Re: Air compressor fittings and hose

On Mar 11, 4:34 pm, dpb <n...@xxxxxxx> wrote:
fftt wrote:

...



But even standard efficiency motors are in the 80%+ range with the new
premeum units having higher than 90%
so 15amps @ 120v = 1800 watts ( 2.4 hp electrical)
factoring in 85% efficiency gives you  ~2 hp
a 20amp circuit would give you 2.7 hp (at 85%)  and nearly 3 hp at 91%
so those mythical motors (1 hp at 800 watts......93.5%) may not exist
but some are pretty close
I see a lot of 1HP motors in my travels and they usually have a FLA in
the 12-13a range on the nameplate.

I see a lot of 1HP motors in my travels and they usually have a FLA in
the 12-13a range on the nameplate. <<<<

I'm not disputing  what you see but I'm pretty sure my calcs & info
are correct; based on the definition of a hp(E)  and typical motor
efficiencies.

Maybe the motors have really bad efficiencies or the mfr's have them
tagged "conservatively" ?

The current draw for even an "old school"  / giant motor   1hp should
be ~7.5 or so...
I remember my dad having a GIANT 1hp rated motor from the 60's & the
nameplate read 7.2 / 3.6

....12 to 13 amps seems way too high.  JMHO

You're leaving out the other factor besides the efficiency (as well as
assuming new motors of only 1 hp are really built to such high
efficiency numbers) which is the power factor.

Spec's for a fairly typical Baldor (not inexpensive) general-purpose 1hp
motor...

Catalog Number:         VL3509
Specification Number:   35C013X964
Horsepower:              1
Voltage:                115/230
Hertz:                  60
Phase:                   1
Full Load Amps:         11.8/5.9
Usable at 208 Volts:    6.1
RPM:                   3450
Frame Size:             56C
Service Factor:         1.25
...
Full Load Efficiency:   68
Power Factor:           82
...

hp = 115*11.8*0.68*0.82/748 --> 1.0

This is a list price motor of $400.

At least a couple in the same general classification were 0.65/0.65
efficience/power factor (at roughly $300 price point).

One of their (very few at this low a hp) premium efficiency 1hp motors is

Catalog Number:         EL3510
Specification Number:   35J385S758G1
Horsepower:             1
Voltage:                115/230
Hertz:                  60
Phase:                  1
Full Load Amps:         8.5/4.25
Usable at 208 Volts:    N/A
RPM:                    1760
...
Full Load Efficiency:   82.5
Power Factor:           91

hp = 115*8.5*0.82.5*0.91/748 --> 0.98

That comes at a price, however -- $643 catalog list

At a high-enough usage and for long enough, eventually one would make up
the initial cost difference, but for intermittent use it would take
quite a long time.

--

Duane-

Thanks for the detailed response. Good comment about super high
efficiency motors being expensive / rare in the 1 hp range.

Your analysis explains why the other post "I see a lot of 1HP
motors in my travels and they usually have a FLA in
the 12-13a range on the nameplate" is, in fact, correct.

I had no idea that typical 1hp motors have efficiencies & PF's that
low. :(

I guess that's why SoCal Edison gives such good rebates on the
purchase of high efficiency pool pump motors.

cheers
Bob
.

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