Feeder

[captainwireman]

Where, specifically, is it stated in the NEC that you can not feed a 240V sub panel that only uses 240 V circuits without utilizing a neutral without including the neutral if the feeder panel includes both phases and the neutral?

 

[jumper]

Are you asking if it required to run a noodle to a sub panel that does not need one?

A noodle is only required to be run with a grounded service supply, SEC.

250.24(C) Grounded Conductor Brought to Service Equipment.
Where an ac system operating at less than 1000 volts
is grounded at any point, the grounded conductor(s) shall
be routed with the ungrounded conductors to each service
disconnecting means and shall be connected to each disconnecting
means grounded conductor(s) terminal or bus. A
main bonding jumper shall connect the grounded conductor(
s) to each service disconnecting means enclosure. The
grounded conductor(s) shall be installed in accordance with
250.24(C)(1) through (C)(4).

 

[captainwireman]

Where, specifically, is it stated in the NEC that you can not feed a 240V sub panel that only uses 240 V circuits without utilizing a neutral without including the neutral if the feeder panel includes both phases and the neutral?

Situation, sub panel with only 240 V branch circuits that do not require a neutral.
Feeder panel: 120-240V single phase with neutral and ground.

 

[jumper]

Situation, sub panel with only 240 V branch circuits that do not require a neutral.
Feeder panel: 120-240V single phase with neutral and ground.

I guess I am a bit dense and still do not clearly understand your question.

 

[augie47]

Where, specifically, is it stated in the NEC that you can not feed a 240V sub panel that only uses 240 V circuits without utilizing a neutral without including the neutral if the feeder panel includes both phases and the neutral?

You will not find such a requirement., As jumper pointed out, the neutral is required at a SERVICE panel on a systems with a neutral, but there is no requirement to extend the neutral beyond the service if it is not needed.

 

[iwire]

I agree with the others, you are never required to bring a neutral to a sub-panel that has no line to neutral loads.

 

[infinity]

I agree too, not required if the circuits are only 240 volts.

 

[mjf]

(sigh) but, we are required to have a neutral in a switch box (for future possible installations).

No hack would ever jump off the OP's sub panel with a 120v circuit in the future and use the ground as the neutral, right?

(sighs again) Just think the NEC should be more uniform. Either require neutral everywhere the ground could possibly (sometime in the future) be used as a neutral or require it as needed presently and deal with the future in the future.

One way or the other.

 

[infinity]

(sigh) but, we are required to have a neutral in a switch box (for future possible installations).

No hack would ever jump off the OP's sub panel with a 120v circuit in the future and use the ground as the neutral, right?

(sighs again) Just think the NEC should be more uniform. Either require neutral everywhere the ground could possibly (sometime in the future) be used as a neutral or require it as needed presently and deal with the future in the future.

One way or the other.

A switch box is one thing because in the past a certain amount of current was permitted on the EGC. I see no benefit of requiring a feeder neutral if you have something like 2000 amp 3?, 3W distribution board that only supplies 3? loads.

 

[jumper]

(sigh) but, we are required to have a neutral in a switch box (for future possible installations).

No hack would ever jump off the OP's sub panel with a 120v circuit in the future and use the ground as the neutral, right?

(sighs again) Just think the NEC should be more uniform. Either require neutral everywhere the ground could possibly (sometime in the future) be used as a neutral or require it as needed presently and deal with the future in the future.

One way or the other.

Good point.

 

[jumper]

A switch box is one thing because in the past a certain amount of current was permitted on the EGC. I see no benefit of requiring a feeder neutral if you have something like 2000 amp 3?, 3W distribution board that only supplies 3? loads.

I think Mike/MJFs point was that in many cases the neutral at the switch box is not needed and maybe never will be.

UL screwed up and the NFPA is trying to fix it.

 

[iwire]

(sighs again) Just think the NEC should be more uniform. Either require neutral everywhere the ground could possibly (sometime in the future) be used as a neutral or require it as needed presently and deal with the future in the future.

One way or the other.

And I prefer rules fit the job at hand, not rules just to keep things the same.


