3200a/3W/480v/Y Service Lateral to Feed Central Eneergy Plant With Small 120v Loads

[Todd Smith]

Question: the EE had designed a 3200a/3W/480v/Y Service Lateral (PVC ductbank) from a secondary bus enclosure off the secondary of the utility transformer, to supply a Central Energy Plant Building that contains some 120v loads for receptacles and lights - should this service lateral contain a neutral? (please see the attachment).

Thanks,
TS

 

[Dennis Alwon]

I am assuming the CEP is a separate building and should need an equipment grounding conductor -- not sure about the neutral as I am assuming their will be a transformer at the building

 

[Todd Smith]

Dennis, yes it's a separate building and it is a service lateral that should not require a grounding conductor as it will be grounded at the first means of disconnect. That is why I'm asking - to see if a neutral is required since the building has 120v neutral loads. Does 250.24.C apply?

 

[david]

Since the utility is a grounded system according to the service run to other buildings I would say you need a grounded conductor

 

[Todd Smith]

Are you saying that 240.24(C) applies?

 

[Todd Smith]

Correction - are you saying that 250.24(C) applies?

 

[david]

Correction - are you saying that 250.24(C) applies?

250.24 Grounding Service-Supplied Alternating-Current Systems.
(A) System Grounding Connections. A premises wiring system supplied by a grounded ac service
(C) Grounded Conductor Brought to Service Equipment

yes

 

[Todd Smith]

Thanks. Anyone else agree/disagree?

 

[Dennis Alwon]

Dennis, yes it's a separate building and it is a service lateral that should not require a grounding conductor as it will be grounded at the first means of disconnect. That is why I'm asking - to see if a neutral is required since the building has 120v neutral loads. Does 250.24.C apply?

Are you saying there is no breaker ahead of these conductors?

 

[petersonra]

Question: the EE had designed a 3200a/3W/480v/Y Service Lateral (PVC ductbank) from a secondary bus enclosure off the secondary of the utility transformer, to supply a Central Energy Plant Building that contains some 120v loads for receptacles and lights - should this service lateral contain a neutral? (please see the attachment).

Thanks,
TS

the 120V loads will be fed from an SDS. the 120V N will be created there.

i think you are required to bring in the N if it is a real service, but no EGC is required.

Of it is a feeder you don't need the N if it is not used but you must have an EGC.

 

[david luchini]

Thanks. Anyone else agree/disagree?

I agree with David

 

[Todd Smith]

Correct, this is a service lateral coming off the secondary of a 480v/277v utility transformer.

 

[david]

Dennis, yes it's a separate building and it is a service lateral that should not require a grounding conductor as it will be grounded at the first means of disconnect. That is why I'm asking - to see if a neutral is required since the building has 120v neutral loads. Does 250.24.C apply?

Please understand I am not saying the service needs to be supplied with a grounded conductor because of the 120 volt loads at the building, I am saying because the building is supplied by a grounded system than you need the grounded conductor to the building service.
The 120 volt loads will be supplied from a transformer past the service equipment at that building and most likely a derived neutral from that system

 

[david luchini]

unless you are using 277V L-N loads, I see no reason to run a N.

:?

250.24(C) Where an ac system operating at less than 1000V is grounded at any point, the grounded conductor(s) shall be run to each service disconnecting means...

The Code requires running a grounded conductor to the service disconnecting means.

 

[Dennis Alwon]

Please understand I am not saying the service needs to be supplied with a grounded conductor because of the 120 volt loads at the building, I am saying because the building is supplied by a grounded system than you need the grounded conductor to the building service.
The 120 volt loads will be supplied from a transformer past the service equipment at that building and most likely a derived neutral from that system

That was my thinking in post #2. The trany could produce the grounded conductor.

So if it is a service conductor going to the other building then I agree no equipment grounding conductor is needed.

 

[Todd Smith]

Okay, it sounds like everyone agrees now we need a neutral (grounded) conductor in lieu of just (3) phases in this service lateral per 250.24(C). Let me know if you disagree.

 

[don_resqcapt19]

Where are the service point and the service disconnects?

 

[Dennis Alwon]

Let's see if we got this right. If there is a 480V service at the building with just 3 phases and no neutral AND the system is a grounded one, then it would appear a neutral is needed just to protect for ground fault of a potential conductor touching the disconnects. If no neutral is run then how would the metal enclosures be bonded if you ran nonmetallic raceways

250.24 (C) requires a neutral to be in the disconnect. The only way I understand that you would not need a neutral run is if the service conductors went to a transformer first where a neutral would be derived.

 

[Todd Smith]

Don - About 750' away from each other.

 

[Smart $]

Where are the service point and the service disconnects?

Don - About 750' away from each other.

Would only make a difference if the service point was the supply terminals of the service disconnecting means... as you would not be able to force the POCO to comply with the NEC... but then the POCO would be installing service lateral or outsourcing its installation. That said, I've never seen nor heard of any POCO not running the Neutral for a 480/277 grounded neutral system.