Wire and conduit size for detached shop building


Hello all. I am running power to detached shop on a hobby farm in rural Missouri. For the work, permits and inspecions are not required.
Power will come from 200 Amp meter box. Straight run to breaker box will be 130'. Trench will have to be moved over some to avoid corner of double wide. I am figuring 160' wire length from meter, through trench, and up to breaker box. Breaker box has 100 amp main that will accept 1/0 wire.
Will be using 230 volt 50amp lincoln 225 arc welder on occasion for equipment repairs. There will be a 3HP 110v air compressor there also. Other electric items will be drills or circular saws on occasion and in the winter we will have a block heater for the tractor plugged in sometimes.
To figure wire size, can I just add up the amps from all the items that I might be using at the same time, or is it supposed to be rated for the breaker size.
The guy at the local supply store suggested 2-2-4 bury grade cable. Can this be put in conduit?
Voltage at the meter box is 125v. If I have a voltage drop of 10 volts in the wire, does this mean I will have 115v at the shop? Is this enough to keep the motors in the tools happy?
On grounding, can I run a ground wire from the breaker box to a nearby freeze proof water hydrant, or should I still plan on puting in a grounding rod? Should the ground and neutral in the breaker box be bonded?
I know this is a lot of questions, but the more I try to read, the more confused I get.
Thank you for your time.
Kevin
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On Mon, 13 Sep 2010 00:09:21 +0000, krifenbu_at_pcassistant_dot snipped-for-privacy@foo.com (krifenbu) wrote:

These should be OK on a 100 amp service.

Short answer? No.
Wire size is based on the size of the main breaker size coming in, not the loads (which can, and will, change over time). If your sub panel has a 100 amp breaker, that's what determines the minimum size wire coming into the sub panel.

1. 2-2-4 What? AL or CU? If AL no, too small for 100 amps.
2. How big is the conduit? 4"?

Standard USA voltage is 120/240, not 125 volts. (Not saying you measured 125 volts, but you work from the standard...) 10 volts drop is too much, wire is too small... Most equipment will work OK on 115 volts, but in fact you must work from 110 volts (120 - 10).

Is this a main panel from the meter, or a sub panel from another panel? Big difference. No you don't ground to a water hydrant... You put in the required number of ground rods (minimum of 2, often more). If the building's floor is cement, and has rebar, you must tie the rebar into the building ground too...

Prepare to be even more confused, you will get a lot of advice, some of it not correct, on Usenet. Go to garagejournal.com, and setup an account. Then post in the right forum (electrical and lighting) and you will get good advice--the guys there are great at this, do it all the time.
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responding to http://www.homeownershub.com/construction/Wire-and-conduit-size-for-detached-shop-building-20215-.htm krifenbu wrote:
PeterD wrote:

Sorry aobut that, the 2-2-4 is aluminum and I was thinking 1-1/2" conduit. If I go to 1/0, 1/0, 2 aluminum, what conduit do you suggest? I will be laying the wire in the trench and sliding the conduit on the wire one piece at a time.
Double wide is not there yet. Will be running the wire for the trailer and the shop into the 200 amp service at meter pole. It has a main 200 amp breaker and place for 3 feeders to attach on each leg. The guy doing the wiring only does trailers and he only deals with 4/0 aluminum. That just costs too much for my use not to mention it won't fit into the breaker in the breaker box in the shop.
Will also be putting pvc water pipe in the same trench and maybe a 3/4" or 1" conduit for bringing phone or ethernet cable to building.
Floor is currently gravel in the shop, The guy that quoted putting concrete said there would only be rebar near the entrance. I will tie it in if I get a chance. What size ground wire is needed?
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On Mon, 13 Sep 2010 12:18:09 +0000, krifenbu_at_pcassistant_dot snipped-for-privacy@foo.com (krifenbu) wrote:

No, and no. #2 Al won't do 100 amps. No way you'll pull that stuff through a 1 1/2" conduit. Technically AWG 1 AL would work for 100 amps, but you probably won't be able to find it, instead you will have to go to #1/0 which is rated at 120 amps.

The 2x1/0 + 1x#2 will work in AL. I'd go with 3" miniimum, and 4" is more realistic. That stuff is stiff and difficult to work with. Also make 100% sure you get cable rated for direct burial, as even with it in a conduit that is necessary to prevent insulation failure in the future.

