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#204781 - 01/09/12 10:10 AM 310.15(B)(6) Last sentence??
Up2code Offline
Member

Registered: 05/15/07
Posts: 55
Loc: Missouri
Could someone please explain the (3) sections that sentence is referring to? Section 220.61(B) seems to be the closest answer I can find.

36 unit apartment building, each dwelling unit supplied by single phase 120/240, 100 amp feeder panel. My question is can grounded conductor to EACH unit be reduced? According to section 220.61(B)(2) & 220.61(C)(1) I would think not.

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#204786 - 01/09/12 08:39 PM Re: 310.15(B)(6) Last sentence?? [Re: Up2code]
George Little Offline
Member

Registered: 01/18/04
Posts: 1492
Loc: Michigan USA
Not quite sure what you mean by "explain the (3) sections that sentence is referring to?" But I would think the code would allow the reduction of the feeder grounded conductor size amounting to 30% of the range, oven, cooktop and dryer load. It's written kinda goofy but the handbook explains it a little bit. The feeder grounded conductor can be reduced the way I read it. Based on the type of feeder being a Delta.
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#204787 - 01/10/12 05:07 AM Re: 310.15(B)(6) Last sentence?? [Re: Up2code]
George Little Offline
Member

Registered: 01/18/04
Posts: 1492
Loc: Michigan USA
Just figured out what you were referencing. It don't change my answer. I was thrown by the subject line being part of question duh.
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#204789 - 01/10/12 09:07 AM Re: 310.15(B)(6) Last sentence?? [Re: Up2code]
Up2code Offline
Member

Registered: 05/15/07
Posts: 55
Loc: Missouri
Thanks George. I definetly could have worded original post differently.

As far reducing the size of each feeder grounded conductor (neutral), 220.61(B) allows 70% reduction ONLY IF...

Service or feeder supplies household electric cooking appliances AND electric dryers.

Let's say for example, 10 feeders were supplying 10 storage units, then no neutral reduction in each feeder, correct?

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#204793 - 01/10/12 12:20 PM Re: 310.15(B)(6) Last sentence?? [Re: Up2code]
HotLine1 Offline

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Registered: 04/03/02
Posts: 6804
Loc: Brick, NJ USA
This text from '08 NEC 220.61 (b)(1) the key word is 'household'
(1) A feeder or service supplying household electric ranges, wall-mounted ovens, counter-mounted cooking units, and electric dryers, where the maximum unbalanced load has been determined in accordance with Table 220.55 for ranges and Table 220.54 for dryers

IMHO, you cannot use this for storage units.

That all said, what type of loads would you have in a storage unit?

Common wiring methods for apartment 'sub-panels' is SER.
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#204796 - 01/10/12 03:58 PM Re: 310.15(B)(6) Last sentence?? [Re: Up2code]
Up2code Offline
Member

Registered: 05/15/07
Posts: 55
Loc: Missouri
Storage unit feeders were just used as examples. I was just trying to find an NEC reference that would state you could or could not reduce the feeder neutral, for NON household loads.

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#204800 - 01/10/12 07:28 PM Re: 310.15(B)(6) Last sentence?? [Re: Up2code]
George Little Offline
Member

Registered: 01/18/04
Posts: 1492
Loc: Michigan USA
Up2Codeó Your neutral only has to be large enough to carry the maximum calculated unbalance load between the neutral and any one ungrounded conductor. So if your storage units had a total load of 50a. and 30 of those amps were 240v. (figure 120/240v feeder) Then your neutral would only have to be rated 20a. But you have to be careful because your neutral can not be smaller than your Grounding Electrode Conductor if this is Service.



220.61(A), 250.24(C)(1)
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