After many years of use the cord on my Sears table saw is running out of
space to wrap electrical tape around it. This is the cord from the
switch not the cord from the motor to the switch. The motor is a 1 hp,
120 volt. The instruction that came with the motor says that a 20 amp
fuse should be used in the circuit to which the motor is connected. (Yes
I am a pack rat)
Would a cord with 12 gauge wire be sufficient for the 6 foot replacement
cord, or would I use a smaller gauge wire.
I can find 14 and 16 gauge readily but 12 gauge is harder to find.
"Keith Nuttle" wrote:
> After many years of use the cord on my Sears table saw is running
> out of space to wrap electrical tape around it. This is the cord
> from the switch not the cord from the motor to the switch. The
> motor is a 1 hp, 120 volt. The instruction that came with the motor
> says that a 20 amp fuse should be used in the circuit to which the
> motor is connected. (Yes I am a pack rat)
>
> Would a cord with 12 gauge wire be sufficient for the 6 foot
> replacement cord, or would I use a smaller gauge wire.
>
> I can find 14 and 16 gauge readily but 12 gauge is harder to find.
-------------------------------------
Go to the electrical section of your favorite DIY and look for molded
cord sets
Buy a 6'-10', 10-2 with ground (black, white, green) extension cord.
Chop off the female end and wire into saw.
Time for a beer.
Enjoy.
Lew
"Chris Friesen" wrote:
> 1 HP at 120 typically draws about 10A. Startup surge isn't an
> issue since the smaller wire can easily handle it briefly.
-----------------------------------
Think you'll find a 1 HP, 120VAC draws closer to 15A, but NBD.
Not concerned about start up inrush but rather the inrush required to
handle a rapid change in power demand with a sudden change in cutting
load.
(Don't try "horsing" a piece of 8/4 hard maple for instance) with a 1
HP motor.
It's a lot easier to push those electrons thru a bigger pipe.
-----------------------------------
> I'm in the Canadian prairies, but that shouldn't matter since Home
> Depot
> is pretty much the same all over. I can get a 100ft #10 cord no
> problem, but certainly not a 6 or 10ft #10 molded cord set.
-------------------------------------------
I can't keep up with H/D.
Last time I looked a 50 ft, 10-3, molded cord set was about $55.
Also had a 10 ft, but don't remember price.
Today I look and can't find either.
Today all I find is a 100 ft 10-3.
Go figure.
Lew
On May 4, 7:59=A0pm, "Lew Hodgett" <[email protected]> wrote:
> =A0"Chris Friesen" wrote:
> > 1 HP at 120 typically draws about 10A. =A0Startup surge isn't an
> > issue since the smaller wire can easily handle it briefly.
>
> -----------------------------------
>
> Think you'll find a 1 HP, 120VAC draws closer to 15A, but NBD.
>
> Not concerned about start up inrush but rather the inrush required to
> handle a rapid change in power demand with a sudden change in cutting
> load.
>
> (Don't try "horsing" a piece of 8/4 hard maple for instance) with a 1
> HP motor.
>
> It's a lot easier to push those electrons thru a bigger pipe.
>
> -----------------------------------> I'm in the Canadian prairies, but th=
at shouldn't matter since Home
> > Depot
> > is pretty much the same all over. =A0I can get a 100ft #10 cord no
> > problem, but certainly not a 6 or 10ft #10 molded cord set.
>
> -------------------------------------------
>
> I can't keep up with H/D.
>
> Last time I looked a 50 ft, 10-3, molded cord set was about $55.
>
> Also had a 10 ft, but don't remember price.
>
> Today I look and can't find either.
>
> Today all I find is a 100 ft 10-3.
>
> Go figure.
>
> Lew
Appropos of not much, i was in lowes over the weekend. 100ft, 12-2
romex, 63$ 250 ft romex, 12-2, 74$
clueless!
shelly
On May 4, 5:52=A0pm, Keith Nuttle <[email protected]> wrote:
> After many years of use the cord on my Sears table saw is running out of
> space to wrap electrical tape around it. =A0This is the cord from the
> switch not the cord from the motor to the switch. =A0The motor is a 1 hp,
> 120 volt. =A0The instruction that came with the motor says that a 20 amp
> fuse should be used in the circuit to which the motor is connected. (Yes
> I am a pack rat)
>
> Would a cord with 12 gauge wire be sufficient for the 6 foot replacement
> cord, or would I use a smaller gauge wire.
>
> I can find 14 and 16 gauge readily but 12 gauge is harder to find.
Rule of thumb is:
14 ga.=3D15 amps
12 ga.=3D20 amps
10 ga.=3D30 amps
8 or 6 ga.=3D50 amps. 6 ga. for long runs (stove w/baking)
RP
"Chris Friesen" wrote:
> I agree with the concept, but I'd go with #12 instead of #10.
---------------------------------------
A 1HP motor @ 120VAC?
Anything less than 10 AWG and you are kidding yourself.
-----------------------------------
> #10 is much harder to find in reasonable lengths around here, and is
> significantly more expensive than #12.
-----------------------------------------
A 6 ft to a 10 ft extension cord isn't readily available from your
local big box store?
What part of Bum Fuck are you living in?
Lew
Keith Nuttle wrote:
> After many years of use the cord on my Sears table saw is running out of
> space to wrap electrical tape around it. This is the cord from the
> switch not the cord from the motor to the switch. The motor is a 1 hp,
> 120 volt. The instruction that came with the motor says that a 20 amp
> fuse should be used in the circuit to which the motor is connected. (Yes
> I am a pack rat)
>
> Would a cord with 12 gauge wire be sufficient for the 6 foot replacement
> cord, or would I use a smaller gauge wire.
>
> I can find 14 and 16 gauge readily but 12 gauge is harder to find.
>
Wire of the same gauge as that you are replacing should be sufficient.
--
Jack Novak
Buffalo, NY - USA
[email protected]
Chris Friesen wrote:
> I was curious, so I went and checked on Baldor's site.
>
> I checked a few 3450rpm 1HP "general purpose" induction motors and
> the
> FLA at 120V ranged from 11.8 to 15A. Worse than I thought. :)
------------------------------------------
Which is why you don't time trying to use "zip cord" for motor loads.
10 AWG solves a lot of problems.
Lew
On May 5, 3:13=A0pm, [email protected] (Doug Miller) wrote:
> In article <[email protected]=
.com>, "[email protected]" <[email protected]> wrote:
>
> >On May 5, 12:30=3DA0pm, Chris Friesen <[email protected]> wrote:
> >> On 05/05/2010 10:59 AM, [email protected] wrote:
>
> >> > On May 5, 11:48 am, Chris Friesen <[email protected]> wrote:
> >> >> A good rule of thumb for most "normal" induction motors is 10A per =
HP =3D
> >at
> >> >> 120V.
>
> >> >> Higher quality motors can do better, of course, but a "premium
> >> >> efficiency" 1HP Baldor motor that costs $500 is still rated at 8.6A=
.
>
> >> > My bet is that a "normal" motor isn't much less. =3DA0There is more =
in
> >> > that motor than a few (more) pounds of copper (like a name plate).
>
> >> I was curious, so I went and checked on Baldor's site.
>
> >> I checked a few 3450rpm 1HP "general purpose" induction motors and the
> >> FLA at 120V ranged from 11.8 to 15A. =3DA0Worse than I thought. =3DA0:=
)
>
> >Gack! =A0You're right. =A0I looked up a few sites and found 12-15A for a
> >general purpose 1-HP 120V motor (I thought motors were far better than
> >50% efficient). =A0Nothing less than 12AWG!
>
> Why? 14AWG wire will safely carry 20A. The NEC limits the *overcurrent
> protection* on a 14AWG circuit to 15A, but also specifically lists the
> ampacity of 14AWG copper as 20A with 60degC and 75degC insulation, and 25=
A
> with 90degC insulation. [2008 NEC, Table 310.16]
At 15A it's getting too close to the limits. Add in the starting
current and 12AWG is clearly better. The cost difference is
insignificant, so no, I'd not use 14GA (and don't).
On May 5, 11:48=A0am, Chris Friesen <[email protected]> wrote:
> On 05/05/2010 09:29 AM, [email protected] wrote:
>
> > On May 5, 9:26 am, "Mike Marlow" <[email protected]> wrote:
> >> Keith Nuttle wrote:
>
> >>> Original Poster: =A0 The motor is a Sears 1 hp motor that came with t=
he
> >>> 10" table saw when it was purchased in 1969. It is a capacitor start
> >>> motor which for the first couple of microseconds draws a quite high
> >>> current.
>
> >> Ok... and this means what? =A0At least, to the discussion as it has pr=
ogressed
> >> at this point?
>
> > It means that the saw, when bogged down, may (or not) draw 6A. =A014GA
> > is fine. =A0Though I'd still go 12GA. =A0;-)
>
> You forgot about power factor and efficiency.
The power factor of an induction motor is pretty close to unity at
full load.
> A good rule of thumb for most "normal" induction motors is 10A per HP at
> 120V.
>
> Higher quality motors can do better, of course, but a "premium
> efficiency" 1HP Baldor motor that costs $500 is still rated at 8.6A.
My bet is that a "normal" motor isn't much less. There is more in
that motor than a few (more) pounds of copper (like a name plate).
Even at 10A, there is still a 60% safety factor with 14AWG and 100%
with 12AWG. Good 'nuff.
