential for the operation of an attachment plug or connector (dead-front construction).

(B) Connection of Attachment Plugs. Attachment plugs shall be installed so that their prongs, blades, or pins are not energized unless inserted into an energized receptacle or cord connectors. No receptacle shall be installed so as to require the insertion of an energized attachment plug as its source of supply.

(C) Attachment Plug Ejector Mechanisms. Attachment plug ejector mechanisms shall not adversely affect engagement of the blades of the attachment plug with the contacts of the receptacle.

(D) Flanged Surface Inlet. A flanged surface inlet shall be installed such that the prongs, blades, or pins are not energized unless an energized cord connector is inserted into it.


406.7 Noninterchangeability.

Receptacles, cord connectors, and attachment plugs shall be constructed such that receptacle or cord connectors do not accept an attachment plug with a different voltage or current rating from that for which the device is intended. However, a 20-ampere T-slot receptacle or cord connector shall be permitted to accept a 15-ampere attachment plug of the same voltage rating. Non–grounding-type receptacles and connectors shall not accept grounding-type attachment plugs.


These sound pretty sensible, right? Different ampacity plugs cannot be interchanged, strain must be kept off connector termination points. All good?

Sure, but what about a single-pole Cam-lok connector that has no separate strain relief, and allows ampacities of 100 to 400 amps to interchange?

Here's how Article 520 deals with it:


K) Single-Pole Separable Connectors. Where single-pole portable cable connectors are used, they shall be listed and of the locking type. Sections 400.10, 406.6, and 406.7 shall not apply to listed single-pole separable connectors and single-conductor cable assemblies utilizing listed single-pole separable connectors. Where paralleled sets of current-carrying, single-pole separable connectors are provided as input devices, they shall be prominently labeled with a warning indicating the presence of internal parallel connections. The use of single-pole separable connectors shall comply with at least one of the following conditions:

(1) Connection and disconnection of connectors are possible only where the supply connectors are interlocked to the source and it is not possible to connect or disconnect connectors when the supply is energized.

(2) Line connectors are of the listed sequential-interlocking type so that load connectors shall be connected in the following sequence:

a. Equipment grounding conductor connection

b. Grounded circuit conductor connection, if provided

c. Ungrounded conductor connection, and that disconnection shall be in the reverse order

(3) A caution notice shall be provided adjacent to the line connectors indicating that plug connection shall be in the following order:

a. Equipment grounding conductor connectors

b. Grounded circuit conductor connectors, if provided

c. Ungrounded conductor connectors, and that disconnection shall be in the reverse order

So, it's important to be careful about invoking "standard" electrical code requirements without knowing if they have been modified by the special occupancy articles, as in the above example.


ST