Electrical question

I am running to a sub panel in a detached garage from my main panel for about 210 feet. I have talked to many people locall and get
different answers.
I finally called the inspector and got a different answer than he had told me previosuly. Once he told me #4 copper with a # 6 ground and another time he told me #3 copper with a #6 ground.
He said I cant use the 2-2-4-6 wire the local supply house is tryign to sell me. He said aluminum would have to be #1 if in conduit and 1/0 if direct buriable. He said copper would be cheaper.
I dont want to tick the guy off but what should I do at this point?
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The ONE thing I know. Do what the inspector says. You need a friend here.
Karl
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What's the load?
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It is a 100 amp sub panel in the detached garage. It will be ran 210 feet to my current attached garage.
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It is a 100 amp sub panel in the detached garage. It will be ran 210 feet to my current attached garage. ************************************************ Do you need that much? Can you use a smaller sub? What do you want to power? Big compressor? Welder? Time machine? I assume 240 V. AL is always cheaper!
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On Wed, 28 Oct 2009 10:35:51 -0400, the infamous "Buerste"

Where's the load? Between stryped's ears. PDFTFT.
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than Christianity has made them good." --H. L. Mencken
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Same exact measurements for me. My electrician said #3 copper with #6 bare ground or aluminum 2/0 direct bury. However, aluminum 2/0 direct bury was $350 for 200', and the same length for 3 lines of copper #3 and #6 was $880. Copper cheaper than aluminum? I don't think so.
Steve
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Is that 360 dollars for 3 strands of wire? What is the difference between 1/0 and 2/0? I assume 1/0 is bigger. He told me if I go direct burial I would have to use 1/0.
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Is that 360 dollars for 3 strands of wire? What is the difference between 1/0 and 2/0? I assume 1/0 is bigger. He told me if I go direct burial I would have to use 1/0.
That would be three strands plus a ground in a direct bury enclosure 2/0 size. I'm not totally sure of this, so the best thing is to ask your electrician. Maybe someone here will know.
Steve
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wrote:

Wire size starting with the smasllest
#10 #8 #6 #4 #3 #2 #1 #0 or 1/0 "one ought" #00 or 2/0 "2 ought" #000 or 3/0 "3 ought" #0000 or 4/0 "4 ought" 350 MCM or 350,000 circular mils. 500 MCM
Normally #4 (in copper) is good for 100 amp, however you must go up one gauge size for every 50 feet. Looks like #0 to me. Ground wire will stay at #6.
Thank You, Randy
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stryped wrote:

