Aircompressor HP

[Draven8795]

I have a 20 gallon puma compressor 2hp. Model: pk5020vp can be wired dual voltage

After doing some reading it seems that a 110v circuit can really only handle a 1.5 hp compressor. Does this mean that.
A) the puma version is efficient enough to handle actually running on that circuit at 2hp?
B) would wiring it to 220 allow the motor to run any different or just run it at a lower amperage?

If i misspoke please correct me, just doing some research on compressor before I start doing some body work on a car and came across the voltage/amp/hp ratings.

 

[cj7jeep81]

My guess is that is "Max 2hp" or "Peak 2hp" or some other claim, and not a true 2hp. Wouldn't think there would be an advantage to 220v for that.

 

[Draven8795]

I believe it says 5hp peak, 2hp running.

 

[rockwithjason]

It will make zero difference to wire it for 220.

 

[rj440]

Check the load it pulls, you may need a 20 amp 110v plug. Smaller compressors often spike a bit over 15 amps on start up so you'll constantly trip a regular 15 amp plug.

 

[Falcon67]

You can figure it from the running amps if the data plate has it. Example:
9 amps X 120V = 1080 watts. 745 watts/hp so 1080/745 = 1.44 HP more or less. That does not account for startup surge as noted above.

You would be correct that if wired for 240V it could use smaller wire. Same watts but higher voltage. Using the same example, 1080w / 240v = 4.5A

 

[StingRay]

746 watts per HP so 110 V x 15A = 1650 watts
1650 / 746 = 2.21 HP worth of energy from a 110/15 circuit

A single phase electric motor is about 80% efficient so 2.21 x 0.80 = 1.76 HP max HP that you could run on 110V/15A.

That's on a 15 amp circuit based on the assumption of 110 volts. 110 volts can theoretically run any horsepower but the current levels at larger Hp ratings become impractical and quickly impossible because of required conductor sizes. Higher voltages allow higher powered equipment with economically priced and practical to run connections.

Our business is stuck on 208 3 phase. Everything is more expensive and difficult because we can't run 600v equipment. Electrical service upgrades at 800 amps are Expensive!

 

[pancho400cid]

The HP on a motor is the mechanical HP at the shaft. You have to divide by efficiency to get the electrical HP (aka "real" power). Then to that you have to add the magnetizing current required by the stator (aka "imaginary" power) - volumes on the interwebs about all that.

My "true" 1.5 HP Speedaire has a Dayton motor rated for 115 VAC / 22 Amps or 230 VAC / 11 Amps. Before somebody lectures us all that distribution voltages are 120/240 please note that motors are usually rated with an assumed voltage drop - so less than the nominal distribution voltage.

On the low voltage set up, my compressor would generally start the first time and run until the pressure switch tripped to shut it off. As I used air and the switch tripped again to run the motor, it would stall and then trip the 20A breaker - which you would expect and even hope for. I switched it to the high voltage set up and it runs fine.

You need to look at the nameplate current on your particular motor, but assuming it is a "true" 2 HP and ratio-ing my HP/Amps you should be in the 22 x (2/1.5) = 29.3 Amp ballpark running and the breaker and wiring would need to be rated significantly higher.... generally not a practical current in a residential setting... if that is what you have....

 

[matt_i]

It will make zero difference to wire it for 220.

I don't agree with this. I think it will start easier under load wired to 240vac. Less current draw = less back-emf.

The thing that sticks out was a tablesaw I had wired for 120vac, it was a 1-1.5 second ramp to full blade speed. Wired to high voltage (240vac) it seemed like it was "instantly at full speed".

 

[N_Jay]

If it is an option always wire for the higher voltage.
Less voltage drop in the wiring.
Most starting torque.
Less heat when running.
Less light flickering due to start up draw.

 

[Draven8795]

This is good stuff. I'll take a look at the nameplate and I can measure the amps so I"ll try that.

I was just curious because it's rated at 2hp but if you do the math it shouldn't be able to run at that hp. I've never had the breaker trip i was just curious on how they came up with the 2hp number.

 

[pancho400cid]

Manufacturer's sometimes exaggerate the HP numbers.... It got so bad on compressors that the govt. stepped in, so not quite as bad nowadays I think.

Sometimes you see "PEAK" or "MAX DEVELOPED" horsepower numbers in giant letters and the actual running HP is in 10 point type on the nameplate somewhere.

Say your compressor is running along and the Jolly Green Giant reaches out and grabs the shaft and stops the motor. The motor starts drawing way more current than when running, and will heat to the point of self destruction in less than a minute if not saved by a correctly sized and functioning over-current protection device (breaker, etc.). It is making lots and lots of torque, but is not turning. That is "MAX DEVELOPED" HP on the ELECTRICAL side of the motor... but.... on the mechanical side, the output HP is ZERO (torque x RPM = 0) and exactly ZERO useful work is being done.

 

[Draven8795]

I took my meter to it, it didn't get the start up amps but right after start up it registered 16 amps and then consistently ran at just under 15 amps.

 

[md21722]

A lot of 2HP air compressors have SPL indicated on the motor, and are actually 1.5-1.6 HP.

I have owned some true 2 HP air compressors. They required a 20A circuit at 120V.

In other cases, a true 2 HP motor can be used, but not loaded 100% so it will run on a smaller circuit.

Your compressor sounds like its a 1.5 HP.

 

[pancho400cid]

If the compressor started with the tank empty (0 psig) that is the minimum running current - basically no load current for the motor. Current will rise while the pressure is rising in the tank and be at max normal running right befor the pressure switch trips and cuts the motor off... you should check that current too, if you care. The second time the compressor starts (with pressure in the tank and starting when the pressure switch trips on low pressure), that will be worst case starting current... but a regular meter will not measure starting current as it is a transient event.