"LRod" wrote in message
...
He stated that 1HP is approximately 750 watts which you concede is
correct. He goes on to say that 750 watts equals a little over 6A at
120V. Either you also agree with that or you think Prof Ohm is an
idiot, because 750 = 120*6.25 (P=IE).


I = (746 * hp) / (eff * pf * voltage)

and that also ignores SF.


My "new" lathe sports a 1HP cap start-induction run nameplated at 14 amps.
Must really be inefficient.

In article ,
Al Reid wrote:
"LRod" wrote in message
.. .
On Thu, 17 Mar 2005 12:10:07 -0500, "Al Reid"
wrote:


Good!! Quit while your behind. No need to continue to make a fool
of yourself.

Ummm, I don't think that's pointed where it belongs.

My advice would be to do yourself a favor and stop answering
electrical related
questions. You just continue to embarrass yourself.

You're dead wrong there. Of all the people that post on the wreck, the
one person whose electrical related answers CAN most be depended upon
is Doug.

Frankly, I think you glommed on to a minor nuance (which could easily
have been interepreted other ways) and chose to make some sort of
usenet stand on it. While you may have been technically correct in the
very strictest sense of what YOU were saying, the fact is, that was
not what Doug was saying. And I reread the thread, so I know what I'm
saying. But, in for a penny, in for a pound appears to be your credo,
so, many posts later, here we are.



Ok so you agree that this statement is, indeed correct?

================
So who has a motor drawing over 15A? He said it's a true 1HP motor. 1HP =
apprpox 750 watts = a little over 6A at 120V.
================

YES, that statement is *precisely* correct. When taken _exactly_as_written_.

Notice the period after the word motor.

1 HP is 745.6999+ watts. 745.6999+ watts is 1HP

By "P = I * E" or it's mathematical equivalent "I = P / E"

745.6999+ watts / 120 volts = 6.214158+ amps.

Which *is* accurately described as "a little over 6A".

It does _not_ say that a '1 shaft HP output" electric motor will draw
only around 6 A.

"Power factor" comes into play *only* if (a) you are talking about A,C.
power, *and* (b) 'something' is inducing a phase shift in the current waveform,
relative to the power waveform. Given a purely 'resistive' (or resistive
=equivalent= -- no net capacitance or reactance, and yes a motor _can_ be
designed to that requirement) "power factor" does _not_ need to be considered.
(because it is 'unity' that is, and multiplying or dividing by 1 is 'silly'

"efficiency" comes into play *only* if something is 'transforming' the
energy.

*ALL* of which, you have blithely "assumed" exist in your calculation.


While Doug is correct that 1 HP = approx 750 watts (746), you cannot make
the leap to say that it equates to a little over 6A at 120V. To say that is
to assume that you have a 100% efficient motor. However,

BZZZT! Thank you for playing. *YOU* just made the _assumption_ that the
calculation is to the power throughput of an electric motor.

I = (746 * hp) / (eff * pf * voltage)

Insufficient definition of terms. Particularly as to "what" and "how" the
"HP" is measured. A _draw_ of 746 watts does equate to an _input_ power of
1 HP to whatever device is drawing that 746 watts.

and that also ignores SF.

"Surprise, surprise." Service factor does *not* have a d*mn thing to do
with the 'shaft output' horsepower of an electric motor drawing a given
amount of input power.

SF simply describes the limits of "continuous operation", without overheating.

In the end, the OP stated that his 1HP motor is rated at 12.5 FLA which is
higher then the "little over 6A at 120V."

Now, if Doug had said that 1 theoretical or mechanical HP translates to
little over 6A at 120V, but that the actual current draw will be higher,
dependent on efficiency and power factor OR if he had just acknowledged that
he had not factored that in to his answer, it would have ended after one
reply from Doug. But to start by saying "So who has a motor drawing over 15A?"
and continuing with the statement that a 1 HP motor draws a littlo over 6A is
at best a little deceiving and at worst complete misinformation. I corrected
Doug and he protested.