the difference is the diameter and current rating at the same temperature.
1/0 is 0 gauge, one size up from 1 guage.
2/0 is 00 gauge, one size up from 0 guage.
http://www.powerstream.com/Wire_Size.htm is a wire chart for copper wire.
http://www.interfacebus.com/Aluminum_Wire_AWG_Size.html is a chart for aluminum wire.
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The handbook says: For a 16 amp 110 V circuit running 200 feet you should use #4 copper for a 2% voltage drop. At 16 amps 220 V you should use #6. This should please the pickiest of inspectors.
Bob Swinney
I am running to a sub panel in a detached garage from my main panel for about 210 feet. I have talked to many people locall and get different answers.
I finally called the inspector and got a different answer than he had told me previosuly. Once he told me #4 copper with a # 6 ground and another time he told me #3 copper with a #6 ground.
He said I cant use the 2-2-4-6 wire the local supply house is tryign to sell me. He said aluminum would have to be #1 if in conduit and 1/0 if direct buriable. He said copper would be cheaper.
I dont want to tick the guy off but what should I do at this point?
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To meet code, the sub panel would have to be fed with wire sufficient to carry the entire rated load of the sub panel. That is why such heavy wire is called for.
Bob Swinney
I am running to a sub panel in a detached garage from my main panel for about 210 feet. I have talked to many people locall and get different answers.
I finally called the inspector and got a different answer than he had told me previosuly. Once he told me #4 copper with a # 6 ground and another time he told me #3 copper with a #6 ground.
He said I cant use the 2-2-4-6 wire the local supply house is tryign to sell me. He said aluminum would have to be #1 if in conduit and 1/0 if direct buriable. He said copper would be cheaper.
I dont want to tick the guy off but what should I do at this point?
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How many amps will the breaker be rated at that feeds this panel from the main panel? That is the number that maters in the calculations.
Wes -- "Additionally as a security officer, I carry a gun to protect government officials but my life isn't worth protecting at home in their eyes." Dick Anthony Heller
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100 amps
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Stryped
One thing that has been forgotten by some of us here, me included, is that the CB in the panel feeding your proposed subpanel has to be sized to protect the wire to the subpanel. One is not allowed by code to use an X amp circuit breaker and feed a wire of less rating. Turnabout is OK under most circumstances.
Copper will be more expensive but certainly not 3X.
100 amp service will require #1 if in conduit or direct burial. Has to do with heat. One or two sizes larger for 200+ feet because of voltage drop.
And all this discusion is based on 220 single phase. 2 hots, a neutral and a ground. Conduit and/or shield, if any, is not allowed as a ground. There are no current or voltage ratings that I am aware for conduit or ground. They serve a different purpose. Use of these creates ground loops.
Bob AZ
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Yup. My home has a 100 amp service. Back when copper was fairly cheap, I ran #2 copper out to the garage in case I upgraded my home's service and also needed more capacity out in the garage.
Currently the garage's 100A sub panel is fed from a 60A breaker in my main panel that protects the wire with room to grow a bit.
Now there is a rule that you want faults to be interupted as close to the fault as possible. The 100A breaker in the sub panel seems to violate that rule but it seems to be a common practice to feed a bigger breaker in this case from a smaller one.
Wes -- "Additionally as a security officer, I carry a gun to protect government officials but my life isn't worth protecting at home in their eyes." Dick Anthony Heller
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Wes
This should be OK although a 60 amp breaker feeding a sub panel usually is acceptable. It is an exception to the code as I remember. The subpanel in this case does not usually employ a main breaker. The panel is fed directly to the buss bars in the sub panel. Probably depends on the inspector. I do this in my shop and the subpanel is a 125 amp panel. The bus bars have a provision to fed them without a breaker. If a main breaker were required it would be fed to the breaker terminals through the breaker onto the buss bars in the subpanel.
There are other types of panels that have terminals to feed the panel and then install a breaker between the terminals and the buss bars. I believe this is called a service panel and the subpanel that is being discussed here is a branch circuit breaker panel or branch circuit panel. Take a look at HD next time at the different panels available.
"<The 100A breaker in the sub panel seems to violate that rule but it seems to be a common practice to feed a bigger breaker in this case from a smaller one.">
This would seem OK but would be simply a breaker that would never see its total capacity since it would be fed with a lower ampacity breaker. Thus negating its purpose. Simply put a device without purpose.
One of the significant items in this thread is that the original poster will probably have difficulty obtaining a 100 amp branch breaker for the panel that feeds the subpanel. The limitation will be that a 100 amp breaker branch breaker will not fit. A 60 amp probably will.
Bob AZ
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snip---

He must own shares in one of the copper wire companies. Copper is not cheaper, although it is better.
Harold
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On Sat, 31 Oct 2009 08:50:11 GMT, "Harold and Susan Vordos"

Copper wire is far less likely to give you trouble in the long run, IF it is pulled in carefully without insulation damage. But it's going to cost you a lot more.
You have to go one or two sizes larger with Aluminum to equal the ampacity at a specified voltage drop compared to Copper wire. But the Aluminum wire costs you SO much less, you can bump it an extra size larger and have less problem with lights dimming.
You can go Way Huge if you can get a full roll of surplus 4/0 or250MCM or 350MCM Aluminum wire for cheap, and you place a big enough 4" or 5" conduit for the way huge wire - the problem is, you'll have to use straight-splice or pin conversion lugs to get the huge wires into the normal size breaker lugs and panel lugs at each end.
Safety grounds don't need to be mega oversized for voltage drop at your distance - they only need to carry enough fault current to trip the breaker, voltage drop isn't a big dea if the resistance is low enough to do it fast.
Stryped: You mentioned somewhere back in the thread using jacketed wire and going partial direct bury over an obstruction - DON'T. That's going to be the one spot that gives you endless trouble. Someone's going to get overly enthusiastic with a pick or a shovel and cause some serious excitement... And could get hurt in the process.
Do it right - either dig your trench way deep and get the conduit under the obstruction (wall fooring or big tree root), or get a jackhammer and blast a slot in the boulder.
If you have no choice but to go over the obstruction and the conduit is going to be less than 18" dirt cover below finished grade, put a few inches of sand and then a 4" to 6" thick reinforced (welded wire or rebar) protective concrete cap over the conduit - preferably mixed with Red concrete colorant so people figure out "Do Not Dig! Power wires here!"
--<< Bruce >>--
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