Power for table saw question 120 or 220?

[Dave]

I bought a new table saw and I can run it on 120 or 220, However, they
recommend 220. What does running it on 220 buy me over 120? Thanks for your
opinions.

 

[Edwin Pawlowski]

I bought a new table saw and I can run it on 120 or 220, However, they
recommend 220. What does running it on 220 buy me over 120? Thanks for
your
opinions.

Faster starting, less likely to bog down. Same operating cost. Smaller wire
size. A few Delta saws have a different set of windings and you get 2 HP
instead of 1.5

Separate circuit is always a plus. When I first go my saw I wanted to try
it out before hte new line was installed. I hit the switch and the
fluorescent lights went out for maybe 5 seconds until the saw got up to
speed. Scary. Next day I ran the new line. .

 

[maradcliff]

I bought a new table saw and I can run it on 120 or 220, However, they
recommend 220. What does running it on 220 buy me over 120? Thanks for your
opinions.

You get more power from any motor running it at 240 (220).

 

[FDR]

Faster starting, less likely to bog down. Same operating cost. Smaller
wire size. A few Delta saws have a different set of windings and you get
2 HP instead of 1.5

Separate circuit is always a plus. When I first go my saw I wanted to try
it out before hte new line was installed. I hit the switch and the
fluorescent lights went out for maybe 5 seconds until the saw got up to
speed. Scary. Next day I ran the new line. .

Yeah, but only scary in the Adaams family kind of way.

 

[SQLit]

I bought a new table saw and I can run it on 120 or 220, However, they
recommend 220. What does running it on 220 buy me over 120? Thanks for your
opinions.

The 240v installation will cost ya more. You will need a motor starter if
one is not supplied. It is always a good idea to have overloads in the motor
starter. Lots of manufactures make a "manual motor starters" Get one that
fits your situation.

http://www.cse-distributors.co.uk/controlgear/abb_manual_motor_starter.htm

Or you can spend more money and get an electrically operated one.

I have a delta saw that draw almost 15 amps under load (120v). I have not
converted over, just lazy and I use it off the genny every once and a while.

 

[Mortimer Schnerd, RN]

The 240v installation will cost ya more. You will need a motor starter if
one is not supplied. It is always a good idea to have overloads in the motor
starter. Lots of manufactures make a "manual motor starters" Get one that
fits your situation.

Some advantages: you won't blow the circuit breaker for the rest of the house
and your lights won't go off if you bog down. You can choose to run a dust
collector at either 110 or 220. If both are 110, you'll probably pop the
circuit breaker when you start both up.

I've got my jointer and bandsaw on 220. My table saw and dust collector are on
a special 30 amp 110V circuit but now I wish they were on 220 as well.

 

[Chris Lewis]

The 240v installation will cost ya more. You will need a motor starter if
one is not supplied. It is always a good idea to have overloads in the motor
starter. Lots of manufactures make a "manual motor starters" Get one that
fits your situation.

If you don't need one for 120v, you won't need one for the same motor wired for 240v.

"Magnetic starters" aren't really "motor starters" per-se. The basic purpose
is as a safety measure to not have the tool come back on after a power failure
is restored. They are essentially nothing more than a relay wired so that
a momentary pushbutton switch activates the coil, and if you lose power, the coil
stays deenergized after the power is restored. It won't turn back on until
you push the button again.

Some "starters" (like the ones SQLit was referencing) contain additional
thermal/current overload protection. But those are generally only necessary
for motors that don't already have thermal overload buttons on them.

 

[Chris Lewis]

Faster starting, less likely to bog down. Same operating cost. Smaller wire
size.

How much of this you'll actually see varies greatly. If the wire length from
the panel is short (<50') and you're not close to the limit on
the circuit, the differences will not be noticable. You're seldom able
to take advantage of a smaller wire size.

A few Delta saws have a different set of windings and you get 2 HP
instead of 1.5

Separate circuit is always a plus. When I first go my saw I wanted to try
it out before hte new line was installed. I hit the switch and the
fluorescent lights went out for maybe 5 seconds until the saw got up to
speed. Scary. Next day I ran the new line. .

Yup, separate is always a plus.

 

[SQLit]

snipped----------------------------------

"Magnetic starters" aren't really "motor starters" per-se.

Magnetic starters ARE motor starters. They do contain over load protection.
Contactors on the other hand are like what you say, "aren't really "motor
starters" per-se. "
Because they do not have overload protection just contacts.

Minor but important point to the less informed.



The basic purpose

is as a safety measure to not have the tool come back on after a power failure
is restored. They are essentially nothing more than a relay wired so that
a momentary pushbutton switch activates the coil, and if you lose power, the coil
stays deenergized after the power is restored. It won't turn back on until
you push the button again.