You read something into his remarks that he did *NOT* actually say.

Yes, his statements were "incomplete", and subject to being mis-read.

"Amplification" of the "incomplete" remarks, to provide the quote missing
unquote information _would_ have been justified.

*CORRECTION* was not called for, however. The 'incomplete' remarks were
_not_ in error.

There are 3 separate sets of "facts" involved, here.

1) what the original poster _intended_ to say,
2) what was actually said
3) what the reader *thought* they read.

#1 is not subject to dispute. *NOBODY* but the original poster knows what
the 'intent' was. Anyone who claims otherwise had better be prepared to
*prove* psychic abilities, or be branded a liar, themselves.

Arguing about #2 requires _careful_ inspection of the words on paper, and
*PARTICULAR*CARE* =not= to invoke any assumptions from #3.

Now, considering that I have a 1930's (!!) handbook that shows the average
efficiency of a 1HP electric motor _in_those_days_ was roughly 82%, and
modern data that indicates the power factor is in the .8-.85 range, means
that a _NINETEEN_THIRTIES_ 1 HP motor should draw about 9.45+ A at 120V AC.

It would seem safe to postulate that motor designs, manufacturing tolerances,
and bearing quality, have improved by a 'non-trivial' amount in the last 70
years, and that 'modern' motor behavior would be somewhat better.


Oh well, life goes on. Doug does normally give out reasonable accurate
information and my statement was made mostly out of frustration.

Lastly, for anyone who is interested here is a link to the rec.woodworking
Electric Motors FAQ.

http://www.faqs.org/faqs/woodworking/motors/

Later
--
Al Reid


And I've had enough of your childishness myself, so I'm through as well.

Good. This took a lot less time than the stoutman/clarke ****fest. Of
course they kept ****ing even after they called "last post" so maybe
this one isn't done yet either.

--
LRod

Master Woodbutcher and seasoned termite

Shamelessly whoring my website since 1999

http://www.woodbutcher.net

In article 1N4_d.75394$Ze3.17749@attbi_s51,
David Merrill wrote:
Motor rated? How is that typically identified on the switch packaging? I
may have to ask the electrical department guy :-)

Not to "belabor the obvious", but it has a _HP_ rating on it, in addition
to the 'amps' rating(s).

Frequently there will be a load (Amps) rating at 120 VAC, a different (Amps)
rating for 240VAC, *and* a HP rating.

You don't exceed _either_ the HP rating, or the relevant Amps limit.

"Why" you ask? simple. motors have *large* inrush currents when starting
up. Leads to arcing, and pitting of contacts not designed to handle the load.
leads to premature switching device failure.



David Merrill

"Doug Miller" wrote in message
news
...snip
You may not be able to find one that's an exact form-and-fit replacement
for
your existing SPST switch, but actually, you shouldn't have any trouble at
all
finding a DPST switch at HD or Lowe's.

In article ,
LRod wrote:
On Thu, 17 Mar 2005 02:28:59 GMT, "David Merrill"
wrote:

And there we have it, after only 63 posts and counting!

May I be allowed an attempt to summarize:

- possibly improved life of jointer motor
(this one still hasn't been clarified to my satisfaction)

I don't remember that being claimed, but I can dispense with it
quickly (I thought I already had in my original response). From the
standpoint of the motor windings, it's always running on 120V. Either
the windings are wired in parallel (120V supply) or the windings are
wired in series (240V). Since the motor windings are always seeing
120V it can't possibly have any different life expectancy based on the
input voltage.

Well, things aren't quite that simple. grin

"All else being equal" -- things like distance from the main breaker
panel, gauge of the distribution wire, etc. -- and which I must note
are usually _not_ equal ;

The 240v powered motor tends not to 'bog down' as much / as fast as the
120V powered one. This is attributable to the lower 'line losses' upstream
of the motor, resulting in what is effectively a "stiffer" power supply.

