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#112926 - 11/30/01 01:21 AM Transformer Bonding  
Admin  Offline

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Joined: Oct 2000
Posts: 3,447
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[Linked Image]
Quote
I removed this transformer today. It was a pretty good installation if you can see through the dust. A couple things puzzled me though. The primary is the conduit on the right. The installing electrician ran the EGC from this conduit through the lug on the grounding bushing. Then he took it unspliced through a lug on the neutral bus and onto a lug on the case. I assume he was trying to establish a bonding jumper. Nice try! Not how it is done. Not to mention the conductor was only a #6 when a #2 is required. (the phase conductors are #4/0) There is a factory installed copper bonding strip that runs from the case to the neutral bus. I can only assume this was the bonding jumper. I haven't seen a transformer with this strip going to the XO. Only the coil frame. (BTW this one goes to the frame too) Not having the original installation instructions I can't be sure if this strip qualifies as a bonding jumper for this transformer.
What do you think?

- Nick


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#112927 - 11/30/01 08:18 AM Re: Transformer Bonding  
Redsy  Offline
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Joined: Mar 2001
Posts: 2,056
Bucks County PA
Nick,

Is the secondary neutral connected directly to a grounding electrode, or just to the primary EGC ?


#112928 - 11/30/01 09:53 PM Re: Transformer Bonding  
Nick  Offline
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Joined: Aug 2001
Posts: 599
Riverside, CA
The secondary neutral is connected to the grounding electrode. You can see the GEC coming in from the right, it is properly bonded then runs directly to the XO bus. It terminates just to the left of the blue C phase conductor.


#112929 - 11/30/01 11:08 PM Re: Transformer Bonding  
Redsy  Offline
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Joined: Mar 2001
Posts: 2,056
Bucks County PA
Got it. It looked like only a lug.


#112930 - 12/01/01 11:07 PM Re: Transformer Bonding  
Scott35  Offline

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Anaheim, CA. USA
Not really within the scope of your questions / comments of this post, but I was just pondering the Manufacturer's choice in the Parallel Secondary Windings on a somewhat small Transformer.
This looks like a 75KVA Transformer.

My views here do not reflect anything more than just why the coils were wound Parallel for a semi-small power rating. But then again, I have seen some really large and complex Transformer cores!
Maybe I am Jaded [Linked Image]

As far as the Grounding goes, I like the fact that the Installing Electrician included the Primary circuit's EGC, but as Nick has said, the #6 bond to the GES for this Transformer's Secondary is insufficiently sized.

I'll probably catch he** from the Inspectors in the forum here, but it looks like someone dropped the ball when this was Inspected!
I say this because all the Transformers I've done, the dead-front covers were left off until Inspection was done [card signed].
If this was done by me, it would have been caught by the Inspector and the good 'ol Non Compliance / correction card comes out!
On the other hand, maybe this was overlooked.

Maybe I'm a show-off [Linked Image], I just want the Inspectors to be able to see something that has been done with an "Artistic" approach, which might never be seen again by another person.
BTW, It's always nice to hear an Inspector say "Look At That Nice Work", since it's hardly ever heard from anyone else [Linked Image]

Scott SET


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

#112931 - 12/02/01 12:58 AM Re: Transformer Bonding  
Nick  Offline
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Joined: Aug 2001
Posts: 599
Riverside, CA
Good guess Scott. It is a 75KVA!


#112932 - 12/02/01 02:06 AM Re: Transformer Bonding  
Scott35  Offline

Broom Pusher and
Member
Joined: Oct 2000
Posts: 2,707
Anaheim, CA. USA
I got it right?!!!? Finally! [Linked Image]

Thanks for the message, Nick.

Scott SET


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!


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