Sub panel needed

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Alwayslearningelec

Senior Member
Location
NJ
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Estimator
Does and outdoor shed type structure , say 10x15'x10' high ' in a backyard HAVE to have a sub panel by or can you just run (2) 20a branch circuits from house panel?
 
busman said:
Wouldn't the MWBC be "one branch circuit"?
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Yes and no. For the purposes of having one supply to a separate structure, yes. Since he needs two 20 amp circuits, no. It's still two 120 volt circuits.
 
How far can you twist this?

But at that point, it's cheaper just to run a single 2-2-2-6.

(B) Common Supply Equipment
Where feeder conductors originate in the same panelboard, switchboard, or other distribution equipment, and each feeder terminates in a single disconnecting means, not more than six feeders shall be permitted. Where more than one feeder is installed in accordance with this section, all feeder disconnects supplying the building or structure shall be grouped in the same location, and the requirements of 225.33 shall not apply. Each disconnect shall be marked to indicate the load served.
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OldBroadcastTech said:
OK, I'm ignorant, I'll bite and am prepared to get slapped down.

WHY a MWBC instead of two hots, two neutrals, and a ground ?
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Baring a few exceptions a separate structure is only permitted to be fed with a single circuit or feeder. In the case of a MWBC (for the purposes of the single circuit requirement) it is considered to be a single circuit. Two circuits with separate neutrals violate the single circuit rule.
 
infinity said:
Yes and no. For the purposes of having one supply to a separate structure, yes. Since he needs two 20 amp circuits, no. It's still two 120 volt circuits.
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Not doubting you, but do you have the Code reference so I don't have to hunt?

Mark
 
busman said:
Not doubting you, but do you have the Code reference so I don't have to hunt?
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Part II. Buildings or Other Structures Supplied by a Feeder(s) or Branch Circuit(s)
225.30 Number of Supplies.
A building or other structure that is served by a branch circuit or feeder on the load side of a service disconnecting means shall be supplied by only one feeder or branch circuit unless permitted in 225.30(A) through (E). For the purpose of this section, a multiwire branch circuit shall be considered a single circuit.
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infinity said:
Baring a few exceptions a separate structure is only permitted to be fed with a single circuit or feeder. In the case of a MWBC (for the purposes of the single circuit requirement) it is considered to be a single circuit. Two circuits with separate neutrals violate the single circuit rule.
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OK, and what is the reason ( purpose, justification, whatever) for this rule ?

Just wondering how and when and why it came to be.
 
OldBroadcastTech said:
OK, and what is the reason ( purpose, justification, whatever) for this rule ?

Just wondering how and when and why it came to be.
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Good question and I have no idea why. A 3-wire MWBC or (2) 2-wire circuits would both require a disconnecting means for their ungrounded conductors at the separate structure so why one is permitted and the other isn't is anyone's guess.
 
Remember, electrical and other codes have evolved over the years.

The MWBC allowance is probably a change from the original 1-circuit exception.
 
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