I'm about to start building my shop in the garage. I currently have an
old small subpanel in there with a bunch of 110 outlets scattered around
that the last owner installed. It's all pretty old stuff but still in
working order.
Many of the new machines I'm going to purchase can handle 110 or 220.
My question is should I rewire the garage with a new subpanel and make
all those machines 220 and scatter some new 110 outlets around as well
or just make everything 110? What's the benefit of running a machine
like a saw or shaper at 220 vs 110? Does it have more power? Can someone
explain the tradeoff?
Monty
"Robert Bonomi" <[email protected]> wrote in message news:[email protected]...
> In article <[email protected]>,
> Bob Davis <[email protected]> wrote:
> >I think you are over rating the heat effect.
>
> If only you knew what you were talking about.
>
> > If wiring overheats, the
> >breaker was oversized. That is why we have breakers. Properly sized wire
> >should have negligible resistive heating.
>
> Depends on what you mean by 'negligible'. To coin a "Clinton". :)
>
> To deliver the same amount of power to the load requires *twice* as much
> current at 120V as is needed at 240V. Losses in the wiring, etc. are
> proportional to the _square_ of the current. Thus the losses in the
> wiring are *four*times* greater at 120V vs 240v, for the same power at
> the load.
>
> In a properly designed system, these losses are "relatively small" at
> either voltage. But, regardless, the losses are only 1/4 as large when
> you run things at 240V.
>
> EVEN WITH 'properly sized' wiring, the allowable voltage drop _in_the_wiring_
> between the panel and the device can be several volts. A 5V drop in the
> wiring, with a 15A load, and the _wiring_ is giving off as much heat as a
> 75 watt light bulb. And that's "within specifications" for a properly
> constructed circuit.
>
>
> > Some people say a dual voltage
> >motor will last longer when run at 220v. I think the biggest motor
> >longevity factor is the quality of the motor itself.
>
> You're free to think whatever you like. :)
>
> Needless to say, the 'quality' of any given motor is *unchanged* by being
> run at 240V instead of 120V. Regardless of whether it's a 'cheapie', or
> a 'top of the line' unit.
>
> Motors are, in general, more efficient when operated at higher voltages.
> This means the internal "losses" are lower at higher voltages.
> This means that there is, all else being equal, _less_ heat build-up in
> the motor, when run at higher voltages.
>
In the interest of further belaboring the point and to do a sanity check on myself consider the following:
Given a dual voltage 120/240v motor where the FLA is 20/10.
When operated at 120 vac the windings are wired in parallel and at 240 they are wired in series.
Ok so far? Lets consider that the winding resistance of .5 ohms per winding and that the heating is a result of I^2 * R.
For the 120v case, the effective resistance of the parallel windings is 0.25 ohms ( [R1 * R2] / [R1 + R2].
The heating loss would therefore be 20^2 * 0.25 = 100Awtts
For the 240v case the effective resistance of the windings in series is 1 ohm ( R1 + R2 )
The heating loss would be 10^2 * 1 = 100 Watts.
Then why are the losses considered to be more when running at 120v rather than 240v?
Looks to me like the same amount of power is lost due to heating.
> Excess heat _is_ one of the biggest enemies of longevity.
>
>
>
> >
> >Bob
> >
> >"John McCoy" <[email protected]> wrote in message
> >news:[email protected]...
> >> Monty <[email protected]> wrote in
> >> news:[email protected]:
> >>
> >> > Man, thanks for taking all the time to answer my question. That all
> >> > makes sense. It seems to be more of an efficiency issue as opposed to
> >> > power.
> >>
> >> Yes, but not quite in the sense you're thinking, I beleive. When
> >> you run 110 you draw more current for a given amount of output
> >> power, which causes "resistive" losses in the wires, etc (so you
> >> have to draw even more current to make up for that). The problem
> >> is in where those resistive losses go - which is into heating up
> >> the wires, motors, and everything else in the circuit. Heat is
> >> not a good thing; at best it shortens the life of the motor, and
> >> at worst it sets the wiring on fire.
> >>
> >> John
> >
> >
>
>
"Frank Ketchum" <[email protected]> wrote in message news:[email protected]...
>
> "Al Reid" <[email protected]> wrote in message
> news:[email protected]...
> >
> > In the interest of further belaboring the point and to do a sanity check
> on myself consider the following:
> >
> > Given a dual voltage 120/240v motor where the FLA is 20/10.
> > When operated at 120 vac the windings are wired in parallel and at 240
> they are wired in series.
> >
> > Ok so far? Lets consider that the winding resistance of .5 ohms per
> winding and that the heating is a result of I^2 * R.
> >
> > For the 120v case, the effective resistance of the parallel windings is
> 0.25 ohms ( [R1 * R2] / [R1 + R2].
> > The heating loss would therefore be 20^2 * 0.25 = 100Awtts
> >
> > For the 240v case the effective resistance of the windings in series is 1
> ohm ( R1 + R2 )
> > The heating loss would be 10^2 * 1 = 100 Watts.
> >
> > Then why are the losses considered to be more when running at 120v rather
> than 240v?
> > Looks to me like the same amount of power is lost due to heating.
> >
>
> There isn't any difference noticed in the motor itself. As you note, the
> motor itself sees the same voltage and current on it's windings. The losses
> are generated from the wiring which supplies the motor. All the way from
> the main electrical panel, through any sub panels, to the outlet and though
> any extension cords.
>
Good, we agree on that. So the 20A 120v motor will need to be fed from a 30 A breaker using #10 wire while the 10A, 240V motor will
need to be fed from a 15A breaker using #14 wire. Givint this installation, there will be negligable difference in the performance
of the motor when the system is examined in total.
> Frank
>
>
"Al Reid" <[email protected]> wrote in message
news:[email protected]...
>
> In the interest of further belaboring the point and to do a sanity check
on myself consider the following:
>
> Given a dual voltage 120/240v motor where the FLA is 20/10.
> When operated at 120 vac the windings are wired in parallel and at 240
they are wired in series.
