Horse power rating on motors

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codeunderstanding

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I have noticed on some bigger up right air compressors that on the name plate that for horse power they dont have a number. Whats there is spl. Does anyone know what that means?
 
I would imagine you would look at the plug that came on it and or in the instructions.

I did some poking around and found references to "SPL" as 'non standard rating' whatever that means.
 
i'm not sure exactly what spl is, but i've heard of this before too. the sound pressure level is the only thing i know of too w/ that acronym. anyway, horsepower is volts x amps x eff / 746. you can get you FLC from there. the nameplate should at least give you the volts and v.a. the only thing i can tell you is to figure the FLC off the horsepower rating listed in the brochure or manual. you can be assured the actual hp is much less.
 
Some up right compressors and many consumer power tools list peak HP. My understanding of this rating is 1. It looks good WOW a 5HP motor 2. Peak is durn near lock rotor. 3. Actual operational HP is below this rating.
 
"Special" because they aren't going to put the actual NEMA rated HP on the name plate.
The HP show on the compressor is the manufacturer's definition and does not relate to a standard so it can't be compared to other compressor manufactures who boast the same HP.
 
If you go to your local big box and check the name plate on the "5 hp" air compressors, you'll note it says SPL. Its 5 hp at LRA or something similar, as they have a 120 volt 15A cord cap. NEC table value on a 5 hp 115 v motor is 53 amps!
 
If I were to make baseless, untested, zero supporting data statements similar to consumer grade compressor marketing, it would be called "lying". The junior engineers club would take my secret decoder ring, break my slide rule, and ban me from thinking in vectors.

When a marketing dept does this, its called "creative".

There is no way a cord and plug, 15A, 120V, single phase motor will produce 5hp - even for milliseconds.

I would like to gently point out a couple of things:
1. At Locked Rotor the power output is zero.

2. Assuming a single phase torque curve looks about like a Design B, 3phase (probably not a bad assumption):
Max torque is about 225% at about 80% rpm which gives a max hp of 2.25 X .8 = 1.8. Now, figure about 1hp continuous is about all you can pull on a 15A, 120V ckt, that equates to 1.8hp max just before it slides down the torque curve into stall.

3. Then someone always says, "Well you can use the number to compare two different units." Really. Humm, both units have the the same VA/A and the same 15A cord cap. One says "5hp" and the other says "3.5hp". Now, which one is better?

carl
 
several years ago one of the major air compressor manufactorers got sued because the hp rating was not correct, spl stands for peak hp at optimal conditions which never happens but it's a good selling tool for them.
 
To find Hp on single phase motors:

Volts x Amps X EFF X PF
_______________________ = HP
746
 
SPL = Sears Power Level or at least it should be, as they seems to be one of the first big offenders of this peak rating system.
 
John Valdes said:
To find Hp on single phase motors:

Volts x Amps X EFF X PF
_______________________ = HP
746
Click to expand...

Hummm where do we get this EFF and PF. I don't think I have ever seen these numbers associated with a consummer grade, motor-driven appliance.

I'd recommend using Table 430.248 - which is a bit conservative. Most of the industrial rated stuff I've seen (quickly admitted - I have very little single phase experience), is about 12A per hp on 120V, for capacitor run. And I don't know what type motor (start winding only, cap start, cap run) is normally used on Lyra brand compressors.

So where am I going with this? If the compressor has a 15A, 120V cord cap, I would bet at least a cup of yuppie coffee (payable at a local-to-me stand) the motor is no more than 1hp contunuous, 1.8hp just before pullout.

carl
 
coulter said:
Hummm where do we get this EFF and PF. I don't think I have ever seen these numbers associated with a consummer grade, motor-driven appliance.

I'd recommend using Table 430.248 - which is a bit conservative. Most of the industrial rated stuff I've seen (quickly admitted - I have very little single phase experience), is about 12A per hp on 120V, for capacitor run. And I don't know what type motor (start winding only, cap start, cap run) is normally used on Lyra brand compressors.

So where am I going with this? If the compressor has a 15A, 120V cord cap, I would bet at least a cup of yuppie coffee (payable at a local-to-me stand) the motor is no more than 1hp contunuous, 1.8hp just before pullout.

carl
Click to expand...


'eff' is efficiency. 'pf' is power factor. to find EFF, use output/input. output is the work, aka HP, input is the primary. for PF, use w/va, which is watts divided by volt-amps, aka, true power/app power. hope this helps.
 
brantmacga said:
... hope this helps.
Click to expand...
Uhhh, not much. I don't recall seeing any of these numbers:
efficiency
power factor
watts
volt-amps
true power
app power

on a consumer grade air compressor nameplate.

carl
 
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