Generator Neutral

[Bjenks]

I am doing a generator replacement and believe there is a problem with the existing wiring, but wanted to make sure I didn't miss something or over react. Basically, the emergency power from the generator has all three phases and the EGC going to the ATS, but the Neutral goes right into the Emergency Panel and bypasses the ATS. The Normal source Has a Shunt Trip Service Disconnect Breaker fed from a gutter that has the service Neutral tapped with one going to an isolates neutral lug of the disconnect and the other going to the Emergency Panel. So the Emergency Panel has two large Neutral conductors on it, from the generator and from the service. Further the service disconnect neutral is not bonded to the frame and stops at that point with no EGC going to the ATS. So it looks like they bypassed the ATS with the neutral all together. I am going to require the following items to be fixed:
1) the Service Disconnect must have a N-G bond and continue on to the ATS with an isolated Neutral and EGC.
2) Remove the Neutral Service Tap to the Emergency Panel.
3) Remove the Neutral Generator Conductor from the Emergency Panel and re-feed it to the ATS Neutral Lug.
4) Re-Circuit the Emergency Panel so the Only Neutral supplying it is the ATS.

So while I know this will be a cleaner install and the service disconnect must be fixed I am wondering if the bypassing of the neutral to the ATS was allowed? Every ATS installation drawing I have seen shows the Neutral, but it also shows the switched neutral as an option. BTW the generator is acting as a separately derived source.

 

[augie47]

I was doing well until the last sentence
The diferrence between a SDS generator and a non-SDS generator is dependent on the ATS switching the neutral.
What do you mean by the last sentence, BTW the generator is acting as a separately derived source.

 

[Bjenks]

I was doing well until the last sentence
The diferrence between a SDS generator and a non-SDS generator is dependent on the ATS switching the neutral.
What do you mean by the last sentence, BTW the generator is acting as a separately derived source.

That?s what I get for throwing one more point in at the last second. Of course all generators are separately derived sources.:ashamed1: I should have said it is a solid neutral ATS arrangement.

 

[augie47]

Then the system & generator are not an SDS.
@1 on your list would, IMO, be a "must".
#2,3 & 4 I don't see as a major issue other than violating 300.3(B). It seems to be commonplace in generator installs.

 

[Bjenks]

Thanks and 300.3(B) is exactly the code I was looking for on my justification.

 

[jap]

It would be nice if the Neutral landed in the Transfer switch, but, I dont see where 300.3b indicates that all
the conductors have to be kept together in an enclosure.

The rule indicates "Where Used".

If the Neutral is not "Used" in the transfer switch, how could you enforce 300.3b in this instance?

 

[david luchini]

The rule indicates "Where Used".

If the Neutral is not "Used" in the transfer switch, how could you enforce 300.3b in this instance?

300.3(B) doesn't indicated the neutral being "used" in the switch, it indicated being "used" in the circuit...ie, 3phase-4 wire vs. 3phase-3wire. The neutral is being used, as there is a 3phase-4 wire circuit.

If the phase conductors are running from the generator to the ATS, and the neutral is running from the generator to the emergency panel, how can they be contained in the same raceway, trench, cable or cord, etc.? (And the same on the 'normal' side)

 

[jap]

300.3(B) doesn't indicated the neutral being "used" in the switch, it indicated being "used" in the circuit...ie, 3phase-4 wire vs. 3phase-3wire. The neutral is being used, as there is a 3phase-4 wire circuit.

If the phase conductors are running from the generator to the ATS, and the neutral is running from the generator to the emergency panel, how can they be contained in the same raceway, trench, cable or cord, etc.? (And the same on the 'normal' side)

If that's the case why did they have to come up with the new rule for installing a neutral to a switch box
wether it was needed or not for future occupancy sensors?

300.3b would make us install a neutral to every location if that's the way it's interpreted.

 

[jap]

Are you saying I'd have to pull a neutral to a 480v 3ph delta load since if I'm running pipe and conductors
out of a 480v 3ph 4w Y panelboard to feed it?