To force a neutral to industrial / commercial panels that have no neutral loads would be a significant expense. Also in those applications it is much more likely that qualified personal are working on it.

On the other hand, as much as I hate it the cost to provide a neutral at a switch box is not much and in homes the likelihood of a DIY working on it is much higher.

(Truth be told I would rather they did not force a neutral at either)

 

[mjf]

Don't get me wrong. I stopped "down on white, back on black" years ago. Long before it was required.

I just think it's wrong to require neutral instead of requiring devices that either don't put voltage on the EGC or can only be installed where neutral is present.

The same homeowner/hack is still going to install devices that need a neutral to operate by making use of the EGC in existing installations.

Are the device requirements also changed/changing?

 

[mjf]

And I prefer rules fit the job at hand, not rules just to keep things the same.To force a neutral to industrial / commercial panels that have no neutral loads would be a significant expense. Also in those applications it is much more likely that qualified personal are working on it.On the other hand, as much as I hate it the cost to provide a neutral at a switch box is not much and in homes the likelihood of a DIY working on it is much higher. (Truth be told I would rather they did not force a neutral at either)

Very good point about who is likely to be working on it.

 

[jumper]

Are the device requirements also changed/changing?

I believe they are supposed to, do not know if UL or other NRTLs have yet.

Don G probably knows, he is good at tracking this stuff.

 

[captainwireman]

This is in a residence. The sub-panel is controlling HVAC equipment. At this point I really need to look into the application because the question asked of me is starting to get a little vague. Surely (hopefully) the equipment maintenance receptacle is installed. Where does it get its power I wonder?

In any case, the agreement seems to be in favor of a neutral only being required on SECs. I was lending to the grouping of multi-wire branch circuit conductors as the argument but they are not feeders. I personally would never allow such an application if I was the AHJ. The point being is this is a residence subject to who knows what kind of future work to be done.

Interesting discussion, thanks all.

 

[captainwireman]

I guess I am a bit dense and still do not clearly understand your question.

No, my attempts to frame a question in a general way makes me the dense one! :dunce:

 

[mjf]

This is in a residence. The sub-panel is controlling HVAC equipment. At this point I really need to look into the application because the question asked of me is starting to get a little vague. Surely (hopefully) the equipment maintenance receptacle is installed. Where does it get its power I wonder?

In any case, the agreement seems to be in favor of a neutral only being required on SECs. I was lending to the grouping of multi-wire branch circuit conductors as the argument but they are not feeders. I personally would never allow such an application if I was the AHJ. The point being is this is a residence subject to who knows what kind of future work to be done.

Interesting discussion, thanks all.

And I apoligize for hi-jacking your thread.

 

[kwired]

The point being is this is a residence subject to who knows what kind of future work to be done.

I don't care if it is a residence or not. Is it a good idea to run a neutral most of the time? Probably yes. But if you are feeding all 240 volt equipment and happen to be using every space in the panel, why run a neutral at all? I understand this may not happen to often, but...

It is a design issue and not a code issue and hopefully it always stays that way.

 

[infinity]

This is in a residence. The sub-panel is controlling HVAC equipment. At this point I really need to look into the application because the question asked of me is starting to get a little vague. Surely (hopefully) the equipment maintenance receptacle is installed. Where does it get its power I wonder?

In any case, the agreement seems to be in favor of a neutral only being required on SECs. I was lending to the grouping of multi-wire branch circuit conductors as the argument but they are not feeders. I personally would never allow such an application if I was the AHJ. The point being is this is a residence subject to who knows what kind of future work to be done.

Interesting discussion, thanks all.

Although I agree that in a residential setting someone might be tempted to use the 240 volt only panelboard for a 120 volt load it currently is permitted by the NEC to run a 240 volt feeder with no neutral. I'm curious to hear what the CMP would say about your proposal.

I don't care if it is a residence or not. Is it a good idea to run a neutral most of the time? Probably yes. But if you are feeding all 240 volt equipment and happen to be using every space in the panel, why run a neutral at all? I understand this may not happen to often, but...

It is a design issue and not a code issue and hopefully it always stays that way.

I agree a design issue.