5hp motor versus 10hp power output

First off before people jump all over me and tell me we need to use a 10 hp motor. I want to state that we have ordered the correct 10hp motor we need with 215t case, power inverter, and magnetic starter.

The situation is we have installed some new equipment that require much more air than our old 220v compressor can keep up with RIGHT NOW. So we are RIGHT NOW adding an extra 120 gallon tank for additional storage capacity, upgrading the pump to one that puts out 43 cfm at 175 psi. Which will require the 10hp motor (220v or 3 phase with inverter) to power it correctly THAT WE ORDERED. But it will be weeks before the correct motor arrives. We do have two 5hp motors from old compressors. Would two 5hp compressor motors be able to power a pump that requires a 10hp motor? THIS IS TEMPORARILY SPEAKING! How would a single 10hp motor power or torque compare to two 5hp motors? Or is two 5hp motors far less or more power than a single 10hp motor? Is there additional information that is require first to determine this like amps, efficiency rating, or some other specifications from the different motors?

Like I have said I am curious if we can run a setup like these two 5hp motors to temporarily run this pump in place of a 10hp motor without completely burning up the 5hp motors? I am not interested in making a mess and destroying these 5hp motors but if we could set this up for a couple weeks and run the system with any level of stability that be great until the correct components arrive here next month. Thanks in advance to anyone who took the time to supply an actual answer or information and not just talk smack.

Practically speaking, what kind of contraption will you have to make to configure the mounting of 2 motors to the pump?
You need a good 150 degree arc of contact on the driving pulley, so it's not enough to just pass the belt over the groove of one motor and think it is going to help. So then you're going to have to mount the second motor on the opposite side via a bunch of bracketry. That isn't going to get done in less time than you can drive somewhere and just pick up the components you need, is it? Never time to do it right but always time to do it over.

I "feel" or "tlar" that it would work fine.

I Think:
If your vfd settings are "soft" in terms of pid parameters, neither motor should much care for a tiny bit lower / higher speeds /amps/loads and the load should spread fairly evenly.
As simple as bolting a second pulley to the previous one, and running a new sectioned belt to the second motor mounted somewhere out of the way.

Neither 3-phase motors nor vfds care about running under/overloaded to some extent.
And the vfds should trip way before anything goes wrong.
And the amps on vfd and motor temps should clearly show that you have fairly good balance.

Maybe thermal paste a 5$ mechanical termometer on each motor case ?

If you had "judder" or heavy inertial peak loads, and were trying to do motion control or steady-state apps I would suspect it´s a bad idea.
For basic loads - probably run just fine.
Imo.

It sounds Rude Goldberg at first, but I know of nothing that makes me think it´s a bad idea.

As long as you can mount them, should be ok but they will not share load equally unless they are matched motors. The slip will be different between the motors which means that one will hog more load (and produce more torque) than the other - but they should be close enough unless you have no head room in horsepower requirement.

Remember that you need separate overload protection for each motor.

HuFlungDung said:

Practically speaking, what kind of contraption will you have to make to configure the mounting of 2 motors to the pump?

Click to expand...

Like I said I already have ordered the correct parts. The new pump and larger 10hp motor are far too large to mount on top of the vertical tanks like the smaller set up is now, we are already building a metal rack for them. Having tall ceilings I would rather keep everything vertical So we are welding something together that either sits above the tanks or next to them. It's not going to be an issue or hoaky based on any design ideas you have in mind of someone rigging things together with duct tape. As for assembly we would place one 5hp motor on either side of the pump so each uses its own groove on the pump pulley and sets up just like a normal compressor would just not on top of the tank itself. The motors both would have the correct pulley to rotate the pump at the same speed. Like I said this is just to keep our machines up and running while the new 10hp motor is being shipped. By ordering the new motor online we got it for less than half (with shipping and no tax) than the cost of going up the street and buying it retail for over $800 plus tax. So if we have to drill a couple extra holes to mount an extra old 5hp motor off to the side of the new pump rack we already are having to build and it gets us up and running now in the meantime and not 3 weeks from now it's by far worth it. I realize one motor may carry a slight more of the load than the other. But my main concern is a 10hp motor basically the same strength as two 5hp motors or is it not comparable where a 10hp motor is more like 3 - 5hp motors, and a 20hp motor is stronger than 3 - 10hp motors. Where the scale jumps to each motor size or something of a deferent scale.