>
> Ok so far? Lets consider that the winding resistance of .5 ohms per
winding and that the heating is a result of I^2 * R.
given I=E/R
at 120V that'd give a per-winding current flow of 'merely' 240A. :)
by the E=I/R rule,
the 'apparent resistance' of a motor drawing 20A at 120V is 6 ohms.
the 'apparent resistance' of a motor drawing 10A at 240V is 24 ohms.
The `total power consumption' is identical, agreed.
For complicated reasons, at the lower voltage you get somewhat _less_
'shaft horsepower' output than at the higher voltage, _given_the_same_power_
_input_. The difference in mechanical power output is typically a few
percentage points. (Although the motor on my delta contractor saw is rated
1.5HP @120V, and 2.0HP @ 240V. with a similar 'mis-match' in current draw
at the two voltages.)
With the same power in, and lower _mechanical_ power out, it should be obvious
that some power is going 'somewhere else'. Which it is. into heat.
In article <[email protected]>,
Bob Davis <[email protected]> wrote:
>I think you are over rating the heat effect.
If only you knew what you were talking about.
> If wiring overheats, the
>breaker was oversized. That is why we have breakers. Properly sized wire
>should have negligible resistive heating.
Depends on what you mean by 'negligible'. To coin a "Clinton". :)
To deliver the same amount of power to the load requires *twice* as much
current at 120V as is needed at 240V. Losses in the wiring, etc. are
proportional to the _square_ of the current. Thus the losses in the
wiring are *four*times* greater at 120V vs 240v, for the same power at
the load.
In a properly designed system, these losses are "relatively small" at
either voltage. But, regardless, the losses are only 1/4 as large when
you run things at 240V.
EVEN WITH 'properly sized' wiring, the allowable voltage drop _in_the_wiring_
between the panel and the device can be several volts. A 5V drop in the
wiring, with a 15A load, and the _wiring_ is giving off as much heat as a
75 watt light bulb. And that's "within specifications" for a properly
constructed circuit.
> Some people say a dual voltage
>motor will last longer when run at 220v. I think the biggest motor
>longevity factor is the quality of the motor itself.
You're free to think whatever you like. :)
Needless to say, the 'quality' of any given motor is *unchanged* by being
run at 240V instead of 120V. Regardless of whether it's a 'cheapie', or
a 'top of the line' unit.
Motors are, in general, more efficient when operated at higher voltages.
This means the internal "losses" are lower at higher voltages.
This means that there is, all else being equal, _less_ heat build-up in
the motor, when run at higher voltages.
Excess heat _is_ one of the biggest enemies of longevity.
>
>Bob
>
>"John McCoy" <[email protected]> wrote in message
>news:[email protected]...
>> Monty <[email protected]> wrote in
>> news:[email protected]:
>>
>> > Man, thanks for taking all the time to answer my question. That all
>> > makes sense. It seems to be more of an efficiency issue as opposed to
>> > power.
>>
>> Yes, but not quite in the sense you're thinking, I beleive. When
>> you run 110 you draw more current for a given amount of output
>> power, which causes "resistive" losses in the wires, etc (so you
>> have to draw even more current to make up for that). The problem
>> is in where those resistive losses go - which is into heating up
>> the wires, motors, and everything else in the circuit. Heat is
>> not a good thing; at best it shortens the life of the motor, and
>> at worst it sets the wiring on fire.
>>
>> John
>
>
Al Reid wrote:
> Are you sure? V=I x R. 2 x the current yields 2 x voltage drop.
Yes, but you are not putting twice the voltage on a single wire, you are
putting 110V on each of two wires but with half the current in each.
In other words, a 10A 220V cable will have two hot wires, each of 10A 110V.
The equivalent in 110V would be 110V @ 20A on a single hot wire.
--
gabriel
"Toller" <[email protected]> wrote in message
news:[email protected]...
>
> "Monty" <[email protected]> wrote in message
> news:[email protected]...
> > I'm about to start building my shop in the garage. I currently have an
> > old small subpanel in there with a bunch of 110 outlets scattered around
> > that the last owner installed. It's all pretty old stuff but still in
> > working order.
> >
> > Many of the new machines I'm going to purchase can handle 110 or 220.
> > My question is should I rewire the garage with a new subpanel and make
> > all those machines 220 and scatter some new 110 outlets around as well
> > or just make everything 110? What's the benefit of running a machine
> > like a saw or shaper at 220 vs 110? Does it have more power? Can someone
> > explain the tradeoff?
> >
> All those answers and so little information.
> 240v is always preferred because you get one quarter the voltage drop for
> the same wire size. That only makes a difference when running if you have
a
> very long cable, but is pretty dramatic when turning the machinery on.
Are you sure? V=I x R. 2 x the current yields 2 x voltage drop.
> Also, you get twice the power capacity for an almost identical
installation
> process.
> Supposedly motors last longer because they don't have to fight the voltage
> drop.
>
> The only downside to 240v is having to change stuff over, and that outlets
> can cost a bit more.
>
>
"Toller" <[email protected]> wrote in message
news:[email protected]...
>
> "Al Reid" <[email protected]> wrote in message
> news:[email protected]...
> > The thing I was taking issue with is the statement that "In other words,
a
> > 10A 220V cable will have
> > two hot wires, each of 10A 110V" Which is not really correct. If you
had
> a
> > neutral and were using a device that references the neutral, then your
> > statement is correct. However, in the context of a 220 v service, there
> is
> > a 220 v potential across the two hots, not 2 sources of 110V. I was
just
> > trying to be sure that anyone else looking at this thread does not get
the
> > wrong impression.
> >
> Okay, ya got two 120v/100w bulbs wired in series, with 240v running
through
> them. Everything works properly; eventhough it is a 240v circuit.
>
> Then you attach a neutral in between them. No current flows down the
> neutral since the circuit is balanced, the lights don't change brightness;
> everything is precisely the same as without the neutral. Everything
works
> properly; eventhough it is now a multiwire 120v circuit.
