50 amp twist lock suggestions

Status
Not open for further replies.
Coppersmith

Coppersmith

Senior Member
Location
Tampa, FL, USA
Occupation
Electrical Contractor
I'm bidding a job where the client wants to power a movable machine with an cord drop and a twist lock male/female.

The machine is single phase 50 amp 208 volt. The drop would be hardwired to a j-box in the middle of the room and then run horizontally through the bar joists about 20 feet before it would drop down from the 18 foot ceiling toward the floor. The idea is the machine can be re-positioned anywhere in the room.

I've never done a 50 amp version of this. Anybody have any suggestions for the cord type (SO?) and twist lock product? (Two hots, ground, no neutral)
 
As far as I know, Hubble still owns the name / right / patents on the twist lock connectors. I want to say off the top of my head you are looking for an L6-50 male and female ends.
 
Chord is not allowed to be strung through the trusses, or fastened to. What I use is bus drop cable, and the proper hangers for it with the spring tension relief. A a loop can be formed at the last hanger, to provide for additional length, when the drop is positioned at less than it's desired maximum reach. Beam clamps and hangers attached to the bottom chord of the truss, to support and protect the cable from strain imposed by movement and pulling stress. Cable grip connectors used at the location that the cable leaves the fixed wiring method.

https://www.adalet.com/Sky-Tie-Bus-Drop-Cable-Clamp

http://www.emerson.com/en-us/catalog/appleton-bus-drop-aec

http://www.cooperindustries.com/con...ucts/wire_mesh_grips/strain_relief_grips.html
tci254.jpg


Sky-TiePhoto2-2837.jpg




appleton-bus-drop-2.jpg
Sky-TiePhoto.jpg
 
Thanks for the product info.

MTW said:
Chord is not allowed to be strung through the trusses, or fastened to.
Click to expand...

Do you have a code reference? I'm not sure why I couldn't string the cord through the trusses. It doesn't look like the cord would be damaged.
 
Coppersmith said:
I'm bidding a job where the client wants to power a movable machine with an cord drop and a twist lock male/female.

The machine is single phase 50 amp 208 volt. The drop would be hardwired to a j-box in the middle of the room and then run horizontally through the bar joists about 20 feet before it would drop down from the 18 foot ceiling toward the floor. The idea is the machine can be re-positioned anywhere in the room.

I've never done a 50 amp version of this. Anybody have any suggestions for the cord type (SO?) and twist lock product? (Two hots, ground, no neutral)
Click to expand...

Your AHJ might have a problem with that.

(MTW beat me to it)
 
At the point where you're stringing the cord through the trusses you're using the cord as a substitute for fixed wiring.

400.8 Uses Not Permitted. Unless specifically permitted
in 400.7, flexible cords and cables shall not be used for the
following:
(1) As a substitute for the fixed wiring of a structure
Click to expand...
 
infinity said:
At the point where you're stringing the cord through the trusses you're using the cord as a substitute for fixed wiring.
Click to expand...

Am I? As I mentioned, the goal is to allow the machine to be moved to any point in the room. That means approximately 20 feet horizontal from a center point before dropping down. The wiring is far from fixed if it has to be movable. If instead of running through the bar joists, the cable was hung from hooks below the joists would that change your opinion?
 
Somewhere around the same code section, It also says you cannot mount a so cord to a building. Quick and easy way is just to put several large Loops in the cord and put some Velcro tape around it. Best way would be a retractable cord reel
 
Have a look at 368.56 B Branches from Busway. Granted your not supplying the circuit from a busway, but the application is the same. I always use these methods and materials for pendent drops for reliability, liability and always passes inspection first time. It used to require that you used a box with a threaded hub and a strain relief, such as an FS style box, but that requirement is now gone.

50A Hard service cable is not lightweight stuff, and requires strong support. When the customer tries to move the machine a little too much, with the drop connected, you will definitely want some strain relief connections, so that they can feel the tension before it comes apart on them. That could be a bad scene. I always put a tag on the drop end to identify where it is fed from, to be able to quickly find it and de-energize it in the case of a mishap, or the machine requiring a lockout.

Also have a look at 400.8 (4) and 400.10 Uses not permitted and Pull at Joints and Terminals
 
Coppersmith said:
Thanks for the product info.