4/0 SE would work for the other service (shop/garage) well. But that's big stuff! Normally 4/0 is used with 200 amp boxes. 1/0 is used with 100 amp boxes. That's why your breaker is rated for 1/0 wire! <g>

True, cost is not the main issue, but it won't fit a 100A breaker.

Make sure you have proper spacing between power and communications lines.

Personally, I use as big as possible, but for a 4/0 feed, a 2/0 neutral. For a 1/0, use of a smaller neutral is acceptable. That third wire is not a ground, it is the neutral, and is a current carrying conductor.
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responding to http://www.homeownershub.com/construction/Wire-and-conduit-size-for-detached-shop-building-20215-.htm krifenbu wrote:
PeterD wrote:

Thank you for the input. I believe I will go with the 2x1/0 1x2 aluminum. I took some pics of the breaker box and meter box if you are interested, they are at http://www.pcassistant.net/land.html
Thanks again.
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To use 4/0 Al for a feeder protected at 200 amps, you need to meet one of a few conditions: (a) the feeder is the main power feeder of a dwelling unit (carrying all the loads and only the loads of the dwelling unit), (b) you do a load calculation for the feeder and it comes out below 180 amps, or (c) you use a wire with a 90C insulation and you take extra measures to allow the use of the 90C rating. Otherwise, you need to use 250 kcmil Al.

I think the OP was asking about the Grounding Electrode Conductor (GEC) to the Ufer ground (the rebar), not the neutral conductor. The GEC is sized based on the largest ungrounded conductor. For Al, 1/0 or smaller requires a #8 Cu GEC, 2/0 or 3/0 requires a #6 Cu GEC, and 4/0 or 250kcmil requires a #4 Cu GEC. For an Al GEC, go up 2 sizes on the GEC. Regardless, connections to a ground rod need not exceed a #6 Cu, and connections to a Ufer ground need not exceed #4 Cu.
Cheers, Wayne
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On 9/12/2010 7:09 PM, krifenbu wrote:

I'll not make a recommendation, because if i do I'll get flamed. But i will tell you this:
We ran a detached garage, with the following equipment and at times a very busy "fab" shop.
Lights, overhead gas unit heater, grinders, 110v air compressor, drop lights, fans, and a Hobart beta mig 200A welder.
The detached garage was fed by a 10/3 wire UNDERGROUND, and hooked to a 30 A breaker in the house panel. NEVER, in the 35 years of being at that location with that setup, did we pop the breaker in the house. So read that as you will. I am currently fixin' to run a wire to my barn which will have similar stuff as mentioned above and i'm gonna run a 6/3 with ground to the pole box. (about 400 feet).
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Faulty 30A breaker?
Cheers, Wayne
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On 9/13/2010 6:07 PM, Wayne Whitney wrote:

who knows? Never was a problem.
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On Mon, 13 Sep 2010 16:34:44 -0500, Steve Barker

Yea, you'd get flamed for saying the above! <g> I'd recommend something a bit bigger than 6/3 if you are going 400 ft. Otherwise the drop will be serious when you start that welder.
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On 9/13/2010 6:13 PM, PeterD wrote:

welders don't pull anything NEAR what people think they do. That's why there's special provision for their wiring requirements. We ran a 200A mig in that detached garage (sometimes nearly wide open) with never a problem with it being fed with a 10ga.
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On Tue, 14 Sep 2010 07:15:04 -0500, Steve Barker

A 200 Amp MIG would probably draw about 25 amps at 240 volts.
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wrote:

receptacle. Many large residences have a three phase supply (like my sister's). 230 V Schuko receptacles go up to 16 A, with a 2,5 mm^2 conductor (#16). A water heater is 20 A (4 kW) #14. A usual service is #10 (35 A). Code says that in all installations a GFCI breaker must be installed, 30mA differential current.
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In US terminology, a GFCI trips at 5 mA differential current. A device that trips at 30 mA differential current would be called GFPE, ground fault protection for equipment. Almost all US AFCI breakers also incorporate GFPE as part of their propietary AFCI technology.
Cheers, Wayne
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wrote:

panel, so if it would be 5mA we would have lots of nuisance trips. There are a few times when we get nuisance trips with 30 mA and I have to play detective to find the leakage (usually humidity or bad insulation). I know that in USA you have GFCI receptacles, but you also have 120 V. IMHO the best brand for breakers is ABB, closely followed by Geyer and Siemens (first Swedish-British, second and third german).
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