"Amps drawn" goes up as the load goes up, with the supply voltage remaining
constant.

*IF* the supply voltage does _not_ remain constant, but 'sags', the amps
drawn goes up even *more*, to compensate for the 'sag'.

A result of 'all of the above", plus some other things: voltage sag is
more pronounced and longer duration at 120V than 240V.

Such "parasitic' losses in the motor go up as the *square* of the current.

This _can_ have an adverse affect on motor longevity.

This is what I understand based on all these posts. Guys, if I'm still
missing or mis-stating something, take your best shot :-)

I think you have probably summarized it accurately with the above
noted exception.

--
LRod

Master Woodbutcher and seasoned termite

Shamelessly whoring my website since 1999

http://www.woodbutcher.net

Al Reid wrote:

"Duane Bozarth" wrote in message
...
Al Reid wrote:

...
Smoke screen? You've got to be kidding me.

...

No, you've only been kidding yourself that there was anything more than
what Doug and LRod to the Doug's original posting ....

Duane,

Could you say that again, perhaps this time in classic VB6 ?g

Well, that came out pretty well hashed, didn't it???

Anyway, I was just trying to say I agreed w/ Al that you jumped on a
perceived interpretation of what Doug said and rode your inference into
the ground...

Perhaps w/ some effort that could be coded, but I'd prefer Fortran altho
I do still watch the VB group as well...

"Robert Bonomi" wrote in message
...
In article ,

================
So who has a motor drawing over 15A? He said it's a true 1HP motor. 1HP =
apprpox 750 watts = a little over 6A at 120V.
================

YES, that statement is *precisely* correct. When taken
_exactly_as_written_.

Notice the period after the word motor.

1 HP is 745.6999+ watts. 745.6999+ watts is 1HP

By "P = I * E" or it's mathematical equivalent "I = P / E"

745.6999+ watts / 120 volts = 6.214158+ amps.

Which *is* accurately described as "a little over 6A".

It does _not_ say that a '1 shaft HP output" electric motor will draw
only around 6 A.


Context. It all must be read in context. They were discussing motors and
current draw 120V vs. 220V. The entire context was about motors. He chides
toller for suggesting that a 1 HP motor would draw 15 A and then attempts to
prove him wrong by doing a calculation. In that context, "I=P/E" is
invalid. We were not discussing the current draw of a resistance heater on
120 vs. 220.

"Power factor" comes into play *only* if (a) you are talking about A,C.

....which we were.

power, *and* (b) 'something' is inducing a phase shift in the current
waveform,
relative to the power waveform. Given a purely 'resistive' (or resistive
=equivalent= -- no net capacitance or reactance, and yes a motor _can_ be
designed to that requirement) "power factor" does _not_ need to be
considered.
(because it is 'unity' that is, and multiplying or dividing by 1 is
'silly'

"efficiency" comes into play *only* if something is 'transforming' the
energy.

*ALL* of which, you have blithely "assumed" exist in your calculation.


The discussion was about AC motors. What else can one assume in a
discussion about whether to run a motor on 120 vs 220? Assume we are
discussing electric heaters? Come on, be serious.


While Doug is correct that 1 HP = approx 750 watts (746), you cannot make
the leap to say that it equates to a little over 6A at 120V. To say that
is
to assume that you have a 100% efficient motor. However,

BZZZT! Thank you for playing. *YOU* just made the _assumption_ that the
calculation is to the power throughput of an electric motor.


It was and is a correct assumption in the context of the discussion.

I = (746 * hp) / (eff * pf * voltage)

Insufficient definition of terms. Particularly as to "what" and "how" the
"HP" is measured. A _draw_ of 746 watts does equate to an _input_ power
of
1 HP to whatever device is drawing that 746 watts.


Once again, it is correct in the context of the discussion.

and that also ignores SF.

"Surprise, surprise." Service factor does *not* have a d*mn thing to do
with the 'shaft output' horsepower of an electric motor drawing a given
amount of input power.


