# How Many HP with 120 vs. 240



## rstenevik (Nov 2, 2009)

I have a Craftsman Contractor Series table saw model 113.299410 that is supposed to be 3 HP, however, it has numbers on the motor for 120 and 240, but nothing where the HP line is.
My questions are:
1. How many HP is it? 
2. Would I get more by wiring for 220? I have 220 in the garage, so it would just require a change on the motor.
3. What do you recomend?

Here is what's on the motor:

AC Motor Moteur C.A.
Motor C.A.
MOD 824370 CAT MFG MOD T55BXHK-1024
HP RPM 2850 & 3450 SF E51954
V 120/240 HZ 50 & 60 PH 1 CODE H
A 13.0/6.5 SFA AMB 40C

RATING REGIME CONT. CL-B


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## levon (Sep 14, 2008)

hi Bob,

i am a novice and just guessing, ok?

ive always heard rpm equals horsepower. so if the rpms are the same, you would end up with the same horsepower. 240 volts will cut down on the amperage drawn. less current burned. some swear by 240 volts and some by 120. my saw is on 120 and i see no need to change it as it works flawlessly now.

thats just my humble opinion.


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## bobj3 (Jan 17, 2006)

Hi Bob

I'm not a pro.but on the newer table saws it's bit of puff, most like to see that big number on the front,it's BS most of the time,and a male thing I think on the newer table saws ,speed = HP just like the router,,they have a way on the router to heep the HP the same at lower speeds but not the table saw yet,,so to say if you slow down the table saw or load it up the HP goes down the tube so to speak, but if you give the motor what it wants Amps.it will draw all it can take on..that's why it's best to use 240 volts if you can,,most outlets are set at a max 20 amps. but the 240 setup can push more down the line to the motor ,30 to 50 amps. the norm. amps.= heat so to speak..
We have some real Pro's on this sub.and they will clock in I'm sure and give you all the math, But I would suggest you stick with 240 if you can...
The motor will work better and not get as hot..heat kills any motor tool... 

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rstenevik said:


> I have a Craftsman Contractor Series table saw model 113.299410 that is supposed to be 3 HP, however, it has numbers on the motor for 120 and 240, but nothing where the HP line is.
> My questions are:
> 1. How many HP is it?
> 2. Would I get more by wiring for 220? I have 220 in the garage, so it would just require a change on the motor.
> ...


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## rstenevik (Nov 2, 2009)

It says the RPM increases from 2850 to 3450 on 220, if I am reading it right; if that is a good thing I'll do it. Does it matter for the blades? What RPM do 3HP cabinet saws turn?


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## bobj3 (Jan 17, 2006)

Hi Bob

I don't recall seeing that, most run at 1750 or 3450 rpm. 120 or 240 but pull less amps. at 240..it's two leg thing  LOL

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rstenevik said:


> It says the RPM increases from 2850 to 3450 on 220, if I am reading it right; if that is a good thing I'll do it. Does it matter for the blades? What RPM do 3HP cabinet saws turn?


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## kp91 (Sep 10, 2004)

The measure of power has more to do with amps. You have 2 Amp specifications on your motor. Since the 110v amps are twice the 220v amps, the power is roughly the same. Drawing 13 amps on a 15 amp circuit (most household circuits) is getting close to the limit. If you have anything else on the circuit you might find yourself tripping breakers all the time. In that case, switching the motor over to 220v might be a better idea, or having a dedicated 115v circuit for your tablesaw.

If you're not a heavy duty user of your table saw, it should be fine wired up as 115v.

The nameplate data with speed differences has to do with running it at 50hz or at 60hz. The motor will run at the same speed whether 220 or 110 as long as the income frequency is the same.

On the inside cover of the motor junction box there is usually a wiring diagram for 110/220v. Your owners manual will tell you if you need a new start/stop switch, or if the one you have is rated for 220v.


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## rstenevik (Nov 2, 2009)

Thanks Doug
Very clear answer and explains alot. How do you figure HP? That's what everyone (including the front of my saw) advertsies.

Bob


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## kp91 (Sep 10, 2004)

rstenevik said:


> Thanks Doug
> Very clear answer and explains alot. How do you figure HP? That's what everyone (including the front of my saw) advertsies.
> 
> Bob


That's the $64,000 question, and a subject of great debate. What horsepower is the maker talking about? Is it the maximum horsepower that the unit can develop before it stalls, or the design horsepower of the machine.

Most 'horsepower' ratings on the front of power tools are 'horse manure'. For a theoretically 100% efficient electric motor, the power produced is

P= I x E. In your motor that is 120v x 13a = 1560w

hp = watts/746

1560/746 = 2.09 HP

If you run the numbers using 240v and 6.5a, it works out about the same.

To compare one motor with another, figure that input voltage is roughly the same, so comparing rated amps is as good a way as any other.

Hope this helps clear things up a little without getting in too deep,


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## harrysin (Jan 15, 2007)

I agree, 2.09 hp on either voltage but where 240 volts are available, that is the way to go, in my humble opinion of course!


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## rstenevik (Nov 2, 2009)

Thank you very much for the facts!

Bob


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## BigJimAK (Mar 13, 2009)

I'm with Doug and Harry that the "power" shouldn't differ significantly between the 120V and 240V unless the electrician wiring it up skrimped on wire size. 

If there's a difference at all, you're likely to see in a brief flicker of other lights in your house, especially if your house has 100 amp service to the power company instead of the newer 200 amp service. If you see it, it would occur because an induction motor will very briefly (for a very small fraction of a second) draw about 6x the amperage that's on the motor. So on 120, that brief startup draw would be about 78* amps (6 x 13 = 78). If it were wired on 240, it would be 6 x 6.5, or about half that. 

My bride sees that very thing every time I turn on my 5hp Unisaw. On the motor it shows it is rated about 20A at 240V. For a brief moment it draws about (6 x 20) 120 amps. Even with though my home has 200 amp service and my Unisaw is on a subpanel, she can see the flicker. It hasn't caused any problems (computers rebooting, etc.), although that is always possible since during that brief moment there is a bit of a reduction in voltage throughout my house.

I'm already at 240V so there's not much I can do about it but if you experience it and want it to stop you could convert it to 240V. The problem *should* go away.

* Note from above: if you are having a problem sometimes tripping a breaker when a tool first turns on but it doesn't trip while you are using it, that surge of amps is likely the cause. That would be another reason to convert.


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