Electrical question

[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! 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 ) 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?

[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 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