Lashing of cables in switchgear

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captainwireman

Senior Member
Location
USA, mostly.
The subject of why and the methods used have been explored previously in the forums to maintain the UL listing and conform to NEC 110.3 B. I found a good general link:
www.dli.mn.gov/CCLD/ElectricalCodesBulletinsCables.asp

The project I am currently involved with is taping the ends together with electrical tape. No knot of any kind. After viewing the effects of high fault conditions imposed on conductors and the strong electro magnetic repulsive forces, I am trying to implement a better method.
The manufacturer of the gear is not being very helpful. Can anyone copy the UL standard here for us to examine? UL SB5.1 Supplement B
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
If the gear is listed and if there is no marking that requires the lashing, it is not required. What is the available fault current on these conductors?
 

captainwireman

Senior Member
Location
USA, mostly.
My question goes to the correct method to tie the rope after the lashing windings are complete.. I can not give all details now but whether or not it is required in this or any other circumstance, is not my point. Has anyone seen any manufacturer data in regards to this?
 

jim dungar

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Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
My question goes to the correct method to tie the rope after the lashing windings are complete...

I have not seen this level of detail in any instructions. The last one I read simple said " after the lacing is completed, attach the loose end of the rope".
 

Tony S

Senior Member
The reason for the cleats to be so substantial is due to this little beauty.
Ft = (0.17 x Ip²)/S

Where
Ft = Maximum Force per unit length of cable (N)
Ip= Peak short circuit current (KA)
S = Centre to centre distance between neighboring conductors (m)

A fault could force the tails to violently throw apart. This had caused the death of an electricians mate when trench covers were thrown in the air due to a fault.

This may convince you

https://www.youtube.com/watch?feature=player_detailpage&v=HmnrJa7Zk0A
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
The reason for the cleats to be so substantial is due to this little beauty.

The OP said the lashing was complete and secure. I got the impression, they wanted to know what to do with the excess rope after the final 'cleat'.
 

captainwireman

Senior Member
Location
USA, mostly.
Thanks Tony S. The forces are huge I am once again emailing several manufacturers to answer the issue of the final knot style or perhaps loose leignth, I just don't know under what condition UL will certify. Any help here from someone more well connected than I would be appreciated.
 

Jraef

Moderator, OTD
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Location
San Francisco Bay Area, CA, USA
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Electrical Engineer
It depends on the equipment involved. For most Metal Clad (draw-out) switchgear built to ANSI C37.20 for example, they are DESIGNED to not need additional cable bracing / lashing, its something you get for buying the most expensive possible option. But if you buy standard UL891 switchgear, often called "Metal Enclosed", or UL845 MCCs (similar construction) you will likely have to brace / lash your cables.

Read this, starting on page 4-3 (sheet 45 of the pdf.) for an example and suggestions.
ftp://raftp.rockwellautomation.com/center1/pubs/2100-IN012B-EN-P.pdf

I don't think UL dictates exactly how you do it, but WHEN you do it for getting a listing under UL891, you have to mark HOW you did it for testing and listing at the rated fault current withstand. Here's how I've seen it worded.

Electrical equipment which has been tested for a rating of greater than 10,000 RMS symmetrical amperes, and which required conductor bracing to be installed during the test, must be marked in accordance with Section SB5.1 of Supplement B.

This section states in relative part that the electrical equipment shall be marked to indicate the "type of bracing to be added to the cables routed through the switchboard between the point of entry and the incoming terminals" and the marking "shall be located adjacent to the incoming terminals."

The marking shall state the following or the equivalent: "Wrap line cables together and, if provided, tap cables together with nominal 3/8-inch nylon rope or rope having a minimum tensile strength of 2000 pounds at (1) 6 inches and 12 inches from the line terminals with five wraps and (2) every additional 6 inches with five wraps or every 1 inch with one wrap." In addition, it is recommended that the manufacturer include a drawing that shows the required cable wrapping.
 
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captainwireman

Senior Member
Location
USA, mostly.
Thanks Jared but I can not access the link. They are requiring a user name and password.
Is it possible that all that is required is the lashing windings and that is it? Maybe doing nothing and leaving the end of the rope just hanging is complaint?

On another note, I sure do hate the auto spell correction feature. I am just embarrassed with what the program comes up with and I keep forgetting to carefully edit. .:rant:
 
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hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
I've installed cam lock cabinets for generator connection that required lashing, but I can't remember the manufacture name to give a link to installation. Should be very similar.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Can anyone copy the UL standard here for us to examine? UL SB5.1 Supplement B
You can view the UL Standards for free, just like you can the NEC, and like the NEC the viewing is not very user friendly, but it is usable. No idea what UL SB5.1 is as that does not look like a UL standard number....maybe 891 for switchboards. https://standardscatalog.ul.com/ProductDetail.aspx?productId=UL891
Click on digital view and you can read it...you do have to register with an email address before you can read it.
 
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