---------------snipped

 

[Colbyt]

I bought a new table saw and I can run it on 120 or 220, However, they
recommend 220. What does running it on 220 buy me over 120? Thanks for your
opinions.

More than likely you will need a dedicated circuit either way. I can't
recall the details but when faced with your choice I went with 220.

Edwin was pretty accurate, except I did not understand the wire size part.
Slightly oversized wire is cheap when compared to the cost of burning your
house down.

Also I think I recall a cooler running, longer lasting motor. But that is a
"I think".


Colbyt

 

[Edwin Pawlowski]

Just curious because I've never worked in a shop with fluorescent lights,
but is it true that the blade on a saw can appear to be stopped due to the
60 cycle strobing of the lights?

I've never seen it, but perhaps at the right rpm it could.

 

[Harry K]

snipped----------------------------------


Magnetic starters ARE motor starters. They do contain over load protection.
Contactors on the other hand are like what you say, "aren't really "motor
starters" per-se. "
Because they do not have overload protection just contacts.

Minor but important point to the less informed.



The basic purpose
---------------snipped

Chris is right. If the saw will run without one on 110, it will also
do it on 220. My saw came with the option of either also and was just
a minor wire change on the motor and that was 20 years ago. Specific
instructions included.

Harry K

 

[Ken]

Just curious because I've never worked in a shop with fluorescent lights,
but is it true that the blade on a saw can appear to be stopped due to the
60 cycle strobing of the lights?

A tidbit that some people might be interested in:

Fluorescent lights will flicker at twice the AC frequency, which would
be 120 Hz for North America. You get two cycles of the light
flickering for each AC cycle because the current flows one way and the
light comes on, then the current goes to zero and the light goes out,
and then flows the other way and the light comes on again. The light
doesn't care which way the curernt is flowing. In theory this happens
with other light sources such as a regular tungsten bulb, but you never
see the flicker in a tungsten bulb because the glowing filament doesn't
cool off quick enough to see any flickering.

A calibrated strobe light is one way to measure the rotational speed of
things. For the case of the table saw, you would gradually adjust the
strobe rate until you got the blade to "freeze". What is really
happening is that the blade moved in integer number of teeth from one
flash to the next. The problem is that you don't know if it moved one
tooth or two teeth, or whatever. You then change the strobe light
frequency until you get the blade to "freeze" again. There is some
procedure and calculations that are used to determine the rotational
speed of the saw based on the strobe frequencies that froze the blade,
but it's been too long since I have done that and I'd have to think too
hard right now to remember how that part works.

So there's today's science lesson.

Ken

 

[Chris Lewis]

Just curious because I've never worked in a shop with fluorescent lights,
but is it true that the blade on a saw can appear to be stopped due to the
60 cycle strobing of the lights?

It _can_. Whether it does, and by how much, depends on a lot of factors.

First requirement is that the blade on the saw is rotating at some
fixed multiple of 120Hz.

Ordinary fluorescents are pretty lousy strobes.

 

[Stormin Mormon]

Allows you to use smaller wire for installation. Other than that, not much.

--

Christopher A. Young
Learn more about Jesus
www.lds.org
www.mormons.com


I bought a new table saw and I can run it on 120 or 220, However, they
recommend 220. What does running it on 220 buy me over 120? Thanks for your
opinions.

 

[Ken]

So then if a saw blade is rotating at a speed which is a multiple of 120
(such as 4800 rpm) then it could appear to be stopped, right?

Yes. Say you had marked one tooth on the saw blade with red paint,
then the saw blade would have rotated 4800/120 = 40 times around
between each "flash" of the fluorescent light, and you would see that
red tooth appear to stand still. For this example, if the saw was
going a little bit faster or slower, you could see it freeze with 39 or
41 revolutions for 39 * 120 = 4680 RPM or 41 * 120 = 4920 RPM.
Rotational speed between these RPM numbers would not result in any
freezing action, so for this example you can see that the effect is
rather sensitive to slight variations in the RPMs of the saw blade.

If you didn't mark one saw tooth, then this sitation becomes even more
sensitive to slight variations in RPMs. Say there are 40 identical
teeth on the saw blade, so each tooth is 1/40th of a revolution (=
0.025). At 4800 RPM, you will freeze the blade because it is exactly
40 revolutions, but you can also freeze the blade with exactly 40.025
revolutions, which would be 40.025 * 120 = 4803 RPM, because on the
next flash of the fluorescent light the adjacent saw blade tooth will
be in the same position as the first saw blade tooth was on the first
fluorescent light flash. So you can freeze the blade at 4800 RPM or
4803 RPM, but between those speeds there will be no freezing.

Ken

 

[~^Johnny^~]

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Fluorescent lights will flicker at twice the AC frequency, which
would be 120 Hz for North America.

Only the old ones with mag ballasts. The newer ones are usually
electronic, and run in the tens of kilohertz.


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