It will effect the current draw of the motor and whether it can ever draw
more than 15 amps.

SF simply describes the limits of "continuous operation", without
overheating.

In the end, the OP stated that his 1HP motor is rated at 12.5 FLA which
is
higher then the "little over 6A at 120V."

Now, if Doug had said that 1 theoretical or mechanical HP translates to
little over 6A at 120V, but that the actual current draw will be higher,
dependent on efficiency and power factor OR if he had just acknowledged
that
he had not factored that in to his answer, it would have ended after one
reply from Doug. But to start by saying "So who has a motor drawing over
15A?"
and continuing with the statement that a 1 HP motor draws a littlo over
6A is
at best a little deceiving and at worst complete misinformation. I
corrected
Doug and he protested.

You read something into his remarks that he did *NOT* actually say.


My mistake for reading his comments in context.

Yes, his statements were "incomplete", and subject to being mis-read.


Then he made them in the context of motors and therefore efficiency and
power factor cannot be excluded, unless one is attempting to be misleading.

"Amplification" of the "incomplete" remarks, to provide the quote missing
unquote information _would_ have been justified.

*CORRECTION* was not called for, however. The 'incomplete' remarks were
_not_ in error.

There are 3 separate sets of "facts" involved, here.

1) what the original poster _intended_ to say,
2) what was actually said
3) what the reader *thought* they read.

#1 is not subject to dispute. *NOBODY* but the original poster knows what
the 'intent' was. Anyone who claims otherwise had better be prepared to
*prove* psychic abilities, or be branded a liar, themselves.

Arguing about #2 requires _careful_ inspection of the words on paper, and
*PARTICULAR*CARE* =not= to invoke any assumptions from #3.


And of course, carfull inspection of the words on paper within the context
of the paragraph and the overall discussion.

Now, considering that I have a 1930's (!!) handbook that shows the average
efficiency of a 1HP electric motor _in_those_days_ was roughly 82%, and
modern data that indicates the power factor is in the .8-.85 range, means
that a _NINETEEN_THIRTIES_ 1 HP motor should draw about 9.45+ A at 120V
AC.

It would seem safe to postulate that motor designs, manufacturing
tolerances,
and bearing quality, have improved by a 'non-trivial' amount in the last
70
years, and that 'modern' motor behavior would be somewhat better.



The only thing one can go by is nameplate data. Small motors tend to be
less efficient than large motors. DAGS on motor data and you will find that
most 1 HP motors fall in the range of 10 to 13 FLA. Someone just posted
that his is shown as 14FLA. The nameplate data from the 1 HP motor that
started this entire thread stated 12.5 FLA. As plain as I can state it, in
the context of the discussion, a 1 horsepower will not draw ~6a. You can
argue Ohms law all you want, but in the context given the statement was
either intentionally misleading or woefully out of context. If you go back
and read it in context, you will have to agree.

In the end, I suspect that we all know the equations and the theory and how
to apply them. This whole thing comes down to being willing to accept the
context in which the remarks were made. I am sure you would not let me get
away with stating or implying that a 1HP = approx 750 watts = a little over
6A at 120V within a discussion of whether I should convert my motor to 220V
or leave it on 120V. You would be one of the first to point out that I had
neglected to take into account efficiency and power factor and that in
reality, the current draw would be higher.

This is the end of the line for me in this thread. The horse is beat and
the OP has already started another thread wherein he is still trying to
decide whether he should convert his 12.5 A 1 HP motor to 220VAC.

Good night.
--

Al Reid

On Fri, 18 Mar 2005 00:03:52 -0000,
(Robert Bonomi) wrote:

In article ,
LRod wrote:

I don't remember that being claimed, but I can dispense with it
quickly (I thought I already had in my original response). From the
standpoint of the motor windings, it's always running on 120V. Either
the windings are wired in parallel (120V supply) or the windings are
wired in series (240V). Since the motor windings are always seeing
120V it can't possibly have any different life expectancy based on the
input voltage.

