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.



wrote in message
...
On Wed, 05 May 2010 20:13:39 GMT, (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.




In article
,
" wrote:
On May 5, 12:30=A0pm, Chris Friesen wrote:
On 05/05/2010 10:59 AM, wrote:

On May 5, 11:48 am, Chris Friesen 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]




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