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Thread: Electrical Geniuses

  1. #1
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    Question Electrical Geniuses

    I currently have one 220V outlet in my shop used for my table saw. I would like to add another 220V tool, a jointer. Is it reasonable to add another outlet in this run? Both tools would NOT be running at the same time. I could just relocate the existing outlet so I can get to it easier and plug and un-plug the two machines but I would like the run the source into a junction box and attach two outlets. If this is fundamentally ok, what is the best way (safest) to make the spice? Wirenuts, ferules, three small buss bars?
    If sawdust were gold, I'd be rich!

    Byron Trantham
    Fredericksburg, VA
    WUD WKR1

  2. #2
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    Yes, reasonable...and I have a couple in my shop set up that way for mobility/convenience. You should branch in a j-box somewhere in the line, however, not by daisy-chaining from the receptical. I believe this is the safest and most flexible way to handle it.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  3. #3
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    Quote Originally Posted by Jim Becker
    Yes, reasonable...and I have a couple in my shop set up that way for mobility/convenience. You should branch in a j-box somewhere in the line, however, not by daisy-chaining from the receptical. I believe this is the safest and most flexible way to handle it.
    Jim, this what I wanted to hear. How did you make the splices in the J-Box?
    If sawdust were gold, I'd be rich!

    Byron Trantham
    Fredericksburg, VA
    WUD WKR1

  4. #4
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    Quote Originally Posted by Byron Trantham
    Jim, this what I wanted to hear. How did you make the splices in the J-Box?
    Wire nuts...and then taped securely. <g></g>
    --

    The most expensive tool is the one you buy "cheaply" and often...

  5. #5
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    Quote Originally Posted by Jim Becker
    Wire nuts...and then taped securely. <g></g>
    Now that's what I'm talkin' about!
    If sawdust were gold, I'd be rich!

    Byron Trantham
    Fredericksburg, VA
    WUD WKR1

  6. #6
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    you can add another outlet to your existing line if (and I mean if) your wire size in large enough to increase amps. For safety sake do not extend an extisting 20 amp and try to run 2 20 amp machine off of iteven tho you say only will run at atime. I say that because sometime down the road you or another homeowner will forget and try to run both machines at the sametime.

    Rewire the exsting line with and 10 gage wire, insert 30 amp switch at panel and then you can extend your exsting outlet to add addition outlets. your machinery will only draw what is needed. (Same as your as in the kitchen. you have 20 amps in a kitchen so you can run more than one counter applicance but the applicance only needs 7amps)

    For those who wonder this passed code in my area.
    How many times must I redo it to get it correct??

  7. #7
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    Byron. Yes it can be done. the junction for the additional receptacle can also be made in the currently installed receptacle if it is big enough and sized properly to handle all the conductors.
    To accomplish this. shut the breaker off. Remove the cover on the receptacle that is currently wired. Disconnect the wires from the receptacle. Cut off the exposed conductors, and strip back a new length of exposed conductor. Bring in the feed to the receptacle that you want to add. Strip it back and match the wire colors to the already stripped wires. Make a 6"-8" piece of black, white and ground wire, Put the black and the white with the already stripped conductors and wire nut these conductors together a wire nut. All the blacks together, all the whites together, and all the grounds together. The grounds will require and additional conductor to carry the ground. Attach the short 6"-8" wires to the original receptacle, observing convention, "BLACK BRASS BUTT" and SILVER WHITE kNIGHT. Reattach your ground to the recptacle and the recptacle box.
    The original receptacle should now be re-wired, and a feeder going to the new receptacle. Connect the new receptacle observing wiring convention, and be sure to connect the ground to the recetacle, and carry the ground to the enclosure.
    If you have access to a DMM you can do the following; turn the breaker back on and go to eac receptacle and measure the volts across the rectacle it should be a nominal 220 across the black and white connections and 115 black to ground and white to ground. It should also be 115 to the ground that you carried to the receptacle enclosure. Do this at both receptacles.

    I will not tell you that this is code, because your code may vary and be different than mine, but it is electrically safe.
    I know that currently there is preference to have each 220 load on a seperate breaker to avoid the situation that Dave Mapes referred too.

    There is also a requirement for "Manual Disconnect" if you cannot see the breaker panel. this can be met with a twist lock style plug and recptacle.
    If all else fails you can make a 220 extension cable and run the one machine off of that. Go oversize on the wire for the extension cord though.

    Addy Protocol. Not a liscensed electrician.