Well, things aren't quite that simple. grin

"All else being equal" -- things like distance from the main breaker
panel, gauge of the distribution wire, etc. -- and which I must note
are usually _not_ equal ;

Points I have often made about 120V vs 240V, some in this thread.

The 240v powered motor tends not to 'bog down' as much / as fast as the
120V powered one. This is attributable to the lower 'line losses' upstream
of the motor, resulting in what is effectively a "stiffer" power supply.

"Stiff" being exactly the term I used in this thread when describing
the supply issues.

"Amps drawn" goes up as the load goes up, with the supply voltage remaining
constant.

*IF* the supply voltage does _not_ remain constant, but 'sags', the amps
drawn goes up even *more*, to compensate for the 'sag'.

Which is not stiff...

A result of 'all of the above", plus some other things: voltage sag is
more pronounced and longer duration at 120V than 240V.

Such "parasitic' losses in the motor go up as the *square* of the current.

Yes, I referred to that earlier in this thread. I described it as
voltage drop is four times higher at 120V vs 240V.

This _can_ have an adverse affect on motor longevity.

I didn't connect those dots, but it's also not necessarily a realistic
expectation, either. I can't imagine trying to quantify the
difference.

--
LRod

Master Woodbutcher and seasoned termite

Shamelessly whoring my website since 1999

http://www.woodbutcher.net

Subject

B O R I N G ! !

I say that as a former motor application sales engineer with a multi
million $ budget that somehow, always exceeded.

Find another worthless horse to beat to death.

Lew

Lew:

Lew Hodgett wrote:
Subject
=20
B O R I N G ! !
=20
I say that as a former motor application sales engineer with a multi=20
million $ budget that somehow, always exceeded.
=20
Find another worthless horse to beat to death.
=20
Lew

I only used them as a designer -- but I would have to agree with you.=20
LOL -- did anything I could to foist that work on another sucker -- er=20
person.

Much preferred CMOS and NAND gates and flip-flops -- and gate expanders=20
are real interesting too and FPGAs - wanna talk about them? ROTFL...

Think I will strip the case off an IC and inlay it in my next jewel=20
box... That will even keep it OT.

Now I'm gonna duck before we both get shot...


--=20
Will R.
Jewel Boxes and Wood Art
http://woodwork.pmccl.com
The power of accurate observation is commonly called cynicism by those=20
who have not got it.=94 George Bernard Shaw

================
So who has a motor drawing over 15A? He said it's a true 1HP motor. 1HP =
apprpox 750 watts = a little over 6A at 120V.
================

Al, you are spitting into the wind. Sure he said that. Sure it is stupid.
Sure he will deny saying it even though is is publically posted. Trying to
convince him otherwise is not a good use of your time. Just killfile the
jerk.

In article ,
LRod wrote:
On Fri, 18 Mar 2005 00:03:52 -0000,
(Robert Bonomi) wrote:

In article ,
LRod wrote:

I don't remember that being claimed, but I can dispense with it
quickly (I thought I already had in my original response). From the
standpoint of the motor windings, it's always running on 120V. Either
the windings are wired in parallel (120V supply) or the windings are
wired in series (240V). Since the motor windings are always seeing
120V it can't possibly have any different life expectancy based on the
input voltage.

Well, things aren't quite that simple. grin

"All else being equal" -- things like distance from the main breaker
panel, gauge of the distribution wire, etc. -- and which I must note
are usually _not_ equal ;

Points I have often made about 120V vs 240V, some in this thread.

The 240v powered motor tends not to 'bog down' as much / as fast as the
120V powered one. This is attributable to the lower 'line losses' upstream
of the motor, resulting in what is effectively a "stiffer" power supply.

"Stiff" being exactly the term I used in this thread when describing
the supply issues.

Aw shucks, we're having an *agreement*!!! Dammit!

"Amps drawn" goes up as the load goes up, with the supply voltage remaining
constant.

