Electrical Geniuses

[Byron Trantham]

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?

[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.

[Byron Trantham]

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?

[Jim Becker]

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>

[Byron Trantham]

Wire nuts...and then taped securely. <g></g>

Now that's what I'm talkin' about! :D

[Dave Mapes]

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.

[Mike Cutler]

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.

[Chris Padilla]

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.... :)

[Byron Trantham]

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. :rolleyes:

[John Miliunas]

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.:) :cool:

[Mike Cutler]

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

[Steve Stube]

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.

[Dev Emch]

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:D 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.

[Mike Cutler]

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.

[Jim Benante]

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?

[Chris Padilla]

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.

Dev,

http://en.wikipedia.org/wiki/Daisy_chain

I think daisychaining is an acceptable term to use in home wiring...rarely is anything put in series in home wiring...everything is assumed parallel or "daisychained."

[Dev Emch]

Chris...
In looking at the art. on daisychaining, I can see where the "CONTEXT" can lead one to agree that the electrical connection is in parallel. They use the series intrepretation of daisychain to suggest that one has one power consumption device following another following another. From a volts and amps perspective, this is in parallel. But as an electrical engineer, this type of loose talk can put a sand burr under my collar.

As to using peanut breakers. Well, folks, here is the deal. Back during the late 60s and early 70s, many homes were built using 60 to 100 amp service centers with very limited space. Many of these centers were made by federal pacific and your safer off by using a penny in a fuse socket. That is why you dont see federal pacific sold today... the UL and CSL cancelled their ratings for safety issues. Whenever I see a federal pacific box, I am ripping it out before the ink on the contract is dry!

Clearly, there is a use for half size breakers or peanut breakers. Under certain loading conditions, the box is simply smaller than that which is allowable given the disconect breaker and incomming service line. Here a little bit of a good thing goes a long way. Replace all your breakers with half height breakers to double your slot count and you can exceed the allowable number of branch circuits for the given incomming service and disconnect. Also bear in mind that the service center back plane may not be rated for all that extra current draw.

So if you need to add one or two extra branch circuits to an existing installation, you should be more or less O.K. Start adding 220 volt, high amp draw circuits, and you may overwhelm your service center.

I have used these before even though I personally do not like them. My experiences with federal pacific hardware has led me to be very critical of this part of the home electrical installation. My favorate breaker and service center hardware is that of square D. Not the Homeline series but rather the QO and QOB series. I have also had good luck with Siemens.

But if your looking for the top of the line electrical gear, you cannot beat the Square D QOB series. This hardware has many unusul features behind it. First of all, there is no "SERVICE CENTER" or "LOAD CENTER" available in this line. Rather, you need to purchase the panel itself. Also, these panels do not come with integral disconnect breakers. They are by default, sub panels. The boxes are sold separately but if you buy the panel, the box cost is $5 dollars. Whoopieee! This was how crescent electric supply sold me the last three of these that I purchased.

If, for example, your installing a main service center and need a service disconnect, you will purchase the disconnect add on kit and the breaker. This will require you to get a longer box which is not an issue if you buy all three items at one time. The breaker it bolts to the panel thereby extending the length of the panel. That is why the box size varies.

Next, you need to know which type of cover your using. There are two types depending on the finish wall. This will affect how deep the panel needs to be set on its studs. The box contains four studs on which the panel mounts.

The QOB breaker is indentical to the QO breaker with one important exception. The B stands for bolt in. These breakers have a retaining bolt on them that secure them to the panel unlike normal breakers which just snap into place. All QOB breakers work with all QOB panels. The panels can be purchased as either two pole panels or three pole panels. The breakers are available as ONE, TWO or THREE pole breakers. Only the THREE pole breaker must be used in a three pole panel. The other two breakers can be used in either two or three pole panels. For the sharp observers, your right..... three pole panels are used for three phase service hook ups.:) Now also note that the three pole panels are more popular than the two pole panels in the particular line up. Thus, it may be cheaper to buy a three pole panel than a corresponding two pole panel.

Because the QOB breaker is a bolt in breaker, there is one other very wird thing you can do with these. You can back feed a breaker! Service disconnect breakers must by code have a solid mechanical retention device. Thus, a snap in breaker would not quality. The QOB breaker does! But these are only made up to 100 amps. If you need more than 100 amps on a service disconnect, you must purchase the dedicated add on disconnect kit and disconnect breaker which I mentioned earlier.

So what is a back fed breaker? If I use a QOB panel setup as a sub panel (i.e. no dedicated disconnect breaker), I can use two slots and a 100 amp QOB breaker to actually add in my service disconnect. The main service input lines are now wired up to the output lugs of the breaker and the breaker works in reverse supplying power to the QOB panel back plane. MAKE SURE YOU APPLY THE MAIN SERVICE DISCONNECT STICKERS TO THIS BREAKER!

For most of us with wood shop issues, this may or may not be of use. But here is one idea that may be of use. Now kiddies, listen up!

If you install one huge hunkin THREE POLE QOB panel in your wood shop, you will be well under way to getting anything and everything running. You can hook up TWO poles of this from either your main service center or from a separate ouside service. If your using your present home's service center to feed this panel, then this is an example of a sub panel. If your using a dedicated external incomming service, then you will need to add the extra add on service disconnect breaker kit (TWO POLE KIT ONLY).