On Tue, 01 Jun 2010 22:06:49 -0500, "[email protected]"
<[email protected]> wrote:
>On Tue, 01 Jun 2010 22:11:40 -0400, [email protected] wrote:
>
>>On Tue, 01 Jun 2010 20:36:38 -0500, "[email protected]"
>><[email protected]> wrote:
>>
>>>On Tue, 1 Jun 2010 14:25:33 -0400, "Josepi" <[email protected]> wrote:
>>>
>>>>Quite a few technical electrical errors there but you concept is almost
>>>>correct.
>>>>A one HP motor make use of 748 Watts, not consumes.
>>>
>>>Nope. A 1-HP motor *delivers* one horsepower of mechanical power
>>>(550ft lbs/second). Only a 100% efficient motor would require only 748W (BTW,
>>>"watts" is not capitalized).
>>>
>>>>120v X 10A = 1200va not watts
>>>>Many 1/4HP furnace motors take about 10A at 120volts. How do you figure that
>>>>one?
>>>
>>>I don't believe you. A 1HP motor may require 1200W at full load, but not a
>>>1/4HP motor.
>>
>>It can draw 1200 watts at startup. Not terribly uncommon. When
>>rotating, a whole lot less.
>
>Agreed.
>
>>>>The new 5HP motors are including the inertia of the rotor and do not specify
>>>>"how long" they can deliver that HP.
>>>
>>>Nope. Well, maybe Crapsman's HP rating. ;-)
>>
>>Foot lbs torque @ rpm- a heavy rotor or flywheel CAN deliver
>>significant horsepower for a matter of seconds - after it has been
>>brought up to speed. In SOME applications, a heavy flywheel will alow
>>a much smaller than normal motor to do the job.
>
>Ok, but that's not the way motors are rated or HP is calculated.
>
><...>
which are you dissagreeing with?
Horsepower is measured as foot/lbs per second - RPM X Ft Lbs
Torque/5252 is horsepower. Period.
And a heavy flywheel will allow a small motor to provide significantly
inproved torque for cyclic loads - making, is some cases, a 1/4 horse
motor do the job a 3 horse motor could not do without a flywheel.
Scaled up that's how punch presses work.
One electric HP is 745 watts, more or less - but to produce that 1 HP
with a motor of 80% efficiency requires 931 watts. And 80% isn't bad
for a "consumer equipment" motor.
And a series wound motor rated at, say 1 HP constant, may be able to
produce upwards of 4HP or more for periods of up to several minutes,
depending on it's thermal mass, and for duty cycles of up to say 15
or 20%. So that motor, rated at continuous service, is a 1HP motor,
and at cyclic service, perhaps legitimately 4 HP.
That said - if it is a 115 volt motor, running on a 15 amp circuit, it
is NOT more than a 2 HP motor - definitely - and more likely not more
than 1.5 if starting under no load or with a slow-trip breaker.
Generally not more than 1 HP if it starts a load on a standard trip
breaker or fuse.
On 05/05/2010 10:59 AM, [email protected] wrote:
> On May 5, 11:48 am, Chris Friesen <[email protected]> wrote:
>> A good rule of thumb for most "normal" induction motors is 10A per HP at
>> 120V.
>>
>> Higher quality motors can do better, of course, but a "premium
>> efficiency" 1HP Baldor motor that costs $500 is still rated at 8.6A.
>
> My bet is that a "normal" motor isn't much less. There is more in
> that motor than a few (more) pounds of copper (like a name plate).
I was curious, so I went and checked on Baldor's site.
I checked a few 3450rpm 1HP "general purpose" induction motors and the
FLA at 120V ranged from 11.8 to 15A. Worse than I thought. :)
Chris
"Martin H. Eastburn" wrote:
> Circuit breakers are the same - some are rated for special loads.
> An oven is a nice resistive load. An air conditioner is highly
> inductive.
> Starting load on some motors require longer high current time.
> Naturally,
> if a start winding cap is bad, more current is needed in the run
> winding...
---------------------------------------
Molded case c'bkrs are thermal-magnetic devices.
The magnetic portion monitors the inrush characteristics of the load
which will cause the c'bkr to trip instantaneously if the inrush
current exceeds rating.
OTOH the thermal portion of the device monitors the thermal
characteristics on an inverse time basis.
(The larger the overload, the quicker the c'bkr trips)
There is also a special purpose molded case device known as a "Mag
only" or "motor protector".
These devices are used in 3 phase combination motor starter units and
would have no application in the typical single phase home shop
installation.
Lew
Fuses are rated in times it takes to blow.
Slo-blow are just one.
Some are super fast. Those are normally in the micro-to-milli amp specs.
Circuit breakers are the same - some are rated for special loads.
An oven is a nice resistive load. An air conditioner is highly inductive.
Starting load on some motors require longer high current time. Naturally,
if a start winding cap is bad, more current is needed in the run winding...
Martin
Martin H. Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
"Our Republic and the Press will Rise or Fall Together": Joseph Pulitzer
TSRA: Endowed; NRA LOH & Patron Member, Golden Eagle, Patriot's Medal.
NRA Second Amendment Task Force Charter Charter Founder
IHMSA and NRA Metallic Silhouette maker & member. http://lufkinced.com/
On 6/3/2010 11:34 PM, Josepi wrote:
> Even breakers and fuses take an overload on a time basis.
>
> I have put more than double the current through fuses and they hold for
> 60-120 seconds. Too many electrical geniuses that have no experience or just
> trolls...take your pick...LOL
>
>
> <[email protected]> wrote in message
> news:[email protected]...
> What's YOUR point? In yopur last post you said that's not how motors
> are rated and horsepower measured. Quote ">Ok, but that's not the way
> motors are rated or HP is calculated"
>
> I just said it is, and you agreed with me except on the "specialty"
> rating of some motors - which ARE rated as I said. A motor CAN have 2
> ratings - a constant (average) HP rating and a peak (cyclic or short
> duty) rating.
>
> Also, the "real" 2HP Baldor Cap-start cap-run motor I have installed
> on my compressor is rated at 20 amps at 115 volts and will start with
> the unloader on a 15 amp slow-blow fuse unless it's cold out.
> It is only about 65% efficient at full load, Like I said, 80% would
> be a pretty good motor (I didn't say 80% was common - I was just
> making the point that EVEN WITH an 80% efficient motor,1.5 or 2HP on a
> 115 volt 15 amp circuit would be MAXIMUM - anyone claiming higher than
> that is "more than suspect".
>
> THAT was the point I was making on the LAST post.
>
>
>
> --- news://freenews.netfront.net/ - complaints: [email protected] ---
On Wed, 02 Jun 2010 21:26:25 -0400, [email protected] wrote:
>On Tue, 01 Jun 2010 22:06:49 -0500, "[email protected]"
><[email protected]> wrote:
>
>>On Tue, 01 Jun 2010 22:11:40 -0400, [email protected] wrote:
>>
>>>On Tue, 01 Jun 2010 20:36:38 -0500, "[email protected]"
>>><[email protected]> wrote:
>>>
>>>>On Tue, 1 Jun 2010 14:25:33 -0400, "Josepi" <[email protected]> wrote:
>>>>
>>>>>Quite a few technical electrical errors there but you concept is almost
>>>>>correct.
>>>>>A one HP motor make use of 748 Watts, not consumes.
>>>>
>>>>Nope. A 1-HP motor *delivers* one horsepower of mechanical power
>>>>(550ft lbs/second). Only a 100% efficient motor would require only 748W (BTW,
>>>>"watts" is not capitalized).
>>>>
>>>>>120v X 10A = 1200va not watts
>>>>>Many 1/4HP furnace motors take about 10A at 120volts. How do you figure that
>>>>>one?
>>>>
>>>>I don't believe you. A 1HP motor may require 1200W at full load, but not a
>>>>1/4HP motor.
>>>
>>>It can draw 1200 watts at startup. Not terribly uncommon. When
>>>rotating, a whole lot less.
>>
>>Agreed.
>>
>>>>>The new 5HP motors are including the inertia of the rotor and do not specify
>>>>>"how long" they can deliver that HP.
>>>>
>>>>Nope. Well, maybe Crapsman's HP rating. ;-)
>>>
>>>Foot lbs torque @ rpm- a heavy rotor or flywheel CAN deliver
>>>significant horsepower for a matter of seconds - after it has been
>>>brought up to speed. In SOME applications, a heavy flywheel will alow
>>>a much smaller than normal motor to do the job.
>>
>>Ok, but that's not the way motors are rated or HP is calculated.
>>
>><...>
>which are you dissagreeing with?
Motor ratings include the energy from the flywheel.
>Horsepower is measured as foot/lbs per second - RPM X Ft Lbs
>Torque/5252 is horsepower. Period.
Ok, 550 ft*lbs/sec. I said that earlier.
>And a heavy flywheel will allow a small motor to provide significantly
>inproved torque for cyclic loads - making, is some cases, a 1/4 horse
>motor do the job a 3 horse motor could not do without a flywheel.
>Scaled up that's how punch presses work.
The motor will still be rated 1/4hp. That's its average output.
>One electric HP is 745 watts, more or less - but to produce that 1 HP
>with a motor of 80% efficiency requires 931 watts. And 80% isn't bad
>for a "consumer equipment" motor.
80% is very optimistic.
