Wire distance from service panel

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  #1  
Old 08-09-05, 06:58 PM
whardy7
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Question Wire distance from service panel

I am running new service from a 320 amp service the util company is putting in. From their pole I will be running copper underground and the distance will need to be about 180'. I need to run two different lines to go to one downstairs panel and one upstairs panel. I am out of city limits and do not have any inspections, but I still want to do it right and safe. What kind of wire should I run to insure proper operation at that distance?

Thank you for any help,
Wayne
 
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  #2  
Old 08-10-05, 03:37 AM
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The installation that you are contemplating cannot be described in two easy paragraphs. IMHO prior to doing this job you should have enough background to already know the answers to the questions that you've asked, thus your asking of these questions makes me think that you will get into trouble on the things that you don't even know to ask. You need to read the appropriate sections of the NEC as well as several wiring books, and then you will need to get your work double checked. Even if inspections are not required, IMHO you should pay an inspector to go over your work.

Now on to details, such as they are:

1) You can't do this with two separate feeders.

You the run from the meter pole to the building is a run between detached structures. So you can only have a single feeder. Additionally, a building requires its own main disconnect, which can either be a single breaker in a single panel, or a grouping of up to six breakers, possibly in 6 panels right next to each other.

2) You need to figure out what circuit capacity you will actually be installing. You must do a demand load calculation for each of the panels. If you are actually installing a 320A service, then you need 350 kcmil conductors, giving less than 2% voltage drop at 320A; voltage drop would not be a problem.

3) You would be using THWN or XHHW conductors in conduit.

-Jon
 
  #3  
Old 08-10-05, 07:09 AM
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Where are you at? Here the poco would run alum feeder to the meter cab. Alum would be cheaper if you had to buy it, 3 wire run of copper big enough for this would be a bit pricey.
 
  #4  
Old 08-10-05, 08:15 AM
whardy7
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Wire distance...

sberry27, I am in Oklahoma - it is CREC.

Winnie, I appreciate your response. I am a little perplexed by it, though. You say prior to this job I should already know these things - it IS prior to this job and I AM trying to learn these things. I have been reading Taunton Press's book, but I have also chosen to gather knowledge through a forum actually called "Do It Yourself". I thought that's why it was a DIY forum - to ask questions about things you don't know, that you are thinking about doing yourself. I am assuming that the knowledge I need to do this right is out there and that I will therefore have the knowledge I need prior to doing the job. Okay, rant over!

Thanks for continuing with the explanation - it helped me better know the questions to ask. Another question, if you wilt tolerate me for a little longer! One reason I was planning on going with two feeds is because the power company is coming out of their box with two feeds and no disconnect. They don't put a disconnect for that size service. What are my options, then?

Wayne
 
  #5  
Old 08-10-05, 08:39 AM
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Here we would put the meter on the building and bring the feed to that . Have you spec'ed this all with the poco field engineer yet? My company charges like 6$ a foot all installed to bring the power in (3 if you have it piped all the way so they dont have to trench, 4 " sewer pipe works great, not for the risers though) what I am wondering is why put it so far away if you dont have to? Yes, this kind of meter base is designed to feed 2 panels but it would be unusual to do it in this fashion and having upstairs and downstairs panels you would need outside disconnects for this type of install. Depending on layout I spose you will anyway here, I dont buy common disconnects, I use a main breaker with main lug feed thru, costs about the same and you can feed outbuildings, well, air cond, etc from it. Personally I would be getting back with the poco engineer here and find out what options I really had before investing, you may be suprised. Some people dont have good luck with those guys but I have great results and I make sure I am right there with him when he makes the drawings, specs the wire and writes the work order. My neoighbor did one,, didnt listen to this advice and took someones word on the phone, he has a dinky little long service drop,,, ha, by having this in solid agreement they bring in wire 1, maybe 2 sizes bigger than they normally would have on mine, (have the same setup as you are describing, 2 200's) I get them to move the pole, upsize wire,,, all for free. I had another one that started with 3000$ install fee at the first conversation my Dad had with them, seemed like a firm deal, by the time I got it ironed out, 0$, it helps to know how they think. Ok, this is beside the point,,, but at first it seems everyone in the office runs things at the poco, but lineman have a lot of discretion, I give each one a qt of berries in season,, might be good for you to give coffee and a couple of cookies,,, ha, I really treat the linemen like gold, they have saved me a LOT of money and headaches over the years. I had one a while back where the office said "there may be a charge for this" I said,,, ok,, I understand, I mention that to the lineman,,, he says,,, I am going to tell the office this was a good idea anyway,, ha
 