I dont think so.

 

[jap]

Scratch my last post, bad example, in that instance the neutral would not be needed or used.


Better Example.

120 or 277v lighting where only the hot and switchleg and ground are installed to the switch locations.
The neutral is used in the circuit but not needed at the switch location.

 

[david luchini]

If that's the case why did they have to come up with the new rule for installing a neutral to a switch box
wether it was needed or not for future occupancy sensors?

300.3b would make us install a neutral to every location if that's the way it's interpreted.

One rule has got nothing to do with the other. The requirement for running a grounded conductor to a switch location that controls lighting loads is precisely for what you mentioned, the future possibility of replacing the switch with a device that requires a grounded conductor. In this case, you are required to run a grounded conductor where it is NOT BEING USED in the circuit. But you are not required to bring the grounded conductor to the switch if the conductors enter the switchbox thru a raceway, or the box is in an open wall cavity. In these instances, it would be possible to add the grounded conductor at the later date.

300.3(B) requires that the grounded conductor be run with the phase conductors of the same circuit when it IS BEING USED. For instance, a feeder to a 3ph, 3w panel would require the 3 phase conductors to be run in the same raceway (grounded conductor is not being used in the circuit.) A feeder to a 3ph, 4w panel would require the 3 phase conductor AND the grounded conductor to run in the same raceway (or cable, etc. - the ground conductor is being used in the circuit.)

Nothing in 300.3(B) would require a grounded conductor to be run in the feeder to the 3-wire panel.

edit: Sorry, I answered the phone and didn't finish typing 'til after your posts 9 & 10. Post 9, no a grounded conductor is not needed for the delta panelboard...see above. Post 10, the neutral is not needed or used for the switch as you've described. 300.3(B) does not apply to that installation. But 404.2(C) requires the grounded conductor to be run to the switch, unless it can be added later as in the exceptions. Again, this has nothing to do with 300.3(B).

 

[jap]

What I'm getting at is if the the neutral is being used, which it is in the case of the 3ph 4w instance and also
in all 120 or 277v instances, if the raceway containing the hot conductors take a path to an outlet or
enclosure then by rights by 300.3b shouldnt the neutral always go along with the phase conductors?

If the neutral doesnt apply as I posted in post 10 for a switch locataion, then why would it be any different
for a transfer switch if it was not needed? it could always be added after the fact also.

 

[Bjenks]

We are talking about an ATS for an Essential Electrical System which to me is a bigger deal than a light switch. If the electrical service needs to be completely removed it can be done without having to expose the emergency panel to pulling out a large conductor, but that is all about good design and not NEC stuff.

BTW: there is more to that reason on running the neutral to the light switch for dimmers use. The UL listing of the dimmers had such a small current draw they were allowed to use the ground wire as a return path. However as I understand there became so many dimmers and occupancy sensor dumping current on the ground they decided they needed to start using a neutral instead to eliminate that potential problem.

 

[david luchini]

What I'm getting at is if the the neutral is being used, which it is in the case of the 3ph 4w instance and also
in all 120 or 277v instances, if the raceway containing the hot conductors take a path to an outlet or
enclosure then by rights by 300.3b shouldnt the neutral always go along with the phase conductors?

Yes, in every 3ph 4w circuit, or every 120v or 277v circuit, 300.3(B) requires that the grounded conductor be run together with the phase conductors. For a 3ph 3W circuit, or a 208V or 480V 1 ph 2W circuit, the grounded conductor is not being used.

If the neutral doesnt apply as I posted in post 10 for a switch locataion, then why would it be any different
for a transfer switch if it was not needed? it could always be added after the fact also.

It is needed by the circuit. The circuit from the generator to the emergency panel (via the ATS) is a 4 wire circuit. The grounded conductor IS BEING USED by the circuit. The end of the feeder is a 3ph 4w panelboard. 300.3(B) says the grounded conductor must be run in the same raceway, cable, etc, as the phase conductors.