>And a series wound motor rated at, say 1 HP constant, may be able to
>produce upwards of 4HP or more for periods of up to several minutes,
>depending on it's thermal mass, and for duty cycles of up to say 15
>or 20%. So that motor, rated at continuous service, is a 1HP motor,
>and at cyclic service, perhaps legitimately 4 HP.
...but it's *not* a 4HP motor.
>That said - if it is a 115 volt motor, running on a 15 amp circuit, it
>is NOT more than a 2 HP motor - definitely - and more likely not more
>than 1.5 if starting under no load or with a slow-trip breaker.
It's not even that. 1.5HP on a 20A circuit is believable.
>Generally not more than 1 HP if it starts a load on a standard trip
>breaker or fuse.
Ok, your point is?
Even breakers and fuses take an overload on a time basis.
I have put more than double the current through fuses and they hold for
60-120 seconds. Too many electrical geniuses that have no experience or just
trolls...take your pick...LOL
<[email protected]> wrote in message
news:[email protected]...
What's YOUR point? In yopur last post you said that's not how motors
are rated and horsepower measured. Quote ">Ok, but that's not the way
motors are rated or HP is calculated"
I just said it is, and you agreed with me except on the "specialty"
rating of some motors - which ARE rated as I said. A motor CAN have 2
ratings - a constant (average) HP rating and a peak (cyclic or short
duty) rating.
Also, the "real" 2HP Baldor Cap-start cap-run motor I have installed
on my compressor is rated at 20 amps at 115 volts and will start with
the unloader on a 15 amp slow-blow fuse unless it's cold out.
It is only about 65% efficient at full load, Like I said, 80% would
be a pretty good motor (I didn't say 80% was common - I was just
making the point that EVEN WITH an 80% efficient motor,1.5 or 2HP on a
115 volt 15 amp circuit would be MAXIMUM - anyone claiming higher than
that is "more than suspect".
THAT was the point I was making on the LAST post.
--- news://freenews.netfront.net/ - complaints: [email protected] ---
Here are some Hubbel fuse curves.
http://www.hubbellpowersystems.com/switching/dist/fuselinks/fuse-curves/30003.jpg
Notice how even the "fast blow" type K types do not clear the circuit under
twice (two times for the Americans = 2x) their rated current level, even
after 5 minutes.
Type K are the fast blow types usually found in better Fluke digital meters
and other sensitive instruments. Other fuses are typically slower than this.
Breakers vary a lot over the years and manufacturer, Most of the cheap panel
ones were thermal and take a lot to trip them out the first time. Then the
rating is not guaranteed and need to be replaced. (read the fine print)
Nobody ever does.
Here is a curve for the thermal magnetic combo units referred to by Lew.
Notice the time curve for long slow overloads starts at 100% as well as the
instantaneous levels at about 800%. Much better protection for you table saw
and other equipment motors.
http://www.sea.siemens.com/us/internet-dms/btlv/Residential/Residential/docs_Circuit%20Breakers/QP_BQ_BL_QT_15-70A_1-Pole.pdf
"Lew Hodgett" <[email protected]> wrote in message
news:[email protected]...
Molded case c'bkrs are thermal-magnetic devices.
The magnetic portion monitors the inrush characteristics of the load
which will cause the c'bkr to trip instantaneously if the inrush
current exceeds rating.
OTOH the thermal portion of the device monitors the thermal
characteristics on an inverse time basis.
(The larger the overload, the quicker the c'bkr trips)
There is also a special purpose molded case device known as a "Mag
only" or "motor protector".
These devices are used in 3 phase combination motor starter units and
would have no application in the typical single phase home shop
installation.
Lew
--- news://freenews.netfront.net/ - complaints: [email protected] ---
On Wed, 02 Jun 2010 22:50:43 -0500, "[email protected]"
<[email protected]> wrote:
>On Wed, 02 Jun 2010 21:26:25 -0400, [email protected] wrote:
>
>>On Tue, 01 Jun 2010 22:06:49 -0500, "[email protected]"
>><[email protected]> wrote:
>>
>>>On Tue, 01 Jun 2010 22:11:40 -0400, [email protected] wrote:
>>>
>>>>On Tue, 01 Jun 2010 20:36:38 -0500, "[email protected]"
>>>><[email protected]> wrote:
>>>>
>>>>>On Tue, 1 Jun 2010 14:25:33 -0400, "Josepi" <[email protected]> wrote:
>>>>>
>>>>>>Quite a few technical electrical errors there but you concept is almost
>>>>>>correct.
>>>>>>A one HP motor make use of 748 Watts, not consumes.
>>>>>
>>>>>Nope. A 1-HP motor *delivers* one horsepower of mechanical power
>>>>>(550ft lbs/second). Only a 100% efficient motor would require only 748W (BTW,
>>>>>"watts" is not capitalized).
>>>>>
>>>>>>120v X 10A = 1200va not watts
>>>>>>Many 1/4HP furnace motors take about 10A at 120volts. How do you figure that
>>>>>>one?
>>>>>
>>>>>I don't believe you. A 1HP motor may require 1200W at full load, but not a
>>>>>1/4HP motor.
>>>>
>>>>It can draw 1200 watts at startup. Not terribly uncommon. When
>>>>rotating, a whole lot less.
>>>
>>>Agreed.
>>>
>>>>>>The new 5HP motors are including the inertia of the rotor and do not specify
>>>>>>"how long" they can deliver that HP.
>>>>>
>>>>>Nope. Well, maybe Crapsman's HP rating. ;-)
>>>>
>>>>Foot lbs torque @ rpm- a heavy rotor or flywheel CAN deliver
>>>>significant horsepower for a matter of seconds - after it has been
>>>>brought up to speed. In SOME applications, a heavy flywheel will alow
>>>>a much smaller than normal motor to do the job.
>>>
>>>Ok, but that's not the way motors are rated or HP is calculated.
>>>
>>><...>
>>which are you dissagreeing with?
>
>Motor ratings include the energy from the flywheel.
>
>>Horsepower is measured as foot/lbs per second - RPM X Ft Lbs
>>Torque/5252 is horsepower. Period.
>
>Ok, 550 ft*lbs/sec. I said that earlier.
>
>>And a heavy flywheel will allow a small motor to provide significantly
>>inproved torque for cyclic loads - making, is some cases, a 1/4 horse
>>motor do the job a 3 horse motor could not do without a flywheel.
>>Scaled up that's how punch presses work.
>
>The motor will still be rated 1/4hp. That's its average output.
>
>>One electric HP is 745 watts, more or less - but to produce that 1 HP
>>with a motor of 80% efficiency requires 931 watts. And 80% isn't bad
>>for a "consumer equipment" motor.
>
>80% is very optimistic.
>
>>And a series wound motor rated at, say 1 HP constant, may be able to
>>produce upwards of 4HP or more for periods of up to several minutes,
>>depending on it's thermal mass, and for duty cycles of up to say 15
>>or 20%. So that motor, rated at continuous service, is a 1HP motor,
>>and at cyclic service, perhaps legitimately 4 HP.
>
>...but it's *not* a 4HP motor.
>
>>That said - if it is a 115 volt motor, running on a 15 amp circuit, it
>>is NOT more than a 2 HP motor - definitely - and more likely not more
>>than 1.5 if starting under no load or with a slow-trip breaker.
>
>It's not even that. 1.5HP on a 20A circuit is believable.
>
>>Generally not more than 1 HP if it starts a load on a standard trip
>>breaker or fuse.
>
>Ok, your point is?
What's YOUR point? In yopur last post you said that's not how motors
are rated and horsepower measured. Quote ">Ok, but that's not the way
motors are rated or HP is calculated"
I just said it is, and you agreed with me except on the "specialty"
rating of some motors - which ARE rated as I said. A motor CAN have 2
ratings - a constant (average) HP rating and a peak (cyclic or short
duty) rating.
Also, the "real" 2HP Baldor Cap-start cap-run motor I have installed
on my compressor is rated at 20 amps at 115 volts and will start with
the unloader on a 15 amp slow-blow fuse unless it's cold out.
It is only about 65% efficient at full load, Like I said, 80% would
be a pretty good motor (I didn't say 80% was common - I was just
making the point that EVEN WITH an 80% efficient motor,1.5 or 2HP on a
115 volt 15 amp circuit would be MAXIMUM - anyone claiming higher than
that is "more than suspect".
THAT was the point I was making on the LAST post.
Keith Nuttle wrote:
>
> Original Poster: The motor is a Sears 1 hp motor that came with the
> 10" table saw when it was purchased in 1969. It is a capacitor start
> motor which for the first couple of microseconds draws a quite high
> current.
Ok... and this means what? At least, to the discussion as it has progressed
at this point?
--
-Mike-
[email protected]
Your comments are mostly from poor reading comprehension of what I posted
and a lack of basic electrical.
Perhaps some electrical theory study and/or experience would help.
You jumped so high (OCD medication need renewing?) you got none of them
right, this time.
<[email protected]> wrote in message
news:[email protected]...
On Tue, 1 Jun 2010 14:25:33 -0400, "Josepi" <[email protected]> wrote:
>Quite a few technical electrical errors there but you concept is almost
>correct.
>A one HP motor make use of 748 Watts, not consumes.
Nope. A 1-HP motor *delivers* one horsepower of mechanical power
(550ft lbs/second). Only a 100% efficient motor would require only 748W
(BTW,
"watts" is not capitalized).
