230 volt wiring question for my metal barn

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Old 01-06-11, 08:40 PM
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230 volt wiring question for my metal barn

I have a metal barn with a concrete floor. It only has a 100 amp service panel. Over the last several years I have gotten into woodworking as a hobby and purchased several machines. So far 4 of them are 230 volt machines. Right now I only have one 230 volt outlet. I would like to have 7 or 8. My panel box won't really accommodate running a separate circuit for each outlet. Plus it seems like overkill since I'm the only person that uses the space and no more than 2 machines could ever be on at the same time (dust collector and whatever I'm using). My question is can I run multiple 230 volt outlets off of a single circuit? The most amperage that could be on at one time from my machines would be a little over 30. One way I could think to do it would be to run a 50 amp feeder circuit that ties into three or four 20 amp circuits that go over to the outlets. But I don't know what is acceptable practice. Ideally, I would like to use two circuits out of the panel box and have seven or eight 230 volt outlets, maybe four outlets on each circuit. Is there a way to do this and meet code?
 
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Old 01-06-11, 08:58 PM
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Without filtering my response through any Codes which may have jursidiction, the quantity of receptacles have no bearing on the power distribution system. However the load has all to do with it.

You need to understand the load, measured in amperage, to figure wire sizes, devices, etc.

I would like someone else to comment on the code issue, because certainly the NEC limits the number of receptacles due to the ability for each and every device to be utilized. In other words you saying that you will only operate two electric motors at a time is one thing, limiting the ability for anyone to do this is another. Be careful.
 
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Old 01-06-11, 10:07 PM
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...can I run multiple 230 volt outlets off of a single circuit?
Yes, but. Generally 240 volt equipment is not cord-and-plug connected but hardwired. You can have multiple receptacles on one circuit provided that all the receptacles meet the requirements (voltage and amperage) of the circuit including the circuit breaker feeding the circuit.

...run a 50 amp feeder circuit that ties into three or four 20 amp circuits that go over to the outlets.
You are using contradicting terms. A "feeder" would be a circuit going to an auxiliary panel containing overcurrent protection (circuit breakers) which would then have multiple 20 ampere circuit breakers for the individual branch circuits to the receptacles.

HOWEVER, if what you are asking is, "May I run a 50 ampere circuit to several 20 ampere receptacles" the answer is absolutely not.

I would suggest that your dust collector be on a dedicated circuit and then you could use a 20 ampere, 240 volt branch circuit to several 20 ampere, 240 volt receptacles as long as all your cord-and-plug connected 240 volt machines utilize a 20 ampere circuit. If some of the machines use a 15 ampere circuit or a 30 ampere circuit then you need to provide branch circuits with the proper circuit breaker, wire sizes and receptacles.
 
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Old 01-07-11, 10:20 AM
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Originally Posted by feltdog View Post
So far 4 of them are 230 volt machines....The most amperage that could be on at one time from my machines would be a little over 30.
Could you give us a more specific rundown of the machines? A 240V/30A machine would be very much on the large side for a home shop; that's approximately a 7.5HP motor. A machine that size should probably be on a dedicated circuit anyway.

Most woodworking shops will be more than adequate with a single 240V/20A circuit run to a few NEMA 6-20R t-slot receptacles around the shop. The dust collector should be on its own circuit, usually 240V/15A (maybe 20A for a large unit).
 
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Old 01-07-11, 12:25 PM
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I have a dust collector that is 3 hp, 13 amps, a table saw that is 3 hp, 13 amps, a Jointer that is 3 hp, 18 amps, and a lathe that I think has under 10 amps but not sure off the top of my head. The dust collector would always be operating (13) amps and one other machine. So in some cases there could be 31 amps on at once. Although it wouldn't necessarily be on the same circuit.

I'm sure I am using some incorrect terms to describe what I want to do. But to try and clear it up, I was thinking about running two 50 amp circuits out of my 100 amp panel. Each circuit could run to another smaller panel. From that panel I would run three or four 20 amp circuits to outlets. Maybe there is a cheaper and better way to do it, because my way would require two more small panel boxes, etc. But that was kind of my thoughts on how it would work. Will that work and is there a better way. The rest of the barn just has several standard 120 volt outlets and some overhead florescent lights.

I made the mistake of not thinking ahead when we installed electricity in the barn years ago. If I had it to do over I would have put in 150 or 200 amp service instead of 100 amp. I really want to get some heat and air conditioning in there so I can fool around out there year around. But I don't think there is a way to do that with just 100 amps. So one lesson learned from this is that anytime you make a major expenditure try to think way down the road and plan for what you might want to do then.
 
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Old 01-07-11, 01:07 PM
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Originally Posted by feltdog View Post
I have a dust collector that is 3 hp, 13 amps
For this one run a dedicated circuit: From a 20A double-pole breaker in the panel, run 12-2g cable to the dust collector. There should be a cord-and-plug or manual disconnect switch within line of sight of the motor for safety disconnect. If the breaker panel is within line of sight that counts as a disconnect.

a table saw that is 3 hp, 13 amps, a Jointer that is 3 hp, 18 amps, and a lathe that I think has under 10 amps but not sure off the top of my head.
These would all be okay on a single 240V/20A circuit as long as you're only doing one machine at a time. You would basically install a 20A double-pole breaker in your panel and from that run #10-2g cable to a NEMA 6-20R receptacle and continue on with the 10-2g cable to other 6-20R receptacles around the shop. [Note: code would allow #12 wire size, but upsizing to #10 is warranted for the motor loads.] You could do as many receptacles as you like, but most shops would be fine with three or so. Use extra deep junction boxes to accommodate the larger wire size.

Each circuit could run to another smaller panel. From that panel I would run three or four 20 amp circuits to outlets. Maybe there is a cheaper and better way to do it, because my way would require two more small panel boxes, etc.
You could do it this way, but it is not really necessary in my opinion unless the barn is huge (long distance from panel to tools).

If I had it to do over I would have put in 150 or 200 amp service instead of 100 amp. I really want to get some heat and air conditioning in there so I can fool around out there year around. But I don't think there is a way to do that with just 100 amps.
I think you're underestimating what you have. You should have no trouble powering heat and AC in addition to the tools you mentioned on a 100A panel.
 
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Old 01-07-11, 01:09 PM
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Just wanted to add that you may need to install conduit to protect the wiring depending on how your building is framed out. Do you have stud walls or wall coverings (drywall, OSB)? Is the ceiling enclosed?
 
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Old 01-07-11, 02:55 PM
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Right now the walls and ceiling are both open. I am going to insulate the barn and cover both after I get the wiring finished. The wiring that is in there now, which was inspected, is not in conduit, but sits on top of one of the 2 x 6s framing members. It is high up though, higher than you can reach.

I hope you are right about the heat and air, that would really make me feel better. The barn is 30 x 34, and I plan on insulating it well. Shouldn't take much to heat or cool I wouldn't think.
 
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