Electrical question

[Jason Morgan]

Im wiring the new Garage/shop and was wondering about wire gauge for my 220V circuits. Am I ok with 220V 1P circuits using 14/3 conductor? or do I need 12 or 10? These are going to be 20A circuits that will I think never see more than about 12 A draw (Im going to keep one tool per circuit)

Thanks

[Jason Morgan]

I did a search and found that I should be using at least 12 gauge and 10 would not hurt, but is not technically needed for 20 A circuits. I dont ever plan on running anything over 3hp motors and if I do, Ill run another dedicated circuit.

[Brian Weick]

Jason, that scenario , although current - may change- you should build in additions to your calculations so you don't have to re-wire your setup all over again. you should calculate the amperage of the machines your hooking up to that as well to determine the Gage of the wire and the circuit breaker at the panel-call your local electrical supply- give them the information of the machines and the E panel box and what you will be running- they will be able to tell you exactly what you need and more than happy to help. - Always go to a electrical supply store in your area to get answers on electrical systems and hookups- you don't want your building turning into ashes! :)
Brian

[Bill Arnold]

Jason,

When wiring my shop, I used 12/2 w/ground for all 110V circuits and 10/2 w/ground for all 220V circuits. At present, the largest motor on any 220V circuit is 3HP, but I wanted to be sure I had plenty of capacity for any future changes. Each 220V machine is on a dedicated circuit. Ceiling lights in each area of the shop are on seperate breakers; no more than five duplex 110V outlets are on a breaker. This arrangement provides for plenty of isolation.

[Jason Hanna]

Isn't the rule of thumb you figure the voltage/amps of the machine, and that tells you the size of breaker you need for the circuit (round up) and then size of the breaker tells you the size of the wire?

Never size the wire to the machine, always the wire to the breaker. If I'm not mistaken, it doesn't do you any good to grossly oversize the wire beyond the breaker unless you forsee swapping out the breaker in the future for a high amp breaker.

[Von Bickley]

Jason,

All my wiring in my shop is #12 and I did electrical work for many years.:D

[Josiah Bartlett]

You may want to wire at least some of the circuits with 3 conductors + ground in case you get a future machine that requires a neutral. Some welders do, and maybe other things will too.

[Eric Gustafson]

Jason,

All my wiring in my shop is #12 and I did electrical work for many years.:D

Von,

What is the highest load in your shop? Any 220v tools? Anything larger than 3 hp?

Just curious as I am determining my shop requirements now, including how large of a subpanel to install.

[Jason Morgan]

Thanks for all the help. I think I am going to go with the "overkill" approach and go 10/2 for the 220's and 12/2 for the 110's. Now to plan the layout and possible future additions. I know that I'll never have it perfect, I am just shooting for the max versitility.

Thanks again.

[Ken Fitzgerald]

Jason,

I built my shop 3 years ago. I wired the 120 circuits with 12/2 and the 220 circuits with 10/2......I just bought a bandsaw.....4.8 hp.....Sure glad I used 10/2 on those 220 circuits. The cost difference between the 12/2 and the 10/2 is miniscule as compared to how much time and effort it would take now to remove the plywood from the walls to rewire or even to run conduit externally to the interior walls. If your walls are open, I'd run 10/2 on the 220 circuits. JMHO....

[Roland Chung]

Jason,

If you want maximum versatility, consider installing a 3/4" emt (or bigger) conduit run from your subpanel and pull the appropriate wires as you need them.

How about a 100 amp panel -

Large compressor - 240v - 20A (or bigger) - 2 spaces
Dust collection - 240v - 20A (or larger) - 2 spaces
Lighting - 120v - 15A-20A - 1 space
Stationary tools - 240v - 20A x 2 - 2 spaces
Stationary tools - 120v - 20A x 2 - 2 spaces
Outlet circuits - 120v - 20A x 2 - 2 spaces

Not that you would be using anything close to the 100amps, but it might be hard to locate a smaller capacity subpanel with enough spaces. If you want to save a bit, only run the conduit and wire for your present needs, the conduit will allow you to pull additional wires as your needs change.

Want it behind the drywall, run flex.

[Von Bickley]

Von,

What is the highest load in your shop? Any 220v tools? Anything larger than 3 hp?

Just curious as I am determining my shop requirements now, including how large of a subpanel to install.

My highest load would probably be my contractor TS. I have it wired for 120 volts and will leave it like that in case I have to take it somewhere to use. I have a couple of 220 volt circuits but the only 220 volt tool that I'm presently using is a squirrel cage fan for air circulation.