>120v X 10A = 1200va not watts
>Many 1/4HP furnace motors take about 10A at 120volts. How do you figure
>that
>one?
I don't believe you. A 1HP motor may require 1200W at full load, but not a
1/4HP motor.
>The new 5HP motors are including the inertia of the rotor and do not
>specify
>"how long" they can deliver that HP.
Nope. Well, maybe Crapsman's HP rating. ;-)
>E.G. Stand in front of a child on bicycle paddling as fast as he can and
>let
>the impact on your groin stop it.
>Feels like more than 5HP right? ...and yet, a seasoned cyclist can only
>produce about 1/2 HP on a racing bike.
Silly.
>Yup, it's the way of our advertising world. You define something and we'll
>find holes in it to twist the facts.
...until someone puts a stop to the practice.
<snip>
--- news://freenews.netfront.net/ - complaints: [email protected] ---
On Tue, 1 Jun 2010 14:25:33 -0400, "Josepi" <[email protected]> wrote:
>Quite a few technical electrical errors there but you concept is almost
>correct.
>A one HP motor make use of 748 Watts, not consumes.
Nope. A 1-HP motor *delivers* one horsepower of mechanical power
(550ft lbs/second). Only a 100% efficient motor would require only 748W (BTW,
"watts" is not capitalized).
>120v X 10A = 1200va not watts
>Many 1/4HP furnace motors take about 10A at 120volts. How do you figure that
>one?
I don't believe you. A 1HP motor may require 1200W at full load, but not a
1/4HP motor.
>The new 5HP motors are including the inertia of the rotor and do not specify
>"how long" they can deliver that HP.
Nope. Well, maybe Crapsman's HP rating. ;-)
>E.G. Stand in front of a child on bicycle paddling as fast as he can and let
>the impact on your groin stop it.
>Feels like more than 5HP right? ...and yet, a seasoned cyclist can only
>produce about 1/2 HP on a racing bike.
Silly.
>Yup, it's the way of our advertising world. You define something and we'll
>find holes in it to twist the facts.
...until someone puts a stop to the practice.
<snip>
On 05/04/2010 04:04 PM, Lew Hodgett wrote:
> Go to the electrical section of your favorite DIY and look for molded
> cord sets
>
> Buy a 6'-10', 10-2 with ground (black, white, green) extension cord.
>
> Chop off the female end and wire into saw.
I agree with the concept, but I'd go with #12 instead of #10.
#10 is much harder to find in reasonable lengths around here, and is
significantly more expensive than #12.
Chris
On May 5, 12:30=A0pm, Chris Friesen <[email protected]> wrote:
> On 05/05/2010 10:59 AM, [email protected] wrote:
>
> > On May 5, 11:48 am, Chris Friesen <[email protected]> wrote:
> >> A good rule of thumb for most "normal" induction motors is 10A per HP =
at
> >> 120V.
>
> >> Higher quality motors can do better, of course, but a "premium
> >> efficiency" 1HP Baldor motor that costs $500 is still rated at 8.6A.
>
> > My bet is that a "normal" motor isn't much less. =A0There is more in
> > that motor than a few (more) pounds of copper (like a name plate).
>
> I was curious, so I went and checked on Baldor's site.
>
> I checked a few 3450rpm 1HP "general purpose" induction motors and the
> FLA at 120V ranged from 11.8 to 15A. =A0Worse than I thought. =A0:)
Gack! You're right. I looked up a few sites and found 12-15A for a
general purpose 1-HP 120V motor (I thought motors were far better than
50% efficient). Nothing less than 12AWG!
On May 5, 4:13=A0pm, [email protected] (Doug Miller) wrote:
> In article <[email protected]=
.com>, "[email protected]" <[email protected]> wrote:
>
> >On May 5, 12:30=3DA0pm, Chris Friesen <[email protected]> wrote:
> >> On 05/05/2010 10:59 AM, [email protected] wrote:
>
> >> > On May 5, 11:48 am, Chris Friesen <[email protected]> wrote:
> >> >> A good rule of thumb for most "normal" induction motors is 10A per =
HP =3D
> >at
> >> >> 120V.
>
> >> >> Higher quality motors can do better, of course, but a "premium
> >> >> efficiency" 1HP Baldor motor that costs $500 is still rated at 8.6A=
.
>
> >> > My bet is that a "normal" motor isn't much less. =3DA0There is more =
in
> >> > that motor than a few (more) pounds of copper (like a name plate).
>
> >> I was curious, so I went and checked on Baldor's site.
>
> >> I checked a few 3450rpm 1HP "general purpose" induction motors and the
> >> FLA at 120V ranged from 11.8 to 15A. =3DA0Worse than I thought. =3DA0:=
)
>
> >Gack! =A0You're right. =A0I looked up a few sites and found 12-15A for a
> >general purpose 1-HP 120V motor (I thought motors were far better than
> >50% efficient). =A0Nothing less than 12AWG!
>
> Why? 14AWG wire will safely carry 20A. The NEC limits the *overcurrent
> protection* on a 14AWG circuit to 15A, but also specifically lists the
> ampacity of 14AWG copper as 20A with 60degC and 75degC insulation, and 25=
A
> with 90degC insulation. [2008 NEC, Table 310.16]
Table 310.16 doesn't apply unless he is replacing the wiring going to
the receptacle that the saw is plugging into. You want to look at
Table 400.5(A) which is the allowable ampacity for flexible cables
(i.e. SJ,SO,SJE,etc.) which is the type of cable that he needs. Then
the limiting factor again is the receptacle/plug combination that he
has been using. If the saw had a 15A/120V plug on it, then 14ga. wire
would be acceptable. If it was a 20A/120V plug on it, then 12ga. would
be acceptable. Table 400.5(A) lists 14ga at 18A and 12 ga. at 25A.
I agree that the saw probably wouldn't draw more than 10A continuous
so anything beyond 14ga. is probably a waste at this point.
Allen
On May 4, 5:52=A0pm, Keith Nuttle <[email protected]> wrote:
> After many years of use the cord on my Sears table saw is running out of
> space to wrap electrical tape around it. =A0This is the cord from the
> switch not the cord from the motor to the switch. =A0The motor is a 1 hp,
> 120 volt. =A0The instruction that came with the motor says that a 20 amp
> fuse should be used in the circuit to which the motor is connected. (Yes
> I am a pack rat)
>
> Would a cord with 12 gauge wire be sufficient for the 6 foot replacement
> cord, or would I use a smaller gauge wire.
>
> I can find 14 and 16 gauge readily but 12 gauge is harder to find.
Go to your local electrical supply house and get 6-10' of 12/3SJ
cord and a 15A 120V straight blade plug unless you have a 20A 120V
straight blade on there right now. The difference is a 15A has 2
prongs parallel to each w/ground and a 20A has the 2 prongs
perpendicular to each other w/ground.
The formula for ampacity when HP is known is:
HP x 746 / E x Eff x pf
Where E=3DVoltage
Eff=3DEfficiency (found on plate with voltage)
pf=3DPower Factor (also found on plate)
Wire size is limited by the plug. I suspect that you have a 15A plug
on there now so anything beyond 12 gauge wire is a waste.
Allen
On 05/04/2010 04:40 PM, Lew Hodgett wrote:
> "Chris Friesen" wrote:
>
>> I agree with the concept, but I'd go with #12 instead of #10.
> ---------------------------------------
> A 1HP motor @ 120VAC?
>
> Anything less than 10 AWG and you are kidding yourself.
Sure. 1HP at 120 typically draws about 10A. Startup surge isn't an
issue since the smaller wire can easily handle it briefly.
Both my 3HP 240V table saw and my 1.5HP 120V dust collector are fine
with #12 on 20A circuits.
>> #10 is much harder to find in reasonable lengths around here, and is
>> significantly more expensive than #12.
> -----------------------------------------
> A 6 ft to a 10 ft extension cord isn't readily available from your
> local big box store?
>
> What part of Bum Fuck are you living in?
I'm in the Canadian prairies, but that shouldn't matter since Home Depot
is pretty much the same all over. I can get a 100ft #10 cord no
problem, but certainly not a 6 or 10ft #10 molded cord set.
Chris
Keith Nuttle wrote:
> After many years of use the cord on my Sears table saw is running out
> of space to wrap electrical tape around it. This is the cord from the
> switch not the cord from the motor to the switch. The motor is a 1
> hp, 120 volt. The instruction that came with the motor says that a
> 20 amp fuse should be used in the circuit to which the motor is
> connected. (Yes I am a pack rat)
>
> Would a cord with 12 gauge wire be sufficient for the 6 foot
> replacement cord, or would I use a smaller gauge wire.
>
> I can find 14 and 16 gauge readily but 12 gauge is harder to find.
12 guage would indeed be sufficient. It is readily available at Home Depot,
Lowes, and all of the other suspects. Definitely not hard to find. An
alternative, if you're so inclined is to just buy a 12 ga extension cord,
cut off the female end, and wire it to your saw.
--
-Mike-
[email protected]
On May 4, 10:21=A0pm, [email protected] (Doug Miller) wrote:
> In article <[email protected]>, "Lew Hodgett" <s=
[email protected]> wrote:
> >"Chris Friesen" wrote:
>
> >> I agree with the concept, but I'd go with #12 instead of #10.
> >---------------------------------------
> >A 1HP motor @ 120VAC?
