Converting an existing equipment grounding conductor to grounded conductor (neutral)

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omz

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Location
Texas, USA
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Electrical Engineer
I am an electrical engineer and on one of my projects the electrician forgot to install a neutral from the secondary side of a buck boost transformer (240V-480V 1Phase) to the secondary fused disconnect switch. The distance between the transformer and the disconnect switch is approximately 1000ft. Wiring routed to the disconnect switch includes 2 hots & 1 ground wire( L1, L2 and G) . My question is: Can I use the ground wire as a neutral (as long as it appropriately sized per NEC Table 250.102 (C)(1)). The existing ground (green) wire will be reconnected to the neutral bus and labeled at each end as neutral. For the secondary disconnect switch grounding conductor, I am planning on running a new grounding electrode conductor from the ground lug of the disconnect switch to the counterpoise, installed at the secondary disconnect switch location, since it will be much cheaper than running a 1000ft of new wire and conduit.
 

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omz said:
I am an electrical engineer and on one of my projects the electrician forgot to install a neutral from the secondary side of a buck boost transformer (240V-480V 1Phase) to the secondary fused disconnect switch.
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Sounds like a step up transformer, not a buck/boost.
omz said:
The distance between the transformer and the disconnect switch is approximately 1000ft. Wiring routed to the disconnect switch includes 2 hots & 1 ground wire( L1, L2 and G) . My question is: Can I use the ground wire as a neutral (as long as it appropriately sized per NEC Table 250.102 (C)(1)). The existing ground (green) wire will be reconnected to the neutral bus and labeled at each end as neutral. For the secondary disconnect switch grounding conductor, I am planning on running a new grounding electrode conductor from the ground lug of the disconnect switch to the counterpoise, installed at the secondary disconnect switch location, since it will be much cheaper than running a 1000ft of new wire and conduit.
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You cannot substitute a Grounding Electrode Conductor for an Equipment Grounding Conductor.

There might be a couple of work arounds depending on the application that don't need a new wire. More details are needed.
 
ActionDave said:
Sounds like a step up transformer, not a buck/boost.

You cannot substitute a Grounding Electrode Conductor for an Equipment Grounding Conductor.

There might be a couple of work arounds depending on the application that don't need a new wire. More details are needed.
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So i do not really need to run a grounding electrode conductor . I just need to provide effective and safe grounding path, when i change the existing grounding conductor to neutral conductor. Please see attached details and let me know if there is work round for this situation.
 

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I may be looking at this wrong so forgive me if so.

240 to 480 single phase
No netural on secondary
If so the neutral voltage would be 240.
Not a good idea or what use would it be.

Now if it 480 to 240 than it make sense.
 
omz said:
So i do not really need to run a grounding electrode conductor . I just need to provide effective and safe grounding path, when i change the existing grounding conductor to neutral conductor. Please see attached details and let me know if there is work round for this situation.
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First thing we need to know is if you have a step up transformer or an auto transformer and what it's for. If it's a step up transformer you need a GEC for the secondary and you need an EGC from the disconnect back to the transformer. If it's RGS all the way back to the transformer that can serve as an EGC as far as the NEC is concerned, but most job specs call for a wire EGC.
If you don't need a neutral for anything ground one of the secondary phases and call it a "neutral" which is more properly called a Grounded conductor anyway.
 
See attached One-line diagram sketch for additional information. It should answer all of your questions. The items in green are the transformer and the disconnect that we are discussing in this thread.
 

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omz said:
See attached One-line diagram sketch for additional information. It should answer all of your questions. The items in green are the transformer and the disconnect that we are discussing in this thread.
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I don't agree that the circuit between the transformers is a branch circuit.
Are the conductors between the two transformers completely outside except at load end disconnect?
Is the secondary of the 240-480 volt transformer a dual winding secondary?
If it is a dual winding secondary, is the grounding electrode conductor conductor connected to the center point of that dual winding.
Where is the grounding electrode system for the secondary of the 408-120/240 volt transformer.
 
omz said:
Required by customer to be installed at each OCPD.
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Ok, so you have a 240V service. You step up to 480V, run 1000 feet, and step down to 120/240V.

No neutral was installed in the 1000 foot run. This application doesn't need a neutral to function as designed.

The customer _requires_ a neutral brought to each OCPD.

Do I have that straight?

Does the customer require a _neutral_ or is a non-neutral grounded conductor sufficient?

Could you convert the system to use 480V H-N for the 1000 foot run, making the 480V OCPD redundant (since primary on a 2 wire to 2 wire transformer provides secondary protection) and also making one of the existing #2 wires a grounded conductor.

-Jonathan
 
winnie said:
Ok, so you have a 240V service. You step up to 480V, run 1000 feet, and step down to 120/240V.

No neutral was installed in the 1000 foot run. This application doesn't need a neutral to function as designed.

The customer _requires_ a neutral brought to each OCPD.

Do I have that straight?

Does the customer require a _neutral_ or is a non-neutral grounded conductor sufficient?

Could you convert the system to use 480V H-N for the 1000 foot run, making the 480V OCPD redundant (since primary on a 2 wire to 2 wire transformer provides secondary protection) and also making one of the existing #2 wires a grounded conductor.

-Jonathan
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What a cool idea. Did you get it from post 9?
 
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