My shop is inside a pole building that we are presently living in part of. We put in a kitchen area, a bath room with washer and dryer, and a bedroom. We will soon be starting construction on a new home and will pull power from the pole building to the new house.

The pole building has a 400 amp service with a 200 amp panel in the shop and temporary living area. We have a 200 amp disconnect outside to take power to the new house, and we have a manual transfer panel in the shop that we can hook up a 4500 watt generator to in case we lose power. The generator would only be used for a few lights, refrigerators and water pump.

[Rick Christopherson]

Thanks for all the help. I think I am going to go with the "overkill" approach and go 10/2 for the 220's and 12/2 for the 110's. Now to plan the layout and possible future additions. I know that I'll never have it perfect, I am just shooting for the max versitility.

Thanks again.Jason, there is nothing wrong with using #10 wire for your 240 volt circuits, just so long as you understand that the likelihood of actually using it is going to be extremely low in a garage workshop. People advise others to do this all the time, telling them to plan ahead, however, this isn't planning ahead.

Just for comparison, a 3hp Delta Unisaw will run from a 15 amp circuit (but I wouldn't recommend it). For the typical garage workshop virtually all of the tools are 3 hp or less. The most notable exception is a 5hp compressor. Even though I have heard of some people putting in 5 hp dust collectors in their garage, this is kind of silly for the amount of space.

Number 10 wire is horrible to work with, and right now it is terribly expensive. Do you really foresee getting any 5 hp tools?

By the way, in your original posting you commented about 3 conductors (plus ground). This is not required, and used even less. I am not an expert on welders, that a previous poster commented on, but to the best of my knowledge, not even they require the neutral.

[SCOTT ANDREWS]

[



The pole building has a 400 amp service with a 200 amp panel in the shop and temporary living area. We have a 200 amp disconnect outside to take power to the new house, and we have a manual transfer panel in the shop that we can hook up a 4500 watt generator to in case we lose power. The generator would only be used for a few lights, refrigerators and water pump.[/quote]


I would kill to have 400 amp service.Nice

[Bob Feeser]

Im wiring the new Garage/shop and was wondering about wire gauge for my 220V circuits. Am I ok with 220V 1P circuits using 14/3 conductor? or do I need 12 or 10? These are going to be 20A circuits that will I think never see more than about 12 A draw (Im going to keep one tool per circuit)








Thanks

I just use the wire at what it is rated for. I am not an electrician, but to me 14/3 is for 15 amp lines, and I use a 15 amp outlet on it. For 20 amp I use 12/2 or 3 with a ground, always a ground, even if it is just to ground the outlet box. Then I put a 20 amp outlet on it, which has the right angle leg on it.

Without going into every line that enters my shop, if I had to do it over again, I would put a load center/panel in my shop. Run one large wire into the panel, thereby eliminating any concerns of wire distance, because thin wires have that concern over greater distances, and thick wires do not. Even more importantly, it is nice to be able to go to a single switch panel and turn the shop off at the end of the day. If electrical storms are present, like they are in my neck of the woods, you don't want all of your high power machines, plugged into outlets, waiting for a lightning arc. Since surge suppressors for 30 or 40 amp tools are hard, and expensive to come by, and the common ones that are rated for 15 amps are annoyingly always tripping when you turn on tools. Even my radial arm saw pops one of them, so 20 amp circuits are very popular for woodworking.

Consider running a couple of outlets off of one line, instead of limiting yourself to one wire for each outlet, especially with the price of copper. But consider which outlets they are, because you don't want your shop vac to be plugged into the same circuit as your tool. If you had an outlet you were sharing with your scroll saw, and the one you plugged your belt sander, or hand tool into, that would not be a concern, since you do not run these concurrently.

With a 200 amp, and a 125 amp panel feeding my house, I was able to run a lot of power into the shop. It is really nice being able to walk over to a dedicated station, and simply flip a switch. My shop is about 725 sq feet, which is sufficient to be able to do that. Positioning and layout helps a lot.

Don't plan your circuits based on what you anticipate the draw will be, but rather what the standard demand parameters dictate. My good buddy is a professional electrician, and I forget all of the specifics because it has been a while since the electric was upgraded. I will say that prior to the upgrade it was a real pain in the butt, having to plug and unplug stuff all of the time.

All of my 220 20 amp circuits are run with 12 gauge wire, except the one that is isolated for my heat pump band heater only. I don't want to jump off topic here about that one. I don't think you will run into too many 15 amp 220 circuits. It doesn't hurt to be running 12 gauge 20 amp for that. They key is to always match the circuit breaker with the gauge of the wire. The thing to be avoided is a 14 guage wire with a 20 amp breaker.

