running power to garage

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  #1  
Old 02-10-02, 09:05 PM
Redd2001
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Question running power to garage

i want to run power from my homes service panel to a garage that is 250-300 ft away.
What type of wire guage is needed?
1. circuit 1- 3-300 watt light bulbs
2. circuit 2- 4-5 outlets grnd faults i think
 
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  #2  
Old 02-11-02, 09:07 AM
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Will there be any special loads on the outlets? Compresser?
Freezer? Space heaters?
 
  #3  
Old 02-11-02, 07:45 PM
Redd2001
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running power to garage

there will be an occassioal power saw, normal garage working stuff. there are 3 -300 watt wiil be on 41 circuit outlets on another 4-6 each
 
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Old 02-11-02, 08:09 PM
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We're talking about National Electrical Code (NEC) requirements with regard to wire size. 250 - 300 feet shouldn't matter under 60 amps. But the wire guage depends entirely upon what breaker size you put in your in your main panel to feed this line. Per Table 210-24 (1999 Code) 15 amps = #14 (although I'd recommend #12), 20 amps = #20, 30 amps = #10. 40 amps = #8, 50 amps = #6, 60 amps = #4. Ground conductor is per article 250, but if you use the same size as the current carrying conductors you will meet or exceed the requirement. Recommended practice is to install a small load center out there. There are disagreements about a ground rod for the garage, but I am of the school that believes you do not need one if you bring an appropriately sized ground conductor with you from the main ground bus in your main panel and don't have a water pipe or metallic conduit also joining the house with the garage. I hope that helps without further confusing the issue for you. If this raises questions post back and we'll try to help further.

Juice
 
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Old 02-11-02, 08:21 PM
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Since you are running sooooo far, do you really want to take the chance of running just two circuits to the garage? I realize it wasn't your question, but I would suggest you run a 60 ampere cirucit to a small load center (6 or 12 circuit panel) in the garage.
assuming 300', 240V, 40 amp load #4AWG conductors will result in less than 3% volt drop.
 
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Old 02-12-02, 09:48 AM
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To my knowledge, the NEC does not allow running multiple branch circuits to a separate building on the same premises.
You'll need to run one set of feeders to the building. Voltage drop is calculated from the point of your utility connection (transformer) to the end of the longest branch circuit outlet away from the sub-panel in the new building. I figured 400 total feet one-way and a 60 amp/240 volt feeder branch circuit in my calculation and come up with:

2 - 1/0 copper hot conducters.
1 - #3 awg copper neutral conductor
1 - #4 awg equipment grounding conductor (based on the large distance to the new building).

2 - 3/0 Aluminum hot conductors
1 - #1 awg Aluminum neutral conductor
1 - #2 awg Aluminum equipment grounding conductor(same reason as copper egc)

Also, if there will be no metallic paths, telephone line, etc., between the service-panel's building and the separate building. You don't need to install the equipment grounding conductor feeder. You can bond the sub-panel and grounding electrode conductor to the neutral at the separate building.

Also, you had better install a ground round at the second building. I have yet to see an electrical inspector waive that requirement. A #6 awg bare copper conductor can be used from the sub-panel's grounding bar to the ground rod.

You can buy direct burial rated single wire and bury it 25" deep (you don't have underground rodent problems?). You'll have to physically protect the wire out of the service panel down into the ground and out of the ground into the new building's sub-panel.

Question: Why the 300 watt lights?
 

Last edited by thinman; 02-12-02 at 10:09 AM.
  #7  
Old 02-12-02, 02:40 PM
Wgoodrich
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Juice, I suspect Thinman is right about the ground rod being required not only by most inspectors but I now believe that a change in the 2002 NEC blows any solid ground for a stance that the 4th wire provides the grounding electrode system to the second building. I think that we need to concede that a grounding electrode [ground rod] must be driven at the second building. Reason for my adjusted stance is a new section added to 250.32 of the NEC. See below;
2002NEC 250.32
(E) Grounding Electrode Conductor. The size of the grounding electrode conductor to the grounding electrode(s) shall not be smaller than given in 250.66, based on the largest ungrounded supply conductor. The installation shall comply with Part III of this article.

If you check most feeders such as SER cable have a grouding conductor sized by 250.122 as an equipment grounding conductor. 250.66 required to size the grounding electrode conductor would require a larger specially installed grounding electrode conductor tying that rod at that first building to that second building. This added rule stops you from being able to say that a grounding electrode is present at the second building as required in 250.50 because the grounding conductor in most feeders are not sized as a grounding electrode conductor but are sized as an equipment grounding conductor.

