Transformer System Bonding Jumper - Factory Strap

[ron]

Trying to find in the code where I am allowed to use the factory supplied transformer system bonding jumper bus of unknown size, rather than have to replace it with a known 250.102(C)(1) wire type.
I know that 250.28(A) allows a wire OR bus, but I have no way to easily convert the bus provided from the manufacturer size to the wire size in the table.

 

[LarryFine]

I would think that the manufacturer's instructions cover it.

 

[ron]

I would think that the manufacturer's instructions cover it.

For service equipment, 408.3(C) allows for the factory jumper to be used, but not for regular separately derived systems.

 

[augie47]

It may not be the case in youe situation but many transformers come with a "strap" that I believe simply bonds the core and is often mistaken for a bonding strap. If there is any question, you might check continuity to assure the strap you describe is actually connected to "XO"

 

[don_resqcapt19]

It may not be the case in youe situation but many transformers come with a "strap" that I believe simply bonds the core and is often mistaken for a bonding strap. If there is any question, you might check continuity to assure the strap you describe is actually connected to "XO"

I agree, as I have never seen a transformer that had a factory installed system bonding jumper.

 

[LarryFine]

Can we see a pic of the strap?

 

[texie]

I agree, as I have never seen a transformer that had a factory installed system bonding jumper.

I haven't either on a dry transformer. But maybe Ron is referring to utility style oil filled units that often have one.

 

[ron]

I haven't either on a dry transformer. But maybe Ron is referring to utility style oil filled units that often have one.

It is a 3MVA transformer and it is far from me, so I do not have a picture handy, but I'm being asked if it has to be replaced with a wire type by guys in the field. I will have them check continuity, just in case.
Thanks

 

[augie47]

I haven't either on a dry transformer. But maybe Ron is referring to utility style oil filled units that often have one.

Unlike the dry transformers I was referencing, I have seen 3MVA transformers with a neutral bond strap and always accepted them it as being correctly sized by the manufacturer.

 

[ron]

Unlike the dry transformers I was referencing, I have seen 3MVA transformers with a neutral bond strap and always accepted them it as being correctly sized by the manufacturer.

Are you aware of a code section like 408.3(C) that would allow it formally?

 

[augie47]

Are you aware of a code section like 408.3(C) that would allow it formally?

Not really. If it's factory supplied I would say 90.7 which precludes factory installed internal wiring of equipment in the same manner we don't question factory main bonding jumpers supplied with switchboards.

 

[ron]

Not really. If it's factory supplied I would say 90.7 which precludes factory installed internal wiring of equipment in the same manner we don't question factory main bonding jumpers supplied with switchboards.

408.3(C) takes care of main bonding jumpers in service equipment.

 

[Hv&Lv]

This thread has me really curious and I expected it to have about 30-40 replies already.
Sort if interested in the pros opinion on this also..
I did find this.. It’s a little old, but…

Is the XO Jumper Sized Correctly?

iaeimagazine.org