>
> So, what does the neutral do? Nothing at all. There is 1.2a running
> through each bulb with or without the neutral.
> So what is the wrong impression?!
>
>
You picked a balanced condition. Just one of many posibilities. Do the
same with a 100w and a 60 w. The neutral will cary the imbalance. In fact,
if you measured carefully, you would find that in your scenario, that there
was a small current in the neutral. In the case of a 220v motor, which was
being discussed, there is no center tap. The windings are wired in series
for 220 and in parallel for 110. So what. In the absence of a neutral, you
have a 220v single phase feed. Period. You can try to call it two 110v
feeds, but you would be wrong. Add a neutral and you would then be correct.
There are so many misleading answers to electrical questions that it is best
to be precise and correct when providing information. Just because "you
could say that" does not make it technically correct.
>
In article <[email protected]>,
LRod <[email protected]> wrote:
>On Fri, 06 Feb 2004 09:48:13 +0000, [email protected]
>(Robert Bonomi) wrote:
>
>>by the E=I/R rule,
>
>Which rule is that?
The 'one with the typo', isn't it obvious? <grin>
E=I*R
I=E/R
R=I/E
I was doing the math right, just got the wrong symbol in the formula.
thanks for the catch.
>>For complicated reasons, at the lower voltage you get somewhat _less_
>>'shaft horsepower' output than at the higher voltage, _given_the_same_power_
>>_input_. The difference in mechanical power output is typically a few
>>percentage points. (Although the motor on my delta contractor saw is rated
>>1.5HP @120V, and 2.0HP @ 240V. with a similar 'mis-match' in current draw
>>at the two voltages.)
>
>If the windings in a dual voltage motor are split and are wired in
>series at 240V and parallel at 120V, how is the motor to know to
>produce less shaft horsepower when the voltage (and current) in the
>individual winding is the same for either source?
I don't know all the theoretical underpinnings, I can state it is "observed
fact" from having motors on a test stand.
The electrical characteristics _are_ different, depending on whether the
windings are in series or parallel. If the windings are not _exactly_
identical, you get different voltage/current relationships depending on the
type of inter-connect. In series, the current through both windings is
identical, but the higher resistance winding will have a larger voltage drop
across it. OTOH, in parallel, the voltage across both windings is identical,
but the lower resistance winding has more current flowing through it.
>
>>With the same power in, and lower _mechanical_ power out, it should be obvious
>>that some power is going 'somewhere else'. Which it is. into heat.
>
>There shouldn't be a difference.
"In theory, there is no difference between theory and practice.
In practice, on the other hand ....."
If you want a _real_ mind-bender, try and figure out why motors run at
1725 RPM or 3450 RPM. The 'obvious' speeds are 3600 RPM, and even
sub-multiples thereof (1800, 1200, 900, 720, 600, etc.), depending on
The number of 'poles' in the motor design. Yet, 4+ percent 'slow' is
nearly universal -- pretty much independent of any combination of
manufacturer, HP, or operating voltage.
I think you are over rating the heat effect. If wiring overheats, the
breaker was oversized. That is why we have breakers. Properly sized wire
should have negligible resistive heating. Some people say a dual voltage
motor will last longer when run at 220v. I think the biggest motor
longevity factor is the quality of the motor itself.
Bob
"John McCoy" <[email protected]> wrote in message
news:[email protected]...
> Monty <[email protected]> wrote in
> news:[email protected]:
>
> > Man, thanks for taking all the time to answer my question. That all
> > makes sense. It seems to be more of an efficiency issue as opposed to
> > power.
>
> Yes, but not quite in the sense you're thinking, I beleive. When
> you run 110 you draw more current for a given amount of output
> power, which causes "resistive" losses in the wires, etc (so you
> have to draw even more current to make up for that). The problem
> is in where those resistive losses go - which is into heating up
> the wires, motors, and everything else in the circuit. Heat is
> not a good thing; at best it shortens the life of the motor, and
> at worst it sets the wiring on fire.
>
> John
Al Reid wrote:
> The current of 10A flows from one pole
> of the breaker, back to the other pole and vs versa. The total
> current in the conductor is 10A. The same motor on 110V would draw
> 20A from hot to neutral.
Which is _exactly_ what I said: "In other words, a 10A 220V cable will have
two hot wires, each of 10A 110V. The equivalent in 110V would be 110V @
20A on a single hot wire."
--
gabriel
That is where you are wrong. The current of 10A flows from one pole of the
breaker, back to the other pole and vs versa. The total current in the
conductor is 10A. The same motor on 110V would draw 20A from hot to
neutral. Therefore, for the same conductor size the voltage drop is
directly proportional to the current. Twice the current, twice the voltage
drop.
Assume that the resistance of the wire is .1 ohms. The voltage drop for the
220 v motor is 10 * .1= 1 volt. For the 110 v motor it is 20 * .1 = 2
volts.
The power supplied is the same in both cases. P=V x I, 220 x 10 = 110 x 20
On the other hand, the power dissipated (P=I^2 x R) is higher by a factor of
4 for twice the current thru the same conductor.
"gabriel" <[email protected]> wrote in message
news:[email protected]...
> Al Reid wrote:
>
> > Are you sure? V=I x R. 2 x the current yields 2 x voltage drop.
>
> Yes, but you are not putting twice the voltage on a single wire, you are
> putting 110V on each of two wires but with half the current in each.
you have 220 line to line, there is no neutral.
>
> In other words, a 10A 220V cable will have two hot wires, each of 10A
110V.
> The equivalent in 110V would be 110V @ 20A on a single hot wire.
>
> --
> gabriel
I always enjoy the creativity and imagination that these 110/220
threads produce.
--
Larry Wasserman Baltimore, Maryland
[email protected]
"GeeDubb" <[email protected]> wrote in message
news:[email protected]...
>
> >>
> >> Ok "William"...
> >> Admit to it ... you are the one we call Norm Abram. We have
> >> discovered his identity on the wreck!
