Siemens Neutral buss issue.

[chris kennedy]

I noticed a lug rotate while torquing a neutral. Today I went in early and took the neutral buss apart. This is an 800A P4 MDP.

In this picture note the 4/0 with the two rings of white tape entering the lug from the left side. This lug rotated while being torqued to 41?ft/lbs.

In this picture you can see how the lug rotated back upon breaking it loose.

Here is the factory installation of the lug in slotted holes in the buss.

I installed the lug in the round holes in the middle of the buss. Problem solved, right?

Nope, slight rotation on torquing, yet the new install feels super tight.

Am I over reacting to this? I have used Siemens gear for years and this is the first time I have seen this.

Thank you.

 

[A-1Sparky]

I'd probably pull it apart like you did before and retorque the lug-to-buss bolts (just make sure they aren't stripped--if they are, you can drill/tap and re-fasten). Then, when you terminate the neutral, you can hold the lug with a large crescent wrench (or pipe wrench or vise grips with cheater bar) while you torque it to specs.

 

[A-1Sparky]

Also, you may want to throw on a couple lock washers for the lug-to-buss bolts.

 

[chris kennedy]

Also, you may want to throw on a couple lock washers for the lug-to-buss bolts.

Lock washers are part of the factory assembly.

 

[LarryFine]

Just to be honest, if those two bolts were tight before, you really didn't accomplish anything. Sorry. :roll:

 

[Power Tech]

With the stiff THHN, this could justify a 2 hole lug. Used to be an industry standard, when twisting may be an issue.

 

[chris kennedy]

With the stiff THHN, this could justify a 2 hole lug.

See pictures 2 and 3. The lug has two threaded holes.

 

[hillbilly]

"Am I over reacting to this? I have used Siemens gear for years and this is the first time I have seen this"


I've seen it before, on the one hole lugs that are fastened directly to the neutral bar using a Torx screw (200A panel).
When it happens, I remove the set screw and re-tighten the lug.

Are you over reacting? Only if the lug is now tight, and you're still worried about it.:smile:

steve

 

[charlietuna]

This normally occurs due to "overtorquing" and can be prevented by holding the lug in place with a large cresent wrench while applying the final torque. Is the torque spec "inch pounds" or "foot pounds" ?

 

[chris kennedy]

This normally occurs due to "overtorquing" and can be prevented by holding the lug in place with a large cresent wrench while applying the final torque. Is the torque spec "inch pounds" or "foot pounds" ?

The torque spec for a ?" recessed allen is 500lb-in.

500?12=41.666...

I set my torque wrench to 41.5 lb-ft. After I reassembled the buss, the lug rotated just before my wrench clicked.

 

[chris kennedy]

Would anyone know where to find the torque specs for the fasteners that hold the lug to the buss?

 

[rkess]

Usually on the inside of the breaker cover/ side covers they put the spec's for tightening bus bars, lugs to the bus bars,etc.

 

[chris kennedy]

Usually on the inside of the breaker cover/ side covers they put the spec's for tightening bus bars, lugs to the bus bars,etc.

Yeah, always see it on the single phase stuff, but on the larger gear that comes custom they don't seem to include spec stickers. I'll check their site.

 

[iwire]

Yeah, always see it on the single phase stuff, but on the larger gear that comes custom they don't seem to include spec stickers. I'll check their site.

It would not be on the cover but it is usually listed somewhere on the panel board dead front. Seriously take a look on the back side of the dead front, sometimes there is a sticker on there as well.