  8. #8
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    Some codes don't allow daisy-chaining 240 V circuits (dunno if it is current limited...maybe only 30 A, 240 V circuits?) and so each must be on its own breaker. Here in San Jose, each 240 V/30 A circuit must be on its on breaker/branch...no multiple outlets. That sure ate up some room in my panel but I had the room to spare....
    Wood: a fickle medium....

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  9. #9
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    Thanks!

    Guys, thanks for all the input. Like Chris said, I am sure our code requires one circuit one outlet. I was just trying to not plug and un-plug machines; but hey, we're not talking about doing this every other hour so I think I will play it safe and remove the short pigtail that comes with the machine and re-install a longer one (10 ga) that will allow me to plug it in when it's needed.
    If sawdust were gold, I'd be rich!

    Byron Trantham
    Fredericksburg, VA
    WUD WKR1

  10. #10
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    Byron, unless your additional 220V machine is in excess of 3hp and/or that extended run will be more than 25' or so, 12ga wire is plenty. Cheaper and easier to handle.
    Cheers,
    John K. Miliunas

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  11. #11
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    Chris. You are correct. It is generally becoming unacceptable to daisy chain 240 receptacles. It can be done, but if you look at the newer NEC requirements for circuit loading and branch loading in the motors sections, it is pretty involved.
    Most electrical inspectors are aware of the "large" motors that a wood shop will have, and know that you will generally be running only two, 240 loads at a time, the DC and something else. Like Dave Mapes pointed out though they are looking down the road. I know of one instance where a "Home garage workshop" was wired for 240, and the inspector required a dedicated, breaker and circuit for each 240 receptacle and a 50 amp receptacle right by the door for a welding machine, even though my friend doesn't even own a welder, or know how to weld.
    The codes vary, and each area seems to have it's little pecadillo's, that's why I generally recommend that the person contact a local liscensed electrician. Byron is probably better off for now using an extension cord, or rewiring his machine with a longer cord, like he plans

  12. #12
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    If you install one of these you will avoid plugin and un-pluging.

    http://i14.ebayimg.com/01/i/03/9c/e7/1f_2.JPG

    and as was already stated, ask a real "electrician". The word Geniuses wasn't a good filter in this case, IMHO.
    Work safe, have fun, enjoy the sport.
    Remember that a guy never has to come down out of the clouds if he keeps filling the valleys with peaks. Steve

  13. #13
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    Maybe.... and this is a pretty big maybe!

    First of all, your not daisychaining. Daisychaining is a series connection and you will have to incure a huge voltage drop on the second receptacle if your using the first. This is bad. To keep the voltage drop from happening, you will need to wire up in parallel.

    Two receps wired in parallel will both have 240 volts on them. But the SUM of the two currents will be drawn from the main service breaker. Here is where life gets nasty. If I have a 30 amp dedicated two pole breaker feeding a single device, then I will need to make sure that every element along this path is rated for 30 amps. For example, if you have a hubble that is rated for 30 amps, your good to go. Your main wire gage will most likely be 10 gage in this application assuming no derates.

    So if I install a second hubble receptacle in parallel, then it to needs to be 30 amps. Under a balanced load, both receps can only pull 15 amps each. But code will require that a single path in a parallel system be rated for the maximum current draw of the total system. In our case, that would be 30 amps.

    Being that these types of circuits in a wood shop are running table saws and jointers, it is allowable by code to size wire on runtime or quiescent current load and not start up current load. This helps. But if I hooked up three or four receptacles on the same circuit, then I will quickly get to a point where a balanced load will not be able to function. In fact, many of my machines cannot function on two balanced receptacle loads driven by a 30 amp branch circuit.

    If you maintain the caveat that only one machine can run at one time, this scheme will work. In fact, many hobbyists using three phase converters are doing exactly this to run the three phase machines. They are parallel branching all machines on a single three phase buss fed by the converter. But this will give any inspector the willies! Fact is, you cannot always control this caveat and you may not always own the property in which this setup was installed. Lastly, your homeowners insurance company really doesnt wish to hear this tidbit of info!

    So in a nutshell, a standard 20 amp branch circuit is capable of sinking that 20 amps through any single path or combination of paths attached to that branch circuit. This works well for hairdryers and electric toothbrushes. It does not work well for woodworking machines, dust collectors and other items such as welders.

