building steel grounding conducter

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Volta

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Columbus, Ohio
220/221 said:
GEC from 208 volt side connects to GEC on 480 side?
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Yes, eventually. The SDS GEC must be connected to the nearest of the Structural Steel Electrode or the Metal Water Pipe Electrode.
Jumpered from the building steel and piping?

I guess I always thought the building steel and metalic piping bonded to the service instead of part of the grounding system.
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The interior piping is bonded to the electrical system, the electrical system is grounded by the underground metallic water pipe. Subtle difference in practice.

Similar with the strucural steel.
 
e57

e57

Senior Member
Location
San Francisco, CA
infinity said:
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:
RE: Pic of transformer
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Hmmmm.... Flexibilty and conduit choices in contradiction.... Good point. LFMC??? Thats more typical here - but now I'm wondering about the hows and whys???
 
e57

e57

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Location
San Francisco, CA
Volta said:
Yes, eventually. The SDS GEC must be connected to the nearest of the Structural Steel Electrode or the Metal Water Pipe Electrode.

The interior piping is bonded to the electrical system, the electrical system is grounded by the underground metallic water pipe. Subtle difference in practice.

Similar with the strucural steel.
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For clarity the water pipe is only allowed to be connect to within 5' unless it's a facilty under control of qualified persons (the exception to 250.52(A)1 ) - The water pipe connection of SDS electrodes went out in '93 along with all the other connections to it - like EGC's that were much easier. Damn plastic....
 
V

Volta

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Location
Columbus, Ohio
220/221 said:
Is the structural steel always part of the GE system? I thought we bonded it as opposed to using it as a ground.
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No, four methods are allowed by 250.52(A)(2), loosely repeated as:
  • 10 or more of structural steel in direct contact with earth or in concrete in earth;
  • metal frame connected to a ground ring or CEE;
  • connection to a rod, driven pipe, or a plate proven to have not more than 25 ohms to ground, or
  • Other approved means.

Otherwise may be required to be bonded per 250.104(C).
 
ohmhead

ohmhead

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ORLANDO FLA
Well this brings up a question for me transformer primary or secondary NEC rule or your personal view or your common spec .

Does it need a bonding bushing on pri or sec with greenfield ?

If a ground is installed in primary & secondary to that transformer and hits the case of that transformer .

We always use building steel and ground rods in tranformers but do we need to use a grounding bushing on the pri /sec feeds.
 
infinity

infinity

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New Jersey
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ohmhead said:
Does it need a bonding bushing on pri or sec with greenfield ?

If a ground is installed in primary & secondary to that transformer and hits the case of that transformer .
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No, IMO it's not required. The FMC is not considered an EGC so what purpose would a bonding bushing connected to it serve?
 
ohmhead

ohmhead

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infinity said:
No, IMO it's not required. The FMC is not considered an EGC so what purpose would a bonding bushing connected to it serve?
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OK let me ask this primary and secondary has feeders and a ground wire with them when you attach flex to a transformer do you install a bonding bushing on transformer ?

I guess what were asking is if the greenfield is not able to ground itself then would this be a code issue ?

Meaning by attaching your ground to it it may be a better ground than not .
 
e57

e57

Senior Member
Location
San Francisco, CA
infinity said:
No, IMO it's not required. The FMC is not considered an EGC so what purpose would a bonding bushing connected to it serve?
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IMO the the bonding is required - but the FMC is not allowed... (Since the FMC is not an EGC - I assume this to be the reasoning why LFMC is more common here - something I never thought about...) But the flexibilty is required for the installation.... Definiatley a contradiction is several codes...
 
iwire

iwire

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Location
Massachusetts
e57 said:
IMO the the bonding is required -
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I am shocked. :grin:

FWIW IMO there is no such thing as a secondary side EGC until after the first secondary side OCPD.

IMO that wire between the transformer and the first OCPD is a bonding jumper.
 
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220/221

Senior Member
Location
AZ
IMO that wire between the transformer and the first OCPD is a bonding jumper.
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That's what I thought.

Now I don't know what to think.

Sometimes, the more I try, the less I truely understand.
 
e57

e57

Senior Member
Location
San Francisco, CA
iwire said:
Relax Mark, just having some fun.

You and I just look at bonding issues differently. Of course I think I am right but I could certainly be wrong.:)
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Yes - we do - beauty is in the eye of the beholder.... :D Some are happy with what they're married to (conceptually) - some seek an ever shifting yet appropriate beauty queen (conceptually) suited to the task and situation. ;)
 
e57

e57

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Location
San Francisco, CA
ohmhead

ohmhead

Senior Member
Location
ORLANDO FLA
Well i have never seen a transformer hard piped .

Most jobs call for flex connections and added vibration pads in addition to the factory internal transformer pads and on some we do the engineer calls for spring mounts .


Heres a good example of springs installed at rated load meaning the weight of transformer after 150 kva the springs get larger we had a transformer that was 8 inches off the house pad and the engineer wanted that brand of spring it was kinda funny you could push on the transformer which was a 300 kva and it would move back and forth like a slinky toy the electrical inspector had a sit down with the engineer that day .
 
iwire

iwire

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Location
Massachusetts
ohmhead said:
Well i have never seen a transformer hard piped .
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Maybe once you get some more experiance you will have seen it all. :)

Most jobs call for flex connections and added vibration pads in addition to the factory internal transformer pads and on some we do the engineer calls for spring mounts .
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No doubt, we deal with that in many buildings. But we get many jobs that do not require any of that and we may use conduit, EMT or wireway.
 
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