> >>
> >> Frank
> >
> >
> > Dam, now I have been outed!! I feel neked where's my flannel
> > shirt:-)
> >
> > William......
> > AKA Norm.... :-)
>
> I'm wearing it!
>
> Wish i had 3-phase. :-(
>
> Gary
Well....
You can......:-) I have a real nice ( 7.5 hp hard start, 15 hp normal )
rotary phase convertor I'm going to be selling soon as I no longer need it.
Starts and runs on a 50 amp @ 240v
>
>
... and exactly what I said... the voltage drop is proportional to the
current flowing in the conductor.
The drop is twice for the same motor running at 110v/20A as for the
220V/10A. Again, the drop in the wire from the voltage source to the motor
is V=I * R. Twice the current, twice the voltage drop. It really is that
simple.
"gabriel" <[email protected]> wrote in message
news:[email protected]...
> Al Reid wrote:
>
> > The current of 10A flows from one pole
> > of the breaker, back to the other pole and vs versa. The total
> > current in the conductor is 10A. The same motor on 110V would draw
> > 20A from hot to neutral.
>
> Which is _exactly_ what I said: "In other words, a 10A 220V cable will
have
> two hot wires, each of 10A 110V. The equivalent in 110V would be 110V @
> 20A on a single hot wire."
>
> --
> gabriel
Man, thanks for taking all the time to answer my question. That all
makes sense. It seems to be more of an efficiency issue as opposed to
power. The motor for a saw is say 5HP and it'll always be 5HP if it's
running at 110 or 220. No more "power" with one or the other. It's just
more efficient to get the current to the motor via two poles (220)
instead of 1 (110). Maybe it'll be harder to bog down at 220 and maybe
the lights in the house won't dim as much if I'm running 220. I think my
question about rewiring the garage to 220 has been answered. It's better
to run them at 220. Thanks.
Mike in Idaho wrote:
>Consider the current being draw through the wires as the air you breathe.
>When you're working hard (running uphill or whatever) you need more air and
>the faster the better, right? The same is pretty much true for your
>equipment. Let's take your table saw. When it starts up it pulls a lot of
>current (I think it's like 40-80amps) right off the bat to get the motor
>spinning at full speed. That's one instance when a lot of current is needed
>right away, another is if you're putting some wood through the blade and it
>pinches a bit (hopefully you have a splitter -- but that's a whole 'nother
>discussion), anyway the motor is now suddenly under load and needs more
>juice to keep the blade spinning.
>
>Ok, now to understand how 220 vs 110 helps with this -- imagine you're
>breathing through a straw, a small one :) Now run up the stairs but only
>breathe through the straw. Don't try this by the way -- you'd probably pass
>out from a lack of oxygen, but that's the key -- you can't pull the air in
>fast enough for your heart/lungs/brain to handle the quick load. On the
>other hand if you were breathing through a large tube it would be pretty
>easy right, might not even notice a difference.
>
>Now the question is why this is a good/bad thing for the equipment. Here's
>where it becomes a bit fuzzy for me. I believe you get a benefit from
>spreading the voltage drop across 2 poles in your house (where most things
>are 1 pole or 110) so you don't have a large drop on a single pole you have
>1/2 the drop on both poles, kind of evens out the load on your house. That
>has various benefits for delicate equipment like stereos, tvs, computers
>etc. Also, I thought I read somewhere that it's better on your motor itself
>and thus it should last longer (don't know if it was heat related or what).
>
>Now, the real question is, is this fact or did I just pass along bad
>information I've gathered over the years? For that you'd probably need to
>ask an EE or electrician. If someone is one of those and has better info
>I'd be happy to have it :) (or even happier to know I've more or less got
>it right ;)
>
>Thanks,
>Mike
>
>"Monty" <[email protected]> wrote in message
>news:[email protected]...
>
>
>>I'm about to start building my shop in the garage. I currently have an
>>old small subpanel in there with a bunch of 110 outlets scattered around
>>that the last owner installed. It's all pretty old stuff but still in
>>working order.
>>
>>Many of the new machines I'm going to purchase can handle 110 or 220.
>>My question is should I rewire the garage with a new subpanel and make
>>all those machines 220 and scatter some new 110 outlets around as well
>>or just make everything 110? What's the benefit of running a machine
>>like a saw or shaper at 220 vs 110? Does it have more power? Can someone
>>explain the tradeoff?
>>
>>Monty
>>
>>
>>
>
>
>
>
"Al Reid" <[email protected]> wrote in message
news:[email protected]...
>
> Good, we agree on that. So the 20A 120v motor will need to be fed from a
30 A breaker using #10 wire while the 10A, 240V motor will
> need to be fed from a 15A breaker using #14 wire. Givint this
installation, there will be negligable difference in the performance
> of the motor when the system is examined in total.
>
I agree. I'm not one that thinks the losses from wiring is a big deal, I
was just sumarizing the other side of the argument. Truth be told, I like
240volt runs mainly because I can run smaller wire which is cheaper and
easier to use.
Frank
"Al Reid" <[email protected]> wrote in message
news:[email protected]...
> The thing I was taking issue with is the statement that "In other words, a
> 10A 220V cable will have
> two hot wires, each of 10A 110V" Which is not really correct. If you had
a
> neutral and were using a device that references the neutral, then your
> statement is correct. However, in the context of a 220 v service, there
is
> a 220 v potential across the two hots, not 2 sources of 110V. I was just
> trying to be sure that anyone else looking at this thread does not get the
> wrong impression.
>
Okay, ya got two 120v/100w bulbs wired in series, with 240v running through
them. Everything works properly; eventhough it is a 240v circuit.
Then you attach a neutral in between them. No current flows down the
neutral since the circuit is balanced, the lights don't change brightness;
everything is precisely the same as without the neutral. Everything works
properly; eventhough it is now a multiwire 120v circuit.
So, what does the neutral do? Nothing at all. There is 1.2a running
through each bulb with or without the neutral.
So what is the wrong impression?!
"CW" <[email protected]> wrote in message
news:[email protected]...
