Transformer

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rasmithircgov

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If their is a transformer located on a 3rd floor of a hotel do you have to run a bonding jumper from the transformer on the 3rd floor to the grounding electrode system located at service on first floor. The hotel exterior and floor are block construction and prescast plank concrete floors. Their is no structural metal located near the transformer. The transformer is located in a room of block and concrete. Interior walls of metal frame and drywall are located 200' on the first floor from transformer located on 3rd floor.
 
Sadly yes, the transformer GEC must connect to the existing GES and without structural steel you will have to run it back as far as it takes.

Creating a neutral or not this has to be done, if you are making ungrounded delta you could skip that step but I highly doubt you need ungrounded delta in a hotel.
 
Thanks iwire
Been along time since Ive been on Mikes forum site. Do you have a code article handy? I started looking in 450.5 and 450.6 and it refered me to 250 or should I have started in 250 Seperatly derived systems?
 
My situation was a 480v to 208v transformer. The transformer was for a fan unit that required no neutral. When I told the engineer about the lack of building steel to ground to he explained that since I was not creating a neutral it didnt need to be bonded to building steel and no ground rod either. Was he wrong?
 
LarryFine said:
Yes, because the 208v is required to be bonded.
Click to expand...

Larry,
devil's advocate here. what if one ignores the 120 tap (XO) completely and treats it as a delta transfiormer ?
Is there a requirement that the XO tap be used ?
 
Flex said:
Would it be a new system considering it is only for the fan?
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Yes, it doesn't matter what it serves, see the definition of Separately Derived System.

Roger
 
augie47 said:
Larry,
devil's advocate here. what if one ignores the 120 tap (XO) completely and treats it as a delta transfiormer ?
Is there a requirement that the XO tap be used ?
Click to expand...

Gus, I would think that 250.20(B)(1) would mandate that this particular system be wye connected. and then there is 250.20(D)

Roger
 
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No, an auto transformer would not meet the definition.

Roger
 
So in my case the gentleman was incorrect. Is it any danger the way it is done? The ground is just spliced (bolted together) through and the transformer itself is bonded.
 
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