Right now everything is setup for 220v where we can just plug in and install 2 - 5hp motors easily. But the phase inverter, and magnetic starter are all being shipping with the new motor. So I am really hoping we can used the 2nd 220v 5hp motor right now just to keep the shop up and running while we have time to get the rest of the parts shipped and assembled without being under the gun of not having any air in the shop. Like I said multiple times this is a temporary fix to keep us up and running while the correct stuff arrives. I don't need a lecture to buy the correct 10hp motor, since I have already done so. I am just curious if the 2 - 5hp motors will function and be safe without worry of burning up or seizing.

Thanks in advance for those who took the time and offered real advice about the performance of 2 - 5hp motors vs a single 10hp motor like I asked for.

I never assumed you would do this in a half-assed manner. That is why I questioned the cost effectiveness of 'saving money' by buying a cheap motor online somewhere. The savings will be eaten up in extra mount work, an extra motor starter and associated wiring and an extra pulley. Plus tearing it down and putting the right stuff on.

One can run a 10 or 15hp pump off of a 5HP motor when in a tight situation.
Reduce the drive pulley size if you can, makes a big difference, back way off the top cutout pressure.
Set the breakers or fuses to the 5hp. I've done this hack more than once.
Bob

viragocafe said:

... my main concern is a 10hp motor basically the same strength as two 5hp motors or is it not comparable where a 10hp motor is more like 3 - 5hp motors, and a 20hp motor is stronger than 3 - 10hp motors.

Click to expand...

No, you gottit fine. Horsepower is horsepower, (2)x(5)=10, it'll work okay. I like the separate belts idea, instead of trying to mate them together somehow.

hmm.. lets see.. 5 + 5, what is that.. oh! 10. it is horsePOWER.

as long as they are NEMA HP rated motors, NOT " compressor duty" motors, that is total bullshit where they don't put the real horsepower on the plate so the compressor manufacturer can claim whatever number they want ("stall" hp?)

oh, and you are doing all this nonsense to save 400? that rates a second one for sure

CarbideBob said:

One can run a 10 or 15hp pump off of a 5HP motor when in a tight situation.
Reduce the drive pulley size if you can, makes a big difference, back way off the top cutout pressure.
Set the breakers or fuses to the 5hp. I've done this hack more than once.
Bob

Click to expand...

If you did this and found yourself still short of air, I'd pick up a cheap unit from HF as a supplemental source.

Sent from my SM-G973U using Tapatalk

I've seen worse contraptions save the day. Properly done you'll be fine.

If one motor draws to many amps and overheats, cut the corresponding sheave on the compressor down slightly.

I've heard of a pump at a mine site being powered off junk pile 2, 3 and 5 Hp motors, they were all the same RPM and were connected to the pump via belts and pulleys. A clamp meter confirmed they were all drawing their rated currents, so it does work but in the event of one motor dropping out there will be overload problems. AC induction motors will exceed their rated power in an attempt to maintain their design RPMs.

As carbidebob said if your demand is low enough you can run it on a 5hp by using a drive pulley half the diameter hence half the speed,same pressure.
Most small recip compressor pumps have at least 2 hp requirements.Most 10hp's I've seen are rated for 7-1/2 or 10hp;the 7-1/2 speed is 75% of the 10hp,same for 5 & 7-1/2hp pumps.The only problem is to low rpm on splash oiled pumps may be a problem.

If you can find the specs for the pump it may tell what the parameters are.

It sounds like a sound idea to me.

Do let us know how it works out. And post some photos.

Be careful slowing the compressor down. Many will have a minimum RPM listed for adequate splash lube.

What you propose will work fine but as SAG180 said make sure both 5hps are the same rpm as the 10hp or else it won't work.Actually the 2 5's may handle an overload better than the 10 as the heat would be dispersed over a larger area.