> Unless you are going to cruise auctions for used industrial machinery, I
> don't think 3 phase is anything to gloat about. I would much rather have
> something I could use.
Like money $$$ ???
Well I guess if you don't run any motors larger then about 1 hp, you really
have no need for 3 phase power. On 2-3 hp motors it's debatable on the
savings, but they start better, and cost a lot less to run and purchase even
it that range. At 5 hp and over there is no contest. And YES the
industrial tools are the way to go, in another thread there was some one
complaining about the PATHETIC performance of a sander and its cheep import
motor popping off the overload, you will not hear me complaining about not
enough power running my 20hp industrial sander :-) That size motor can be
wired @ 480v using ONLY 10ga wire in 3/4" conduit, run a smaller breaker,
smaller starter etc.. saving even more $$$$
William....
> "William" <wac@_nospam_gene-o-tech.com> wrote in message
> news:mroUb.226882$xy6.1158679@attbi_s02...
> >
> > "Don Mackie" <[email protected]> wrote in message
> > news:[email protected]...
> > > Pardon me for interrupting - but I have to gloat about the 3-phase 240
> > > volt supply at my house.
> > >
> >
> >
> > Well then do it right! 600 amp @ 480 volt in my house/shop
> >
> > William....
> >
> > http://wacworkshop.com/html/shop_services_gallery_0.html
> >
> >
>
>
"Frank Ketchum" <[email protected]> wrote in message
news:[email protected]...
>
> "William" <wac@_nospam_gene-o-tech.com> wrote in message
> news:HTxUb.232846$na.370476@attbi_s04...
> >
> > you will not hear me complaining about not
> > enough power running my 20hp industrial sander :-) That size motor can
be
> > wired @ 480v using ONLY 10ga wire in 3/4" conduit, run a smaller
breaker,
> > smaller starter etc.. saving even more $$$$
> >
> > William....
> >
>
> Ok "William"...
> Admit to it ... you are the one we call Norm Abram. We have discovered
his
> identity on the wreck!
>
> Frank
Dam, now I have been outed!! I feel neked where's my flannel shirt:-)
William......
AKA Norm.... :-)
>
>
"Al Reid" <[email protected]> wrote in message
news:[email protected]...
>
> In the interest of further belaboring the point and to do a sanity check
on myself consider the following:
>
> Given a dual voltage 120/240v motor where the FLA is 20/10.
> When operated at 120 vac the windings are wired in parallel and at 240
they are wired in series.
>
> Ok so far? Lets consider that the winding resistance of .5 ohms per
winding and that the heating is a result of I^2 * R.
>
> For the 120v case, the effective resistance of the parallel windings is
0.25 ohms ( [R1 * R2] / [R1 + R2].
> The heating loss would therefore be 20^2 * 0.25 = 100Awtts
>
> For the 240v case the effective resistance of the windings in series is 1
ohm ( R1 + R2 )
> The heating loss would be 10^2 * 1 = 100 Watts.
>
> Then why are the losses considered to be more when running at 120v rather
than 240v?
> Looks to me like the same amount of power is lost due to heating.
>
There isn't any difference noticed in the motor itself. As you note, the
motor itself sees the same voltage and current on it's windings. The losses
are generated from the wiring which supplies the motor. All the way from
the main electrical panel, through any sub panels, to the outlet and though
any extension cords.
Frank
,,and misinformation. your voltage drop calcs are wrong.
"Toller" <[email protected]> wrote in message
news:[email protected]...
> All those answers and so little information.
> 240v is always preferred because you get one quarter the voltage drop for
> the same wire size.
Al Reid wrote:
> "Toller" <[email protected]> wrote in message
> news:[email protected]...
>>
>> "Al Reid" <[email protected]> wrote in message
>> news:[email protected]...
>>> The thing I was taking issue with is the statement that "In other
>>> words, a 10A 220V cable will have
>>> two hot wires, each of 10A 110V" Which is not really correct. If
>>> you
> had
>> a
>>> neutral and were using a device that references the neutral, then
>>> your statement is correct. However, in the context of a 220 v
>>> service, there is a 220 v potential across the two hots, not 2
>>> sources of 110V. I was just trying to be sure that anyone else
>>> looking at this thread does not get the wrong impression.
>>>
>> Okay, ya got two 120v/100w bulbs wired in series, with 240v running
>> through them. Everything works properly; eventhough it is a 240v
>> circuit.
>>
>> Then you attach a neutral in between them. No current flows down the
>> neutral since the circuit is balanced, the lights don't change
>> brightness; everything is precisely the same as without the neutral.
>> Everything works properly; eventhough it is now a multiwire 120v
>> circuit.
>>
>> So, what does the neutral do? Nothing at all. There is 1.2a running
>> through each bulb with or without the neutral.
>> So what is the wrong impression?!
>>
>>
>
> You picked a balanced condition. Just one of many posibilities. Do
> the same with a 100w and a 60 w. The neutral will cary the
> imbalance. In fact, if you measured carefully, you would find that
> in your scenario, that there was a small current in the neutral. In
> the case of a 220v motor, which was being discussed, there is no
> center tap. The windings are wired in series for 220 and in parallel
> for 110. So what. In the absence of a neutral, you have a 220v
> single phase feed. Period. You can try to call it two 110v feeds,
> but you would be wrong. Add a neutral and you would then be correct.
>
> There are so many misleading answers to electrical questions that it
> is best to be precise and correct when providing information. Just
> because "you could say that" does not make it technically correct.
As you stated. Two 110/120 legs is a common misconception, as is the
misconception that everything always has to be referenced to a grounded
conductor, or that there is something sacred about center-tapped transformer
configurations.
Monty <[email protected]> wrote in
news:[email protected]:
> Man, thanks for taking all the time to answer my question. That all
> makes sense. It seems to be more of an efficiency issue as opposed to
> power.
