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electrifier, Master Electrician
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I am wiring an outbuiding 200 feet away, the house has a 200

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I am wiring an outbuiding 200 feet away, the house has a 200 amp breaker panel connected to 200 feet of #6 underground wire that is connected to my shop,to a 100 Amp breaker panel. Question one is, what is the largest breaker I can run in this outbuiding? In this outbuiding I am wiring a 5 HP. 240 volt planer with maximum draw of 40 amps. and a dust collector 2 HP. 240 volt maximum draw of12 amps, can I run both of these at once? 50 amp breaker for the planer and 30 amp breaker for the dust collector?Last question is,for a 240 volt circut do I run 2 hot wires with a ground? or two hot wires, neutral, and ground?Can the ground be one size smaller than the leads?
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200 feet of direct burial #6 copper will support 50 amps with a 4% voltage drop. The code recommends no more than 3% drop in a feeder. 40 amps would give you a 3.2% drop.
Your 5 HP motor has a 28 amp draw and you are correct on the 2 HP at 12. For starting purposes you are going to need to start the planer with nothing else running. The starting current will spike to 168 amps momentarily and then drop back. Lighting is going to dim badly in the outbuilding. Flourescent may shut off and come back on. Starting the dust collector with the planer running will also dim your lights but not as badly.
You are really cutting this down below advisable levels with voltage drop included. You need a full 47 amp capacity to be code compliant and you can't get that without almost 5% voltage drop. Increase your 2 current conductors to #4 AWG and you will get 60 amps at 3% drop. This will take care of your needs. The motors don't use a neutral so that load is not critical. Run PVC conduit all the way with 2 #4 and 2 #6 for ground and neutral and all will be good for your installation.
Where did you get the 50 amp and 30 amp breaker ratings? Were they in the equipment as minimum requirements?
We still have to size the feeder breaker to be enough for the entire building with lighting loads included.
This will give you the feeder requirements and suggestions, the breaker sizes will be in the next answer.

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Customer: replied 8 years ago.
Thank you for listening, your feedback important, as i want to do the right job however the #6 feed wire is already buried and cannot easily be changed.Can I get away with what is already there?
Customer: replied 8 years ago.
I got the ratings from the electrical suppy store, thinking that if something is rated at 40 amps that 50 amps would do, and if rated at 12 amps that 30 would do, am I mistaken ?So back to my original question, what amp breaker should I run the out building off the house 200 amp panel?
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The thing about motors is you may get away with a smaller breaker because you start the planer with no load at all and the 5 HP comes into play when you plane wood with it. That being said, I would try a 40 amp breaker for the planer and a 20 for the dust collector. Of course you will need a motor starter for both motors.
For the feeder try a 60 amp breaker. You are allowed to go up to 250% for the load so you could go to 100 amps and be just over 200%. Try the 60 amp breaker and if it works you saved some money because that breaker costs about $7 or 8 and a 100 amp breaker costs about $30. 70 amps is where the price jumps.
Running the motors together will take 47 amps and the #6 is good for that with a 5% voltage drop. If brownouts become a problem with the lighting it's because of the wire size so whoever told you #6 was enough was mistaken. Starting the 5 HP with no load will save you however. It all depends on how hard you push these motors. They will only draw enough to do the job you ask them to do. The 2 HP might be oversized and only draw 8 amps but you don't know until you run the equipment. You now know what you are allowed to do within the code and what you should have done for ideal circumstances. Good luck and come back if you have more questions. I'll be happy to help you thru anything you come up against.
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Customer: replied 8 years ago.
sorry it took so long for me to get back to you, as we had 2 feet of snow since I last contacted you. I just want to thank you for all the Info you supplied me with. If need be I will contact yiou in the Future. Enjoy your life!
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Thanks so much. We've had a foot of snow the past few days in Michigan. Lake effect is so much fun.

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