Make sure you wire up L1 and L2 such that you can install ONE and TWO pole breakers using only your incomming service. Leave the L3 buss on its own. Install a 60 amp or less two pole breaker and use this dedicated circuit to run your phase converter. Feed it through a switchable disconnect box to make things easy for now. Throw the switch on the disconnect box and your phase converter comes to life. Now the phase converter has four wires going into it. The green one is a ground. The other two input leads supply power to the converter and these are fed by the afore mentioned double pole breaker circuit. The last wire is the phase converter output line. This wire goes straight into the L3 lug of your three pole QOB load panel. You have now activated the third leg of your three phase system. Any three pole breakers are now able to run woodworking machines like your oliver table saw and newman jointer, etc.

The beauty here is that you can start with one panel. A single pole QOB breaker can run your light circuit or your 110 volt receptacle branch circuit just as before. Then you can add on a two pole breaker to run your single phase unisaw or grizzley planer. Then you can add on a three pole breaker to run your newman jointer or other hunk of old three phase iron.

Should you overload the three phase system, the two pole dedicated circuit that runs the phase converter will trip and take the converter offline. The only issue you need to be aware of here is that the machine tool may now go into single phasing. IT will continue to run but at a huge loss of power and will exhibit some strange behavior and make some wird sounds. Just shut down and let things cool down and reset your converter breaker. My system solves this problem by disconnecting all three phase lines including L1 and L2 upon a loss of any leg including L3. But this requires multiple service panels and is much more complex. What I have just described is hard enough to understand and I dont wish to complicate matters more by describing what I have done. My system has three QOB panels! One is 240 single phase. The second is 240 three phase. The last is 440 three phase.

This is an example of back feeding a phase converter into a single service center. There are a lot of technical issues to consider when doing this and you need to discuss this with your local inspector and have him talk to the engineers at companies like Square D or the phase converter maker. Also note that three pole panels use slots in groups of three. So if I use a single pole breaker, I can actually use a second single pole breaker on the second slot. So I have one breaker on slot 1, a second breaker on slot 2 and slot three is left empty. I DO NOT WISH TO USE THIS SINGLE SLOT FOR NORMAL USE! This is actually a good thing as the two single pole branch circuits work to balance the neutral in the service panel so this is something I actually want to have happen. When I install a two pole breaker, I lose the third slot. So, here I can install a two pole breaker in slot 4 and 5 and slot 6 remains empty and never used. Lastly, I can install a three pole breaker in slot 7, 8 and 9.

Hope this makes some sense and gives you an idea of the power and versatility of using the square D QOB panel system in your home, your shop and your business.

Regards...

[Chris Padilla]

Chris...
In looking at the art. on daisychaining, I can see where the "CONTEXT" can lead one to agree that the electrical connection is in parallel. They use the series intrepretation of daisychain to suggest that one has one power consumption device following another following another. From a volts and amps perspective, this is in parallel. But as an electrical engineer, this type of loose talk can put a sand burr under my collar.

I do signal integrity work (I'm an EE, too) and we use daisychaining all the time in routing boards although we must be very careful in high-speed/high-density routing. I dunno if the word is totally correct but it is common and understood in my area of EE.

[Von Bickley]

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.

Byron,
Jim Becker and John Miliunas gave you all the information you need. Yes, you can do it and yes, it is safe.

Von
Wantabe woodworker and Certified Electrician... ;)

[Dev Emch]

Von....

I agree that it is safe *IF* you follow my caveats; however, even as a EE I was not able to convince our inspectors. Even though we follow the NEC, this was one area where they did not want it. Period. If its a 220 circuit, then its on it own branch. I guess its like the example of forcing shop owners to install 50 amp welding receptacles by the main door even though many real world welders use way more than that and have to be hard wired to avert the nasty purchase of pin and sleeve.

Or how about this one. I just got word from a steamboat job that yampa power wants a 3 inch conduit for the service feed. This is a 200 amp main line service to an upscale domestic damacile! Its more like the chunnel for gofers than a conduit. Oh well, dem is da rules and I am just an dumb electrical engineer so we get to run 3 inch conduit tommorow.

So Bryon, I would check it with the inspector. I call mine all the time when I have procedure questions. Just remember that should your house burn down due to electrical issues and an out of code item of recent install is uncovered, you may be left out in the cold with no insurance claim. Its not worth it for me. And in the final analysis, its your house and your policy.

Regards

[Dev Emch]

Chris...

Yes, its used all the time in communications. Most of your communication protocols have provisions for it. For example, check out how fiber channel works. Another example would be the soon to be obsolete SCSI protocols. Yet another would be ESCON and FICON used by IBM.

But in this case of daisychaining, you need to check your line impedance values. Signals are often isolated and repeated. And today, many are now optical in nature. That gives you noise isolation and signal integrity and speed not to mention very high impedances hence, virtually no voltage drops. An extreme low impedance line has another name.... its called a short circuit. Some signal devices also have an active backplane pass through. Even if the device is offline, the active backplane is still routing traffic through it, thus, not cutting the chain and allowing traffic for other nodes through.

Another thing to consider is that many signals are not riding voltage levels but rather amps. For example, in old school process control systems, your singnal is based on a 4 to 20 milliamp signal. In this case, voltage drop over long distances due to copper loss is not relavent. What is relavent is the amperage comming out the other end which does not change. Tap into this line and it will change!