Yes, but not quite in the sense you're thinking, I beleive. When
you run 110 you draw more current for a given amount of output
power, which causes "resistive" losses in the wires, etc (so you
have to draw even more current to make up for that). The problem
is in where those resistive losses go - which is into heating up
the wires, motors, and everything else in the circuit. Heat is
not a good thing; at best it shortens the life of the motor, and
at worst it sets the wiring on fire.
John
"Al Reid" <[email protected]> wrote in
news:[email protected]:
> Given a dual voltage 120/240v motor where the FLA is 20/10.
> When operated at 120 vac the windings are wired in parallel and at 240
> they are wired in series.
>
> Ok so far? Lets consider that the winding resistance of .5 ohms per
> winding and that the heating is a result of I^2 * R.
>
> For the 120v case, the effective resistance of the parallel windings
> is 0.25 ohms ( [R1 * R2] / [R1 + R2]. The heating loss would therefore
> be 20^2 * 0.25 = 100Awtts
>
> For the 240v case the effective resistance of the windings in series
> is 1 ohm ( R1 + R2 ) The heating loss would be 10^2 * 1 = 100 Watts.
>
> Then why are the losses considered to be more when running at 120v
> rather than 240v? Looks to me like the same amount of power is lost
> due to heating.
Two things - one is that these are AC motors, and so there's
inductive effects (so I^2 * R isn't accurate, you need to consider
the impedance and the phase angle); and secondly because you're
drawing more current at 110, the drop in the circuit to the motor
is greater, in order to produce the same output power you need more
than twice the current than the 220 motor draws.
John
"Bob Davis" <[email protected]> wrote in news:6dcUb.11892
[email protected]:
> I think you are over rating the heat effect.
Buildings catch fire due to electrical problems fairly often (I wouldn't
be surprised if it wasn't the most common cause of fires now-a-days).
Sometimes it's due to improper wiring ("oversized" breakers, etc),
sometimes it's due to degradation of the wiring over time (the old
frayed extension cord phemonemon).
Which isn't to say the OP might be at risk of fire - but in looking
at the worst case problem he could see, certainly fire would be
that, particularly if his shop is in an elderly building.
John
Unless you are going to cruise auctions for used industrial machinery, I
don't think 3 phase is anything to gloat about. I would much rather have
something I could use.
"William" <wac@_nospam_gene-o-tech.com> wrote in message
news:mroUb.226882$xy6.1158679@attbi_s02...
>
> "Don Mackie" <[email protected]> wrote in message
> news:[email protected]...
> > Pardon me for interrupting - but I have to gloat about the 3-phase 240
> > volt supply at my house.
> >
>
>
> Well then do it right! 600 amp @ 480 volt in my house/shop
>
> William....
>
> http://wacworkshop.com/html/shop_services_gallery_0.html
>
>
Consider the current being draw through the wires as the air you breathe.
When you're working hard (running uphill or whatever) you need more air and
the faster the better, right? The same is pretty much true for your
equipment. Let's take your table saw. When it starts up it pulls a lot of
current (I think it's like 40-80amps) right off the bat to get the motor
spinning at full speed. That's one instance when a lot of current is needed
right away, another is if you're putting some wood through the blade and it
pinches a bit (hopefully you have a splitter -- but that's a whole 'nother
discussion), anyway the motor is now suddenly under load and needs more
juice to keep the blade spinning.
Ok, now to understand how 220 vs 110 helps with this -- imagine you're
breathing through a straw, a small one :) Now run up the stairs but only
breathe through the straw. Don't try this by the way -- you'd probably pass
out from a lack of oxygen, but that's the key -- you can't pull the air in
fast enough for your heart/lungs/brain to handle the quick load. On the
other hand if you were breathing through a large tube it would be pretty
easy right, might not even notice a difference.
Now the question is why this is a good/bad thing for the equipment. Here's
where it becomes a bit fuzzy for me. I believe you get a benefit from
spreading the voltage drop across 2 poles in your house (where most things
are 1 pole or 110) so you don't have a large drop on a single pole you have
1/2 the drop on both poles, kind of evens out the load on your house. That
has various benefits for delicate equipment like stereos, tvs, computers
etc. Also, I thought I read somewhere that it's better on your motor itself
and thus it should last longer (don't know if it was heat related or what).
Now, the real question is, is this fact or did I just pass along bad
information I've gathered over the years? For that you'd probably need to
ask an EE or electrician. If someone is one of those and has better info
I'd be happy to have it :) (or even happier to know I've more or less got
it right ;)
Thanks,
Mike
"Monty" <[email protected]> wrote in message
news:[email protected]...
> I'm about to start building my shop in the garage. I currently have an
> old small subpanel in there with a bunch of 110 outlets scattered around
> that the last owner installed. It's all pretty old stuff but still in
> working order.
>
> Many of the new machines I'm going to purchase can handle 110 or 220.
> My question is should I rewire the garage with a new subpanel and make
> all those machines 220 and scatter some new 110 outlets around as well
> or just make everything 110? What's the benefit of running a machine
> like a saw or shaper at 220 vs 110? Does it have more power? Can someone
> explain the tradeoff?
>
> Monty
>
You are correct, as stated in % voltage drop.
"Toller" <[email protected]> wrote in message
news:[email protected]...
>
> >
> > Are you sure? V=I x R. 2 x the current yields 2 x voltage drop.
> >
> I guess I should have said, "the % voltage drop is one quarter."
> The voltage drop is one half, but it is figured into twice the voltage; so
> the % drop is one quarter.
>
> Since the actual voltage drop is irrelevant I was a tad sloppy; sorry.
>
>
Go with 220 when you can. Machines will run cooler and more
efficiently
John
On Wed, 04 Feb 2004 18:29:27 GMT, Monty <[email protected]> wrote:
>I'm about to start building my shop in the garage. I currently have an
>old small subpanel in there with a bunch of 110 outlets scattered around
>that the last owner installed. It's all pretty old stuff but still in
>working order.
>
>Many of the new machines I'm going to purchase can handle 110 or 220.
