Bolted Lug Connections

[rbulsara]

For the first time I am stumped on a nut& bolt question in 20+yrs of experience!

We typically do not specify what type of nut, bolt and washer to use while termianting low volage cables (or anything for that matter). A good contractor normally uses grade 5 steel bolts with flat washers on both sides plus a locking washer on nut side.

A not so good contractor installed (on copper bus to copper lug connections)grade 2 steel bolts without any washers. Also some bolts were not protruding beyond the nut etc. We (Owner and I)want him to correct his work.

Besides being a good practice, I can not readily find any standard or code (In the USA) or even manufacturer's recommendations that requires proper way of installing nut and bolt connections specially for electrical terminations. Does any body know of such requirement in a 'enforceable' standard? NEMA, ASTM or such.

Funnily NEC has long write up as to how to install a screw terminal and wire nuts but no word on bolted connections

Specifying engineers please take note!

 

[busbar]

There is

http://www.fciconnect.com//products/technical_01_01_11.asp

but it is manufacturer’s literature and not a "standard".

In the US, for NRTL-listed/-labeled components, installation instructions are typically considered part of the listing, and intended to be used for correct installation of the component.

 

[CHDean]

If the connections were made in UL listed or ANSI certified equipment there is most likely a grade specification by the manufacture. If sub-standard hardware is used it could potentially void listing/approvals.

 

[sngpl]

Seems to be more a matter of common sense and common courtesy on part of the contractor!

 

[dpc]

For a UL-listed termination, I would think they have specific installation requirements.

You might also check with NECA (contractors association) to see if they have any requirements for this. We used to reference NECA 5055, but I no longer have a copy.

It is also typical to require that equipment be installed in accordance with manufacturer's instructions, but you indicate you didn't find any help here.

If this is a union job, you could also contact IBEW.

I seem to recall that our specs used to use some motherhood statements such as "workman-like manner", and "generally accepted installation practices".

Interesting question.

 

[RAMConsult]

rbulsara, Don't be surprised by your inability to find any definitive standard on bolted connections. There is an absolute dearth of consensus standards that deal with the actual metal-to-metal, current-carrying connection. The closest I could come was multiple references to the torque requirements in UL #486A&B. Even the IEC was silent on the topic except for a reference in IEC #60999-1 & 2. There is a table in a US Bureau of Reclamation bulletin

http://www.usbr.gov/power/data/fist/fist3_3/3_3_6.htm

this was the only non-manufacturer provided table that I could find.

In the utility where I worked we specified all aspects of the connection- surface preparation; nut, bolt and washer type; and new and in-service torque limits. Belleville washers were used to ensure a consistent connection resistance on most high current connections; however, if the equipment vendor specified or supplied the hardware, that's what was used unless it was in total conflict with our standards.

 

[rbulsara]

Thank you all. Now I feel better