overhead branch circuit conductors/ sub panel

[Riograndeelectric]

I have a jop to run a sub panel to a detached barn that is about 150 foot away from the house . I can not find anythning in the code or am not looking in the right place but what is the maximum length of overhead conductors allowed between suuports or can you run a 150 foot span and support wire at both ends only. this will be #4 triplex for a 50 amp sub panel
Thanks

 

[aline]

I have a jop to run a sub panel to a detached barn that is about 150 foot away from the house . I can not find anythning in the code or am not looking in the right place but what is the maximum length of overhead conductors allowed between suuports or can you run a 150 foot span and support wire at both ends only. this will be #4 triplex for a 50 amp sub panel
Thanks

See Article 225.6

 

[charlie]

. . . to a detached barn that is about 150 foot away from the house . . . maximum length of overhead conductors allowed . . . can you run a 150 foot span . . . #4 triplex . . .

The length of the span is a function of the strength of the neutral. I can tell you that the determining factor for the standard #4 triplex is the anchoring points at the house and barn for just 150 feet, not the strength of the neutral.

 

[mdshunk]

I sure wouldn't span 150 feet, even if you insisted. Put one pole, midspan. Otherwise, the thing will need to be strung up tight as a banjo string in the winter, and it'll be super-saggy in the summer. The tension on the house knobs will be incredible.

 

[charlie]

Marc, those charts were developed by an electric utility to make sure they never had a problem with a leaning pole. If you have an eye bolt on each end and follow the manufacturer's charts for stringing tension (not the ones by any electric utility), you can string #4 triplex 150 feet with no problem. It is OK to be tight to a point and you don't put long spans of triplex on P knobs. :smile:

 

[mdshunk]

It is OK to be tight to a point and you don't put long spans of triplex on P knobs. :smile:

You don't put them on screw-in knobs, but many people do. 150 feet is still nuts, if you ask me.

 

[ItsHot]

inground

inground

Why not go inground?

 

[mdshunk]

Why not go inground?

I might guess that anyone that wants to go 150 feet in one shot, without a pole, is probably interested in "cheap".

 

[charlie]

Marc, we install spans of #4 and #2 triplex all the time with a span and a drop to install a service. The span will be as long as 200 feet and the service drop will be no more than 125 feet. The span conductors will be pulled up pretty tight while the service drop will be pretty slack because of the sideways pull on the pole. We use a set of blocks to get tension and a P knob (house knob or screw-in knob) is not going to hold.

 

[Riograndeelectric]

I might guess that anyone that wants to go 150 feet in one shot, without a pole, is probably interested in "cheap".

not being cheap!!!! . I asked the forum for help so I know how to bid this job. I was trying to determine if you could go 150 foot but I had my doubts but that is what this forum is about. . the customer does not want to trench due to sprinkler line locations are not known . I my self would prefer to go underground.

 

[mdshunk]

not being cheap!!!! . I asked the forum for help so I know how to bid this job. I was trying to determine if you could go 150 foot but I had my doubts but that is what this forum is about.

I was talking about the customer, not you. I work for cheap people all the time, so I'm pretty used to hearing that requirement. Charlie says no problem. I say there's no way I'd do it. I'd really like to see a span chart from Southwire or someone, but I can't find one. Is there ice and snow load to consider in your area? #4 is only good for 1884 pounds, and you'll get there pretty quick when the wind blows icy cable that's already strung up tight.

 

[charlie]

. . . you'll get there pretty quick when the wind blows icy cable that's already strung up tight.

You are absolutely correct! That is why you need to do all of the calculations before doing this type of work. We use a program called Sag 10 to generate our sag charts. :smile:

 

[Buck Parrish]

the customer does not want to trench due to sprinkler line locations are not known . I my self would prefer to go underground.[/QUOTE]


Those sprinkler lines are easy to repair. I have in the past brought water pipe fittings with me and instead of taking time to try not to hit the water lines I just trench right through them.
It doesn't hurt that my brother is a licensed plumbing contractor.
But really thier easy to repair.

 

[iwire]

Those sprinkler lines are easy to repair.....

That does not matter.

The customer does not want to go unerground....

Please answer the questions asked.

 

[iwire]

I am curious, if I was to sting this triplex 150' how much sag would I be looking at in summer?

What I am getting at is the points of attachments are going to have to be pretty high to maintain the required clearances in the middle of the span and of you use a mast it is going to have to be pretty stout.

 

[charlie]

I am curious, if I was to sting this triplex 150' how much sag would I be looking at in summer?

What I am getting at is the points of attachments are going to have to be pretty high to maintain the required clearances in the middle of the span and of you use a mast it is going to have to be pretty stout.

Sorry Bob, I will not go in to work until Tuesday and that is where the program lives. However, you are correct on your assumptions. Remember that a utility will normally install a service drop about 125 feet (that is our maximum) and will string spans of 200 feet. The service drops will leave the pole at about 20 feet and hit the home at about 13 1/2 feet to leave the low point at 12 feet fairly close to the home. The spans and drops are anchored to the poles with through bolts so the cable will break before pulling loose from the pole. We generally will not accept P knobs on homes for the anchoring point. :smile: