hillbilly1
Senior Member
- Location
- North Georgia mountains
- Occupation
- Owner/electrical contractor
Most common is at the transformer, but it can be as shown in the drawing. One or the other, but not both.
Transformer grounding detail
- Thread starter hhsting
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Tulsa Electrician
Senior Member
- Location
- Tulsa
- Occupation
- Electrician
I had a question. Does the SDS set outside.
Also can you share the transformer wire information shown on plans.
Attachments
- Location
- Illinois
- Occupation
- retired electrician
Because the code says: "If the source of a separately derived system and the first disconnecting means are located in separate enclosures, a supply-side bonding jumper shall be installed with the circuit conductors from the source enclosure to the first disconnecting means enclosure..."
- Location
- Illinois
- Occupation
- retired electrician
Since the GEC has to be terminated at the location of the system bonding jumper, I install it a the location that results in the easiest installation of the GEC.
The drawing states a delta primary and a 4 wire 208/120V wye secondary. The primary voltage isn’t shown, but probably 480.
Another C10
Electrical Contractor 1987 - present
- Location
- Southern Cal
- Occupation
- Electrician NEC 2020
thank you for the insight .. I'm not a transformer expert obviously. I didn't realize a delta could be 480.
I suppose the learning never ends.
The delta in this scenario only means that there are only 3 phase conductors involved in feeding the primary of the transformer since no neutral is needed on the primary.
Not always but most times the Delta (or 3 wire feed) to a transformer originates from a 480v Y service upstream.
JAP>
hhsting
Senior Member
- Location
- Glen bunie, md, us
- Occupation
- Junior plan reviewer
The transformer and secondary panelboard are inside in electrical shed. Below is complete picture of schematic
I don't see the need for the 2/0 jumper from the ground rod to the transformer casing but also I don't see the harm in it if someone wanted to do so.
Also,
Most Service Rated Panelboards will come with their own factory bonding jumpers and there's not the need of having to install your own wire type jumpers as what is shown as 2/0 jumpers in the Panel or Enclosed Circuit Breaker.
Jap>
Also,
Most Service Rated Panelboards will come with their own factory bonding jumpers and there's not the need of having to install your own wire type jumpers as what is shown as 2/0 jumpers in the Panel or Enclosed Circuit Breaker.
Jap>
wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
Because this is in an electrical shed, the ground rod for the SDS may not be part of the GES for the primary supply (which could be from a remote building). Then if the transformer case is not factory bonded to X0, the only connection between the factory case and X0 would be through the earth. In which case a fault from say X1 to the transformer case would energize the case (as well as cause current from X1 to the primary EGC to the primary GES through the earth to the secondary GES, which circuit has no overcurrent devices in it).
So surely the transformer case is required to be bonded to the secondary system via a SSBJ. [I haven't checked the relevant code sections.]
Proper bonding and grounding is seldom shown on a Transformer wiring diagram, and, yes XO must be bonded to clear a fault.
The attached drawing seems awkward to me the way it's drawn.
I wouldn't be taking a bonding jumper from a ground rod to the case of the transformer.
My bonding from XO to the ground rod or GES would either be inside the transformer or the 1st means of disconnect depending on which location I choose to bond at.
I'm either going to bond XO to the case inside the transformer and extend a Neutral and EGC to the first means of disconnect keeping them seperate at the diconnect, and, install my bonding jumper from XO in the transformer to the ground rod or GES,
or,
I'm going to extend an EGC from the case of the transformer and a Neutral from XO to the first means of disconnect, bond the Neutral to Ground inside that 1st means of disconnect, and extend my bonding jumper from that point to a ground rod or GES.
All this is generally easier done than said.
JAP>
Tulsa Electrician
Senior Member
- Location
- Tulsa
- Occupation
- Electrician
Thank you for the reply.
I was wondering if the note,
'Refer to transformer scheldule for conduit and wire sizes" would help shed more light on the install.
My take on it is. An SSBJ
Should be installed and the conductor from transformer case to electrode should be removed.
An SSBJ would be required unless it has metal conduit continues between the two with proper bonding.
If the schedule in the note called for PVC for some reason. Than a wire type SSBJ is required.
The primary EGC and the SSBJ shall land in the same bar inside the transformer.
Another item I was thinking about was a primary disc in or on the separate structure since it is fed with a feeder.
I was going to do more read on this. Since this is a new structure where is the uffer.
I would think the whole grounding detail
would need to be reworked if a primary disc is required. I think it is.
Others may chime in on that one. I know that was not your question I was just thinking it through based on where the install is located.
Again thank you for sharing the information.
Tulsa
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