GAP of running overhead to detached shed

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lordofpi

lordofpi

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New Jersey
I just listened to a message from a good customer of mine asking me to run lighting to a storage shed that sits 50' behind his business. I've done similar projects before, but always in residential: dig trench, run in NMRC, etc.; but in this case, he specifies that he just had his lot paved a few months ago and does not want it cut up just for me to run a cable. The shed itself, if I remember correctly, is only a 10' x 15' single-story. Main building is also single-story.

Basically what this job entails is not even a feeder, but a single circuit for a 75 W bulb and maybe a single receptacle. What is my best strategy? I am a small guy, so I'm not messing around with auger trucks to sink telephone poles. I was thinking maybe a piece of angle-iron up from the building and another up from the shed to bring the wires in.

Along with the logistics of running it, are there any NEC issues which might arise -- other than the obvious need for a disconnect outside. Also, ought I to put a sub-panel in the shed for this, or is a line-side breaker sufficient?

I really appreciate all your help on this one!
 
Depending what type of vehicles you have using this lot will dictate the clearances. Refer to 225.18.

We would be allowed to use a triplexed ACSR cable strung between the buildings or from 2" rigid or IMC masts. The size of the lot will dictate how you support the cable. Use the carrier as the EG.
 
Thanks for the reference; even though the point where the wires would traverse sees very little truck traffic, I'll play it safe and go with the 18' clearance (d).

Is there any acceptable formula for calculating cable sag to ensure I don't screw this up?

Also, this will be my first time using ACSR, how do I size the conductor? Would simply using THHN/THWN-2 be allowed here (especially taking into account that the whole building, including the POCO service drop, is Cu)? I'm not hooking up to another service or panel, but really just bringing one or two 20A circuits to a remote location, so to speak.
 
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lordofpi said:
Also, this will be my first time using ACSR, how do I size the conductor?
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Considering the loads the available conductor sizes will likely be larger then you need.

Have you ever strung up cable?

It is not easy, plan on using a block and tackle or a winch etc.
 
Lordofpi,

What are you talking about regarding angle iron to bring the drop in? Also, as Bob mentioned using a jack rope or block and tackle with a chicago grip will do the job.
 
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dcspector said:
Lordofpi,

What are you talking about regarding angle iron to bring the drop in? Also, as Bob mentioned using a jack rope or block and tackle with a chicago grip will do the job.
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Well, I was tentatively suggesting that I may be able to merely support the cables with an angle-iron mast and bring them down along it, form the drip loop, and pierce the shed wall using just the cable (i.e., no conduit). I am in NJ, which leads me to doubt how acceptable this would be to the AHJ, but it is worth considering.

Also, block & tackle is a very good idea. Believe it or not, this is my first overhead string; as I said initially, I've done underground distribution runs more times than I would care to count, but for some reason I never ran into this situation. That is why I said I don't know if I might be able to get away with THWN-2 or something in that league.
 
lordofpi said:
...sits 50' behind his business. ...but a single circuit for a 75 W bulb and maybe a single receptacle. What is my best strategy? ...I really appreciate all your help on this one!
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I think 225.6(A)(1) would come into play here if you pull individual conductors. I've done this in the past, not too bad to work with.
 
1793 said:
I think 225.6(A)(1) would come into play here if you pull individual conductors. I've done this in the past, not too bad to work with.
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Okay, so it may be a single 20 A branch circuit being pulled (it appears that that is what will happen), and I will use 8 AWG. Sounds good. I guess what's jibbering me up is where does it state (NEC) that wires must be strung in a listed assembly for inside a structure, but for outside they can just be individual?
 
ACSR is not suitable for use inside a building any way shape or form.

We use a mast and weather head in this area. SE cable may be acceptible in yours. 6/3 ACSR is not very hard to string. Even 100' feet is doable by yourself. Pulley or block & tackle is a good idea, you will use them again. Don't stretch it to tight. You will know. Just that last 6 inches can add considerable strain to your supports.
 
ptonsparky said:
ACSR is not suitable for use inside a building any way shape or form.

We use a mast and weather head in this area. SE cable may be acceptible in yours. 6/3 ACSR is not very hard to string.
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Well, if I could get away with ACSR, I suppose I would have to have a splice box somewhere on the outside before I go up the mast and again on the shed after coming down.

Either way, no one seems to be saying whether or not standard THWN-2/THHN is usable in this case?
 
This is a typical mast and ACSR intallation. It happens to go directly to the panel, via a roof flashing, but use a jbox or whatever. Secure it well. I used crimp connections but inline setscrew buttsplices or split bolts will work. If this is not typical for your area, OK it first with the AHJ.
http://i229.photobucket.com/albums/ee174/ptonsparky/PB200046.jpg

You may be able to use a UF cable supported by a cable and sunlight resistant cable ties.
 
ptonsparky said:
This is a typical mast and ACSR intallation. It happens to go directly to the panel, via a roof flashing, but use a jbox or whatever. Secure it well. I used crimp connections but inline setscrew buttsplices or split bolts will work. If this is not typical for your area, OK it first with the AHJ.
http://i229.photobucket.com/albums/ee174/ptonsparky/PB200046.jpg

You may be able to use a UF cable supported by a cable and sunlight resistant cable ties.
Click to expand...


Thanks to all for the info; sorry to be so persistent about this, but I want to make sure I do this right. The only reservation I had about ACSR was going from a copper THHN/THWN-2 to aluminum ACSR, but enough of you seem to do it regularly without any problems.

A friend of mine who is a city inspector in another town knows this place and suggested that the shed to which I am running is not a permanent structure since it is up on planks and does not have a footing, meaning I may have to jack a telephone pole in there after all.

Does ACSR cable isolate the grounded conductor and the EGC since this is not a service drop but rather a subpanel feeder?

I guess I'm off to the supply house for some ASCR messenger attachment spools....
 
I thought that the triplex cable was not listed so....you better get your AHJ to bless it before you use it!
 
jjhoward said:
I thought that the triplex cable was not listed so....you better get your AHJ to bless it before you use it!
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I think article 396.2(3) would allow this cable assembly.
Rick
 
RUWired said:
I think article 300.3 and 310.8(D) would prohibit this as arial cable.
Rick
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I've just looked those sections up, and I have to think otherwise. Examine the exception below:

300.3(A) Single conductors specified in Table 310.13(A) shall only be installed where part of a recognized wiring method of Chapter 3.
[B]Exception[/B]: Individual conductors shall be permitted where installed as separate overhead conductors in accordance with 225.6.
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Things are still a little tentative, but if we follow it to 225.6, we get no ostensible prohibition of THHN, merely a sizing restriction:
225.6(A) Overhead spans. Open individual conductors shall not be smaller than the following:
(1) For 600 volts nominal, or less, 10 AWG copper or 8 AWG aluminum for spans up to 15 m (50 ft) in length, and 8 AWG copper or 6 AWG aluminum for a longer span unless supported by messenger wire.
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You may be correct about 310.8(D), however; I'll have to check to see if the THHN/THWN-2 I use is UV resistant.
 
RUWired said:
I think article 396.2(3) would allow this cable assembly.
Rick
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It seems you are right; "messenger-supported wiring" is definitely an NEC accepted cable assembly, though I will check with AHJ just the same.
 
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