Clearing up confusion on bonding and grounding solidly grounded transformers
Clearing up confusion on bonding and grounding solidly grounded transformers
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Excellent description! The only improvement that I would suggest would be to include a one line diagram or something to that effect. A diagram that shows all of the applicable conductors, names them, and shows their points of connection.
Just curious, The two neutrals on the XO tap, is that additional neutral conductor for a high leg panel, I'm sure one neutral is for the 120 volt return from the secondary voltage, panel but the 2nd neutral, again for a high leg 208v ? ... I didn't notice anything else paralleled on the secondary side.
Mark,
The intent of the two neutrals is to support the harmonic currents created by the non-linear loads supplied by this transformer (200% neutral).
Would you take the transformer XO's grounding conductor back to the service ground independantly, or would you allow it to be bonded to every piece of equipment (un-interupted) on the way back to the service ground.(ie - XO point to supply panel, to conduit run, to pull boxes, to disconnect, to splitter, to service ground)
Excellent question, that is what lead me to this article. Grounding the secondary of the transformer to the XO is clear however the need for grounding the service disconnect is there value? Bonding the service disconnect yes, grounding the service disconnect not so much. Is there clarity in 250 or 450 or even 100 on this.
I am currently on a job site where the contractor has used regular romex connectors as a point of entry into a dry-type transormer. I dont feel this is correct but the contractor has said otherwise. does anyone know if this is a code violation ? i am aware that the hardware must be listed for such use but i have not found a cut sheet from any manufacture that says you shall not use it so.
thanks for your help.
As long as the contractor is using nm cable (romex is a trademark brand of southwire) as the feed/load then there should be no issue with code.
Do I ground H O on a 208 to 480 transformer to building steel and supply side grounding conductors?
is the first panel after transformer considered a knew service needing ground and neutral to be bonded and its owen ground rod?If so does it need to have a main breaker? We do have a fused desconnect no the primary side of transformer.
What if this transformer was feeding a piece of equipment. Does it still fall under the SDS rules of bonding to building steel or is it only for premise wiring feeding a subpanel? We are having a discussion with a step down transformer feeding a CNC machine. Thanks
This is an ongoing problem in the industrial control arena. Industrial control technicians use the equipment grounding conductor to make grounded conductors on the secondary side of the control transformers. Given the right circumstances, this could cause serious injury. Essentially, this method injects the transformer secondary into the grounding system, potentially energizing cabinets, junction boxes, and other components of the equipment grounding system.
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