building steel grounding conducter

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infinity

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New Jersey
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Journeyman Electrician
The last job I was on had a note in the spec that all transformers must be able to move laterally (at the top anyway) a minimum of 1.5" in each direction, even the ones that were pad mounted. That meant spring vibration eliminators and FMC into the transformer. Even the big 4200#, 500 KVA sat on springs.
 

Dave58er

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Location
Dearborn, MI
I don't get the issue here. In the interest of keeping this shorter lets say I get that there are three different requirements here based on conductor size.

We agree that FMC is not allowed when the GEC is subject to physical damage right?

If that's the case then these situations where flex is used protection from physical damage is not an issue, but, flexibility is. So why sleeve it at all?

A bare conductor is at least as flexible as one sleeved in flex. Run the bare wire to a sleeve of either PVC or when PVC is not allowed a steel pipe bonded accordingly.

What about smaller than 6 AWG? Up-size. It's worth it right?
 

Dave58er

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Location
Dearborn, MI
In some places it's common to enclose the GEC in FMC when going to building steel. You can see such an installation in the upper right corner:


This stacked transformer installation is new to me. To be honest it kinda scares me. :)

It seems the upper unit will be taking all the heat from the lower unit. You know that sticker inside that says "keep all conductors below these arrows?"
I get they mean in the enclosure but the point is the heat is going up right?

I guess my question is was this treated like a standard installation?
 

infinity

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New Jersey
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That's a standard installation when space is limited. I really don't think that heat would be an issue but who knows.

The stickers you're referring to I don't see any more. In fact most of the transformers I see now have the connections at the top. Here's a new 45 KVA:

 

yired29

Senior Member
What if protection isn't required and you just want the FMC for aesthetic value?
The only thing that comes to mind is 250.118 (5) b. If FMC is only good for 20 amps as a EGC would that limit its use as a raceway for a GEC?

We should know that FMC is not allowed where subject to physical damage no matter what type of conductors are installed it 348.12 (7). The title of 250.64 (B) does not allow FMC.
 
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