Greetings,
Perhaps you folks can explain to me the advantage of 110v motors that require 20 amp circuits. It seems that these are of no benefit on a standard home circuit, yet Grizzly markets both a cabinet saw and now their new hybrid saw in this configuration.
I would like to see a 1023sl Grizzly with a 1.5 hp motor that I could use at home without upgrading to 220v. Perhaps this smaller motor could have a frame size that would allow an easy upgrade to a three horsepower later, if needed. I don’t need the power but would like the precision of a cabinet saw.
I e-mailed their technical service about such a saw, but they replied that if I wanted a 1.5 hp saw I should look at their contractor saws.
What am I missing here?
Edited 1/22/2006 4:28 pm ET by nolan
Replies
I've wondered the same thing about their 2hp motors that draw 24 amps...they actually require a 30 amp circuit. I've heard the new hybrid only draws 20 amps which is a step in the right direction, but I don't know for certain what the actual amp draw is. The 1023S110 makes no sense to me at all. It still needs electrical work and is only $30 less than the 3hp version.
Just a reminder that a motor needs to draw at least as much horsepower from the outlet as it delivers. In practice, a motor is not 100% efficient, so it actually draws more horsepower than it produces. The conversion formula is:HP = Volts x Amps x Efficiency/746By this point, some readers may be wondering how that shop vacuum or compressor can produce the advertised 6 HP and still be plugged into a 110 outlet. The truth is that it can't. Along the way, some manufacturers adopted "peak horsepower" for ratings. Imagine if someone calculated the horsepower associated with crashing a car into a wall, and then used that as the rating for the engine. That's "peak horsepower".In other words, there are physical limitations on how low they can go, and what you're describing is close to those limits.I just googled up this article which covers it in more detail.http://users.goldengate.net/~kbrady/motors.htmlPete
To figure out what is really going on as the previos poster states there is some math involved. There are numerous ways that companies rate horsepower that purposefully cloud the issue. Here is my guess on the Grizzly 2 HP that uses a 120V circuit at 20 amps. Its a slightly under powered 2 HP motor however the feature list that many will use to compare saws with will say 2HP which is a step up from the 1.5 HP model many have. I have a "real" 1.5 HP saw and would like a real "2 HP" saw. That said most home owners/weekend warriors only have a 120V outlet(s) in their shop and don't want to run or worse yet pay to have an electrician run a 220/240 volt line to the shop. So Grizzly is giving you the opportunity to have a "2.0 HP" saw on a more common 120V circuit. I would bet most 2.0 HP saws that are pre-wired to 220 will out perform this saw.
Some motors can be wired for 110 or 220. Why would one wire such a motor either way?My goal is for my work to outlast me. Expect my joinery to get simpler as time goes by.
I am not an electrician so read this at your own risk. As a previous poster correctly wrote:
HP = Volts x Amps x Efficiency/746
The induction motor for the most part can be wired for either 240 or 120. IMHO Grizzly is trying to sell you on the idea of a 2 HP motor that requires no modification to your shop e.g. you can put it on a 120V 20 amp breaker. Most real 2 HP motors will require a 30 amp breaker if wired to 120 V which most homes don't support in the breaker box. However wire the same motor at 240v then you can use a 15 Amp breaker wired in your box to 240v. If you look at the above equation and plug in the numbers and solve for efficiency you'll see that you are getting an inefficient 2HP motor ( 2 x 746 ) / 120 V x 20 A. Wood magazine did an article a while ago on the advantages of running motors that provide the 120/240 V option at 240. I don't recall the details exactly but I'm sure someone else can provide a thorough explaination here.
"The induction motor for the most part can be wired for either 240 or 120. IMHO Grizzly is trying to sell you on the idea of a 2 HP motor that requires no modification to your shop e.g. you can put it on a 120V 20 amp breaker. Most real 2 HP motors will require a 30 amp breaker if wired to 120 V which most homes don't support in the breaker box. "
I like alot of the Grizzly products and their value....my beef with the Grizzly 2hp motors is that they won't run on a standard 20 amp 110v circuit...they tend to draw a nominal 24 amps and require a 30 amp circuit, which usually requires electrical work, in which case you should just have the 220v circuit installed IMO.
...Wonder how many people have bought a 2hp machine thinking they could run it on their standard 110v hookup?
> my beef with the Grizzly 2hp motors is that they won't run on a standard 20 amp 110v circuit...This isn't unreasonable. A 2HP Baldor will draw around 22-24A.Pete
Hi Pete - I agree that the amp draw isn't unreasonable for the HP rating. The problem is that some of those motors are marketed as 110v machines, but they'll typically still require some electrical work. My guess is that many people don't realize this, and Griz doesn't make it overly clear in some cases.Example:
This is what's on the website for the 1023S110 cabinet saw:"G1023S110 10" Table Saw 2 HP Single-Phase 110V
- 2 H.P. single-phase, 110V, TEFC motor"But if you dig into the specs that are buried in a pdf. file, you'll find that the amp draw is 24 amps @ 110v....which requires a 30 amp circuit. My guess is that people have bought these hoping to run them on their existing 110v wiring only to find out the circuit won't handle it. I know I wouldn't be happy if I fell into that situation.
I get it now. You're right. What they really mean is "single phase 110V, though on any typical circuit it'll blow the breaker immediately." ;-)There's another thread on Griz expecting owners to size their circuit breakers for motor protection. Also not very customer friendly.Pete
I think it is unreasonably. How many approved 110 volt house circuits have you seen that were more that twenty amp?
Switching from 115 to 230v. In escence you have half the internal line voltage loss. Hence better voltage at the motor with less electricity usage.
"Why would one wire such a motor either way?" [the usual "I'm not an electrician" disclaimer applies....] From a practical standpoint? One would wire 110 because that's all that's available in the shop. One would wire 220 in order to..........
[OK, I edited that out. See the reply below. Any additional info will be appreciated. Edit #3: Well, I'm just finding out that the earth is not only not flat, it's not even round; it's actually shaped like a baby rattle! I'm getting an education here and at WWA on electricity and 220 and amps and watts and how none of it is as straightforward as it looks. Thanks, all. ]
Now, if that's totally bogus, would the electrical specialists please let me know!
forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)Another proud member of the "I Rocked With ToolDoc Club" .... :>)
Edited 1/24/2006 5:00 pm by forestgirl
Edited 1/25/2006 4:44 am by forestgirl
Edited 1/26/2006 12:58 am by forestgirl
Next month or so, when the 220V outlets get put in, and rewire the motors on those tools, the circuits won't be getting maxed out every time I turn on the saw, DC or jointer. And a lower percentage of the total amps available from the sub-panel are being used.
Now, if that's totally bogus, would the electrical specialists please let me know!
I'm afraid that's 'totally bogus', to borrow your term.
A load drawing 14A at 120V is getting all it's current through one hot leg and the neutral. The same load, connected for 240V, draws 7A of current through both hot legs. If you have a 50A panel, then you would be using 14A out of 50A on one leg, and none from the other. At 240V, you'd be using 7A of the 50A available on each leg.
Either way, with a 50A panel, you have a nominal 100A at 120V, or 50A at 240V. Either way, you have 24kVA (volts x amps), and any combination of 120V and 240V loads will still total 24kVA when the breaker is carrying it's rated current on both legs. Reconfiguring a dual-voltage load for 240V halves the current draw, but it's now on both legs, instead of all of it being on one leg.
The panel has the same capacity no matter how you configure the loads, but at least with 240V load, you don't have to concern yourself with balancing the loads between the two legs. But there are other added benefits to the higher voltage, not the least of which is the great reduction in voltage losses in the lines, which gets important with larger motors and/or longer runs of wire.Be seeing you...
there are other added benefits to the higher voltage, not the least of which is the great reduction in voltage losses in the lines, which gets important with larger motors and/or longer runs of wire.
That's what I was looking for, thanks... less voltage loss. So there's nothing in the motor's internal efficiency per se, just that having two hots 240v apart each carrying half the amperage loses less in transmission from the panel?My goal is for my work to outlast me. Expect my joinery to get simpler as time goes by.
There are other bennefits as well to 240. Less heat. Heat kills they say. By each leg drawing less amps then the heat will be reduced.
OK, now I'm getting a headache. But I do appreciate your post!
So, although the motor plate says, for example, 9 amps when wired to 220, that's not the load on the subpanel? Leads one to wonder what good those motor plate numbers are for the average Joe (or JoAnn). A resulting question: In the 9amp/220V example, does that mean that circuit would require a 20Amp or so breaker?
And then there's "with a 50A panel, you have a nominal 100A at 120V."
No wonder electricians make so much money. I really do want to understand this better, but have to go to work right now. Will keep an eye on the thread.
forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)Another proud member of the "I Rocked With ToolDoc Club" .... :>)
Edited 1/24/2006 3:54 pm by forestgirl
> The same load, connected for 240V, draws 7A of current through both hot legsIt's still just a 7A circuit going through the motor. That's another (minor) benefit of 240, you can use lighter wire for the same horsepower.Pete
Very good explanation but I think you could elaborate that when using both legs equally that the neutral is carrying zeroe amps, hence no voltage loss. The whole line loss to the machine is one half of drawing the power compared to a 110 volt source with twice the ampacity
Edited 1/24/2006 11:52 pm ET by tinkerer2
Bogus, stick to your guns, Jamie. You are absolutely correct in what you said. Of course, you left a lot out. I think I might have misread one of your distractors and given him credit where it was'nt due. Sorry. It is getting late.
I printed his post out. We have an electrician coming over this week (I hope!) and I'm going to run that explanation by him so I can get a better understanding. It's one of those things that makes sense, but then again doesn't.... I can't really "stick to my guns" since electrical is mostly a mystery for me. I can rewire a floor lamp, replace an outlet or light fixture, but that's about it.
forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)Another proud member of the "I Rocked With ToolDoc Club" .... :>)
Edited 1/25/2006 3:52 am by forestgirl
The quote from t he magainze, seen below, is what I have always thought was the case. It's proving to be untrue though. It appears that the authors fell into the same "common sense" trap that I did, but their mistake got in print. The bottom line seems to be, you have a certain number of watts available in your panel, and that's all you have, whether you're using 110, 220, or a mixture of the two.
So, read but do not quote the following, as it isn't exactly the way things are:
A Knots colleague sent me some info that touches on one of the questions, that of how using 220 lessens the load on the panel. I'm waiting for the details on the magazine name and authors, but I'll quote on that one topic in the meantime:
forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)Another proud member of the "I Rocked With ToolDoc Club" .... :>)
Edited 1/26/2006 1:01 am by forestgirl
You've got it down pretty good. I think one thing you must consider is that just because the panel will provide x amps doesn't mean the motor will draw that many amps, and just because the panel is supplying x volts doesn't mean the motor is getting that many volts. In the first instance the motor has a given impedance that will limit the amps it will take. In the second instance, the line has a given resistance that is going to rob some of the voltage the motor will get. There is no perfect conductor nor is there a perfect insulator.
As far as the name plates are concerned. I have this suspicion that the manufacturer might stretch their data a tad bit. When it comes to advertisers - I think they out right "don't tell the truth." See, I avoided saying that bad word. How can a 7.5 HP motor run on a line that will supply only a fraction that amount of power.
I've always been interested in electricity, and mechanical things. In my adult life my interest in woodworking has kind of taken the place of that in mechanics. What did I take in school? Would you believe Agronomy. The study of soils and plants.
Tinkerer2, maybe this will help a bit. I think you'll see that HorsePower is really a very broad array of nested variables.
http://en.wikipedia.org/wiki/Horsepower#History_of_the_term_.22horsepower.22
After reading this you can pretty much blow out the electron theory when it comes to horsepower that manufacturers state.Steve
"You can either be smart or pleasant, I was once smart but now I'm pleasant. I like being pleasant better." Jimmy Stewart - Harvey
Horsepower: Thanks for the article. That is interesting.
You're welcome. As you can see, horsepower can be just about be anything we want to make it. I was showing the article to a customer yesterday and we (humourously) figured that if we could tow a Bosch 4000-9 saw behind our truck it would be a 300hp saw.Steve
"You can either be smart or pleasant, I was once smart but now I'm pleasant. I like being pleasant better." Jimmy Stewart - Harvey
Horsepower: But what happened to the 33000 lbs. per ft. rule?
Edited 1/28/2006 10:31 pm ET by tinkerer2
We haven't had one of these amoebic electricity threads in a long, long time. The topic is so complex and multi-faceted that a thread such as this one gets amazingly spread out very quickly. I'm guessing it'll go to 75 posts pretty easily, LOL.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-) Do unto others as you tell them they should do unto you....
Sorry for taking so long to respond. Here's a first poke at a real explanation. I had to redraw some diagrams that I had posted back when, but can no longer find (what happened to my post count? - it was a few hundred last I checked) You're right, though, that this subject isn't as simple as it seems, but once you know how it works, it's not as complex as it looked at first glance, at least until you toss in the effects of voltage drop on motor performance. :(
The four attachments below are diagrams of various loads on a typical "Edison" 3-wire system*, which is how your house is wired. The arcs on L1 and L2 represent the two poles of the circuit breaker, and the dashed line indicates that they are mechanically connected to each other - when one opens, the other does too.
Edison 1 shows a 120V 50A load (or combo of smaller loads) on L1 only - current comes from L1, goes through the load(s), and goes back to the transformer center tap via the neutral. One-half cycle later (1/120 of a second), current is flowing in the opposite direction. On the right side is the same thing, but the load is connected to L2 only. It helps to remember that the neutral is really not a "return", as some folks refer to it - current comes in through the neutral from the transformer just as much as it goes back to the t-former through it (a half cycle later).
Edison 2 shows two 120V 50A loads, one each on L1 and L2. You can see on the left side that the L1 current goes through the load and back to the transformer through the neutral, but the other load (on L2) takes current from the neutral, which goes through the load and back to the transformer through L2. The diagram on the right is what really goes on in that the current from L1 never makes it back to the transformer, since it's used by the load on L2. There's a rule in electric circuits that all the current into a node must equal the current out of that node. Since 50A flows into the neutral connection from L1, 50A must flow back out. The entire 50A is needed by the load on L2, so nothing is left to go back to the transformer through the neutral.
Edison 3 shows a 120V 10A load on L1, and 120V 50A loads on L2. This is typical of any panel with 120V loads - it would be coincidence for both L1 and L2 to carry the same load at any point in time. Since the currents into and out of the neutral connection between the L1 loads and the L2 load must equal zero, there will be some current flowing through the neutral. I deliberately showed the heavier current on L2, to get away from the notion of the neutal as a 'return', but 1/120 second later, the magnitude of the currents is still the same, but their directions are reversed - current is going back to the transformer through the neutral.
An interesting thing to note is that the neutral will never carry more current than either L1 or L2, since it only carries the difference between them.
Edison 4 shows two configurations of a 120/240V motor. On the left is the 120V configuration, with both main windings connected to each other in parallel. At rated output, the 14A rated current (hypothetical) flows from L1, through both windings (half the current, or 7A, through each winding), and goes back through the neutral. 1/120 second later, current is flowing in the opposite direction.
On the right the motor is connected for 240V, which means both run windings are connected in series, and the motor leads connect to L1 and L2 with no neutral connection. The 7A it's rated for passes through first one winding, then the other. Since the windings have the same impedance (AC resistance), they each drop the same voltage - 120V across each.
In both cases, each winding 'sees' 120V, and each winding carries 7A. As long as the voltage at the motor leads is exactly what the motor nameplate says (usually 115 and/or 230V for US motors), the windings don't know or care - they get exactly the same voltage and current regardless of the configuration.
