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
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
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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, ......."
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.
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.
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.
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, I thik the messanger is the support system. You would have to have rings and saddles, though. Is that what you are saying?
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
You would have to have rings and saddles, though
Or weather proof tie wraps, or lace it to the messenger cable with string.
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I do not know anything that spells out how we have to support the UF to the messenger.
I agree. Bubble gum might even work!
I was fixin to ask what we thought an approved method was. I notice the cable company has a cool "serving" machine (for you sailors) that wraps a wire around the strand and the cable as it goes along. I am not sure what the wire is but it does seem to hold up in the sub tropics.
How about messenger suppurted Liquidtight Metalic Cunduit?
Tom
Nope. Don't even think about it. Only cables as listed in Table 396.10(A).Unless your in an Industrial setting then you can use a few other conductors.
sides likidtite can only be 36" long max??
Just joking.
Liguidtite flexable metal conduit has no NEC limit to length. As long as you have no more than 4 bends, it's not subject to damage, the operating tempiture is observed & supported per 351-8.
Not saying I would do unneeded piping with LFMC just that there is no NEC limit.
Tom