grounding and bonding xfmrs

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hacim23

hacim23

Journeyman Electrician
Location
washington, DC
Occupation
Electrician
I know how to do this but I cannot find all of the code articles about it. My biggest question is on the gec. So it goes to xo, and must be bonded where it enters the xfmr case right? I have read about and have seen special connectors that create a bond where your gec enters the case but cannot find the code article on it. thanks
 
Sometimes this guide helps.
As ActionDave states, 250.30 has your basic requirements.

transformer.jpg
 
thanks guys

thanks guys

thank you guys,

Ok so what about where the gec enters the xfmr case? I have read that passing it through the bottom mesh is not compliant because it is not bonded where entering. The job I'm on now we have been using an mc connector and stripping the gec at that point where it enters but I know that an mc connector is not listed for that use.

I also realize I should've posted this in 'grounding vs bonding' :)
 
hacim23 said:
I have read that passing it through the bottom mesh is not compliant because it is not bonded where entering.
Click to expand...

That is the issue that comes up. But the NEC does not actually say the bonding has to be done at the point the GEC enters people assume that part.



Apparently some inspectors require the use of the 'Kenny clamp' to bring a GEC into an enclosure. In my opinion that is beyond what the NEC requires.
 
iwire said:
Apparently some inspectors require the use of the 'Kenny clamp' to bring a GEC into an enclosure. In my opinion that is beyond what the NEC requires.
Click to expand...

I agree, you would only need to bond it separately if you were using a metallic raceway. If you needed a listed fitting to enter the enclosure then you might need the Kenny clamp. I would ask if you were using PVC would you need a Kenny clamp or a bonding bushing?
 
iwire said:
If I run say EMT directly into the transformer cabinet isn't the raceway already bonded to the GEC at XO?
Click to expand...

Yes, same as using EMT to run a GEC into a service enclosure but it seems that many people (inspectors and electricians) believe that you would still need to bond the GEC directly to the EMT with a bonding bushing. I see no point in that for the reason that you've mentioned.
 
iwire said:
... But the NEC does not actually say the bonding has to be done at the point the GEC enters people assume that part.
...
Click to expand...
Here is the source of where others disagree. 250.64...

(E) Raceways and Enclosures for Grounding Electrode Conductors

(1) General. Ferrous metal raceways and enclosures for
grounding electrode conductors shall be electrically continuous
from the point of attachment to cabinets or equipment
to the grounding electrode and shall be securely fastened
to the ground clamp or fitting. Ferrous metal
raceways and enclosures shall be bonded at each end of the
raceway or enclosure to the grounding electrode or grounding
electrode conductor. Nonferrous metal raceways and enclosures
shall not be required to be electrically continuous.

(2) ...
Click to expand...
 
Smart $ said:
Here is the source of where others disagree. 250.64...
Click to expand...

Here's the 2017 version which intended to clear up the confusion with some new wording:

(E) Raceways and Enclosures for Grounding Electrode
Conductors.
(1) General. Ferrous metal raceways and enclosures for grounding electrode conductors shall be electrically continuous from the point of attachment to cabinets or equipment to the grounding electrode and shall be securely fastened to the ground clamp or fitting. Ferrous metal raceways and enclosures shall be bonded at each end of the raceway or enclosure to the grounding electrode or grounding electrode conductor to create an electrically parallel path. Nonferrous metal raceways and enclosures shall not be required to be electrically continuous.
Click to expand...
 
infinity said:
Here's the 2017 version which intended to clear up the confusion with some new wording:
Click to expand...

(E) Raceways and Enclosures for Grounding Electrode
Conductors.
(1) General. Ferrous metal raceways and enclosures for grounding electrode conductors shall be electrically continuous from the point of attachment to cabinets or equipment to the grounding electrode and shall be securely fastened to the ground clamp or fitting. Ferrous metal raceways and enclosures shall be bonded at each end of the raceway or enclosure to the grounding electrode or grounding electrode conductor to create an electrically parallel path. Nonferrous metal raceways and enclosures shall not be required to be electrically continuous.
Click to expand...

To me that new wording makes it sound like you do need a bond bushing or special clamp of some sort.
 
ok, in this case it is run in pvc. the pvc does not connect directly to the xfmr case, it stops just short and the wire enters through with the mc connector.

now with a metal raceway we would need a bond bushing to prevent impedance and 'choke points' right? that is my concern with the mc connector.
 
hacim23 said:
ok, in this case it is run in pvc. the pvc does not connect directly to the xfmr case, it stops just short and the wire enters through with the mc connector.

now with a metal raceway we would need a bond bushing to prevent impedance and 'choke points' right? that is my concern with the mc connector.
Click to expand...

Your mc connector is a tiny raceway that is bonded to GEC because the case of the transformer is bonded. A full length metal raceway would be bonded the same way on the transformer end and would need a bonding connector of some sort on the other end.

I don't know how much length is involved before the choke effect becomes an issue but it's a whole lot more than the length of a connector. I don't think you need the mc connector at all, but if it is there it is not going to cause any interference.
 
ActionDave said:
Your mc connector is a tiny raceway that is bonded to GEC because the case of the transformer is bonded. A full length metal raceway would be bonded the same way on the transformer end and would need a bonding connector of some sort on the other end.

I don't know how much length is involved before the choke effect becomes an issue but it's a whole lot more than the length of a connector. I don't think you need the mc connector at all, but if it is there it is not going to cause any interference.
Click to expand...


:thumbsup:
To me this means that the GEC must be bonded to the ferrous raceway right at the end of the raceway, but does not necessarily need to be bonded to the transformer frame and case at that point.
So IMO going through a mesh bottom not suitable for bonding would not be a problem as long as you used a suitable connector or clamp on the end of the raceway and then bonded the GEC to the transformer metal at or near the X0 terminal.

Not in the code AFAIK, but one could argue that there could be a choke effect (very small) just from going through the wall of a ferrous metal enclosure. If that turned out to be a legitimate concern, then you would have to bond the incoming raceway to the case and the case to the X0 in addition to running the GEC to the X0.
 
GoldDigger said:
...
Not in the code AFAIK, but one could argue that there could be a choke effect (very small) just from going through the wall of a ferrous metal enclosure. If that turned out to be a legitimate concern, then you would have to bond the incoming raceway to the case and the case to the X0 in addition to running the GEC to the X0.
Click to expand...
In the op's case there is no incoming raceway. Just a pvc sleeve which terminates prior to the GEC penetrating the transformer enclosure.
 
GoldDigger said:
:thumbsup:
To me this means that the GEC must be bonded to the ferrous raceway right at the end of the raceway, but does not necessarily need to be bonded to the transformer frame and case at that point.
So IMO going through a mesh bottom not suitable for bonding would not be a problem as long as you used a suitable connector or clamp on the end of the raceway and then bonded the GEC to the transformer metal at or near the X0 terminal.

Not in the code AFAIK, but one could argue that there could be a choke effect (very small) just from going through the wall of a ferrous metal enclosure. If that turned out to be a legitimate concern, then you would have to bond the incoming raceway to the case and the case to the X0 in addition to running the GEC to the X0.
Click to expand...

Are there suitable connectors listed for single conductors?
 
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