You know their are exceptions to every rule, and I am sure their is an electrical professional right now, blowing a breaker reading this, so take what I say with a little skepticism, like I said, I am not an electrician.

Instead of trying to make one circuit do all, think in terms of multiple outlets, each with their own rating and purpose. Hooking up a 15 amp tool to a 20 amp line is not going to give you the kind of protection for the tool overheating, let's say with a lockup, or jam, than if you had hooked it up to a 15. (Assuming the 15 amp breaker would break before the motor would cook completely)

On the other hand a 30 amp tool doesn't like to be starved with a smaller line either. Run as many different size outlets into the shop as you can, and use each of them at their ratings. Shop lights can run a lot of them off of a single 15 amp 14 guage wire.

Heavier equipment especially 220 volt 30 amp level is best run off of a dedicated line.
Hey at least I know enough to be dangerous. :D Hope this helps.

[Tom Veatch]

... I am not an expert on welders, that a previous poster commented on, but to the best of my knowledge, not even they require the neutral.

I believe you are correct. Both my Miller Thunderbolt AC/DC stick welder and my Millermatic 180 MIG welder are 240 volt machines. Neither of them have any need whatsoever for 120 volt power so running 3 + ground cable for them just means the neutral conductor is unused. Of course, I can't say there are absolutely no 240 volt welders in existance that require simultaneous 240 and 120 volt feeds. There are dual voltage welders but I think they are either/or instead of simultaneous.

So why did I run 3 conductor cable for my welding circuit. Well, I plug my welding cart into the wall, plug the welder into the cart, and also plug the 120 volt angle grinder into the cart. (My welding prowess is such that I use a greater mass of grinding wheels and flap disks than I do welding wire :o :D) So, for code compliance (can't use the safety ground as a conductor), I need the neutral wire for the 120 volt tools on the cart, but not for the welder.

[Rod Sheridan]

Hi, the highest HP machine I own is a General 650 saw with a 3 HP motor, which has a full load current of 12.2 amperes, or the shaper with the same motor. My bandsaw is 2HP, as is the planer, the jointer and lathe are 1 HP.

This is at the limit of a 15 ampere feeder, so my shop is wired with a 15 ampere 240/120 feed that feeds a 240V 15A receptacle, and a 120V 15A receptacle in split configuration, both in the same 4 inch square box.

These receptacles are located every 6 feet along the shop wall.

This allows the use of a 240 V machine, such as my tablesaw, planer, jointer, bandsaw, shaper, and lathe, or any 120V tool such as my grinder, scrollsaw and drill press.

A 15a 120V drop cord above the bench, is fed from via a GFCI receptacle, for safety when using hand held power tools, this is on its own 15A breaker.

A second 15A 240V feeder runs the 1.5 HP Oneida cyclone.

So, this yields a system that meets code, runs all my 240 and 120V machinery from a single 2 pole 15A breaker.

The second 2P 15A breaker runs the cyclone, and a 1P 15A breaker feeds the drop cord.

My design is limited to one piece of machinery at a time, however so is my dust collection system limited to one piece of machinery at a time. Also I'm not dextrous enough to run two pieces of machinery at a time!

I know that the bigger is better theory is common, however as a person who does electrical system design for a living, you can go overboard on the issue.

If you are not going to use 5HP machinery, and your voltage drop calculations are fine, use a 20 ampere feeder.

Note that you will have to check your machinery nameplate rating. My saw and shaper have premium efficiency motors, they draw much less current than an inexpensive motor.

Regards, Rod.

[Chris Friesen]

Isn't the rule of thumb you figure the voltage/amps of the machine, and that tells you the size of breaker you need for the circuit (round up) and then size of the breaker tells you the size of the wire?

Normally one would size both the wire and the breaker to the expected load and the circuit design. For instance, motor circuits let you do funky things with the breakers (like oversizing by 250%) because you're supposed to have overload protection right at the machine as well. Fixed electrical baseboard heating loads are allowed to have larger breakers than mixed receptacle/lighting loads, etc...

[Tom Veatch]

... For instance, motor circuits let you do funky things with the breakers (like oversizing by 250%) ...

Let me see if I'm understanding you correctly. Assume a motor circuit - special purpose circuit with a hardwired motor load - that is wired with 12ga NMC. That will typically call for a 20 amp breaker. If I understand you correctly, you are saying that the breaker for that circuit could be oversized by 250%. IOW, a 50 amp breaker on 12 ga wire?