*IF* the supply voltage does _not_ remain constant, but 'sags', the amps
drawn goes up even *more*, to compensate for the 'sag'.

Which is not stiff...

"All things are relative". grin

A result of 'all of the above", plus some other things: voltage sag is
more pronounced and longer duration at 120V than 240V.

Such "parasitic' losses in the motor go up as the *square* of the current.

Yes, I referred to that earlier in this thread. I described it as
voltage drop is four times higher at 120V vs 240V.

This _can_ have an adverse affect on motor longevity.

I didn't connect those dots, but it's also not necessarily a realistic
expectation, either. I can't imagine trying to quantify the
difference.

Quantitative difference depends totally on the *precise* circumstances
involved.

Given _sufficiently_detailed_ information a quantitative evaluation of
reduction in life expectancy is possible. The thought of actually _getting_
said detail in a USENET posting is laughable. It is probably *not*
realistic to expect anyone to have, or be able to produce, sufficiently
detailed source data for such an analysis of a real-world situation.

That said, everything mentioned works _against_ life-expectancy at 120V,
relative to life-expectancy at 240V. 'Best possible case' scenario is that
120V operational life is "as long as" 240V life. If there are _any_
differences, they will be in favor of the 240V operation. "Empirical"
data, from motors in near-continuous use, under varying, but peaking fairly
heavily, load, indicates a 'few' percentage points of life expectancy in
favor of the higher-voltage operation.

I'm taking issue _only_ with the "_can't_possibly_ have _any_ effect on life
expectancy" part of your recent statement.

I'd agree totally with "*probably* won't have any -significant- effect..."

'Possible/probable minor increase in motor longevity' would, it seems to me,
qualify as "one more reason" to favor 240V over 120V wiring; *not*, however,
a 'compelling reason' to change, in and of itself.

On Fri, 18 Mar 2005 02:55:57 -0000,
(Robert Bonomi) wrote:


I'm taking issue _only_ with the "_can't_possibly_ have _any_ effect on life
expectancy" part of your recent statement.

I'm going to have to quit couching my sentiments in absolute terms.
That's the second hammering on that score I've taken in the last
couple of months. Of course, I was absolutely, er, uh, pretty darn
correct in the other one.

--
LRod

Master Woodbutcher and seasoned termite

Shamelessly whoring my website since 1999

http://www.woodbutcher.net

WillR wrote:


Much preferred CMOS and NAND gates and flip-flops -- and gate expanders
are real interesting too and FPGAs - wanna talk about them? ROTFL...



Naw, much prefer women, booze, money and sailing.

Not necessarily in the order listedG.

After all, you are talking to a salesman who got out of engineering.

Lew

In article , "toller" wrote:

================
So who has a motor drawing over 15A? He said it's a true 1HP motor. 1HP =
apprpox 750 watts = a little over 6A at 120V.
================

Al, you are spitting into the wind. Sure he said that. Sure it is stupid.
Sure he will deny saying it even though is is publically posted. Trying to
convince him otherwise is not a good use of your time. Just killfile the
jerk.

You know, toller, if you would put one-tenth as much energy into reading a
couple of good books on electrical wiring as you put into trying to defend
your ridiculous misunderstandings and attacking the people who correct them,
you might actually learn enough that you wouldn't be dangerous any more.

Yes, I said that. No, it isn't stupid. I'm obviously not going to deny it,
because I *did* say it, and it *is* correct.

I will, however, deny saying that any actual 1HP motor exists that draws only
6A/120V, as your buddy continues to falsely claim.

--
Regards,
Doug Miller (alphageek at milmac dot com)

Nobody ever left footprints in the sands of time by sitting on his butt.
And who wants to leave buttprints in the sands of time?

"LRod" wrote in message
...
On Fri, 18 Mar 2005 02:55:57 -0000,
(Robert Bonomi) wrote:


I'm taking issue _only_ with the "_can't_possibly_ have _any_ effect on
life
expectancy" part of your recent statement.

