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#93666 06/06/05 05:52 AM
Joined: Jun 2004
Posts: 613
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Is there any restriction on the use of 12-2 UF wire for a overhead span between a dwelling and an accessory building?

The length of the run is 80 feet over a driveway not subject to truck traffic.

I'm aware of the hieght rules. (12ft)

Does the UF wire have to be a minumum size for the length of the span?

I can't go underground because of the paved driveway.

shortcircuit

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#93667 06/06/05 08:00 AM
Joined: May 2005
Posts: 23
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It's not single conductor cable, so that rule doesn't apply.

It has to be installed as messenger-supported wiring, compliant with Article 396, that's all I see [Linked Image]

#93668 06/06/05 08:08 AM
Joined: Jan 2004
Posts: 1,507
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Member
My answer would be that the code does not permit this type of installation in residential. I went to Article 340 on UF cable and read that it's not permitted per 340.10(11) that sends you to Article 396. In 396.10(B) the first words are "In industrial establishments only, ......."


George Little
#93669 06/06/05 08:37 AM
Joined: Aug 2003
Posts: 1,374
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Moderator
Quote
225.18 Clearance from Ground.
Overhead spans of open conductors and open multiconductor cables of not over 600 volts, nominal, shall have a clearance of not less than the following:
(1) 3.0 m (10 ft) — above finished grade, sidewalks, or from any platform or projection from which they might be reached where the voltage does not exceed 150 volts to ground and accessible to pedestrians only
(2) 3.7 m (12 ft) — over residential property and driveways, and those commercial areas not subject to truck traffic where the voltage does not exceed 300 volts to ground
(3) 4.5 m (15 ft) — for those areas listed in the 3.7-m (12-ft) classification where the voltage exceeds 300 volts to ground
(4) 5.5 m (18 ft) — over public streets, alleys, roads, parking areas subject to truck traffic, driveways on other than residential property, and other land traversed by vehicles, such as cultivated, grazing, forest, and orchard

340.10 says that you must comply with part II of Article 396. George, I think you are only quoting one of the rules found in part II, which is for individual conductors.


Ryan Jackson,
Salt Lake City
#93670 06/06/05 08:38 AM
Joined: May 2005
Posts: 41
L
Member
Type SE and UF cables are not the same, as listed in the code. RE: Article 340.12 Uses not permitted. 9) Where exposed to direct rays of the sun, unless identified as lunlight resistant, and, 11) As overhead cable, except where installed as messenger-supported wiring in accordance with Part II of Article 396.
I do not believe 396 excludes this installation for residential, but you might double check. It DOES have section B that specifically addresses Industrial, but is not inclusive of this section in its requirements, only the type of support systems.
Also, refer to 225.6, which list minimum sizes for these installations, which would be #8 cu, #6 AL, for over 15'.
BUT, the cable must be sunlight resistant.

#93671 06/06/05 08:52 AM
Joined: May 2005
Posts: 41
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Member
Whooops, sorry. 225.6 is for individual conductors. Guess it's just a support system, clearance to ground, and sunlight resistant cable, as far as I can see.
Hey, what about triplex; it has a built in messanger cable.

#93672 06/06/05 09:29 AM
Joined: Jan 2004
Posts: 1,507
G
Member
Your correct Ryan, I only referenced part of the Article but, read the definition of Messinger Supported Wiring and when I read it I don't see using UF 12/2 for this type of application with out a support system.

After reading Article 396 more closely, I guess it would be permitted to install UF cable in a "Messenger Supported Wiring system, as discribed in 396.2. It also appears that it would be more practical to install triplex.

[This message has been edited by George Little (edited 06-06-2005).]


George Little
#93673 06/06/05 09:43 AM
Joined: Aug 2003
Posts: 1,374
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Moderator
George, I thik the messanger is the support system. You would have to have rings and saddles, though. Is that what you are saying?


Ryan Jackson,
Salt Lake City
#93674 06/06/05 03:16 PM
Joined: Jun 2004
Posts: 613
S
Member
Messenger supported UF wire?

I just assumed it was OK to run UF as an overhead span because I've seen it so many times around here in New England to feed sheds or accessory buildings.

With a porcelin screw-in anchor on each end of the span, proper drip loops, and enough ground clearance, what danger could UF wire present compared to single conductor or a triplex overhead span installation?

Was UF ever allowed as an open non-mesenger supported overhead span?

shortcircuit

#93675 06/06/05 04:51 PM
Joined: Jan 2003
Posts: 4,391
I
Moderator
Quote
You would have to have rings and saddles, though

Or weather proof tie wraps, or lace it to the messenger cable with string. [Linked Image]

I do not know anything that spells out how we have to support the UF to the messenger.


Bob Badger
Construction & Maintenance Electrician
Massachusetts
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