>
> 1HP =3D approx 750 watts =3D 6+ amps @ 120V, so that, in and of itself, i=
s
> perhaps slightly unusual but hardly impossible. On top of that, you're
> forgetting this from the original post: "...my Sears table saw..."
Remember the starting current.
> 1 Sears HP =3D approx 0.3 real HP, so even allowing for inefficiency, it'=
s
> unlikely that it pulls any more than 3A.
If it's a real table saw, with an induction motor, the 1HP rating is
probably good. If it's one of the table top toys with the universal
motor it would probably be rated at six or ten horsepower.
> >Anything less than 10 AWG and you are kidding yourself.
>
> Don't be silly. 10AWG is rated for 30A, which at 120V =3D 3600W =3D a bit=
less
> than 5HP. There's absolutely no need for even 12ga, let alone 10ga, for a=
ny
> 1HP motor =A0at 120V -- especially a Sears "1HP" motor. A 14ga power cord=
is
> quite sufficient.
I'd go with 12GA anyway, just because. Both 12GA and 14GA SJ cable
are readily available at the big box stores. 12GA SJ should be
something just over a buck a foot.
On May 4, 11:15=A0pm, [email protected] wrote:
> On May 4, 7:59=A0pm, "Lew Hodgett" <[email protected]> wrote:
>
>
>
> > =A0"Chris Friesen" wrote:
> > > 1 HP at 120 typically draws about 10A. =A0Startup surge isn't an
> > > issue since the smaller wire can easily handle it briefly.
>
> > -----------------------------------
>
> > Think you'll find a 1 HP, 120VAC draws closer to 15A, but NBD.
>
> > Not concerned about start up inrush but rather the inrush required to
> > handle a rapid change in power demand with a sudden change in cutting
> > load.
>
> > (Don't try "horsing" a piece of 8/4 hard maple for instance) with a 1
> > HP motor.
>
> > It's a lot easier to push those electrons thru a bigger pipe.
>
> > -----------------------------------> I'm in the Canadian prairies, but =
that shouldn't matter since Home
> > > Depot
> > > is pretty much the same all over. =A0I can get a 100ft #10 cord no
> > > problem, but certainly not a 6 or 10ft #10 molded cord set.
>
> > -------------------------------------------
>
> > I can't keep up with H/D.
>
> > Last time I looked a 50 ft, 10-3, molded cord set was about $55.
>
> > Also had a 10 ft, but don't remember price.
>
> > Today I look and can't find either.
>
> > Today all I find is a 100 ft 10-3.
>
> > Go figure.
>
> > Lew
>
> Appropos of not much, i was in lowes over the weekend. 100ft, 12-2
> romex, 63$ =A0250 ft romex, 12-2, 74$
> clueless!
>
> shelly
Did you happen to note the prices for the 500' rolls?
On May 4, 5:52=A0pm, Keith Nuttle <[email protected]> wrote:
> I can find 14 and 16 gauge readily but 12 gauge is harder to find.
Hey there, not to worry. For the six feet you are running to the wall
the original gauge will do (as it so far has done) fine. My gues is
that teh original cord was 14 gauge stranded and that such a
replacement would do you fine. No need to ask us, just take a section
of your old cord and strip it apart/down and count the wires and note
the colors and measure the wire gauge and be done with it.
Having said all that, LOWES and HD offer an "extension cord" intended
for an Air Conditioner that is likely 10GA (chop off the female end)
and may offer one or two that are 12GA and GOING DOWN never really
hurt anyone, right?
BTW, If you go long, you must go down!
Enjoy
On May 5, 9:26=A0am, "Mike Marlow" <[email protected]> wrote:
> Keith Nuttle wrote:
>
> > Original Poster: =A0 The motor is a Sears 1 hp motor that came with the
> > 10" table saw when it was purchased in 1969. It is a capacitor start
> > motor which for the first couple of microseconds draws a quite high
> > current.
>
> Ok... and this means what? =A0At least, to the discussion as it has progr=
essed
> at this point?
It means that the saw, when bogged down, may (or not) draw 6A. 14GA
is fine. Though I'd still go 12GA. ;-)
On Tue, 01 Jun 2010 20:36:38 -0500, "[email protected]"
<[email protected]> wrote:
>On Tue, 1 Jun 2010 14:25:33 -0400, "Josepi" <[email protected]> wrote:
>
>>Quite a few technical electrical errors there but you concept is almost
>>correct.
>>A one HP motor make use of 748 Watts, not consumes.
>
>Nope. A 1-HP motor *delivers* one horsepower of mechanical power
>(550ft lbs/second). Only a 100% efficient motor would require only 748W (BTW,
>"watts" is not capitalized).
>
>>120v X 10A = 1200va not watts
>>Many 1/4HP furnace motors take about 10A at 120volts. How do you figure that
>>one?
>
>I don't believe you. A 1HP motor may require 1200W at full load, but not a
>1/4HP motor.
It can draw 1200 watts at startup. Not terribly uncommon. When
rotating, a whole lot less.
>
>>The new 5HP motors are including the inertia of the rotor and do not specify
>>"how long" they can deliver that HP.
>
>Nope. Well, maybe Crapsman's HP rating. ;-)
Foot lbs torque @ rpm- a heavy rotor or flywheel CAN deliver
significant horsepower for a matter of seconds - after it has been
brought up to speed. In SOME applications, a heavy flywheel will alow
a much smaller than normal motor to do the job.
>
>>E.G. Stand in front of a child on bicycle paddling as fast as he can and let
>>the impact on your groin stop it.
>>Feels like more than 5HP right? ...and yet, a seasoned cyclist can only
>>produce about 1/2 HP on a racing bike.
>
>Silly.
>
>>Yup, it's the way of our advertising world. You define something and we'll
>>find holes in it to twist the facts.
>
>...until someone puts a stop to the practice.
><snip>
On 5/4/2010 6:19 PM, Chris Friesen wrote:
> On 05/04/2010 04:04 PM, Lew Hodgett wrote:
>> Go to the electrical section of your favorite DIY and look for molded
>> cord sets
>>
>> Buy a 6'-10', 10-2 with ground (black, white, green) extension cord.
>>
>> Chop off the female end and wire into saw.
>
> I agree with the concept, but I'd go with #12 instead of #10.
>
> #10 is much harder to find in reasonable lengths around here, and is
> significantly more expensive than #12.
>
> Chris
Thank you for the quick responses. I have spent the afternoon in
hardware stores, and one of the big box stores but could not find what I
was looking for. My plan was to do exactly what was suggested, buy a
short extension cord, cut of the female end, and wire it into the switch
box.
If all else fails, I will buy the cord and plug and make one myself.
At least I know I that I was right in not buying anything less than 12
gauge.
On 5/4/2010 6:40 PM, Lew Hodgett wrote:
> "Chris Friesen" wrote:
>
>> I agree with the concept, but I'd go with #12 instead of #10.
> ---------------------------------------
> A 1HP motor @ 120VAC?
>
> Anything less than 10 AWG and you are kidding yourself.
> -----------------------------------
>> #10 is much harder to find in reasonable lengths around here, and is
>> significantly more expensive than #12.
> -----------------------------------------
> A 6 ft to a 10 ft extension cord isn't readily available from your
> local big box store?
>
> What part of Bum Fuck are you living in?
>
> Lew
>
>
>
Indianapolis! But we pay taxes to support the Colts and their big new
expensive stadium.
Keith Nuttle wrote:
...
> ... My plan was to do exactly what was suggested, buy a
> short extension cord, cut of the female end, and wire it into the switch
> box.
>
> If all else fails, I will buy the cord and plug and make one myself.
...
Buy the long one and a plug. Use the molded plug end for the saw
section and put the store-bought plug on the remainder and you now have
a nice heavy duty extension cord besides.
--
On 5/4/2010 7:03 PM, Keith Nuttle wrote:
> On 5/4/2010 6:19 PM, Chris Friesen wrote:
>> On 05/04/2010 04:04 PM, Lew Hodgett wrote:
>>> Go to the electrical section of your favorite DIY and look for molded
>>> cord sets
>>>
>>> Buy a 6'-10', 10-2 with ground (black, white, green) extension cord.
>>>
>>> Chop off the female end and wire into saw.
>>
>> I agree with the concept, but I'd go with #12 instead of #10.
>>
>> #10 is much harder to find in reasonable lengths around here, and is
>> significantly more expensive than #12.
>>
>> Chris
>
> Thank you for the quick responses. I have spent the afternoon in
> hardware stores, and one of the big box stores but could not find what I
> was looking for. My plan was to do exactly what was suggested, buy a
> short extension cord, cut of the female end, and wire it into the switch
> box.
>
> If all else fails, I will buy the cord and plug and make one myself.
>
> At least I know I that I was right in not buying anything less than 12
> gauge.
12 should be fine. If you want to use 10, look near the generators in
Lowes or Home Depot. The cords will have a twist-lock connector though
so you'll have to cut that off and put a regular one on, or else put in
a special outlet.
>
>
In article <[email protected]>, "Lew Hodgett" <[email protected]> wrote:
>"Chris Friesen" wrote:
>
>> I agree with the concept, but I'd go with #12 instead of #10.
>---------------------------------------
>A 1HP motor @ 120VAC?
1HP = approx 750 watts = 6+ amps @ 120V, so that, in and of itself, is
perhaps slightly unusual but hardly impossible. On top of that, you're
forgetting this from the original post: "...my Sears table saw..."
