Bolts for Ground lugs

[jrannis]

That lug is at the bottom of a 500 KVA transformer. There are two incoming and four outgoing EGCs along with one main bonding jumper.

Here is the total view and before anyone asks the lugs on the transformer did not stay as they are in the picture.

How did you come up with using the 600kcmil to bond the core to the EGC and the case?
Seems like a piece of 4/0 would have been more than sufficient for a 500kva transformer.

 

[iwire]

How did you come up with using the 600kcmil to bond the core to the EGC and the case?

It was laying on the floor, the drawings likely indicated a size but I did not bother matching it.

This job had about 6000' of 600s and 5000' of 500s, a few more feet installed was not a big deal.

 

[mivey]

Here is the total view and before anyone asks the lugs on the transformer did not stay as they are in the picture.

OK, I won't ask if they stayed that way, but what did you change?

Also, have you ever tied any of the conductors? I seem to recall a thread a while back about doing that to reduce flailing around during a fault. I never have, but it might be an interesting calc.

 

[iwire]

OK, I won't ask if they stayed that way, but what did you change?

I was not happy with the lugs overhanging the bus bars. I sent an RFI to the jobs EE, he replied to move them and make my own holes.

I have no issue with that he is the engineer of record and as far as I know he may have talked to GE, the transformer manufacturers.

I have never tied conductors, some equipment requires tieing the conductors at certain fault current levels.

 

[petersonra]

"Four grade 3 - 1/2" bolts in each lug hole. "
Question: Where do you buy a "grade 3 " bolt?

grade 3 bolts are the cheap ones you get at the hardware store.

 

[iwire]

grade 3 bolts are the cheap ones you get at the hardware store.

No, the cheapest hardware store bolts are 'no grade' and they could be made out of any material and do not have to meet any standard of strength.

One you move into graded hardware there are standards that must be meet, of course that assumes you not getting counterfeit junk.

When I worked at the amusment park we would call ungrded bolts 'butter bolts' meaning soft and weak as butter. Most of the hardware we had to use would be Grade 8 but in some places weaker bolts where required by the ride manafaturers.

 

[petersonra]

No, the cheapest hardware store bolts are 'no grade' and they could be made out of any material and do not have to meet any standard of strength.

One you move into graded hardware there are standards that must be meet, of course that assumes you not getting counterfeit junk.

When I worked at the amusment park we would call ungraded bolts 'butter bolts' meaning soft and weak as butter. Most of the hardware we had to use would be Grade 8 but in some places weaker bolts where required by the ride manafaturers.

I looked this up after I made the post, and found that unlabeled bolts can be anything up to grade 2. I did not even now there was a grade 2. I thought there was only grade 3, 5, and 8, with 3 being the cheapest one. I learn something every day.

 

[jim dungar]

... in some places weaker bolts where required by the ride manafaturers.

I call those "shear pins".

 

[iwire]

I call those "shear pins".

In most cases that was the intent.

A few spots they used over sized 'soft' bolts as hinge pins in ways that had to tolerate flexing.

 

[wasasparky]

Nope, did not need one on either end.

You used non-ferrous raceway? Can't tell from the pic...