Then if you check the commentary added in by the Handbook they not only confirm it in words but confirm it with drawings showing the intent that a rod also must be installed at each building.

While the 2002 didn't change that much the addition of part E of 250.32 does change your stance from being on solid ground in my opinion.

Thinman, I don't think HandyRon was implying that 60 amp was a demand or connected load of that building that Redd2001 was discribing but a safe amacity to be able to carry the load and then some to suggest adequacy of load and compensating from voltage drop in the same statement of his implied 60 amp suggested service size to that detached structure. I suspect that from what redd2001 was discribing that he probably would have a demand load more realistically of about 25 to 35 amps in that accessory building if going by the info he provided us. I am not disagreeing with you as to the calculations your provided using the numbers you started with, just thought I would mention what I interpreted HandyRon to be saying as a generic 60 amp referance of a safe service sizing.

If it were me I think I would jump up to the 4 awg copper and consider it a 100 amp service to that detached structure. Cost should be about the same between a 6 awg and 4 awg feeder. Extra cost might be worth the future growth that may occur.

Hope this helps

Wg
 
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Old 02-13-02, 09:37 AM
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Good morning Wgoodrich,

Yeah, I suppose my 60 amp load calc is a bit beefy. Just wanted to cover the "fudge factor." I've seen load centers installed that were based on only the present load. Then down the road, things get added increasing the load, or can't get added because the capacity is not there. Redd2001 can base the VD on a Ron's estimated amp load and use smaller conductors than what my calc came up with. If I had a garage, I would go with the larger feeders taking future additions into consideration. It would be nice to know the actual total distance to the garage and approximate length of the furthest branch circuit outlet from the sup-panel. Just my two-cents.
 
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Old 02-13-02, 07:48 PM
Redd2001
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Thank you for your comments. I had stated that this was a garage, I did this for what I thought was going to be an easy answer to an easy project. I did not realize all the "bits" to it.
My project is a barn that i built two years ago. 36'X32'. To avoid frther misleads, hopefully, I have enclosed a design to my electricall plans.
I belive that my first step was to bury the "wire" to the barn, that is the #4 or #6 awg underground type cable, correct??

Here are a few answers to questions ya'll have posted
300 watt lights to lite up all of barn
very seldom will there be a load on the outlets at the same time
use would be circular saw, water tank heater , electric fence, not much past that
in the diagram i have shown an oulet for a welder that is a dream to a need at this time, one of you said, an additional load for the future, that is one.
Please help me on some of the electrical terms you use, I probably know what you are talking about just not is these terms

1.grouding conductor
2.grounding electrode conductor, equipment grounding conductor.
3.branch circuit outlet
4. 2 - 1/0 copper hot conducters.
1 - #3 awg copper neutral conductor
1 - #4 awg equipment grounding conductor
Thanks for your help,
redd
 
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Old 02-13-02, 08:05 PM
Redd2001
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running power to garage

hope fully i can send diagram
 
  #11  
Old 02-13-02, 08:22 PM
Redd2001
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running power to garage

hope fully i can send diagram
 
  #12  
Old 02-13-02, 08:34 PM
Redd2001
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running power to garage

hope fully i can send diagram
 
  #13  
Old 02-14-02, 05:35 AM
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You're starting to stutter, Redd.

You have to post thae image to a web page, then link to it here using img and /img code. See the VB code info at the bottom of the page.

for example: This picture


is displayed by coding the following:
{img]http://forum.doityourself.com/readersdigest/images/handymanmagazine.jpg[/img}

Change the first and last { } to square brackets [ ]
 
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Old 02-14-02, 12:30 PM
Wgoodrich
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Abnormal, I think making replies on this forum can make us all stutter at times but it was fun watching someone else do the stuttering other than me and your reply to him was prescious.

Loved it and laughed,

Wg
 
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Old 02-14-02, 05:54 PM
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Wg, although installed prior to 2002.250.32 I'm afraid that my garage will now have to be fitted with a GEC. I have to agree with your logic and your quotations of the Code, and now that I know what I know it's just going to bug me that my installation could be better/safer than it is. Thanks for the explanation, and keep on rockin'.

Juice
 
  #16  
Old 02-14-02, 11:25 PM
Redd2001
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I think i finally have stopped sttt uuu tterr ring!!
if you cannot read the text:
3- red are 3-300 watt lights on one light switch
yellow are outlets all on 1 circuit
the rectangle on topside is where the circuit panel will be
the welder site is for the future

any advice or info will be a great help
redd

 
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