[Rick Christopherson]

Yes Tom, I believe that is correct, but it is not the type of information that should be presented here because it can be very misleading. I have seen the references cited, but I didn't personally review them because this is not something that I would ever present to anybody on a woodworking forum. The person that did cite these (on another forum) actually knows these sections of code better than I do, so I had no reason to question them. For everybody's benefit, it is probably best to forget that the topic was ever brought up.

[Wes Crawford]

Jason, there is nothing wrong with using #10 wire for your 240 volt circuits, just so long as you understand that the likelihood of actually using it is going to be extremely low in a garage workshop. People advise others to do this all the time, telling them to plan ahead, however, this isn't planning ahead.

Just for comparison, a 3hp Delta Unisaw will run from a 15 amp circuit (but I wouldn't recommend it). For the typical garage workshop virtually all of the tools are 3 hp or less. The most notable exception is a 5hp compressor. Even though I have heard of some people putting in 5 hp dust collectors in their garage, this is kind of silly for the amount of space.

Number 10 wire is horrible to work with, and right now it is terribly expensive. Do you really foresee getting any 5 hp tools?

By the way, in your original posting you commented about 3 conductors (plus ground). This is not required, and used even less. I am not an expert on welders, that a previous poster commented on, but to the best of my knowledge, not even they require the neutral.

As a licensed electrician with over 40 years of field experience, I must weigh in here and set the record straight on some of the more seriously flawed advise offered in this thread. First, we have one contributor that has it right. Circuit size is always determined by the size of the overcurrent device protecting the circuit (and your life) and always determines the ampacity of the circuit. The NEC (National Electrical Code) mandates (with technical exceptions) #14 wire for a 15A circuit, #12 wire for a 20A circuit, and #10 wire for a 30A circuit. That said, it is wise in a typical home workshop to provide a 30A, #10 240V circuit for each dedicated machine. That allows flexibility to move the machines to different locations without rewiring the shop. A machine that is say 1 HP can be adequately protected by a 15A circuit breaker, while your 3 HP saw will require a 30A breaker. This way, if you decide your 1 HP machine should switch places with your 3 HP machine, all you have to do is switch breakers in the panel, and your valuable machines will be protected from melt-downs. Another tip: The NEC stipulates a maximum ampacity for a single dedicated circuit of 80% of the circuit rating. So a 30A circuit can serve a maximum 24A load as an example. There are many other corrections that are in order, but that is enough for now. Except...don't believe that bit about ground wire not required. Think of it as your "lifeline". Respectfully submitted, Wes Crawford

[Jason Morgan]

Thanks Wes for your input. You said it very simply and I will follow your advice. Dedicated #10 wire for each 240V 30V dedicated circuit and #12 120V 20A for all the plugs. Lights will be #14 120V 15A.

Now the easy part (not!)...deciding where to put everything...:D

[Rod Sheridan]

Hi Wes, well said except for the part about the 1 HP machine being protected from meltdown by the breaker.

The breaker does not provide overload protection for the motor, that is provided by the starter or thermal overload device built into the motor.

The breaker provides branch circuit, and short circuit protection only.

regards, Rod.

[Tom Veatch]

Yes Tom, I believe that is correct, ....

Thanks, Rick. It may be correct and in accordance with code for certain special applications, but just between you, me, and the fence post, I don't think I'm going to be hanging a 50amp breaker on 12ga wire anytime in the near future.

[Tom Veatch]

.... The NEC (National Electrical Code) mandates (with technical exceptions) #14 wire for a 15A circuit, #12 wire for a 20A circuit, and #10 wire for a 30A circuit. ...

Minor quibble, Wes, but would it be more correct to say that the mandate is for "no smaller than" 14 ga for 15A, etc. Am I correct in assuming, for example, using 12ga wire in a circuit protected by a 15A breaker might be excess to code requirements, but wouldn't be a violation.

[Rod Sheridan]

Yes it is a minimum gauge requirement. Larger gauges are frequently used, such when your branch circuit voltage drop exceeds 3 %. you go to a larger gauge to achieve 3% voltage drop, or lower.

Regards, Rod.

[Wes Crawford]

Hi Wes, well said except for the part about the 1 HP machine being protected from meltdown by the breaker.

The breaker does not provide overload protection for the motor, that is provided by the starter or thermal overload device built into the motor.

The breaker provides branch circuit, and short circuit protection only.

regards, Rod.

