3-wire Sub Panel

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davedottcom said:
If a sub-panel is for 240 volt loads only, is it a violation to feed it with only 3 wires? (No Neutral)
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No problem if it is past the service equipment. This is a design issue but I would take a neutral "just in case". :)
 
charlie said:
No problem if it is past the service equipment. This is a design issue but I would take a neutral "just in case". :)
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I agree. If you don't run the neutral than someone will just use the EGC for the neutal later.
 
C3PO said:
I agree. If you don't run the neutral than someone will just use the EGC for the neutal later.
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They would be guilty of a violation, but is the 3-wire sub panel a violation if clearly marked "240 Loads Only - No Neutral Available"?
 
davedottcom said:
They would be guilty of a violation, but is the 3-wire sub panel a violation if clearly marked "240 Loads Only - No Neutral Available"?
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It would not be a violation if you did that. Personally though I would run the neutral, but I agree that you are not required to.
 
davedottcom said:
is the 3-wire sub panel a violation if clearly marked "240 Loads Only - No Neutral Available"?
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The marking is not a violation of the Code. ;-p
 
Consider a service supplying 208/120 3? to a building where the tennant brings in a bunch of single phase 240 volt loads (imagine woodworking shop).

When I set a boost autotransformer, I can supply 240 Volt to a sub panel but I can't get a neutral.

If the design doesn't require a neutral, why penalize the customer with a higher bill?
 
davedottcom said:
They would be guilty of a violation, but is the 3-wire sub panel a violation if clearly marked "240 Loads Only - No Neutral Available"?
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As charlie stated, it is not a violation to have a 3-wire 240 volt 3-phase panel without a neutral.

It is not a violation to have a 3-wire 240 volt 3-phase delta service panel without a neutral if the utility transformer does not have a neutral point.

On a related note, I went to do some work in an old "grocery store" that had a high-leg delta sservice. There were several walk-in freezers for storage. These were all 240 3-phase units. A feeder from the service hit a gutter with discoonects for the freezers.

I did not know at the time, but someone before me had installed a small load center to the gutter. The neutral bar was connected to the panel can. They fed 120 volt loads out of this. So, the conduit system and enclosures were being used as the neutral.

Being an old store, much of the original EMT was in bad shape, not strapped properly, rusty, loose connectors and couplings. I was crawling around in the dark attic with a flashlight, and I bumped one of the conduits, and sparks shot out around the couplings! Woah! I checked in a j-box and one of the cast locknuts was laying in the bottom of the box, it was melted in half with a pool of cooled down molten metal beside it.

I discovered the load center, I called my boss and requested he come out so we could explain to the owner what we had found, and just how dangerous this was. The owner agreed, and we replaced the feed from the service to the gutter and fixed all the messed up stuff.

I'll always remember the sparks flying in that attic when I bumped the pipe.
 
al hildenbrand said:
Consider a service supplying 208/120 3? to a building where the tennant brings in a bunch of single phase 240 volt loads (imagine woodworking shop).

When I set a boost autotransformer, I can supply 240 Volt to a sub panel but I can't get a neutral.

If the design doesn't require a neutral, why penalize the customer with a higher bill?
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Obviously it would depend on the situation, but most of the time I would run the neutral anyway.
 
davedottcom said:
Do you mean the marking is not required?
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Nope, but nice to have (sorta like the neutral if it is needed at some time in the future). Really now, a neutral takes some material and a touch more labor but marking a panelboard with a permanent marker inside the cover is free. :smile:
 
If you do pull a neutral the 2005 NEC requires it to be sized based on the OCD per table 250.122, and not the unbalanced load.
 
davedottcom said:
Do you mean the marking is not required?
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I apologize if my twist of the phrase missed my intended mark. As you wrote your question, I read that the label "240 V only - no neutral", itself, would be against Code.

Used to be, awhile back, we had a smilie choice of a "Razz", a little face sticking its tongue out. ;-p
 
al hildenbrand said:
I apologize if my twist of the phrase missed my intended mark. As you wrote your question, I read that the label "240 V only - no neutral", itself, would be against Code.

Used to be, awhile back, we had a smilie choice of a "Razz", a little face sticking its tongue out. ;-p
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Ya mean a
rasberry.gif
?
 
480sparky said:
Ya mean a
rasberry.gif
?
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That one's OK, but I liked the one that an earlier version of the UBB code supported. As I recall, the tongue went in and out, and included a sense of "wryness".
 
al hildenbrand said:
That one's OK, but I liked the one that an earlier version of the UBB code supported. As I recall, the tongue went in and out, and included a sense of "wryness".
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So one more like
icon_razz.gif
?
 
480sparky said:
So one more like
icon_razz.gif
?
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Yup. This smilie has the gist of my recollection.

I was just casting about in the corners of this Forum for the old one, but the absence is undoubtably a function of the differences between the older UBB code and this version's VB code. Maybe even a little management discretion.
 
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