Location for Grounding & Bonding in a transformer

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mjc1060

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I have a 480V 60A primary Delta & a 208/120V 100A secondary Wye. I was given a two barrel lug for X0 & the grounding ribbon has a 3 barrel lug. The primary & secondary are flexed with grounding bushings that contain a lug. This gives me termination points for two equipment grounds for the conduit,one for the grounding electrode conductor, one for the system bonding jumper( that is terminated on one end on a two barrel lug at X0 with the neutral conductor). Can I bond all these conductors at the grounding ribbon for the transformer?
 

augie47

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Short answer "yes"
The fact that your flex does not qualify as an equipment grounding conductor means that the use of grounding bushings is of no value, IMO but there is no harm in bonding them.
This graphic pretty well covers the basics:
transformer installations.jpg
 

electricalist

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dallas tx
I like these illustrations although it seems like we put a thriple lug to the frame and the equipment grounds would go there as well as the GES would go through the other uncut and end at xo where we put a double lug 1 space for the neutral 1 for the bonding jumper.
The pic shows the egc on the right going to where ? xo.
can the op put lugs on the outside of his flex connectors and run his egc from lug to lug?
 

infinity

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The pic shows the egc on the right going to where ? xo.
can the op put lugs on the outside of his flex connectors and run his egc from lug to lug?


In the graphic, the "EGC" on the right is the SSBJ (supply side bonding jumper) and goes directly to the X0. Regarding the second question I would say no.
 

don_resqcapt19

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Because if the flex is less than 6' then it's a suitable egc?
While the flex may be suitable for use as an EGC in some cases, it is never suitable for use as a Supply Side Bonding Jumper. A Supply Side Bonding Jumper is always required between the transformer and the first OCPD.
 

infinity

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While the flex may be suitable for use as an EGC in some cases, it is never suitable for use as a Supply Side Bonding Jumper. A Supply Side Bonding Jumper is always required between the transformer and the first OCPD.

Good point and a good illustration of why the terminology specific to it's application is so important.
 

electricalist

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dallas tx
Sorry.
The secondary is in conduit, so it can be the egc . the small green wire coming from the secondary lb and appears to go to xo. I assumed it's the equipment ground and would land on the xfmr frame.
 

don_resqcapt19

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Thanks. Terminology can make a big difference in many situations. From xo to is both the egc and ssbj or just the ssbj and the flex is the egc?
The connection between XO and the EGCs at the transformer would be the system bonding jumper. You still need a supply side bonding jumper between the transformer and the first OCPD. Non-flexible metallic conduit is permitted to be used as the required supply side bonding jumper, but flexible metallic conduit is not permitted for that use.
 

don_resqcapt19

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Now I see. Thanks for your patience. Mr. Don my mis use of words only confuses me.
You are not the only one who has issues with this. We have multiple terms that are very similar for grounding and bonding, and it is easy to be confused by all of the differing terms.
 

rambojoe

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phoenix az
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a question please-am I correct in assuming the original question was if the primary raceway could be run w/o a equipment ground? the picture provided in the second post shows emt and no egc....
second question-I've always put a 3barrel on the xo and land the neutral and building steel. then with a appropriate jumper to the enclosure lugs for all the equipment grounds. the pic shows the steel bond going to the enclosure first then jumped to xo. -is my way ok? and what do you folks prefer? bond to xo or enclosure first?
 

don_resqcapt19

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a question please-am I correct in assuming the original question was if the primary raceway could be run w/o a equipment ground? the picture provided in the second post shows emt and no egc....
EMT is permitted to be used as the required Equipment Grounding Conductor.
second question-I've always put a 3barrel on the xo and land the neutral and building steel. then with a appropriate jumper to the enclosure lugs for all the equipment grounds. the pic shows the steel bond going to the enclosure first then jumped to xo. -is my way ok? and what do you folks prefer? bond to xo or enclosure first?
Either way is fine as long as the grounding electrode conductor lands on a bus and the bus in connected to XO with wire bonding jumper.
 
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