    If you do something like this, you will need to add up or summate the runtime currents of each machine on this branch. So if I had a drill press at 10 amps and a tablesaw at 20 amps and a jointer at 15 amps, that would be grand total of 45 amps. The main supply line now needs to be sized for say 50 amps by rounding 45 up to 50. The branch breaker now needs to be set to 50 amps and the wire will be about a gage 6 or 8. Whatever, it will be FAT! At each junction, you will need a fused disconnect box rated for 50 amps. The input gage to each of these three disconnect boxes needs to be the same as your 50 amp buss wire. Then the slow blow fuses used in each disconnect box needs to be sized in accordance with the load on them. Lastly, you can a length of SO cord sized also according to each individual load below its corresponding fuse box.

    The first thing you will notice is that the breaker in the afore mentioned example protects the ENTIRE circuit and not any one single machine tool. Each machine tool is initially protected by its own disconnect box equipped with the appropriate slow blow fuses. As you can see, this is not a pleasant or cheap solution and most of the time, its not done correctly. It is proving easier and safer to just require each 240 volt circuit to be on its own dedicated branch circuit. Also bear in mind that this code was written to prevent folks from hooking up the wall heater, hot tub and stove on the same branch circuit. Ufortunately, most of the NEC code that relates to large motor loads, etc. actually apply to industrial applications which are governed by even stricter rules. Rules that most hobbyists often dont follow.

    As to codes requiring shops to have welder receptacles. That is a joke. Welders that use their own plugs are often 50 amp arc welders such as the one used by farmer John on the weekend. Many newer welders are using much more than that. My miller welder which is both a tig and arc welder needs a dedicated 90 amp circuit. The problem is that the highest allowable current load on a receptacle is 50 or 60 amps. In order to use a disconnect cable on machines that use more than 50 or 60 amps, you need to go to pin and sleeve connectors. These are those big fat blue connectors you see at macdonalds that hook the french fry machine to the grid. They are often inline and work from drop cables. Pin and Sleeve connectors are extremely expensive!

    When you look at all the rules, etc. you come to the conclusion that its quicker, cheaper and faster to just run a dedicated circuit to the service center. Well almost cheaper. In actual industrial environments, the dedicated machine tool branch circuit must terminate in a disconnect box. This can be on the tool or on the wall but must provide quick access to the disconnect should something bad happen. IT is customary to run SO cable from this box into your saw and this can be from a drop cable or a junction box comming up out of the floor. You will also find that many old iron woodworking machines such as yates, newman, oliver, northfield, etc. all have these disconnect boxes attached to the tools themselves. Not all had these but those that came from military or large industry had these.

    I have spent many hours talking to inspectors about these issues. They dont like it when you show up with phase converters, buck boost transformers and other novel toys that you just dont find in the typical home these days This is more an issue of them not knowing how to classify these items and subsequently find the rules that govern these items. This is esp. true for those of us who live in communities that have their own unique electrical codes. I am lucky. The county I live in simply applies the the NEC code. But each case is unique and you need to call your inspector and ask him what he wishes to see. You can hire an electrician but bear in mind that he too is not the expert here. He also needs to contact the final judge who is the inspector. Also understand that an electrician is nothing more than a wire monkey. He installs hardware according to how the engineers wish to see it. Force him to deviate from his small setset of rules and he is likely to make a mistake. So call your inspector and pester him.

    Hope this long diatribe helps. In actuallity, I can write a sizeable book on the electrical engineering of the home woodworking shop. As more folks take the plunge to three phase, this is becomming more of an issue every day.
    Had the dog not stopped to go to the bathroom, he would have caught the rabbit.

  14. #14
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    Well written Dev. When the inspector "required" the welding receptacle be installed by the garage door, the first question, was why do I need a welding receptacle? and second, why does it have to be by the garage door?
    He never did get a good answer, but the receptacle is there waiting for the ubiquitous welder to someday magically appear.
    Code requirements and interpertations are kinda odd at times, but they really are a necessary evil. Some of the home wiring I've helped undo was flat out frightening.

  15. #15
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    If I was you I would look into quad or peanut breakers. Even if your panel has no open slots you can usually replace a breaker with a quad breaker. They are used often and really easy to install. Here is what one looks like. I added one to my panel so I could add a 220 outlet for my table saw.

    http://www.electricsuppliesonline.com/mucrhibrmp47.html

    You need to check your panel to ensure you use the correct brand of breaker. I'm sure other here can provide more info, but a quad basically adds another breaker to your panel without requiring an open slot. As was said before although you may know about the outlet wiring is it safe for others who might own the home in the future?
    The man who makes no mistakes does not usually make anything. ~Edward Phelps

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