I'm going to have to quit couching my sentiments in absolute terms.
That's the second hammering on that score I've taken in the last
couple of months. Of course, I was absolutely, er, uh, pretty darn
correct in the other one.


Ya gotta remember - if there is a point of minutia that can be taken up
here, it will be taken up. And it will be argued as if the very fate of
mankind rested on the matter.
--

-Mike-

"J. Clarke" wrote in message
...
Kim wrote:


"LRod" wrote in message
...
On Wed, 16 Mar 2005 10:40:45 -0800, "Kim" wrote:


Geez, where do you guys get this stuff?

IEEE, NEC, short circuit and load flow studies, breaker/device
coordinations.

You can blindly claim all the initialed documents you want, but cite
just one specific paragraph in any reputable regulatory document that
supports your statement: "[m]aximum breaker size 15A as your motor is
only about 8A at 220V."

That's pure nonsense, and I'll be the first to apologize ot you were
you to come up with something. Of course that's a safe promise,
because you not only can't, but you won't.

Local AHJs don't count as their specific requirements are not germane
to the discussion, but I'd be happy to see them if they do exist.

--
LRod

Master Woodbutcher and seasoned termite



Shamelessly whoring my website since 1999

http://www.woodbutcher.net

Here is a portion of your statement in context as related to the above:

"Maximum breaker size 15A as your motor is only about 8A at 220V.

Where do you get that from? And if there were some sort of
relationship to breaker size and load demand, why would 15A breaker
with an 8A load be okay but not 20A or 30A breaker?"

NEC Table 430-152, dependent on the motor type, the inverse time
breakers
could go either 150%, 200% or 250% of motor load. In other words, if the
motor has no code letter, for example, you could go up to a 20A breaker
based on 8A motor running nameplate load. If the restriction falls on
200%
or 150%, then 15A CB only. But as a general practice the lowest breaker
setting should be used, hence 15A. There is no reason why, from a
protection point of view, you would want to use an 20A, 30A or larger
breaker where a 15A breaker would do. 15A CB is what I would use.

I think you're confusing code requirements for permanently installed
machinery with code requirements for portable tools.

OK you got me, but the information Table 430-152 should apply, although not
mandatory for portable tools as you suggested, as motor and breaker
characteristic don't change or care if the installation is permanent or not.
For sure motor inrush current was one of the reasons for this table perhaps
also fire and electrical faults from over sized breakers - who knows what
the historical reasons were for the NEC panel decisions but you can be sure
it has much to do with safety. Don't throw out the baby with the bath water.
All I'm saying was the best protection for this motor is a 15A circuit
breaker based on the OP's situation. (I've used "maximum' and perhaps that
was a wrong word choice.)



There is no reason, from a protection point of view, why you would want to
call an electrician and have him remove a perfectly good 30 amp breaker
and
the associated 30 amp receptacle and replace it with a 15 amp breaker and
15 amp receptacle just because you are plugging in a saw instead of a
dryer
for example.


Sure from a protection point of view a 30A breaker doesn't see the same long
time overcurrent or instantaneous trip points as a 15A breaker. In other
words, the 30A breaker doesn't see the 1hp motor as well as a 15A breaker
and, therefore, you get better protection with a smaller breaker.

Just a question, not an argument: don't you still need to change the 30A
breaker to GFI if its now used for both dryer and portable tool(s)?








--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)

Gee, some people just have to have the last word. Otherwise, its a
very entertaining flame thread.

Mutt.

Kim wrote:


"J. Clarke" wrote in message
...
Kim wrote:


"LRod" wrote in message
...
On Wed, 16 Mar 2005 10:40:45 -0800, "Kim" wrote:


Geez, where do you guys get this stuff?

IEEE, NEC, short circuit and load flow studies, breaker/device
coordinations.

You can blindly claim all the initialed documents you want, but cite
just one specific paragraph in any reputable regulatory document that
supports your statement: "[m]aximum breaker size 15A as your motor is
only about 8A at 220V."