>My question is should I rewire the garage with a new subpanel and make
>all those machines 220 and scatter some new 110 outlets around as well
>or just make everything 110? What's the benefit of running a machine
>like a saw or shaper at 220 vs 110? Does it have more power? Can someone
>explain the tradeoff?
>
>Monty
"Toller" <[email protected]> wrote in message
news:[email protected]...
>
> All those answers and so little information.
> 240v is always preferred because you get one quarter the voltage drop for
> the same wire size. That only makes a difference when running if you have
a
> very long cable, but is pretty dramatic when turning the machinery on.
> Also, you get twice the power capacity for an almost identical
installation
I find it funny that you would criticize people for lack of information and
immediately follow it with wrong information!
What I think you are referring to is that there will be one quarter less
power wasted due to wiring resistances.
P = VI
I = V/R, V = IR
therefore, the power lost in wiring due to resistance in the wire is
P=I^2R.
When the current is cut by a factor of 2, the power lost is cut by a factor
of 2 squared, or 4.
Frank
In article <[email protected]>, "CW"
<[email protected]> wrote:
> Unless you are going to cruise auctions for used industrial machinery, I
> don't think 3 phase is anything to gloat about. I would much rather have
> something I could use.
It's there to power a kiln. I do have a couple of big motors I picked up
as scrap for entertainment and, since I have it, am building a linear
motor which should be fun...
--
"Any PC built after 1985 has the storage capacity to house an evil spirit,"
Reverend Jim Peasboro
On Fri, 06 Feb 2004 09:48:13 +0000, [email protected]
(Robert Bonomi) wrote:
>by the E=I/R rule,
Which rule is that?
>For complicated reasons, at the lower voltage you get somewhat _less_
>'shaft horsepower' output than at the higher voltage, _given_the_same_power_
>_input_. The difference in mechanical power output is typically a few
>percentage points. (Although the motor on my delta contractor saw is rated
>1.5HP @120V, and 2.0HP @ 240V. with a similar 'mis-match' in current draw
>at the two voltages.)
If the windings in a dual voltage motor are split and are wired in
series at 240V and parallel at 120V, how is the motor to know to
produce less shaft horsepower when the voltage (and current) in the
individual winding is the same for either source?
>With the same power in, and lower _mechanical_ power out, it should be obvious
>that some power is going 'somewhere else'. Which it is. into heat.
There shouldn't be a difference.
LRod
Master Woodbutcher and seasoned termite
Shamelessly whoring my website since 1999
http://www.woodbutcher.net
>
> Are you sure? V=I x R. 2 x the current yields 2 x voltage drop.
>
I guess I should have said, "the % voltage drop is one quarter."
The voltage drop is one half, but it is figured into twice the voltage; so
the % drop is one quarter.
Since the actual voltage drop is irrelevant I was a tad sloppy; sorry.
On Wed, 04 Feb 2004 18:58:43 GMT, Monty <[email protected]> wrote:
>Man, thanks for taking all the time to answer my question. That all
>makes sense. It seems to be more of an efficiency issue as opposed to
>power. The motor for a saw is say 5HP and it'll always be 5HP if it's
>running at 110 or 220. No more "power" with one or the other. It's just
>more efficient to get the current to the motor via two poles (220)
>instead of 1 (110). Maybe it'll be harder to bog down at 220 and maybe
>the lights in the house won't dim as much if I'm running 220. I think my
>question about rewiring the garage to 220 has been answered. It's better
>to run them at 220. Thanks.
There isn't any decision to make if you have a 5HP motor. That
probably draws something on the order of 18 amps on 220V. In order to
run it on 110V (even if the motor is convertible) you will need to run
it on a 40 amp circut breaker and #8 wire. Hardly a fun wiring job. On
220V, all you need is a 20 amp breaker and #12 wire.
By the way, it's neither efficiency or power as far as 110V vs 220V is
concerned. The only difference to the motor is if the feed is a long
distance. The voltage drop will be less at 220V by a factor of four.
Otherwise, the watts is the same for either voltage.
LRod
Master Woodbutcher and seasoned termite
Shamelessly whoring my website since 1999
http://www.woodbutcher.net
"Don Mackie" <[email protected]> wrote in message
news:[email protected]...
> Pardon me for interrupting - but I have to gloat about the 3-phase 240
> volt supply at my house.
>
Well then do it right! 600 amp @ 480 volt in my house/shop
William....
http://wacworkshop.com/html/shop_services_gallery_0.html
The thing I was taking issue with is the statement that "In other words, a
10A 220V cable will have
two hot wires, each of 10A 110V" Which is not really correct. If you had a
neutral and were using a device that references the neutral, then your
statement is correct. However, in the context of a 220 v service, there is
a 220 v potential across the two hots, not 2 sources of 110V. I was just
trying to be sure that anyone else looking at this thread does not get the
wrong impression.
Ok. Truce. ;^}
"gabriel" <[email protected]> wrote in message
news:[email protected]...
> Al Reid wrote:
>
> > ... and exactly what I said... the voltage drop is proportional to the
> > current flowing in the conductor.
>
> Ok, then maybe i'm missing smoething or you were disagreeing with the
wrong
> person because I don't disagree with you...
>
> --
> gabriel
Thanks John,
I think this is what I had read about heat and motor wear. That makes
sense.
Thanks,
Mike
"John McCoy" <[email protected]> wrote in message
news:[email protected]...
> Monty <[email protected]> wrote in
> news:[email protected]:
>
> > Man, thanks for taking all the time to answer my question. That all
> > makes sense. It seems to be more of an efficiency issue as opposed to
> > power.
>
> Yes, but not quite in the sense you're thinking, I beleive. When
> you run 110 you draw more current for a given amount of output
> power, which causes "resistive" losses in the wires, etc (so you
> have to draw even more current to make up for that). The problem
> is in where those resistive losses go - which is into heating up
> the wires, motors, and everything else in the circuit. Heat is
> not a good thing; at best it shortens the life of the motor, and
> at worst it sets the wiring on fire.