1 Sears HP = approx 0.3 real HP, so even allowing for inefficiency, it's
unlikely that it pulls any more than 3A.
>
>Anything less than 10 AWG and you are kidding yourself.
Don't be silly. 10AWG is rated for 30A, which at 120V = 3600W = a bit less
than 5HP. There's absolutely no need for even 12ga, let alone 10ga, for any
1HP motor at 120V -- especially a Sears "1HP" motor. A 14ga power cord is
quite sufficient.
On Jun 1, 6:00=A0am, [email protected] wrote:
> On Wed, 05 May 2010 20:13:39 GMT, [email protected] (Doug Miller) wrote=
:
> >In article <[email protected]=
s.com>, "[email protected]" <[email protected]> wrote:
> >>On May 5, 12:30=3DA0pm, Chris Friesen <[email protected]> wrote:
> >>> On 05/05/2010 10:59 AM, [email protected] wrote:
>
> >>> > On May 5, 11:48 am, Chris Friesen <[email protected]> wrote:
> >>> >> A good rule of thumb for most "normal" induction motors is 10A per=
HP =3D
> >>at
> >>> >> 120V.
>
> >>> >> Higher quality motors can do better, of course, but a "premium
> >>> >> efficiency" 1HP Baldor motor that costs $500 is still rated at 8.6=
A.
>
> >>> > My bet is that a "normal" motor isn't much less. =3DA0There is more=
in
> >>> > that motor than a few (more) pounds of copper (like a name plate).
>
> >>> I was curious, so I went and checked on Baldor's site.
>
> >>> I checked a few 3450rpm 1HP "general purpose" induction motors and th=
e
> >>> FLA at 120V ranged from 11.8 to 15A. =3DA0Worse than I thought. =3DA0=
:)
>
> >>Gack! =A0You're right. =A0I looked up a few sites and found 12-15A for =
a
> >>general purpose 1-HP 120V motor (I thought motors were far better than
> >>50% efficient). =A0Nothing less than 12AWG!
>
> >Why? 14AWG wire will safely carry 20A. The NEC limits the *overcurrent
> >protection* on a 14AWG circuit to 15A, but also specifically lists the
> >ampacity of 14AWG copper as 20A with 60degC and 75degC insulation, and 2=
5A
> >with 90degC insulation. [2008 NEC, Table 310.16]
>
> A one horsepower motor is always 748 Watts,
Must be nice to live in a perfect world, where everything is perfectly
efficient.
> so you're "rule of thumb" is 120v x
> 10A =3D 1200watts, a bit on the high side of one HP. =A0In the past, manu=
facturers
> would sometimes get carried away trying to show that their motors were be=
tter
> than the competitions by making statements like "it DEVELOPS xx horsepowe=
r"
> which was a far cry from it's real HP when you calculated it from the cur=
rent
> and voltage clearly marked on the nameplate.
Even better, perpetual motion is everyday, in your world.
>=A0Almost all compressor
> manufacturers were guilty of this type of deception. =A0Finally the FEDS =
stepped
> in and threatened to start fining these companys for false advertising. Y=
ou
> cannot have a motor that draws 15a at 220v produce 5 hp and be telling th=
e
> truth. =A0They sure confused everyone so much that misunderstandings cont=
inue to
> exist, but there is certainly no magic and it is pretty basic. =A0
Tell that to Sears.
Stuart <[email protected]> wrote in
news:[email protected]:
> In article <[email protected]>,
> Josepi <[email protected]> wrote:
>> A one HP motor make use of 748 Watts, not consumes.
>
> Curious! When I was at school I was taught that 1hp=746w
>
>
Perhaps it's the difference between US and British Horsepower... Our
pints are different, why not our horsepower?
Actually... According to "Pocket Ref" you're right:
1 HP (mech) = 745.7W
1 HP (electric) = 746W
1 HP (metric[!]) = 735.499W
Puckdropper
--
Never teach your apprentice everything you know.
In article <[email protected]>,
Josepi <[email protected]> wrote:
> A one HP motor make use of 748 Watts, not consumes.
Curious! When I was at school I was taught that 1hp=746w
In article <[email protected]>,
Josepi <[email protected]> wrote:
> Quite probably. It has been a long time since I have looked that one up,
Just one of those numbers that sticks in my head, like the log of 2, =
0.30103, must have used it a lot for something when I was at school, or
was it all those equations with 2*PI in? I used to remember the log of PI
too.
What did I do two days ago - nah can't remember that :-)
> I knew it was close and I just copied what the doorknob posted. The
> point was motors are not 100% efficient and do not run at unity pf.
Indeed, when I started work we had some big MG sets and when you started
them up, you went over to the wall where there was a big manually operated
oil circuit breaker which switched in a /large/ capacitor for power factor
correction.
Quite a few technical electrical errors there but you concept is almost
correct.
A one HP motor make use of 748 Watts, not consumes.
120v X 10A = 1200va not watts
Many 1/4HP furnace motors take about 10A at 120volts. How do you figure that
one?
The new 5HP motors are including the inertia of the rotor and do not specify
"how long" they can deliver that HP.
E.G. Stand in front of a child on bicycle paddling as fast as he can and let
the impact on your groin stop it.
Feels like more than 5HP right? ...and yet, a seasoned cyclist can only
produce about 1/2 HP on a racing bike.
Yup, it's the way of our advertising world. You define something and we'll
find holes in it to twist the facts.
<[email protected]> wrote in message
news:[email protected]...
On Wed, 05 May 2010 20:13:39 GMT, [email protected] (Doug Miller) wrote:
A one horsepower motor is always 748 Watts, so you're "rule of thumb" is
120v x
10A = 1200watts, a bit on the high side of one HP. In the past,
manufacturers
would sometimes get carried away trying to show that their motors were
better
than the competitions by making statements like "it DEVELOPS xx horsepower"
which was a far cry from it's real HP when you calculated it from the
current
and voltage clearly marked on the nameplate. Almost all compressor
manufacturers were guilty of this type of deception. Finally the FEDS
stepped
in and threatened to start fining these companys for false advertising. You
cannot have a motor that draws 15a at 220v produce 5 hp and be telling the
truth. They sure confused everyone so much that misunderstandings continue
to
exist, but there is certainly no magic and it is pretty basic.
[email protected]
>In article
><a1c2b2c1-9cef-4430-94a0-13f5cc1af622@r11g2000yqa.googlegroups.com>,
>"[email protected]" <[email protected]> wrote:
>>On May 5, 12:30=A0pm, Chris Friesen <[email protected]> wrote:
>>> On 05/05/2010 10:59 AM, [email protected] wrote:
>>>
>>> > On May 5, 11:48 am, Chris Friesen <[email protected]> wrote:
>>> >> A good rule of thumb for most "normal" induction motors is 10A per HP
>>> >> =
>>at
>>> >> 120V.
>>>
>>> >> Higher quality motors can do better, of course, but a "premium
>>> >> efficiency" 1HP Baldor motor that costs $500 is still rated at 8.6A.
>>>
>>> > My bet is that a "normal" motor isn't much less. =A0There is more in
>>> > that motor than a few (more) pounds of copper (like a name plate).
>>>
>>> I was curious, so I went and checked on Baldor's site.
>>>
>>> I checked a few 3450rpm 1HP "general purpose" induction motors and the
>>> FLA at 120V ranged from 11.8 to 15A. =A0Worse than I thought. =A0:)
>>
>>Gack! You're right. I looked up a few sites and found 12-15A for a
>>general purpose 1-HP 120V motor (I thought motors were far better than
>>50% efficient). Nothing less than 12AWG!
>>
>Why? 14AWG wire will safely carry 20A. The NEC limits the *overcurrent
>protection* on a 14AWG circuit to 15A, but also specifically lists the
>ampacity of 14AWG copper as 20A with 60degC and 75degC insulation, and 25A
>with 90degC insulation. [2008 NEC, Table 310.16]
--- news://freenews.netfront.net/ - complaints: [email protected] ---
Quite probably. It has been a long time since I have looked that one up, I
knew it was close and I just copied what the doorknob posted. The point was
motors are not 100% efficient and do not run at unity pf.
It was a useless attempt for the trolls. I was suckered, for a time.
"Stuart" <[email protected]> wrote in message
news:[email protected]...
Curious! When I was at school I was taught that 1hp=746w
In article <[email protected]>,
Josepi <[email protected]> wrote:
> A one HP motor make use of 748 Watts, not consumes.
--- news://freenews.netfront.net/ - complaints: [email protected] ---
On Wed, 05 May 2010 20:13:39 GMT, [email protected] (Doug Miller) wrote:
>In article <a1c2b2c1-9cef-4430-94a0-13f5cc1af622@r11g2000yqa.googlegroups.com>, "[email protected]" <[email protected]> wrote:
>>On May 5, 12:30=A0pm, Chris Friesen <[email protected]> wrote:
>>> On 05/05/2010 10:59 AM, [email protected] wrote:
>>>
>>> > On May 5, 11:48 am, Chris Friesen <[email protected]> wrote:
>>> >> A good rule of thumb for most "normal" induction motors is 10A per HP =
>>at
>>> >> 120V.
>>>
>>> >> Higher quality motors can do better, of course, but a "premium
>>> >> efficiency" 1HP Baldor motor that costs $500 is still rated at 8.6A.