 

[jap]

It's not a question of a bid deal or a little deal.

To me 300.3b indicates that a neutral where used,shall be run with the phase conductors and grounding
conductors of the same circuit, period.
(Which would be the case for any 3ph 4w circuit or any single phase circuit requiring a neutral)

So if either of these circuits were traveling down a conduit, raceway, gutter or whatever, and then
made a turn or branched off to go to an outlet box (even if the neutral wasnt
needed at that location) by 300.3b shouldnt the neutral go with the hot conductors all the time ?

I'm now starting to question how we ever got away with installing just a hot and a switchleg down a conduit
to a switch outlet location without installing a neutral per 300.3b.

 

[GoldDigger]

I'm now starting to question how we ever got away with installing just a hot and a switchleg down a conduit
to a switch outlet location without installing a neutral per 300.3b.

You got away with it because the neutral was not being used at the location of the switch. In the situation you describe where there is one location that uses the neutral so you have to wire it with the phase conductors, and a separate location down that same branch where it is not being used (specifically where there is no place to terminate it!) then it does not have to go in that direction.
Unless, as a separate issue, you are required to have a neutral there. That requirement for a neutral is the new player in the game. And the neutral must come from the same circuit as the phase conductors and follow the same path (at least when it arrives at the switch outlet.

PS: I do see your point though.

 

[david luchini]

So if either of these circuits were traveling down a conduit, raceway, gutter or whatever, and then
made a turn or branched off to go to an outlet box (even if the neutral wasnt
needed at that location) by 300.3b shouldnt the neutral go with the hot conductors all the time ?

No, assume you had a 3ph 4w branch circuit to say a electric unit heater that had a 3 phase heater and used the grounded conductor for a small single phase fan motor, and you spliced on to the circuit to feed another small 3 phase fan motor...the grounded conductor is NOT being used by the splice circuit running to the 3 phase fan motor. Nothing in 300.3(B) would require the grounded conductor to be run to the new motor (as the grounded conductor is not being used by the circuit.)

I'm now starting to question how we ever got away with installing just a hot and a switchleg down a conduit
to a switch outlet location without installing a neutral per 300.3b.

Because 300.3(B) doesn't require that a neutral be run to the switch outlet location together with the hot and the switch leg. Think of it this way, if 300.3(B) did require that, then why would they have needed to add 404.2(C)?

 

[Bjenks]

I think I found the code and reasoning why your snap switch use to be legal without a neutral:
1) NEC 300 is for general wiring methods.
2) NEC 404 is for switches and if you look at 404.2 Exception in Mike Holts illustrated Guide it says :A neutral conductor isn't required in teth same reaceway or cable with travelers and switch leg (switch loops) conductors. In the NEC Handbook it says the exception holds because the supply and return of the ungrounded conductor is in the same conduit. Thus no heating could happen and a short wouldn't do anything but turn on the light.

So the rule is correct with the exception of a switch leg ran in the same conductor or conduit.

 

[jap]

I think I found the code and reasoning why your snap switch use to be legal without a neutral:
1) NEC 300 is for general wiring methods.
2) NEC 404 is for switches and if you look at 404.2 Exception in Mike Holts illustrated Guide it says :A neutral conductor isn't required in teth same reaceway or cable with travelers and switch leg (switch loops) conductors. In the NEC Handbook it says the exception holds because the supply and return of the ungrounded conductor is in the same conduit. Thus no heating could happen and a short wouldn't do anything but turn on the light.

So the rule is correct with the exception of a switch leg ran in the same conductor or conduit.

In the same conduit might be the key phrasing.
So if we used one large nipple into the transfer switch and kept all the conductors in the same conduit
would we still need a neutral to the transfer switch even though it is not being utilized?

 

[GoldDigger]

So the rule is correct with the exception of a switch leg ran in the same conductor or conduit.

Which is, IMHO, not directly relevant when the switch in question is a transfer switch between POCO and an SDS.