Grounding the transformer case

[ecirplr]

I have been wondering and cannot find it in the NEC about the requirements for bonding the case of a transformer. In times past we were instructed to drill a hole, scrape the paint off the case so the lug will make contact with it. If you are required to use the threaded hole in a 1900 box why shouldn't it also be required to have a treaded stud or tapped hole for a transformer. I recalled reading here last week that it now stipulates the # of threads that are required for grounding/bonding in the 1008 NEC. Just a thought.

 

[celtic]

You might want to take Mike up on his generous offer/s of free graphics and videos:

Free Graphics (View Actual Course Instruction Illustrations)

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(So what if it's a marketing ploy....IMHO, his publications are worth the price of admission)

 

[romeo]

Grounding the transformer case

You might want to take Mike up on his generous offer/s of free graphics and videos:

Free Graphics (View Actual Course Instruction Illustrations)

Free Video (View Actual Course Instruction Videos)

(So what if it's a marketing ploy....IMHO, his publications are worth the price of admission)

This forum is lucky to have you celtic

 

[celtic]

This forum is lucky to have you celtic

ME?


I'm lucky to have this forum!

 

[tom baker]

We complicate transformers too much.
The transformer case is bonded to the EGC in supply circuit.
The secondary X0 is bonded to the case by the SBJ and the GEC bonded to the same location. If you think about it, the secondary EGC is bonded to the primary EGC and back to the service grounding electrodes, the purpose of the GEs at the transformer, when inside is not really clear.

 

[cadpoint]

Here a nice read for ya.

Here a nice read for ya.

Heres a long but interesting article on threading and bolted connections.

Maybe bolts with solid lubrication "For maximum service life, the recommended preload force holding the threaded connection together should be 80 percent of the bolt's yield strength. ... Too much torque permanently deforms the bolt and destroys its strength."

Its a thick but interesting read... I studied this stuff, yikes , Ok its been awhile ...

http://www.plantservices.com/articles/2003/236.html?page=1

via Google "compression of threaded connections"

 

[ecirplr]

Sorry about the confusion. In my original post what I was looking for was not the subject of grounding and bonding but input about the mounting of the lugs for EGC to facilitate the grounding /bonding utilizing theaded studs/bolts. Sorry about not clarifying more clearly