>
> John
"Robert Bonomi" <[email protected]> wrote in message
news:[email protected]...
> If you want a _real_ mind-bender, try and figure out why motors run at
> 1725 RPM or 3450 RPM. The 'obvious' speeds are 3600 RPM, and even
> sub-multiples thereof (1800, 1200, 900, 720, 600, etc.), depending on
> The number of 'poles' in the motor design.>
>
In the real world, there are inefficiencies which contribute to actual
performances being different than calculated performances.
Frank
[email protected] (Robert Bonomi) wrote:
> If you want a _real_ mind-bender, try and figure out why motors run at
> 1725 RPM or 3450 RPM. The 'obvious' speeds are 3600 RPM, and even
> sub-multiples thereof (1800, 1200, 900, 720, 600, etc.), depending on
> The number of 'poles' in the motor design. Yet, 4+ percent 'slow' is
> nearly universal -- pretty much independent of any combination of
> manufacturer, HP, or operating voltage.
It's only a mind-bender if you've never studied how an induction motor
works. There are many different ways to build a motor. The most common
design that you find in shop machinery is what's called an induction
motor.
The electric field created by the stator windings rotates at 3600 RPM
(for a 2-pole motor). The rotor rotates a little slower than that (say,
3450 RPM). The difference, 150 RPM or 2.5 Hz, is what induces current
to flow in the rotor windings (hence the name). There are no brushes.
As the load increases, the rotor slows down and the slip frequency
increases, causing the rotor current to increase. It's a very clever
design.
One of the drawbacks of induction motors is that the rotational speed is
not constant. As load increases, the rotor speed drops. For many
applications, this is not a problem.
On Thu, 5 Feb 2004 13:45:27 -0500, "Al Reid"
<[email protected]> wrote:
>
>Good, we agree on that. So the 20A 120v motor will need to be fed from a 30 A breaker using #10 wire while the 10A, 240V motor will
>need to be fed from a 15A breaker using #14 wire. Givint this installation, there will be negligable difference in the performance
>of the motor when the system is examined in total.
Nobody who cares about I^2 * R losses and voltage drop is going to
take the trouble to run a motor on 240V and then turn around and cheap
out by using #14 wire just because it's legal to do so. Most people
would use #12 wire or better (I personally would never use #14 for
anything, given a choice; the stuff is a gift to the power companies.
Feel a piece of #14 romex when it's carrying 10A or so sometime - it
is noticeably warm).
And if you really want to go overboard, you could even use #10 for
your 10A, 240V motor, in which case your I^2R losses would be one
fourth of what they would be in your example for the same #10 wire
at 120V, 20A. Bottom line is, if you've got room for the double pole
breaker, there is no good reason not to use 240V for your motors, it
can't hurt and will always same some amount of energy over time, even
if it isn't huge.
>> Frank
>>
>>
>
Tim Carver
[email protected]
"William" <wac@_nospam_gene-o-tech.com> wrote in message
news:HTxUb.232846$na.370476@attbi_s04...
>
> you will not hear me complaining about not
> enough power running my 20hp industrial sander :-) That size motor can be
> wired @ 480v using ONLY 10ga wire in 3/4" conduit, run a smaller breaker,
> smaller starter etc.. saving even more $$$$
>
> William....
>
Ok "William"...
Admit to it ... you are the one we call Norm Abram. We have discovered his
identity on the wreck!
Frank
"Monty" <[email protected]> wrote in message
news:[email protected]...
> I'm about to start building my shop in the garage. I currently have an
> old small subpanel in there with a bunch of 110 outlets scattered around
> that the last owner installed. It's all pretty old stuff but still in
> working order.
>
> Many of the new machines I'm going to purchase can handle 110 or 220.
> My question is should I rewire the garage with a new subpanel and make
> all those machines 220 and scatter some new 110 outlets around as well
> or just make everything 110? What's the benefit of running a machine
> like a saw or shaper at 220 vs 110? Does it have more power? Can someone
> explain the tradeoff?
>
All those answers and so little information.
240v is always preferred because you get one quarter the voltage drop for
the same wire size. That only makes a difference when running if you have a
very long cable, but is pretty dramatic when turning the machinery on.
Also, you get twice the power capacity for an almost identical installation
process.
Supposedly motors last longer because they don't have to fight the voltage
drop.
The only downside to 240v is having to change stuff over, and that outlets
can cost a bit more.
The analogy about efficient breathing is really not valid for electric power
usage. In fact trying to explain electric power in terms of any fluid is not
really a valid analogy.
The two biggest practical advantages of 220v are:
1. you can run larger motors (already mentioned) over typical sized wiring.
2. You can carry more load for a given size wire. I had a 1.75 HP tablesaw
on a #12 circuit. By converting to 220v, I could add a 2 HP dust collector
on the same circuit.
Bob
"Monty" <[email protected]> wrote in message
news:[email protected]...
> I'm about to start building my shop in the garage. I currently have an
> old small subpanel in there with a bunch of 110 outlets scattered around
> that the last owner installed. It's all pretty old stuff but still in
> working order.
>
> Many of the new machines I'm going to purchase can handle 110 or 220.
> My question is should I rewire the garage with a new subpanel and make
> all those machines 220 and scatter some new 110 outlets around as well
> or just make everything 110? What's the benefit of running a machine
> like a saw or shaper at 220 vs 110? Does it have more power? Can someone
> explain the tradeoff?
>
> Monty
>
"Monty" <[email protected]> wrote in message
news:[email protected]...
> What's the benefit of running a machine
> like a saw or shaper at 220 vs 110? Does it have more power? Can someone
> explain the tradeoff?
>
As an example, a 20 amp circuit at 220 will have twice as much power as a 20
amp circuit at 110. Power is current x voltage.
For motors around 2 hp or larger, you most likely will not have a choice.
You will have to run them at 220. If I were wiring from scratch, I would
put everything at 220, but since you would have to rewire, probably just put
the larger motors on 220. It's up to you
Sometimes, I think the efficiency issue is exaggerated.
Frank - EE