If I could jump in here, I have a question/comment re air compressors in general. As will most likely become apparent quickly I am no expert on the subject, but at least we may get some sarcastic witty replies.
So I hook up my air tool, say a real air hog die grinder what have you. Start working away 4 5 min later the tool starts slowing down then the cnc drops out of cycle due low shop air, then and only then does the jeesless compressor kick on. Granted the system as is it ain't to bad, allows time for a coffee and cigarette while coming up to pressure once again for the third time.
We are running a Quincey Q10 I think, it has an 80 gallon tank, 10 hp mtr and 2" ID pipe supplying the shops drops. It has the standard little gray box, sensing when to turn on, yes it is adjusted correctly.
I was thinking the other day why not use an Arduino, or equivalent little brain box, cheapo sensor (measuring cfm) to sense quickly how many CFMs are exiting the tank and a VFD. Configure the system to start the compressor when CFM use jumps up and use the VFD to keep the motor running faster or slower depending on demand. Yes I realize has many pit falls, including letting the smoke out of your motor. Hey its what us arm chair enginerds do. But for small shop like ours would it not be a viable idea???
So instead of putting together a huge mechanical contrivance put your vfd on the 5hp mtr and give her all the Hz she will suffer till your 10 HP arrives. If ya blow up your 5 hp motor, well you have a 10 coming in.
Here hold my beer I'll show you how it is done.

doug8cat said:

Here hold my beer I'll show you how it is done.

Click to expand...

LOL! I'm too fragging frugal to blow money on false economy and expect the so-called saving to run the core business FOR me that I've had to neglect for the sake of diverting to take-on a monkey-patching project for no real payback time.

Yah NEED the bugger to earn a crust, yah DON'T order a 10 HP motor that takes multiple weeks. Yah picks it up same-day or orders one that SHIPS same-day, expedited delivery and get 'er DONE! High-volume dealers that ship fast are also price competitive. That's why they HAVE high volume.

Meanwhile?

Call the rental agency, get a serious jobsite trailer mount 'presser over, oh-dark daylight and a half of tomorrow morning, park the bitch, run a line and some conditioning foo plumbing with pressure-buffering to the tank so we can ALL get TF back to earning a crust!

TEN HP is a piss-ant, you got a crew running demo hammers.

Doesn't even have to carry the max pressure. Carry the heavy-lifting on volume, the 5 HP can do the pressure top-up:

Here. Sunbelt. They sure as hell have local competition:

Gas Powered & Electric Air Compressor Rentals | Sunbelt Rentals

She'll do, mate.

$400 buck saving was that important? PLAN FURTHER AHEAD next go!

Else close the shop and go fishing 'til the savings arrive and you can save HVAC, wages and overhead, too.

Monkey-patching has a higher priority than wiser planning, make sure it is fish you can eat, 'coz you may have to get used to that diet.

Now.. about having yer ass kicked clear up between yer shoulder blades, and into the middle of next week as well? Side bizness, I happen to know a good tailor can cut a suit so nicely as to make a hunchback look like a f*****g Hollywood movie star - or even a US President, yah don't mind a cheap orange wig and half a Kotex - recycled if the budget is really that tight - stuffed into each cheek. (You wondered why he's always saying dumb stuff? Distraction might do that, yah think?)

Didn't really think I was doin' this Old Fart Advice shit for FREE didja?

gbent said:

Be careful slowing the compressor down. Many will have a minimum RPM listed for adequate splash lube.

Click to expand...

Yes, half speed is too slow for almost all pumps. Not only lube but long run times.
Think more about a 15-25% reduction and a 25% pullback on cutout.
It is not right but sometimes you need to do what you need to do.
Bob

CarbideBob said:

Yes, half speed is too slow for almost all pumps. Not only lube but long run times.
Think more about a 15-25% reduction and a 25% pullback on cutout.
It is not right but sometimes you need to do what you need to do.
Bob

Click to expand...

Look at you, being a Practical Machinist.