True, Rod.."Melt-down" is misleading in this instance. The circuit breaker provides fault current circuit interruption, not over heating protection. That is one of the reasons that magnetic switches with provisions for thermal overload elements are the right approach for protecting your valuable tools. I hope this dialog will help the SMC faithful to do things the right way and not risk everything by shortcutting the electricals. Wes

[Wes Crawford]

Tom, Yes, you are correct. These are minimum sizes. You can always go over, and in some cases should. (Rule of thumb: Increase 1 size for every 100 feet) It is better to be a little over sized than under. Undersized produces more heat which shortens the like of electrical components. Wes

[Josiah Bartlett]

You should also consider the starting current of a motor. A machine that has close to the circuits capacity in run mode is not going to start very well, especially older machines with marginal start capacitors or R/I motors. The resistance of the wire is going to drop the available voltage to the motor and give long-term trouble. All my 240V circuits are 30 amps.

[Eric Gustafson]

You should also consider the starting current of a motor.

From what I have seen the starting current of a motor is huge. Such as, well over a hundred amps, but it only lasts for a second or two. It seems it would be impractical, if not impossible to size your wiring to consider startup current. Running amps seems like the only real solution.

[Randy Denby]

Most motor start amps are close to the LRA (locked rotor amps) and is usually about 3 -4 times the RLA (run load amps) but as stated lasts for just a split second and this is handled by time delay or slo-blow breakers.

[Rick Christopherson]

As a licensed electrician with over 40 years of field experience, I must weigh in here and set the record straight on some of the more seriously flawed advise offered in this thread. First, we have one contributor that has it right. Circuit size is always determined by the size of the overcurrent device protecting the circuit (and your life) and always determines the ampacity of the circuit. The NEC (National Electrical Code) mandates (with technical exceptions) #14 wire for a 15A circuit, #12 wire for a 20A circuit, and #10 wire for a 30A circuit. That said, it is wise in a typical home workshop to provide a 30A, #10 240V circuit for each dedicated machine. That allows flexibility to move the machines to different locations without rewiring the shop. A machine that is say 1 HP can be adequately protected by a 15A circuit breaker, while your 3 HP saw will require a 30A breaker. This way, if you decide your 1 HP machine should switch places with your 3 HP machine, all you have to do is switch breakers in the panel, and your valuable machines will be protected from melt-downs. Another tip: The NEC stipulates a maximum ampacity for a single dedicated circuit of 80% of the circuit rating. So a 30A circuit can serve a maximum 24A load as an example. There are many other corrections that are in order, but that is enough for now. Except...don't believe that bit about ground wire not required. Think of it as your "lifeline". Respectfully submitted, Wes Crawford I am not real thrilled that you quoted my response in your dissertation that there was misinformation in this thread as though I was the source of all the misinformation you were citing.

That being said, this issue of putting 30 amp circuits in for all 240 volt tools is the most frequently misapplied and misinterpreted aspect of the NEC on these forums. The reason being is that you read a section of the NEC and mistakenly assumed it applied to the type of equipment found in a wood shop.

Let’s begin with your example of a 3 hp tablesaw. For starters, something like a tablesaw is not a continuous load, and even when it is in operation, it is not drawing FLA. As a matter of fact, a tablesaw spends the majority of its life at an idle. Now consider that the 3 hp Delta Unisaw ships from the factory with a NEMA 6-15 plug installed, and you just advised everybody to put this saw on a 30 amp circuit. Is it your assertion that the NEC will permit you to install a NEMA 6-15R receptacle onto a 30-amp circuit? I should hope not.

Since the NEC won’t let you put a 15 or 20 amp outlet on a 30 amp circuit, and because the Unisaw carries a UL listing, and since part of the UL certification is to ensure the tool conforms to the NEC, don’t ya think it may be a misinterpretation that a 30 amp circuit should be used for all 240 volt outlets?

What I don't understand, is that even if you did misinterpret NEC in this fashion, a 20 amp circuit would still be sufficient for a 3 hp tool, and a 30-amp circuit is still applicable for a 5 hp tool. So where the heck did this notion come from for installing a 30 amp circuit for a 3 hp tool?

[Rod Peterson]

[snipped]...So where the heck did this notion come from for installing a 30 amp circuit for a 3 hp tool?

I think I have an idea. I can't attest to it personally, although I think you might be able to, but more than one friend on various woodworking message boards has claimed that the instructions which came with their 3HP blurfl indicated a requirement for a 30A circuit. It is no surprise to me that someone writing the manual may not be as well informed as they should be in comparison to someone in the engineering department, but it doesn't take many kernels of misinformation like that to propagate geometrically and lead us to this discussion.

I don't want to name any names but my recollection is that the culprit in this misinformation is a tool purveyor who's named for an animal of the genus ursus.