That's pure nonsense, and I'll be the first to apologize ot you were
you to come up with something. Of course that's a safe promise,
because you not only can't, but you won't.

Local AHJs don't count as their specific requirements are not germane
to the discussion, but I'd be happy to see them if they do exist.

--
LRod

Master Woodbutcher and seasoned termite



Shamelessly whoring my website since 1999

http://www.woodbutcher.net

Here is a portion of your statement in context as related to the above:

"Maximum breaker size 15A as your motor is only about 8A at 220V.

Where do you get that from? And if there were some sort of
relationship to breaker size and load demand, why would 15A breaker
with an 8A load be okay but not 20A or 30A breaker?"

NEC Table 430-152, dependent on the motor type, the inverse time
breakers
could go either 150%, 200% or 250% of motor load. In other words, if the
motor has no code letter, for example, you could go up to a 20A breaker
based on 8A motor running nameplate load. If the restriction falls on
200%
or 150%, then 15A CB only. But as a general practice the lowest breaker
setting should be used, hence 15A. There is no reason why, from a
protection point of view, you would want to use an 20A, 30A or larger
breaker where a 15A breaker would do. 15A CB is what I would use.

I think you're confusing code requirements for permanently installed
machinery with code requirements for portable tools.

OK you got me, but the information Table 430-152 should apply, although
not mandatory for portable tools as you suggested, as motor and breaker
characteristic don't change or care if the installation is permanent or
not.

No, they don't. But unless you are going to put some kind of exotic plug on
that tool there is no way to guarantee that it is always going to be
plugged into the outlet that has your special breaker and the guy who plugs
his dryer into that outlet is going to be really ****ed when the breaker
pops for no good reason other than that you decided to makes it undersized
to protect a tool that is now plugged in somewhere else.

For sure motor inrush current was one of the reasons for this table
perhaps also fire and electrical faults from over sized breakers - who
knows what the historical reasons were for the NEC panel decisions but you
can be sure it has much to do with safety. Don't throw out the baby with
the bath water. All I'm saying was the best protection for this motor is a
15A circuit breaker based on the OP's situation. (I've used "maximum' and
perhaps that was a wrong word choice.)

The BEST protection for this motor is a purpose made contactor with
overcurrent protection designed specifically for the purpose of protecting
motors, not a general purpose breaker stuck in a breaker panel.

If there is a hole in the wall into which a cord is to be plugged, then the
breaker on the circuit to which that hole is connected should be sized to
protect the wiring--the architect, the engineer, the inspector, the
electrician, and everyone else involved have NO control over what gets
plugged into that outlet.

There is no reason, from a protection point of view, why you would want
to call an electrician and have him remove a perfectly good 30 amp
breaker and
the associated 30 amp receptacle and replace it with a 15 amp breaker and
15 amp receptacle just because you are plugging in a saw instead of a
dryer
for example.


Sure from a protection point of view a 30A breaker doesn't see the same
long time overcurrent or instantaneous trip points as a 15A breaker. In
other words, the 30A breaker doesn't see the 1hp motor as well as a 15A
breaker and, therefore, you get better protection with a smaller breaker.

If your purpose is to protect the motor on a tool that is plugged into a
receptacle, then PUT THE PROTECTION ON THE TOOL because there is no
guarantee that it is always going to be plugged into the same receptacle.

Just a question, not an argument: don't you still need to change the 30A
breaker to GFI if its now used for both dryer and portable tool(s)?

Generally speaking the code does not address anything that happens beyond
the receptacle. There is certainly no requirement in any code I've ever
heard of that one change existing work just to plug in a tool.

If there is a requirement for a GFI on the receptacle then it will be
required regardless of what you plan to plug into it.

--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)

--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)

Just wondering if Mark Cooper ever got his jointer going or if he was
too busy alternating between laughing and getting frustrated with the
whole flamejob that was going on over a simple question. lol

How'd it work out for ya, Mark?