Compressor determination??

[whejdak]

I have a large IR compressor. The unit has what I believe to be the original compressor pistons (unit}. I don't believe the motor is original nor do I believe the HP rating on the motor that came with it. I.e. I think the motor doesn't belong to this compressor.
How do you determine what HP the compressor (cyclinder head part) requires. It says that it is an IR 234 - *** unit but no indication of HP ratings.
I've seen similar unit on line with 3 phase motors, I have also seen similar units with single phase 5 hp units.
I'm still away from hydro testing the tank. It's to feak'en cold out. But, assuming it passes that test I will be putting the unit back together and try to compress some air. I'm afraid that the Vevor 5 hp single phase unit is not the right one. Don't know why, but I bought it before thinking it out.
I can always get a VFD to create the 3 phase for a 3 phase motor, but a cost prohibitive way of doing it.
Thoughts on how to calculate HP size motor for this compressor.

 

[GrayFlattop]

You need to find out what the model number is of the pump. Any given pump can be operated off of a range of motor (within limits), but at different pump speeds. My champion pump was supplied from the factory with 5, 7.5 and 10 HP motors, but would use a different size pulley on the motor. It isn't really a guessing game, you need more information.

Anything over 5HP will be a challenge with single phase power (and the motor cost rises quite a bit). Beware of "fake" horsepower ratings on motors for compressors. The "fake 5" motors only draw around 12-13 amps @230V a real 5 hp motor will draw closer to 23-24 amps@ 230V.

 

[Monza Harry]

The "fake 5" motors only draw around 12-13 amps @230V a real 5 hp motor will draw closer to 23-24 amps@ 230V.

My IR 5HP has a Baldor with an amp draw of 26.4 FLA so yeah 15 amps is only a 3HP. Harry

 

[The Cobbler]

as said, you need the model of the pump and see what the HP ratings are. otherwise you're guessing. and the RPM of the pump matters, for splash lubricated pumps the RPM needs to be within spec'd parameters to assure proper " splash "

 

[whejdak]

As I said, the name plate on the pump only gives the Model number and serial number. No HP ratings. I've looked up the model number and haven't found anything related to the HP.
I've been thinking this over. PSI and CFM and Volume. With an empty take, all compressor pumps would be at minimum load.
So, mimimum HP needed at first. AS the PSI builds, the HP requirements would start to rise until the tanks regulator is sustained.
So really, the real quesition is "how much HP do I need to attain a certain PSI rating." Right. Assuming I don't care about the CFM's right now.
I also know that there has to be a certain speed that the pumps can go up and down without blowing apart. That is controlled by the pulley's and the motor speed.

So right now i'm down to this. Motor 3400 speed, shaft 2 inch , driven pully shaft about 13 inches. This should keep a resonable speed.
How long it will take to do it is unknown and what size HP motor will be needed to get the PSI top rating that I want.

Does this make sense?

 

[BobnCO]

With the model number of the pump you can get he design H.P. rating. Might have to call I.R. , however I have looked up to a older pumps on their website within prior year

 

[whejdak]

With the model number of the pump you can get he design H.P. rating. Might have to call I.R. , however I have looked up to a older pumps on their website within prior year

You have to get someone form IR to respond. That's the real problem. Thought about this already and tried.

 

[stonesfan68]

The IR 234 compressor is rated from 3 - 5HP. The power goes up as the speed of the compressor goes up. The compressor sheave is a standard size. The motor pulley size is dependent on the motor RPM and power rating. Your local distributor can get you the engineering data page for the bare compressor.

 

[whejdak]

I think you mean that the HP needed will increase as the PSI in the tank rises. The speed would be for CFM.
3-5 sounds resonable. I'll have to play with the pulley sizing. I purchased 4", 2 1/2" and 2" pulley's in addition to the 6 inch that was on the motor provided with the unit.
No such thing as getting engineering data page for the bare compressor from my local distributor. Who ever that might be.
But thanks for your input.

 

[TRWham]

I think you mean that the HP needed will increase as the PSI in the tank rises. The speed would be for CFM.
3-5 sounds resonable. I'll have to play with the pulley sizing. I purchased 4", 2 1/2" and 2" pulley's in addition to the 6 inch that was on the motor provided with the unit.
No such thing as getting engineering data page for the bare compressor from my local distributor. Who ever that might be.
But thanks for your input.

Power also increases with increased compressor speed because more work is required to compress more air even at the same pressure differential.

 

[whejdak]

Although you are right about needing more HP to get to the high pressure point sooner. I don't care about that.
I need to find HP size motor to run from the start to the end pressure point. It looks like pulley sizing will play a big part in this. If it takes 1 minute or it takes 1 hour, the HP needed to get there is what I'm looking for. At some point while loading up the motor is going to hit a wall unless the HP is large enough to overcome the resistance in pressure against it.

I thank all that have commented and will pursue suggestions.

 

[carlaisle]

The HP required in the application of a compressor of this type has (virtually) nothing to do with PSI. Rather, it is a function of pump RPM. The more CFM you want the pump to put out at a given pressure, the more HP you need. Any compressor duty motor with a nameplate rating of at least 2 HP should be capable of running your compressor with the appropriate size motor pulley installed. You could actually get away with a smaller HP motor as long you are A) willing to accept a lower CFM and B) the compressor minimum RPM rating is not violated.

A brief search on the model number you provided indicates it came equipped from IR with a 2, 3, or 5 HP motor which will deliver 7, 9.2, or 14.3 CFM at 175PSI. You said the flywheel is about 13". I found it listed as 13.75". The only other two things you need to find via your internet sleuthing are the minimum and maximum rated RPM for your compressor model. Use a pulley calculator to derive the appropriate motor pulley size based on the motor RPM you intend to use.

A 2" pulley driven by a 3,400 RPM motor will turn a 13.75" flywheel at 541 RPM. This is "probably" within the minimum/maximum range for your compressor, but it would be wise to confirm. Turning it too slow can provide inadequate lubrication and thus cause premature wear. I see two Vevor 5HP compressor motors, one with a 22 amp rating and one with 15. Either one should be capable with the 2" pulley. Try it and check the amp draw. If you have room to run, move to the bigger one to if more CFM is desired.

 

[whejdak]

Carlaisle,
Very good explanation. You found more info on this unit then I could find. Good stuff.
Also an unknown was the compressor speed. I've seen several comments on keeping it in the less then 1000 rpm range for compressors.
I have a large guard over the belts and kind of guessed at the 13" range on the compressor wheel. 13.75" sounds right.
Right now it's about 27 degrees in my pole barn. so not much going on out there. my next step is the hydro test the tank. If it passes, I'm all in on what you said above.
Thanks

 

[whejdak]

One more and the last input here
IR contacted through e-mail. Got exactly what I need from them.
They actually found the Engineering Data Sheet for the 234 compressor that I have.
Great job from IR