No neutral

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hhsting

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I have generator which plans show is separately derived, wye windings, however ATS is 3 poles, and there are no neutral loads or unbalanced loads so no neutral is brought from gen to load. The gen has main breaker.


Questions:


1. I thought in order to be separately derived ATS has to be 4 poles no?

2. Gen Wye winding would have to be grounded with GEC and GES regardless of neutral or no neutral at the GEN no?

3. How would this work no neutral? Should their be system bonding jumper at gen main breaker above situation?

4. Where would the EGC connect to if no system bonding jumper at the GEN?

5. In the event load becomes unbalanced in future would not be objectionable current thru EGC thru metallic enclosure thru system bonding jumper to GEN i.e EGC act as neutral?


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1. No, not really. The number of poles is not strictly determined by the definition of a separately derived system. For example, if the system were a true 3-wire delta then only 3 poles would be required. Since there is no neutral installed, not having a switch pole for it does not change whether it is separately derived. Now, one might argue that a provision to switch the neutral should be installed because the system could have a neutral added in the future. But I'm not aware if there's a code section that would explicitly require that.

2: Maybe not strictly, but practically speaking, probably yes. See 250.20(B) where it says specifically 'where the the neutral is used as a circuit conductor.' However if it were not grounded then ground detectors would be required per 250.21(B).

3: Yes, if the system is grounded. There must be something to create an effective ground-fault current path.

4: See 3.

5. I don't see how. That would require some kind of fault or an EGC improperly connected to a load to act as neutral.
 
electrofelon said:
this doesn't make sense. You say grounded wye, but then you say no neutral conductor. Which one is it?
Click to expand...



The Generator has wye windings. Gen main breaker and gen itself is all in one enclosure outside. It’s big generator enclosure that has separate rooms for big gen, breaker etc. No neutral is brought from generator main breaker to downstream equipment. All balance load.

The question was with no neutral bought to downstream equipment, should the generator wye windings be grounded with grounding electrode conductor and grounding electrode system at the gen main breaker or not and should their be system bonding jumper at gen breaker or not?


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There would be no current on it, other than fault current, so it is not a neutral, and with the supplied loads not requiring a conductor for unbalanced currents, the bonding would only be for return of fault currents, so it would be treated as an equipment ground when it leaves the generator.
 
hillbilly1 said:
There would be no current on it, other than fault current, so it is not a neutral, and with the supplied loads not requiring a conductor for unbalanced currents, the bonding would only be for return of fault currents, so it would be treated as an equipment ground when it leaves the generator.
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The generator neutral point is still a neutral point. A green conductor between the neutral point and the first overcurrent device is a supply side bonding jumper. (This conductor could be white and called a neutral, it would make no practical difference.) From the first overcurrent device onward the green conductor is an EGC.
 
jaggedben said:
The generator neutral point is still a neutral point. A green conductor between the neutral point and the first overcurrent device is a supply side bonding jumper. (This conductor could be white and called a neutral, it would make no practical difference.) From the first overcurrent device onward the green conductor is an EGC.
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But if this was a corner grounded delta, would the corner be the neutral? I think not. Doesn’t matter where the bond is, if the system does not use the common as a conductor, it is not a neutral,
 
hhsting said:
The Generator has wye windings. Gen main breaker and gen itself is all in one enclosure outside. It’s big generator enclosure that has separate rooms for big gen, breaker etc. No neutral is brought from generator main breaker to downstream equipment. All balance load.

The question was with no neutral bought to downstream equipment, should the generator wye windings be grounded with grounding electrode conductor and grounding electrode system at the gen main breaker or not and should their be system bonding jumper at gen breaker or not?


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Click to expand...
Ok, so there is a neutral in the generator compartment? In the flesh, accessible, you can touch, feel, smell, or lick it?
 
hillbilly1 said:
But if this was a corner grounded delta, would the corner be the neutral? I think not. Doesn’t matter where the bond is, if the system does not use the common as a conductor, it is not a neutral,
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In a corner grounded system the white would not be a neutral even though it would be a circuit conductor. It would still be a grounded conductor. The location of the bond affects whether the conductor between the generator and the overcurrent device is considered a grounded circuit conductor or a supply side bonding jumper. The code requirements for those two, and for EGCs, have minor differences.
 
electrofelon said:
Ok, so there is a neutral in the generator compartment? In the flesh, accessible, you can touch, feel, smell, or lick it?
Click to expand...

What does regular wye windings generator all in one enclosure with main breaker come with? Do they have neutral to main breaker or not?


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hhsting said:
What does regular wye windings generator all in one enclosure with main breaker come with? Do they have neutral to main breaker or not?


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Click to expand...

Ok, you must have a neutral at the generator, just not brought to ATS. Some stuff you said in this thread and the other one on the same topic, made it sound like there was no neutral anywhere.
 
jaggedben said:
1. No, not really. The number of poles is not strictly determined by the definition of a separately derived system. For example, if the system were a true 3-wire delta then only 3 poles would be required. Since there is no neutral installed, not having a switch pole for it does not change whether it is separately derived. Now, one might argue that a provision to switch the neutral should be installed because the system could have a neutral added in the future. But I'm not aware if there's a code section that would explicitly require that.

2: Maybe not strictly, but practically speaking, probably yes. See 250.20(B) where it says specifically 'where the the neutral is used as a circuit conductor.' However if it were not grounded then ground detectors would be required per 250.21(B).

3: Yes, if the system is grounded. There must be something to create an effective ground-fault current path.

4: See 3.

5. I don't see how. That would require some kind of fault or an EGC improperly connected to a load to act as neutral.
Click to expand...

#1: NEC 2014 section 100 separately derived says electrical source other than service having no direct connection to circuit conductors of any other electrical source other than those established by grounding and bonding. So if neutral is not brought at all how can this be separately derived?

#2: 250.20(B) says 4 wire wye shall be grounded if neutral is used as circuit conductor. If no neutral is brought from gen breaker how is it used as circuit conductor? I am still confused does it need to be grounded?


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Will the ATS function without a neutral brought to it? Does it need it for the internal operation?
 
hhsting said:
#1: NEC 2014 section 100 separately derived says electrical source other than service having no direct connection to circuit conductors of any other electrical source other than those established by grounding and bonding. So if neutral is not brought at all how can this be separately derived?
Click to expand...

Think it through. You're getting it backwards. Normally an unswitched neutral is what makes it not separately derived, since if it is not switched then the neutral circuit conducutors from both sources are directly connected to each other. If there's no neutral then no circuit conductor would have a direct connection. Therefore it is separately derived.

#2: 250.20(B) says 4 wire wye shall be grounded if neutral is used as circuit conductor. If no neutral is brought from gen breaker how is it used as circuit conductor? I am still confused does it need to be grounded?
Click to expand...

Already answered this. Read the code sections cited. You seem to be getting it backwards again. In your case the neutral is not used as a circuit conductor. Therefore the system is not strictly required to be grounded, it can have ground detectors instead. But it must have one or the other.
 
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