[Rick Christopherson]

I think I have an idea. .... tool purveyor who's named for an animal of the genus ursus.Oooh, you couldn't strike a deeper nerve if you tried! :D:D I can't even begin to count how many times I have heard people use this four-legged product manual to justify their claims.

As a technical writer myself (plus Electrical Engineer), I know exactly how these errors end up in manuals, and it is part of the reason why I have such contempt for my own profession (well, one of my professions at least).

Isn't it ironic that the same four-legged company that advises you to use a 30-amp circuit in one manual, also warns you that installing their equipment on too large of a circuit will void your warranty?

Yup! It is misinformation like this that cascades through the forums. Frankly, I don't oppose 30-amp circuits, but it is the widespread misinformation about this that requires that I take the balancing stance on the topic. It makes it sound like I am opposing a topic, when all I am trying to do is keep the discussion in perspective.

[Bruce Wrenn]

I would consider using TWO lighting circuits. If one breaker kicks out, you aren't totally in the dark. Don't ask how I know, but I do. Despite the fact that Rick and I had a disagreement on multi- wire branch circuits, I would trust him over most other posters on electrical questions.

[Randall Davis]

Im wiring the new Garage/shop and was wondering about wire gauge for my 220V circuits. Am I ok with 220V 1P circuits using 14/3 conductor? or do I need 12 or 10? These are going to be 20A circuits that will I think never see more than about 12 A draw (Im going to keep one tool per circuit)

Thanks



as others have stated 12 gauge for you 120 volt circuits and 10 gauge for your 240 volt circuits is pretty safe. Unless you get a monster machine over 5 hp.

[Rick Christopherson]

as others have stated 12 gauge for you 120 volt circuits and 10 gauge for your 240 volt circuits is pretty safe. Unless you get a monster machine over 5 hp.This is Exactly the reason why I entered this discussion in the first place. Why is it that people automatically assume that 240 volt circuits require 30 amps? People repeat this as though it was some sort of standard to the point that other people begin to assume that it is a requirement. And then those people repeat it, and so on, and so on!

There is nothing wrong with using a 30 amp circuit, but it is statements just like this one that cause this to be repeated without forethought.

So let me ask you, how many 5 hp tools do you have in your shop? What are the chances that someone that bought a 3 hp tablesaw is going to trade it in for a 5 hp saw? Of all the people that advise this "just to plan for the future", well how many of those forward thinking people Actually used them in the future?!? The answer is, very few; especially when it comes to a garage workshop, which is the most common.

[Bob Feeser]

Rick I have to agree with you, but what if your "Tim the Toolman"? Grrrrhhhh! :) I have several 220v 20 amp runs/outlets in my shop. I use one for my 2 hp jointer.

Referring to other discussions in the thread, I would like to share my experience with the amperage/table saw motor size dilemma. I have to mention that the amperage for tablesaws is something I know is best left to the electrical engineers, of which I am not. IMHO I have a Sears vintage 50's contractor saw with 1 hp 110v, and it was hooked up to a 15 amp line. When cutting really heavy stock, like north of 4/4, it would smoke the wood like the dickens, and between the breaker popping, and having to reset the red button on the motor, it was all the frustration I could handle. Then I discovered the cast iron top had a bow in it, because the motor was attached to the top instead of the cabinet. That was all I could take. Since I had the 1 hp angst, I decided to go with the 5hp PM machine just to be sure. Norm at NYW uses a 3, and from what I hear that is all you need.

So back to the electrical. I converted the Sears 1 hp over to 220v which helped somewhat, but still didn't do the trick. Then the monster machine arrived, and I called PM about the electrical needs, and they, like others, mentioned that although the 5hp motor draws 24 amps, allowing for headroom of about 20% (don't quote me on that:eek: ) brings you right up to the edge of 30 amps. Rather than take a chance of the occassional breaker going, they advise you to go 40 amps instead. Therefore they specifically tell you to use 8 gauge wire in the walls. (Although they advise you to use a 10 guage rubber cord wire to the outlet)

I know from the consumer perspective, nothing is more dis-instilling of confidence in the quality of a tool, then one that is throwing breakers.

(Not that I am saying that 3hp machines will throw a 20 amp breaker, because I don't have any experience with that) I think the Delta dust collector had a problem with that for a while, as I recall, and was getting slammed on Amazon from people as being a piece of trash, while recently it has won some awards as being the best.
So what experience I have had is 15amp for a 1hp is too little under challenging cuts, and according to PM the 40 amp is required for a 5. So taking that logic a little further, I assumed it would be a best bet to use a 30amp for a 3 hp. It appears that many people are successfully using a 20 amp line for that. I guess that is why I mentioned that I'm not an electrician, and I know enough to be dangerous.