In the 120V case, one leg of the main breaker carries the whole 14A, and the other carries nothing. In the second, both carry 7A - the current coming out of L1 goes back through L2. Since each leg, L1 and L2, can carry 50A (if it's a 50A panel, for this example), using 14A from one and 0A from the other out of a total of 100A for both is the same thing as using 7A from L1 and returning it through L2, where it also counts as 7A. It may be half the current at 240V, but it's counted twice, since it passes through each half of the main breaker.
So you're correct that a 50A breaker will only handle 50A of current (see the right hand side of Edison 2), but with 120V circuits, the current coming from the L1 side and driving those loads is then used on the L2 side to drive those loads, giving you 100A of 120V power. It's the same current, being pushed by L1 through it's connected loads, but then it's being pulled by L2 through the loads on the L2 side of the panel. When the system is loaded to the max (50A, for example), there is no current through the neutral, and the whole 50A comes in through L1 and goes out through L2 - same current, no matter how it's divided up to go through the connected loads, but that current drives loads on the L1 side and then on the L2 side, or straight from L1 to L2 through a load that's connected for 240V. A 50A panel is good for 12,000 watts, no matter how you work it.
I'm afraid there are no free lunches in your panel, and you don't save any capacity by using 240V instead of 120V. There are other advantages to using 240V, but that discussion would really take some bandwidth. I wrote a couple of diatribes on the subject already, but I don't know if they're still available in the archives.
I hope that sheds more light than heat.
*Thos. Edison invented this circuit for the original DC circuits to reduce voltage drop (since it was generated at the final voltage and couldn't go far without too much voltage drop - can't use a transformer on DC). George Westinghouse eventually won with his AC system, but the 3-wire system prevailed both for economy and for safety - neither leg is more than 120V to ground, even when using 240V loads.
Be seeing you...
Edited 1/25/2006 11:47 am ET by TKanzler
Many thanks, TK, for taking the time to provide such a detailed explanation. In most ways, it makes sense to me the layperson. (I still get a headache though, LOL. Just kidding.) Can you help explain why reconfiguring some motors to 220V reduces or eliminates the light-dimming brownouts in the shop (when compared to 110)? Thanks!forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-) Do unto others as you tell them they should do unto you....
Nicely done, and thanks!My goal is for my work to outlast me. Expect my joinery to get simpler as time goes by.
Nolan, General makes two saws (contractor 50-175/185-M1 and hybrid 50-220C-M1) with 2hp motors that run on a 15amp circuit. The current required by a motor has much to do with the quality of the materials used during construction. I'll let you put 2 and 2 together. General manages to do it with a 13/6.5amp dual voltage motor.
Of course we've always contested the fact that they are actually capable of 2hp because the current requirments would indicate nearly 100% efficency.
Now then, you also have to find out if they are talking about brake horsepower or clutch horsepower like the ratings you find on the portable table saws. For instance, the Bosch 4000-09 is rated at 4.5hp and runs just fine on 200ft zip cord. Yes, those manufacturers are sneaky little buggers aren't they. LOL.
FYI: I don't even try to explain it to customers anymore. I tell them to call the manufacturer.
Steve
"You can either be smart or pleasant, I was once smart but now I'm pleasant. I like being pleasant better." Jimmy Stewart - Harvey
Edited 1/25/2006 9:32 pm ET by WhatKnot
OK, I will take a shot at this. Hope it makes sense.
To run a motor you need power. To caluculate electrical power the formula is simple: Power = Volts X Current or P=IV.
In a perfect world of pure conductors power consumed by 10amps X 100V would be the same as 1amp X 1000V. But we do not have the motors built of perfect conductors (wire) or superconductors. Therefore, the 10amps X 100V setup is less efficient because energy is wasted in the form of heat... due to the voltage drop consumed by the conducting wire. Heat is the product of the energetic electrons flowing (current) through out the wire. The more violently the electrons jiggle and collide through out the wire's structure (lattice) the hotter the wire is. Therefore, the resistance of a wire changes with a wires change in temperature or greater current flow. As a wire's temperature increases so does its resistance. The more a wire's resistance changes the more it consumes voltage also known as voltage drop. This is why for the same power need it is generally more efficient to have the setup where less current is used by proportionately increasing the voltage.
Cheers
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