building steel grounding conducter

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rosie06

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does the grounding conductor from building steel for a 75 kva transformer in green field entering the transformer need to have a bonding bushing and does the ground need to go thru the lug on the bushing
 
If you have a GEC going thru metal raceway then a bonding bushing is required on both ends to avoid the choke effect.
 
Although Dennis's answer is an acceptable practice, some people, myself included, will say that it's not required. The FMC is bonded to the case, the case is bonded to the XO and the XO is bonded to the case. That makes the bonding bushing redundant and IMO not required.
 
infinity said:
What if protection isn't required and you just want the FMC for aesthetic value?
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Rob,

I think it is still protecting the GEC and if you want aesthetic value use the methods listed

in 250.64(B). Rob, this is jmo and no 'attack' on anyone. My house may not need a paint

job but if I want to change the color, the new paint will still provide protection.
 
benaround said:
Dave,

FMC and cable armor are not the same item !
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You are right! :)

Now could you tell how me this relates to what we are talking about? :confused:

The OP mentioned green field which I assume to be FMC. Each post since has mentioned FMC.

FMC is not among the allowable protection for GECs 6 AWG and smaller.

IMO a GEC 4 AWG and larger is permitted to be protected with whatever method you choose.

Btw benaround I really like your house paint analogy. :)
 
If you have a GEC going thru metal raceway then a bonding bushing is required on both ends to avoid the choke effect.
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The grounding conductor from building steel is not the GEC.....is it?

I thought this would be a bond wire going TO the steel.

I can't keep this stuff straight. I thought GEC was to A) ufer, B) ground rods, C) water pipe (in some cases)
 
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Educate me please.

SDS...seperately derived system?

They use the building steel as a grounding electrode for the transformer which is a seperately derived system?

The transformers is an SDS because?

Thanks.
 
infinity said:
What if protection isn't required and you just want the FMC for aesthetic value?
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Whatever you call it - it is still there and a metallic enclosure around a GEC and should be appropriately installed for being on the GEC.

(OT recently I got to re-do the wiring methods for an out of town FA guy. He heard about a local code for "Metallic Raceway requirements" for FA systems here - so he picked up scraps of MC sheath and slid that on everywhere where the FA cable was exposed... "For protection - it's metallic......" Went down with the inspectors like a ton of bricks.)
 
220/221 said:
Educate me please.

SDS...seperately derived system?

They use the building steel as a grounding electrode for the transformer which is a seperately derived system?

The transformers is an SDS because?

Thanks.
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Because it's seperate from the system conductors feeding the transformer... ;) The grounding for that "system" starts there...

And as such it's connection to the electrode system - which can be made to building steel. (If that is - if an electrode or connected to one - i.e. not isolated from everything else...)
 
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:

Rob%27s%20Work%20024.JPG
 
Rob I know it is common, I just don't know if that makes it NEC compliant.

I see your point about it being 'required or not' but at the same time the NEC went to the trouble of specifically making a list of acceptable methods.

At best I would say the issue is muddy.
 
iwire said:
Rob I know it is common, I just don't know if that makes it NEC compliant.

I see your point about it being 'required or not' but at the same time the NEC went to the trouble of specifically making a list of acceptable methods.

At best I would say the issue is muddy.
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I agree, muddy. :)

Funny thing that job in the photo was just inspected on Tuesday and passed.
 
Because it's seperate from the system conductors feeding the transformer... The grounding for that "system" starts there...
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480 volt SES w/ufer ground.
Transformer inside for the 208 stuff is a SDS.

Got it.

GEC from 208 volt side connects to GEC on 480 side?
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.
 
iwire said:
I do not doubt it in the least. :)

I don't think anyone would look at it and think 'Gee that is unsafe and might be an NEC violation.'
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IMO this section could be worded better to allow any raceway to be used when protection of the GEC from physical damage is not required.
 
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