Grounded Conductor / Service Equipment Question

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Daking

Member
I have a question in regard to the grounded conductor brought to service equipment. I am installing an outdoor 500 kVA 3-phase 480V transformer that will feed a new facility. The transformer is 60 feet from the facility. Inside the facility will be a main power panel with main breaker, fed by three phase conductors and a neutral, where I plan to install the main bonding jumper to connect the grounded conductor (neutral) to the equipment grounding conductors, enclosure, and building grounding electrode system, per 250.24(A). At the transformer, the neutral is connected to the secondary X0 bushing, and this X0 bushing is connected to a transformer low voltage grounding electrode per 250.24(A)(2). All this is fairly straightforward.
The issue I have is that as part of the service, there will be a fused disconnect switch and metering cabinet, located 10 feet from the transformer. The way I read the code, the ?Service Equipment? would still be the main power panel in the facility, and the service disconnecting means would be the power panel main breaker, not the outdoor disconnect switch located remotely from the facility. Therefore I would not be required to make the neutral-to-ground connection at the disconnect switch, would not have to run a neutral conductor and separate ground conductor from the disconnect switch to the facility main power panel, and can make the bonding connection at the facility as planned. The disconnect switch enclosure would be bonded to the grounded conductor, which would provide a fault path directly back to the transformer X0 point.
Does this sound correct? It is the disconnect switch that I am questioning, as most people state that the neutral-to-ground connection must be made at the first disconnecting means.
 

Twoskinsoneman

Senior Member
Location
West Virginia, USA NEC: 2020
Occupation
Facility Senior Electrician
I have a question in regard to the grounded conductor brought to service equipment. I am installing an outdoor 500 kVA 3-phase 480V transformer that will feed a new facility. The transformer is 60 feet from the facility. Inside the facility will be a main power panel with main breaker, fed by three phase conductors and a neutral, where I plan to install the main bonding jumper to connect the grounded conductor (neutral) to the equipment grounding conductors, enclosure, and building grounding electrode system, per 250.24(A). At the transformer, the neutral is connected to the secondary X0 bushing, and this X0 bushing is connected to a transformer low voltage grounding electrode per 250.24(A)(2). All this is fairly straightforward.
The issue I have is that as part of the service, there will be a fused disconnect switch and metering cabinet, located 10 feet from the transformer. The way I read the code, the ?Service Equipment? would still be the main power panel in the facility, and the service disconnecting means would be the power panel main breaker, not the outdoor disconnect switch located remotely from the facility. Therefore I would not be required to make the neutral-to-ground connection at the disconnect switch, would not have to run a neutral conductor and separate ground conductor from the disconnect switch to the facility main power panel, and can make the bonding connection at the facility as planned. The disconnect switch enclosure would be bonded to the grounded conductor, which would provide a fault path directly back to the transformer X0 point.
Does this sound correct? It is the disconnect switch that I am questioning, as most people state that the neutral-to-ground connection must be made at the first disconnecting means.

How can this fused disconnect 10 feet from the transformer not be considered your service disconnect?
 

Twoskinsoneman

Senior Member
Location
West Virginia, USA NEC: 2020
Occupation
Facility Senior Electrician
The issue I have is that as part of the service, there will be a fused disconnect switch and metering cabinet,

Actually after consideration if this disconnect is on the supply side of the meter (as allowed in 230.82(3) ) then you may be able to get away with it but I was under the impression this would have to be consider utility owned equipment.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
Actually after consideration if this disconnect is on the supply side of the meter (as allowed in 230.82(3) ) then you may be able to get away with it but I was under the impression this would have to be consider utility owned equipment.

We treat it that way to an extent.. if the disconnect ahead of the meter is POCO controlled then it is not treated as the building service disconnect but as part of the "metering". Locally when POCO has those they lock the operating handle so the property owner has no way of using it as a disconnect.
 

Smart $

Esteemed Member
Location
Ohio
... I am installing an outdoor 500 kVA 3-phase 480V transformer that will feed a new facility. ...
The pertinent question is who owns the transformer. If customer owned, the service disconnecting means must be on the primary side of the transformer.
 

Daking

Member
The utility owns the transformer. It seems to me that the power running from the disconnect switch to the facility would be considered to be a service lateral, when looking at the definition in Article 100. Therefore the connection inside the facility would comply with 250.24(A)(1). It only makes sense to make the GEC connection as close as possible to the grounding electrode system, which is part of the facility foundation. If the connection is made at the disconnect switch, the connection would be made 60 feet from the GES.
 

Twoskinsoneman

Senior Member
Location
West Virginia, USA NEC: 2020
Occupation
Facility Senior Electrician
The utility owns the transformer. It seems to me that the power running from the disconnect switch to the facility would be considered to be a service lateral, when looking at the definition in Article 100. Therefore the connection inside the facility would comply with 250.24(A)(1). It only makes sense to make the GEC connection as close as possible to the grounding electrode system, which is part of the facility foundation. If the connection is made at the disconnect switch, the connection would be made 60 feet from the GES.

Is the disconnect ahead of the meter?
 
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