Last edited by sberry27; 08-10-05 at 08:53 AM.
  #6  
Old 08-10-05, 10:33 AM
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If the metering equiptment is at the utility pole, and the POCO requires that any connections on the "load" side of the metering equiptment are the customers reponsibility, then you will need two 3-wire sets of 2/0 copper cable for the Service Entrance Conductors. This presumes each set conducts 150 amps for a distance of 200 ft.

At the house, each set of 3 cables will terminate on a 150 amp circuit-breaker. This "seperation" at the "Load" end is permitted by Art 230.2. Art 230.71 permitts two sperate Dis-connecting Means.

Good Luck & Enjoy the Experience!!!!!!!!
 
  #7  
Old 08-10-05, 09:48 PM
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Whardy give this a read. It addresses your situation where it talks about installing a service greater than 200 amps and less than 400 amps.
http://www.selfhelpandmore.com/homew...eter/index.htm
 
  #8  
Old 08-11-05, 03:56 AM
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Sorry about my rant; if you look through the archives, you will see several situations where people started buying and installing things without doing the research, backed themselves into 'well, I spent lots of money on this wire that you are telling me is wrong, what can I do to make it work...'

What I meant to say was 'You should be reading certain things, including a couple of general books on wiring, and most of the beginning sections of the NEC. You should learn about how to do demand load calculations and voltage drop calculations. With this background, the answers to most of the above questions will be obvious, and you will likely have several new questions.'

PATTBAA, thanks for the pointer to 230.2...I had to read closely on that one. There is a _general_ requirement that one building have a single 'service', fed by a _single_ set of service entrance conductors. That was why I said 'you can't do what you want to do' and suggested a single set of 350 kcmil conductors. However what PATTBAA points out is NEC 230.2, which itself points to 230.40 Exception 2. Essentially, if you have two separate 'service disconnecting means' _right next to each other_ in your home, you can feed each with a separate 'set' of conductors, and have it count as the single permitted 'set' of conductors. You are still limited to having these service disconnects in a single location, so that you can go to one point and turn off power.

Given this, and your desire to have one panel 'upstairs' and one 'downstairs', then what I would do is bring the conductors in at the location where you want your downstairs panel, and at this location install a panel and a 'disconnect' for the upstairs panel. Finally you would run a 'feeder' from the disconnect to the upstairs panel.

Some additional thoughts: rather than separating 'upstairs' and 'downstairs' I would suggest separating 'large loads' and 'small loads'. In particular, with the long service entrance conductor run, you _will_ experience some voltage drop. You can minimize this to 'acceptable' levels, however if you have a large central air unit, your lights _will_ flicker every time it kicks in. If you put all of your lights, computers, small devices, general appliance outlets on one of the service entrance conductor sets, and all of the large loads (Electric heaters, AC, range, etc) on the other, then you could have relatively large voltage drop one one set, and much smaller on the other.

Check with your power company. Many will allow more than 320A worth of breakers (for example, 2 200A panels) fed from a 320A meter base, as long as the calculated load is less than 320A. Others will actually let this be used as a calculated 400A service.

Sberry makes good points about getting the power company to do a larger part of this run. One downside is that when the power company does the run, _they_ get to decide how thick the wire is, and they generally use thinner wire than you might prefer, especially for a long run. This can lead to voltage drop problems. But as Sberry notes, you may be able to get them to use larger wire.

Good luck!

-Jon
 
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