4th Conductor needed?

[randynavarro]

I can post pics if needed but hopefully it's easy enough to describe without them.

Subpanel is supplied with 3 conductors, not 4.

All circuits in the subpanel are 240 volt for electric wall heaters. So, all white conductors are fed from breakers. There are no "neutrals" or neutral bus.

Would 4 feeder conductors still be required? There's no neutrals to isolate from grounding conductors.

[Jim Katen]

Originally posted by randynavarro

I can post pics if needed but hopefully it's easy enough to describe without them.

Subpanel is supplied with 3 conductors, not 4.

All circuits in the subpanel are 240 volt for electric wall heaters. So, all white conductors are fed from breakers. There are no "neutrals" or neutral bus.

Would 4 feeder conductors still be required? There's no neutrals to isolate from grounding conductors.

In that case, there's no need for the 4th wire.

It might be a good idea to have a 4th wire and a neutral terminal to allow for future use, but it's not a requirement.

- Jim Katen, Oregon

[Jeff Remas]

250.142(B) does not have an exception for what you are describing.

Jim, please explain or verify.

[StevenT]

The 4th conductor is not necessary because everything is wired for 220 and there is no neutral, just two hots and a ground.

So long as no 120 appliances are being fed from this panel, a neutral is not needed.

The whites should be taped black (or red)

I do not know how that relates to the specific code you mention.

[Jim Katen]

Originally posted by Jeff Remas

250.142(B) does not have an exception for what you are describing.

Jim, please explain or verify.

Hi Jeff,

250.142(B) lays out the conditions under which you can use a grounded circuit conductor to ground non-current carrying parts of equipment on the load side of a service disconnect.

Since the installation that Randy described has no grounded circuit conductor, 250.142(B) doesn't apply.

- Jim Katen, Oregon

[Jeff Remas]

Yes it does apply. How do you bond the panel to equipment ground without violating 250.142(B)?

One of the factors in this situation is what code cycle it is under.

The next factor is whether or not it is within the same building or a separate structure.

What I need to see is what specific code section allows this.

I would not allow this in my jurisdiction and would cite what I already did as one of the violations. I need to be proven wrong with code sections, not opinion.

[Jeff Remas]

OK, after reviewing and THINKING about your responses, I will have to back down but under conditions on this one.

There is nothing that would required a 4th wire, However:

1) If you ran 2/2/4 SER cable to the sub panel then the 4awg wire would have to go to the equipment grounding terminal bar. Nothing can be connected to the neutral (grounded conductor) bar. This way in the future, connecting a 120vac circuit would not work.

2) The bonding screw for the neutral bar would have to be left out.

3) As an AHJ I would want a sticker on the panel stating 240vac loads only on 240vac dbl pole breakers.

So you are right, nothing in the NEC prohibits this but it all depends on how you make the connections in the panel.

[Jim Katen]

Originally posted by Jeff Remas

OK, after reviewing and THINKING about your responses, I will have to back down but under conditions on this one.

There is nothing that would required a 4th wire, However:

1) If you ran 2/2/4 SER cable to the sub panel then the 4awg wire would have to go to the equipment grounding terminal bar. Nothing can be connected to the neutral (grounded conductor) bar. This way in the future, connecting a 120vac circuit would not work.

2) The bonding screw for the neutral bar would have to be left out.

Well, that would be one acceptable way of doing it, but certainly not the only way. You could just as easily use the neutral/grounding terminal bar that's supplied with the load center and leave the bonding screw in place. This is done all the time in commercial installations that have only 240v loads and no grounded conductor.

3) As an AHJ I would want a sticker on the panel stating 240vac loads only on 240vac dbl pole breakers.

And what would be your code reference to back you up?

It sounds like you object to the design of the installation and want there to be a provision for a future change to accommodate 120v circuits. The NEC doesn't address such design issues and it certainly doesn't require that someone install provisions for future expansion.

I agree that your suggestions would be prudent, but they'd hardly be required.

- Jim Katen, Oregon

[Jeff Remas]

In and industrial setting or commercial setting like I am used to, I understand. My requests are reasonable and I don't think that any of the electricians would fight me on them. I keep a good relationship with the contractors just for this reason.

That would be my call.

BTW on all of the 480/3ph power panels that I worked on or any power panel that did not utilize a grounded conductor, all of the connections were to the equipment grounding lug or bar, not the neutral with the bonding screw in place.

[StevenT]

In my neck of the woods, the commercial work I deal with is EMT and BX. Unless an isolated ground is necessary and/or a neutral is necessary for an appliance that needs 240 & 120, we only run 2 wires.

[StevenT]

By the way, I don't particularly care for using EMT as a ground. I can't count how many times I've come across disconected EMT.