Do you have a code reference? I'm not sure why I couldn't string the cord through the trusses. It doesn't look like the cord would be damaged.
Click to expand...
Letting it lay on the floor and becoming a trip hazard is fine with NEC, draping it over or suspending it from trusses so you don't trip over it is permanent wiring and not allowed - makes a lot of sense right?:D

Though I have to admit that is what it seems to say.

That said, three pole 4 wire or even California style, may be easier to come by or cost less then a two pole three wire, nothing says you would need to use all three poles.
 
kwired said:
That said, three pole 4 wire or even California style, may be easier to come by or cost less then a two pole three wire, nothing says you would need to use all three poles.
Click to expand...

I agree. After an extensive search for a NEMA standard male and female, I settled on using this:

https://www.homedepot.com/p/Southwi...PIPHorizontal1_rr-_-205751569-_-205751568-_-N

I'll cut it a couple of feet from the male end and hardwire it to the machine with the appropriate strain relief. It's probably more expensive than just getting the parts, but I'll save on assembly labor.
 
Sierrasparky said:
What is California style?
Click to expand...

Link in post 14 has one in it.IIRC someone once posted about why those CS configurations came about. They are not on NEMA lists, but some of them are pretty common. The one I have used the most is 50 amp 480 volt rated. Is easier for me to come up with then a NEMA rated plug.

Have seen a few 120/240 generator inlets that use a CS plug as well, and were probably the same plug that is in the link in post 14.
 
kwired said:
I know, but we were talking NEC reqirements.
Click to expand...
It drifted to the NEC but in the OP no code was questioned. In commercial or industrial applications OSHA would be as big or a bigger player than the NEC.

Here's an excerpt from an OSHA answer to a question about cords being used as permanent wiring

May 5, 2006
Mr. Robert E. Jones
Senior Nuclear Analyst, Maintenance Technical
Seabrook Station
FPL Energy, LLC.
P.O. Box 300
Seabrook, NH 03874

Dear Mr. Jones:

Thank you for your September 8, 2005, letter requesting clarification of the Occupational Safety and Health Administration (OSHA) standard, 29 CFR 1910.305(g), pertaining to flexible cords and cables. This letter constitutes OSHA's interpretation only of the requirements discussed, and may not be applicable to any questions not delineated within your original correspondence. We apologize for the delay in our response. Your paraphrased scenario, question, and our response are provided below.


Question: Does 1910.305(g)(1)(iii) suggest that flexible wiring and cables cannot be run through walls, ceilings, floors, doorways, windows, or similar openings when used in temporary service applications? Or, does this section only prohibit the practice when used as a substitute wiring method in permanent applications?

Response: In accordance with 1910.305(g)(1)(iii), flexible cords may not be used in permanent installations as specified in (A) through (E) below:
(A) As a substitute for the fixed wiring of a structure;
(B) Where run through holes in walls, ceilings, or floors;
(C) Where run through doorways, windows, or similar openings;
(D) Where attached to building surfaces; or
(E) Where concealed behind building walls, ceilings, or floors.​
When these cords (including extension cords) are used in temporary wiring installations, 1910.305(a)(2)(iii)(G), allows them to run through doorways or other pinch points, such as windows or other similar openings, provided they are protected from damage. This provision does not, however, except them from the other four prohibitions, (A), (B), (D), and (E) above.

In other words, flexible cords when used in temporary wiring may be run through doorways, windows, or similar openings provided they are protected from damage, but cannot be used as a substitute for the fixed wiring of a structure; run through holes in walls, ceilings, or floors; attached to building surfaces; or concealed behind building walls, ceilings, or floors.

Thank you for your interest in occupational safety and health. We hope you find this information helpful. OSHA requirements are set by statute, standards, and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at www.osha.gov. If you have any further questions, please feel free to contact the Office of General Industry Enforcement at 202-693-1850.

Sincerely,



Richard E. Fairfax, Director
Directorate of Enforcement Programs
Click to expand...



Roger
 
roger said:
It drifted to the NEC but in the OP no code was questioned. In commercial or industrial applications OSHA would be as big or a bigger player than the NEC.

Here's an excerpt from an OSHA answer to a question about cords being used as permanent wiring





Roger
Click to expand...
And very well a driving factor in wanting to run cord through the trusses, but NEC doesn't really allow that.
 
Status
Not open for further replies.
Top