Electrical question for new workshop

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Hopefully, this is a simple question that someone can answer. I'm looking for the type/size cable to run (inside conduit) from my house underground to my new shop.
I am building an unattached workshop in my backyard. I am planning on running my electrical off of my house's panel. I am going to install an auxuillary panel in the workshop (100 Amp). I'm planning on two 15 Amp circuits for outlets, One 220V circuit, and 1 circuit for lighting. The distance between the house and the shop will be about a 40' run.
I know I'll have to have an electrician come out and finish the work, but I want to purchase the correct size wire when I purchase my building materials.
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rlz wrote:

You'll get as many opinions as responses. Just suffice to say, that we ran a detached garage for over 30 years , 300 feet from the house, on an underground direct burial 10/3 . Yes, we had lights, fans, forced air heat, welder, grinders, air compressor, stereo, the whole gammut of equipment you'd find in the average home fabricators shop. Never once in 30 years, did we trip the 30A breaker in the house. YMMV.
steve
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Steve Barker TB wrote:

Let me go on to say, if _I_ were doing what you're doing today, I'd probably run a 6/3 with ground and hook it to a 50A breaker. That's going to be more than plenty for a home shop. That's what I plan to do for the feed to my current 30x40 that is about 400' away. The size of the sub panel can be dictated by how many breakers you want to break it down into. A 100A sub is a bit of an overkill in my opinion. An eight breaker panel would probably be enough, unless you plan to have more than one 220V outlet, or device.
steve
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At 400' away, you had best perform a voltage drop calculation, which will probably lead to increasing the wire size above #6 Cu for a 50 amp circuit.
Cheers, Wayne
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Wayne Whitney wrote:

I hear ya, but as i stated before, we ran a shop 300 feet away for 30 years on a 10ga. The barn i have now, will probably never see a welder, and if it does, it'll be seldom used. Right now, it's been run on a 12 ga. NM-b laying on top the ground for two years. Lights and door openers are all that i have in regular use.
steve
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A quick google for "voltage drop calculator" gave me a web site which claimed that for 30 amps on #6 Cu for 400 feet (one-way), the voltage drop for a 240 volt circuit would be 4.8%. So go ahead and use your #6 Cu, but put it on a 30 amp circuit breaker instead of a 50 amp circuit breaker.
Cheers, Wayne
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Wayne Whitney wrote:

I'll do what works. The #6 is actually good for about 70A. The 50 will be fine. Right now, i'm running a refrigerator, lights, two door openers and two 1000 W. tank heaters on a 12-2 NM-b laying on the ground. The #6 will be WAY WAY overkill, but that's what I'll do. I'll never pull anywhere nears 30A anyway.
s
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wrote:

Turn all that shit on at the same time and then measure the voltage. You'll be surprised.
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jamesgangnc wrote:

118
thanks
steve
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Don' believe you. Make sure it's actually on, not just turned on. In other words both your tank heats are putting out heat. Two 1000 watt tank heats are about 16 amps. There's no way you're running 16 amps over 400 feet of 12/2 and not seeing a voltage drop. Nevermind the refer and the lights which have to be pushing you up to 20 amps total if they kick in while both tank heaters are on. I'd consider a lockout circuit so that only one tank heater can be on at a time if you want to keep the wire size down.
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snipped-for-privacy@gmail.com wrote:

Everything works just fine the way it is. Believe it or not, it doesn't really matter to me what you believe.
steve
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The tank heaters don't care if it's 115 or just 100. But it's hard on that refer compressor when it has to start up wiht both tank heaters on.
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snipped-for-privacy@gmail.com babbled some shit he knew nothing about:

Not hard on it 'cause the voltage is always around 115 - 118. YOU seem to have a problem with comprehension. You don't seem to understand what you've been told. So, here's the deal. I'll drop the thread, and you can fuck off.
s
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babbled some shit he knew nothing about:

You just don't like being confronted with the facts. You don't run 16 amps 400 feet on 12/2 wire and not have a voltage drop. And telling someone else it's ok is bad advice.
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wrote:

A 400 ft run of 12 AWG, at 120 volts, a 15 amp load, will drop 23.7 volts, giving a terminal voltage of about 96.3 volts. The power lost will be 355 watts over the run. Power available at terminal will be 1450 watts.
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PeterD wrote:

so much for the pencil pushers. Mine doesn't do that.
s
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On Tue, 10 Feb 2009 00:17:39 -0600, Steve Barker

Then you are not drawing 15 amps, or don't have 12 AWG, or are not 400 ft from the source, or just plain have not a clue. Idiot... Your problem is one of not understanding the physics of the matter.
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Real world results do vary a bit from the calculations because of quality control of the wire. But apparently some of us live in a magical 5th dimension where the normal laws of physics do not apply.
No inspector in the country would let that go. I'm no particular fan of building inspectors but there is nothing wrong with complying with the code. If for no other reason than to avoid complications when you sell the property.
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*For 100 amps a 1 1/2" PVC conduit will suffice using 2 -#1s, 1 -#4, and 1 #6 aluminum single conductors such as THWN. There is no reason to spend the extra money for cable in a conduit. You could use copper conductors as the price has gone down quite a bit. For copper you can use one size smaller for each conductor.
Something else to consider is a conduit for a telephone or TV line. A 1" PVC conduit should suffice for that.
I wouldn't purchase any wire until you are ready to install it. It could get damaged or stolen and you don't know what the final length will be until everything is in place. No sense paying for waste.
You may want to consult with your electrician ahead of time so that your work will be to code and that he has no problem finishing the job that you started.
For the circuits that you have planned, 100 amps sounds like overkill unless you have plans to add more down the road.
For more info on this topic you can do a search of the newsgroup alt.home.repair on Google. This subject has been covered a lot there.
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As the originator ofthis thread, let me say thanks for all of the posts. I decided my 100 Amp panel was overkill and decided to go with 50 amp panel instead. I purchased 50' of 6/3 w.Grnd at Lowes and ran it inside 1.5" conduit. When the inspector came out, he said that the cabling was not "W" weather-rated, such as TNHW rating. Apparently, it was for inside work and labeled NM-B. I went back to lowes and talk to the older guy who I had previously worked with. He was surprised and then said that they sell this for that exact purpose. Well, I then bought 3 sections of #6(Blk,Wht,Red) and 1 section of #10 for ground.
But Lowes did take the cut wire back and give me a refund, so I commend them on that.
robin
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