>>>
>>> > My bet is that a "normal" motor isn't much less. =A0There is more in
>>> > that motor than a few (more) pounds of copper (like a name plate).
>>>
>>> I was curious, so I went and checked on Baldor's site.
>>>
>>> I checked a few 3450rpm 1HP "general purpose" induction motors and the
>>> FLA at 120V ranged from 11.8 to 15A. =A0Worse than I thought. =A0:)
>>
>>Gack! You're right. I looked up a few sites and found 12-15A for a
>>general purpose 1-HP 120V motor (I thought motors were far better than
>>50% efficient). Nothing less than 12AWG!
>>
>Why? 14AWG wire will safely carry 20A. The NEC limits the *overcurrent
>protection* on a 14AWG circuit to 15A, but also specifically lists the
>ampacity of 14AWG copper as 20A with 60degC and 75degC insulation, and 25A
>with 90degC insulation. [2008 NEC, Table 310.16]
A one horsepower motor is always 748 Watts, so you're "rule of thumb" is 120v x
10A = 1200watts, a bit on the high side of one HP. In the past, manufacturers
would sometimes get carried away trying to show that their motors were better
than the competitions by making statements like "it DEVELOPS xx horsepower"
which was a far cry from it's real HP when you calculated it from the current
and voltage clearly marked on the nameplate. Almost all compressor
manufacturers were guilty of this type of deception. Finally the FEDS stepped
in and threatened to start fining these companys for false advertising. You
cannot have a motor that draws 15a at 220v produce 5 hp and be telling the
truth. They sure confused everyone so much that misunderstandings continue to
exist, but there is certainly no magic and it is pretty basic.
[email protected]
On 5/4/2010 11:21 PM, Doug Miller wrote:
> In article<[email protected]>, "Lew Hodgett"<[email protected]> wrote:
>> "Chris Friesen" wrote:
>>
>>> I agree with the concept, but I'd go with #12 instead of #10.
>> ---------------------------------------
>> A 1HP motor @ 120VAC?
>
> 1HP = approx 750 watts = 6+ amps @ 120V, so that, in and of itself, is
> perhaps slightly unusual but hardly impossible. On top of that, you're
> forgetting this from the original post: "...my Sears table saw..."
>
> 1 Sears HP = approx 0.3 real HP, so even allowing for inefficiency, it's
> unlikely that it pulls any more than 3A.
>
>>
>> Anything less than 10 AWG and you are kidding yourself.
>
> Don't be silly. 10AWG is rated for 30A, which at 120V = 3600W = a bit less
> than 5HP. There's absolutely no need for even 12ga, let alone 10ga, for any
> 1HP motor at 120V -- especially a Sears "1HP" motor. A 14ga power cord is
> quite sufficient.
Original Poster: The motor is a Sears 1 hp motor that came with the
10" table saw when it was purchased in 1969. It is a capacitor start
motor which for the first couple of microseconds draws a quite high
current.
On Tue, 01 Jun 2010 04:00:38 -0700, [email protected] wrote:
>On Wed, 05 May 2010 20:13:39 GMT, [email protected] (Doug Miller) wrote:
>
>>In article <a1c2b2c1-9cef-4430-94a0-13f5cc1af622@r11g2000yqa.googlegroups.com>, "[email protected]" <[email protected]> wrote:
>>>On May 5, 12:30=A0pm, Chris Friesen <[email protected]> wrote:
>>>> On 05/05/2010 10:59 AM, [email protected] wrote:
>>>>
>>>> > On May 5, 11:48 am, Chris Friesen <[email protected]> wrote:
>>>> >> A good rule of thumb for most "normal" induction motors is 10A per HP =
>>>at
>>>> >> 120V.
>>>>
>>>> >> Higher quality motors can do better, of course, but a "premium
>>>> >> efficiency" 1HP Baldor motor that costs $500 is still rated at 8.6A.
>>>>
>>>> > My bet is that a "normal" motor isn't much less. =A0There is more in
>>>> > that motor than a few (more) pounds of copper (like a name plate).
>>>>
>>>> I was curious, so I went and checked on Baldor's site.
>>>>
>>>> I checked a few 3450rpm 1HP "general purpose" induction motors and the
>>>> FLA at 120V ranged from 11.8 to 15A. =A0Worse than I thought. =A0:)
>>>
>>>Gack! You're right. I looked up a few sites and found 12-15A for a
>>>general purpose 1-HP 120V motor (I thought motors were far better than
>>>50% efficient). Nothing less than 12AWG!
>>>
>>Why? 14AWG wire will safely carry 20A. The NEC limits the *overcurrent
>>protection* on a 14AWG circuit to 15A, but also specifically lists the
>>ampacity of 14AWG copper as 20A with 60degC and 75degC insulation, and 25A
>>with 90degC insulation. [2008 NEC, Table 310.16]
>
>A one horsepower motor is always 748 Watts, so you're "rule of thumb" is 120v x
>10A = 1200watts, a bit on the high side of one HP. In the past, manufacturers
>would sometimes get carried away trying to show that their motors were better
>than the competitions by making statements like "it DEVELOPS xx horsepower"
>which was a far cry from it's real HP when you calculated it from the current
>and voltage clearly marked on the nameplate. Almost all compressor
>manufacturers were guilty of this type of deception. Finally the FEDS stepped
>in and threatened to start fining these companys for false advertising. You
>cannot have a motor that draws 15a at 220v produce 5 hp and be telling the
>truth. They sure confused everyone so much that misunderstandings continue to
>exist, but there is certainly no magic and it is pretty basic.
>[email protected]
Don't forget power factor in your formula or you'll have trouble
starting some motors or be surprised at what the actual current is.
Mike M
In article <e1e47d77-b9b3-40d1-8f75-f7b5975646c5@q32g2000yqb.googlegroups.com>, "[email protected]" <[email protected]> wrote:
>On May 4, 10:21=A0pm, [email protected] (Doug Miller) wrote:
>> In article <[email protected]>, "Lew Hodgett" <s=
>[email protected]> wrote:
>> >"Chris Friesen" wrote:
>>
>> >> I agree with the concept, but I'd go with #12 instead of #10.
>> >---------------------------------------
>> >A 1HP motor @ 120VAC?
>>
>> 1HP = approx 750 watts = 6+ amps @ 120V, so that, in and of itself, is
>> perhaps slightly unusual but hardly impossible. On top of that, you're
>> forgetting this from the original post: "...my Sears table saw..."
>
>Remember the starting current.
Remember the brand name. If Sears claims it's a 1HP motor, you can depend on
it that it's no more than 1/2 HP.
>
>> 1 Sears HP = approx 0.3 real HP, so even allowing for inefficiency, it's
>> unlikely that it pulls any more than 3A.
>
>If it's a real table saw, with an induction motor, the 1HP rating is
>probably good.
Sears is notorious for overstating their motor ratings.
>If it's one of the table top toys with the universal
>motor it would probably be rated at six or ten horsepower.
>
>> >Anything less than 10 AWG and you are kidding yourself.
>>
>> Don't be silly. 10AWG is rated for 30A, which at 120V = 3600W = a bit less
>> than 5HP. There's absolutely no need for even 12ga, let alone 10ga, for any
>> 1HP motor at 120V -- especially a Sears "1HP" motor. A 14ga power cord is
>> quite sufficient.
>
>I'd go with 12GA anyway, just because. Both 12GA and 14GA SJ cable
>are readily available at the big box stores. 12GA SJ should be
>something just over a buck a foot.
Well, there's no harm in using 12ga (except to the wallet), but it's not
needed for a motor that small. And 10ga is just silly.
In article <[email protected]>, Keith Nuttle <[email protected]> wrote:
>On 5/4/2010 11:21 PM, Doug Miller wrote:
>> In article<[email protected]>, "Lew
> Hodgett"<[email protected]> wrote:
>>> "Chris Friesen" wrote:
>>>
>>>> I agree with the concept, but I'd go with #12 instead of #10.
>>> ---------------------------------------
>>> A 1HP motor @ 120VAC?
>>
>> 1HP = approx 750 watts = 6+ amps @ 120V, so that, in and of itself, is
>> perhaps slightly unusual but hardly impossible. On top of that, you're
>> forgetting this from the original post: "...my Sears table saw..."
>>
>> 1 Sears HP = approx 0.3 real HP, so even allowing for inefficiency, it's
>> unlikely that it pulls any more than 3A.
>>
>>>
>>> Anything less than 10 AWG and you are kidding yourself.
>>
>> Don't be silly. 10AWG is rated for 30A, which at 120V = 3600W = a bit less
>> than 5HP. There's absolutely no need for even 12ga, let alone 10ga, for any
>> 1HP motor at 120V -- especially a Sears "1HP" motor. A 14ga power cord is
>> quite sufficient.
>
>Original Poster: The motor is a Sears 1 hp motor that came with the
>10" table saw when it was purchased in 1969. It is a capacitor start
>motor which for the first couple of microseconds draws a quite high
>current.
Again: if Sears says it's 1HP, it's probably really no more than 1/2 HP.
In any event, even if it's really 1HP, 14ga is enough to handle the load. The
inrush current is of a short enough duration to not be a problem.