[Randall Davis]

This is Exactly the reason why I entered this discussion in the first place. Why is it that people automatically assume that 240 volt circuits require 30 amps? People repeat this as though it was some sort of standard to the point that other people begin to assume that it is a requirement. And then those people repeat it, and so on, and so on!

There is nothing wrong with using a 30 amp circuit, but it is statements just like this one that cause this to be repeated without forethought.

So let me ask you, how many 5 hp tools do you have in your shop? What are the chances that someone that bought a 3 hp tablesaw is going to trade it in for a 5 hp saw? Of all the people that advise this "just to plan for the future", well how many of those forward thinking people Actually used them in the future?!? The answer is, very few; especially when it comes to a garage workshop, which is the most common.


Rick, are you taking your pills as prescribed? :confused:

[Chris Friesen]

What I don't understand, is that even if you did misinterpret NEC in this fashion, a 20 amp circuit would still be sufficient for a 3 hp tool, and a 30-amp circuit is still applicable for a 5 hp tool. So where the heck did this notion come from for installing a 30 amp circuit for a 3 hp tool?

Maybe when the manufacturer recommends a 30A circuit for their machine with a NEMA 6-15 plug they're expecting you to use a 15/20 A receptacle, with #12 wiring, and a 30A breaker? Given that this is a motor circuit, this is totally legit.

Personally, I have my "3HP" saw (FLA of 12.7A) on #12 wire with a 20A breaker and I have yet to pop the breaker.

[Tom Veatch]

...Personally, I have my "3HP" saw (FLA of 12.7A) on #12 wire with a 20A breaker and I have yet to pop the breaker.

Ditto - about 5 years now without a single complaint from the 20 amp breaker (NEMA 6-15R Wall receptacle)

I don't think a 30 amp breaker would be legit in my case since there are several 5-15/6-15 combination receptacles (http://www.levitonproducts.com/catalog/model_5031-I.htm?sid=BEA7959F88BB9AD2AB89D64B921093B5&pid=1208) on that circuit making it impossible to call it a dedicated motor circuit.

[Rick Christopherson]

Maybe when the manufacturer recommends a 30A circuit for their machine with a NEMA 6-15 plug they're expecting you to use a 15/20 A receptacle, with #12 wiring, and a 30A breaker? Given that this is a motor circuit, this is totally legit.No it is NOT totally legit. You read something that a very experienced person (and a friend) stated, but you have repeated it out of context. If you had continued reading the subsequent discussions, you would have seen that both he and I were in complete agreement that this information goes right out the window when you put a receptacle on the circuit. NEC does not permit you to install a 15 or 20 amp outlet on a 30 amp circuit. To the best of my knowledge, there are no known exceptions to this, even for motors.

[Rick Christopherson]

Rick, ...If you are looking to get a rise out of me, this isn't a very effective way to do it. Posting misinformation is a more effective method for getting my attention than an insult. If you don't have the experience or wherewithal to levy a proper argument, shouldn't this be a clue to you that you are stepping into something that is over your head? I would have much preferred that you tried to contradict the information instead of this.

The last part of my posting was an open question to anyone repeating the same type of misinformation, but I can fully understand how you took it personal, and for that, I apologize. My closing question was not intended to be personal, but I mistakenly worded it that way. Nevertheless, since you were repeating the information, can you refute the question?

No, I am not offended by your reply, and I did not fully quote it so that you could delete it without embarrassment after you realized that it was inappropriate for SMC.

[Chris Friesen]

No it is NOT totally legit. You read something that a very experienced person (and a friend) stated, but you have repeated it out of context. If you had continued reading the subsequent discussions, you would have seen that both he and I were in complete agreement that this information goes right out the window when you put a receptacle on the circuit. NEC does not permit you to install a 15 or 20 amp outlet on a 30 amp circuit.

Actually I'm not quoting from anything else in this forum, but from my own reading of the code. Could you point out the thread for my own interest, or what section of the code prohibits a cord-and-plug connected 3HP motor?

By my reading, a 3HP motor (FLA of 12.7A in my case) a continuous duty application requires a conductor ampacity of 125%, which is a bit more than 15A, so we bump it up to 20A. A 15/20A receptacle is thus acceptable (as specified in the second part of 430.42 (c). Then, under table 430.52 a breaker of up to 250% of the FLA may be used.

In any case, I didn't want to confuse future owners of my house so I didn't oversize the breakers for any of my circuits.

[Philip Giangarra]

Yes, the code states a minimum wire size, not a maximum one. Using a larger size wire reduces resistance in the branch, and thus delivering more current to your motor (or other load). It also lets you upgrade the circuit breaker to a bigger size without changing the wire.

