Does a 480/277 volt main disconnect need a neutral conductor?

[LadyDi]

As already pointed out by others, if this is a grounded service then the neutral must be brought to the service disconnect in a compliant manner. The fact that the load does not require a neutral is irrelevant as you know for fault return path.
That conductor you mention that is marked as an EGC is of interest. Do you know where it connects at the other end? If it is connected to the POCO transformer X0 terminal you may have a fault return path, just not a technically compliant one. To be compliant the conductor should be marked white and terminate in a proper neutral bar in the service disconnect and have a proper main bonding jumper. Also, I don't see any evidence of a GES.

Thank you for responding.

I believe Roger pointed out the question that I needed to ask: Is the system grounded? If so, then the answer is yes regardless of the type of load.

I’m am considering your notion that although non-compliant a pathway existed back to the source, and the fuses would blow. Idk, I’m thinking.

Again, thanks for responding.

Sincerely,
Diana

 

[LadyDi]

What are those ............open air #12 fuse links all about?

Yes, and Yikes. I do not know who installed the wires to act like fuses. I did, however, say an explicative when I opened the disconnect and saw the situation.

Thanks for asking.
Best,
Diana

 

[texie]

Thank you for responding.

I believe Roger pointed out the question that I needed to ask: Is the system grounded? If so, then the answer is yes regardless of the type of load.

I’m am considering your notion that although non-compliant a pathway existed back to the source, and the fuses would blow. Idk, I’m thinking.

Again, thanks for responding.

Sincerely,
Diana

Just as an FYI, it would be very unlikely that this would be an ungrounded supply from the POCO as these days it is a very rare thing. And even it was then you would have other compliance issues to consider.

 

[LadyDi]

Just as an FYI, it would be very unlikely that this would be an ungrounded supply from the POCO as these days it is a very rare thing. And even it was then you would have other compliance issues to consider.

True.

 

[Frank DuVal]

Isn't the definition of a 277/480 service include neutral? With no neutral, it is just a 480 service. Very common with motor loads. Then run a transformer for the 120/208 loads. No neutral needed.

So, remark the service 480 Volts and call it a day!:lol:

 

[roger]

Isn't the definition of a 277/480 service include neutral?

Yes it does which is some of the responders are missing

Roger

 

[texie]

Isn't the definition of a 277/480 service include neutral? With no neutral, it is just a 480 service. Very common with motor loads. Then run a transformer for the 120/208 loads. No neutral needed.

So, remark the service 480 Volts and call it a day!:lol:

No, you can't have a "480 service" that does not include the neutral if it is supplied by a grounded Y by the POCO.

 

[electrofelon]

Isn't the definition of a 277/480 service include neutral?

Yes it does which is some of the responders are missing

Roger

277/480 isnt a proper designation per ANSI C.84.1 so it doesnt mean anything

 

[LarryFine]

Yes, and Yikes. I do not know who installed the wires to act like fuses. I did, however, say an explicative when I opened the disconnect and saw the situation.

Actually, way back when I was but a little helper, I'd seen small wires used in place of fuses when energizing a transformer (unloaded, of course) for the first time, in case of internal defect, and warmed the transformer to drive out any moisture before fusing at capacity.

 

[LadyDi]

Isn't the definition of a 277/480 service include neutral? With no neutral, it is just a 480 service. Very common with motor loads. Then run a transformer for the 120/208 loads. No neutral needed.

So, remark the service 480 Volts and call it a day!:lol:

Lol. Yes!

Also, I do not need to remark the disconnect because it’s not labeled. I measured the voltage across L1 to L2, L1 to L3, L2 to L3. Then I measured each phase to the EGC (I suspect).

 

[LarryFine]

I measured the voltage across L1 to L2, L1 to L3, L2 to L3. Then I measured each phase to the EGC (I suspect).

Keep in mind that a volt-meter will measure most ungrounded systems as if they were grounded due to capacitance between the wires and, well, everything else.

 

[LadyDi]

Keep in mind that a volt-meter will measure most ungrounded systems as if they were grounded due to capacitance between the wires and, well, everything else.

Thank you.

 

[LadyDi]

Thank you.

Reconsidering the situation, if no neutral exist then the service is indeed a straight 480 volt system. The outside transformer is labeled 480/277, but the referenced disconnect is in fact a 480 volt disconnect.

I would read 277 phase voltage ( phase to ground) if it’s a star configuration because 480/1.732 is 277. Eureka, am I thinking correctly?


Nevertheless, as the main, the disconnect needs a neutral per the 2017 Code 250.24 (c) regardless of the type of load and also, of course, a properly sized GEC and electrode.

 

[electrofelon]

Reconsidering the situation, if no neutral exist then the service is indeed a straight 480 volt system. The outside transformer is labeled 480/277, but the referenced disconnect is in fact a 480 volt disconnect.

The question remains as to whether this is a grounded system or not. It could be:
1. fed from a wye bank with the wye point grounded, but not brought to the service disconnect (code violation) or that green conductor is the neutral and its colored wrong (also a code violation).
2. fed from a wye bank with the wye point floating and ungrounded

I would read 277 phase voltage ( phase to ground) if it’s a star configuration because 480/1.732 is 277. Eureka, am I thinking correctly?

The problem is capacitive coupling with a high impedance meter. I have measured 277 to ground on the money on an ungrounded 480 delta. You would need to take the measurement with a low impedance meter or better yet find out if and where the system grounding connection is.

Nevertheless, as the main, the disconnect needs a neutral per the 2017 Code 250.24 (c) regardless of the type of load and also, of course, a properly sized GEC and electrode.

If its a grounded system yes the neutral is needed at disconnect. Both grounded and ungrounded systems need a GEC and grounding elecrode system.

It is probably a grounded system, unless some one messed up.

 

[roger]

Reconsidering the situation, if no neutral exist then the service is indeed a straight 480 volt system. The outside transformer is labeled 480/277, but the referenced disconnect is in fact a 480 volt disconnect.

I would read 277 phase voltage ( phase to ground) if it’s a star configuration because 480/1.732 is 277. Eureka, am I thinking correctly?


Nevertheless, as the main, the disconnect needs a neutral per the 2017 Code 250.24 (c) regardless of the type of load and also, of course, a properly sized GEC and electrode.

OK, let's see if we can stop all the guessing everybody is doing.
Where is the meter located?
Is the disconnect you show the only Service Equipment?
What else is supplied in the building (or whatever) from the same transformer?
If you can call the POCO ask them what the service is? (Easiest solution)

Roger

 

[LadyDi]

OK, let's see if we can stop all the guessing everybody is doing.
Where is the meter located?
Is the disconnect you show the only Service Equipment?
What else is supplied in the building (or whatever) from the same transformer?
If you can call the POCO ask them what the service is? (Easiest solution)

Roger

Yes, you are right; I’ll call the utility company.

Also, the meter is located on the side of the outside transformer and goes straight into the building into the referenced disconnect. Then, the feeders run to another disconnect about 150 feet from the main disconnect.

Best,
Diana

 

[LadyDi]

OK, let's see if we can stop all the guessing everybody is doing.
Where is the meter located?
Is the disconnect you show the only Service Equipment?
What else is supplied in the building (or whatever) from the same transformer?
If you can call the POCO ask them what the service is? (Easiest solution)

Roger

Here is a few pics to help illustrate the layout.

 

[LadyDi]

The LB into the building straight into the back of the referenced disconnect.

 

[LadyDi]

The referenced disconnect.

 

[LadyDi]

The second disconnect located across the building.