In article <a1c2b2c1-9cef-4430-94a0-13f5cc1af622@r11g2000yqa.googlegroups.com>, "[email protected]" <[email protected]> wrote:
>On May 5, 12:30=A0pm, Chris Friesen <[email protected]> wrote:
>> On 05/05/2010 10:59 AM, [email protected] wrote:
>>
>> > On May 5, 11:48 am, Chris Friesen <[email protected]> wrote:
>> >> A good rule of thumb for most "normal" induction motors is 10A per HP =
>at
>> >> 120V.
>>
>> >> Higher quality motors can do better, of course, but a "premium
>> >> efficiency" 1HP Baldor motor that costs $500 is still rated at 8.6A.
>>
>> > My bet is that a "normal" motor isn't much less. =A0There is more in
>> > that motor than a few (more) pounds of copper (like a name plate).
>>
>> I was curious, so I went and checked on Baldor's site.
>>
>> I checked a few 3450rpm 1HP "general purpose" induction motors and the
>> FLA at 120V ranged from 11.8 to 15A. =A0Worse than I thought. =A0:)
>
>Gack! You're right. I looked up a few sites and found 12-15A for a
>general purpose 1-HP 120V motor (I thought motors were far better than
>50% efficient). Nothing less than 12AWG!
>
Why? 14AWG wire will safely carry 20A. The NEC limits the *overcurrent
protection* on a 14AWG circuit to 15A, but also specifically lists the
ampacity of 14AWG copper as 20A with 60degC and 75degC insulation, and 25A
with 90degC insulation. [2008 NEC, Table 310.16]
12 is all you will need in that short length.
Martin
Keith Nuttle wrote:
> After many years of use the cord on my Sears table saw is running out of
> space to wrap electrical tape around it. This is the cord from the
> switch not the cord from the motor to the switch. The motor is a 1 hp,
> 120 volt. The instruction that came with the motor says that a 20 amp
> fuse should be used in the circuit to which the motor is connected. (Yes
> I am a pack rat)
>
> Would a cord with 12 gauge wire be sufficient for the 6 foot replacement
> cord, or would I use a smaller gauge wire.
>
> I can find 14 and 16 gauge readily but 12 gauge is harder to find.
>
On 05/05/2010 09:29 AM, [email protected] wrote:
> On May 5, 9:26 am, "Mike Marlow" <[email protected]> wrote:
>> Keith Nuttle wrote:
>>
>>> Original Poster: The motor is a Sears 1 hp motor that came with the
>>> 10" table saw when it was purchased in 1969. It is a capacitor start
>>> motor which for the first couple of microseconds draws a quite high
>>> current.
>>
>> Ok... and this means what? At least, to the discussion as it has progressed
>> at this point?
>
> It means that the saw, when bogged down, may (or not) draw 6A. 14GA
> is fine. Though I'd still go 12GA. ;-)
You forgot about power factor and efficiency.
A good rule of thumb for most "normal" induction motors is 10A per HP at
120V.
Higher quality motors can do better, of course, but a "premium
efficiency" 1HP Baldor motor that costs $500 is still rated at 8.6A.
Chris
On Tue, 01 Jun 2010 22:11:40 -0400, [email protected] wrote:
>On Tue, 01 Jun 2010 20:36:38 -0500, "[email protected]"
><[email protected]> wrote:
>
>>On Tue, 1 Jun 2010 14:25:33 -0400, "Josepi" <[email protected]> wrote:
>>
>>>Quite a few technical electrical errors there but you concept is almost
>>>correct.
>>>A one HP motor make use of 748 Watts, not consumes.
>>
>>Nope. A 1-HP motor *delivers* one horsepower of mechanical power
>>(550ft lbs/second). Only a 100% efficient motor would require only 748W (BTW,
>>"watts" is not capitalized).
>>
>>>120v X 10A = 1200va not watts
>>>Many 1/4HP furnace motors take about 10A at 120volts. How do you figure that
>>>one?
>>
>>I don't believe you. A 1HP motor may require 1200W at full load, but not a
>>1/4HP motor.
>
>It can draw 1200 watts at startup. Not terribly uncommon. When
>rotating, a whole lot less.
Agreed.
>>>The new 5HP motors are including the inertia of the rotor and do not specify
>>>"how long" they can deliver that HP.
>>
>>Nope. Well, maybe Crapsman's HP rating. ;-)
>
>Foot lbs torque @ rpm- a heavy rotor or flywheel CAN deliver
>significant horsepower for a matter of seconds - after it has been
>brought up to speed. In SOME applications, a heavy flywheel will alow
>a much smaller than normal motor to do the job.
Ok, but that's not the way motors are rated or HP is calculated.
<...>
On Tue, 1 Jun 2010 22:48:57 -0400, "Josepi" <[email protected]> wrote:
>Your comments are mostly from poor reading comprehension of what I posted
>and a lack of basic electrical.
You're clueless.
>Perhaps some electrical theory study and/or experience would help.
Indeed it would. You should try it.
>You jumped so high (OCD medication need renewing?) you got none of them
>right, this time.
Nice deflection, but the *fact* is that you're full of shit (notice the lack
of defense).
I believe pricing like that. It might be logical to you,
but for the builder they buy the big roll and the small shop
or electrician the small roll since it is likely plenty.
Higher profit on the short - builder likes his/her price.
The electrician buys from electric company or there - and passes on
the cost as needed.
Martin
On 5/6/2010 3:27 PM, Hoosierpopi wrote:
> On May 4, 11:15 pm, [email protected] wrote:
>> On May 4, 7:59 pm, "Lew Hodgett"<[email protected]> wrote:
>>
>>
>>
>>> "Chris Friesen" wrote:
>>>> 1 HP at 120 typically draws about 10A. Startup surge isn't an
>>>> issue since the smaller wire can easily handle it briefly.
>>
>>> -----------------------------------
>>
>>> Think you'll find a 1 HP, 120VAC draws closer to 15A, but NBD.
>>
>>> Not concerned about start up inrush but rather the inrush required to
>>> handle a rapid change in power demand with a sudden change in cutting
>>> load.
>>
>>> (Don't try "horsing" a piece of 8/4 hard maple for instance) with a 1
>>> HP motor.
>>
>>> It's a lot easier to push those electrons thru a bigger pipe.
>>
>>> -----------------------------------> I'm in the Canadian prairies, but that shouldn't matter since Home
>>>> Depot
>>>> is pretty much the same all over. I can get a 100ft #10 cord no
>>>> problem, but certainly not a 6 or 10ft #10 molded cord set.
>>
>>> -------------------------------------------
>>
>>> I can't keep up with H/D.
>>
>>> Last time I looked a 50 ft, 10-3, molded cord set was about $55.
>>
>>> Also had a 10 ft, but don't remember price.
>>
>>> Today I look and can't find either.
>>
>>> Today all I find is a 100 ft 10-3.
>>
>>> Go figure.
>>
>>> Lew
>>
>> Appropos of not much, i was in lowes over the weekend. 100ft, 12-2
>> romex, 63$ 250 ft romex, 12-2, 74$
>> clueless!
>>
>> shelly
>
> Did you happen to note the prices for the 500' rolls?
"Keith Nuttle" <[email protected]> wrote in message
news:[email protected]...
> After many years of use the cord on my Sears table saw is running out of
> space to wrap electrical tape around it. This is the cord from the switch
> not the cord from the motor to the switch. The motor is a 1 hp, 120 volt.
> The instruction that came with the motor says that a 20 amp fuse should be
> used in the circuit to which the motor is connected. (Yes I am a pack rat)
>
> Would a cord with 12 gauge wire be sufficient for the 6 foot replacement
> cord, or would I use a smaller gauge wire.
>
> I can find 14 and 16 gauge readily but 12 gauge is harder to find.
>
12ga is rated for 20 amps
basilisk
On Wed, 5 May 2010 10:12:30 -0400, "Mike Marlow"
<[email protected]> wrote the following:
>Keith Nuttle wrote:
>> After many years of use the cord on my Sears table saw is running out
>> of space to wrap electrical tape around it. This is the cord from the
>> switch not the cord from the motor to the switch. The motor is a 1
>> hp, 120 volt. The instruction that came with the motor says that a
>> 20 amp fuse should be used in the circuit to which the motor is
>> connected. (Yes I am a pack rat)
>>
>> Would a cord with 12 gauge wire be sufficient for the 6 foot
>> replacement cord, or would I use a smaller gauge wire.
>>
>> I can find 14 and 16 gauge readily but 12 gauge is harder to find.
>
>12 guage would indeed be sufficient. It is readily available at Home Depot,
>Lowes, and all of the other suspects. Definitely not hard to find. An
>alternative, if you're so inclined is to just buy a 12 ga extension cord,
>cut off the female end, and wire it to your saw.
I got 90' of 12ga cable for my 240v items and wired them up to the new
outlets I installed for them. Now I can move all 3 around the shop, or
out into the driveway, with plenty of cord to spare. L6-20 twistlocks
went on the ends to keep 'em plugged. I think it cost about $75
total, including the 250' of 12/2/grounded Romex, 3 outlets, 3 plugs,
and the cable. I use the rest of the Romex to run lights into the
unfinished attic for the guys to install the HVAC. Carrier Infinity,
96% efficient, with A/C. I now have a conditioned shop. </smugness>
Dual 16x20" furnace filters keep the dust out of the house and
equalize the air.
--
All national institutions of churches, whether Jewish, Christian,
or Turkish, appear to me no other than human inventions, set up
to terrify and enslave mankind, and monopolize power and profit.
--Thomas Paine