Phil Giangarra

[Rick Christopherson]

...or what section of the code prohibits a cord-and-plug connected 3HP motor?No one has said you couldn't put a motor on a cord and plug circuit, so I don't know where you got this idea from. What is at issue is that the NEC does not permit a 15 or 20 amp receptacle on a 30 amp circuit. If anyone is so inclined to oversize their circuit for a tablesaw, then they are required to cut off the factory 6-15 plug and either replace it with a 6-30 plug, or hardwire it.

Nevertheless, I think you missed the original point. The topic came up because some people, while quoting their credentials, are advising others that a 30 amp circuit is required for 3 hp tools, or even worse, some people are suggesting that all 240 volt circuits need to be 30-amp.
By my reading, a 3HP motor (FLA of 12.7A in my case) a continuous duty application requires a conductor ampacity of 125%, which is a bit more than 15A, so we bump it up to 20A. A 15/20A receptacle is thus acceptable (as specified in the second part of 430.42 (c). Then, under table 430.52 a breaker of up to 250% of the FLA may be used.First off, most home woodworking tools are not classified as continuous duty, so it is not required to derate the circuit. This is where the whole discussion got started. As long as i am repeating myself, I will repeat the same example.

A DeWalt DW625 router is rated at 15 amps, and comes with a NEMA 5-15 plug.
The Jet JWP-13DX planer is rated at 15 amps and comes with a NEMA 5-15 plug.
And as was already stated, the 3 hp Unisaw comes with a NEMA 6-15 plug.

If it was required to derate the circuit that these tools were connected to, then UL would not permit the manufacturer to sell the tool with a power cord that equaled (or nearly equaled) the amperage rating of the tool. All of these tools would require either a NEMA 5-20 plug for 120 volts, or a NEMA 6-20 plug for 240 volts. The reason why we have 20 amp plugs is so you cannot plug a tool that draws more than 15 amps on a 15 amp circuit.

As you pointed out, the section of the NEC that is so often misquoted on this topic is dealing with continuous duty loads, and most woodworking machines are not continuous duty.

[Chris Friesen]

Maybe I wasn't totally clear in my earlier post, so I'll go over my logic again.

In the case of the motor circuit I mentioned above, it could be argued that the "circuit" is actually a 20A circuit. Because it is a motor circuit, and the tool itself must have built-in overload protection, it is allowed to have an oversized breaker. (The breaker is really only to protect against dead shorts.)

If this interpretation is valid, then it would be acceptable to use a 6-20 receptacle. This receptacle accepts a 6-15 plug, so manufacturers ship with that because it allows maximum flexibility (ie, the machine will also plug into 6-15 receptacles).

I definately agree that you don't require #10 wire for 3HP tools.

The continuous duty thing is interesting. I believe most woodworking-style motors are continuous-duty rated even though they're not being used as such. Under table 430.22(E) a continuous-rated motor requires conductors of at least 140% of the FLA regardless of the actual use of the motor--which is actually heavier-duty conductors than is required under 430.22(A).

[Rick Christopherson]

Chris,
I do understand your logic, but I do not believe it would pass code. Maybe this would make more sense to you if you go through it one more time, only this time, unplug the tool and sell it first. Now take a look at the circuit you leave behind. That's the reason why this is not appropriate on a cord and plug application.

[Randall Davis]

If you are looking to get a rise out of me, this isn't a very effective way to do it. Posting misinformation is a more effective method for getting my attention than an insult. If you don't have the experience or wherewithal to levy a proper argument, shouldn't this be a clue to you that you are stepping into something that is over your head? I would have much preferred that you tried to contradict the information instead of this.

The last part of my posting was an open question to anyone repeating the same type of misinformation, but I can fully understand how you took it personal, and for that, I apologize. My closing question was not intended to be personal, but I mistakenly worded it that way. Nevertheless, since you were repeating the information, can you refute the question?

No, I am not offended by your reply, and I did not fully quote it so that you could delete it without embarrassment after you realized that it was inappropriate for SMC.


I stand by my original opinion "12 and 10 are pretty safe" with minimal added cost. I did not say it is required! Your interpretation of my statement is what will mislead people. That being said I wired my shop with 12 gauge wire for the 120 volt and 240 volt outlets and 14 gauge for the lighting. To answer your question, most people that own 3 hp table saw's will not upgrade to a 5hp saw. If a person has a smaller saw 1 or 1 1/2 hp and is looking to upgrade he may be more likley to spend the extra $ for a 5hp saw. "safe" not required!