Compressor motor questions - Ingersoll Rand T30 7100

[Jason Copland]

Hello all,
I recently acquired an Ingersoll Rand T30 7100 compressor for very little money (it needs a new pressure switch and the garage I got it from just bought a new, bigger compressor rather than fix this one). I got it very cheap :-)
I have questions on the motor and what options I might have. Currently the compressor is fitted with a huge three phase motor - unfortunately the id tag is illegible so I don't know exactly what size the motor is but according the Ingersoll Rand's data sheet it will either be a 10 or 15hp motor. I don't have mains three phase in my home workshop, I use a rotary phase converter for my 3 phase machines but that's rated at only 7.5hp so it won't be man enough to power the compressor.
So what are my best options? I could try to find a single phase motor of 10hp rating but that's going to draw probably around 100amps at full start load and my home wiring is only 60amp so that's not an option really.
I could get a larger RPC but they are quite spendy and I don't really need the extra capacity it for anything other than this compressor.
Could I muck about with a smaller hp motor and different pulley sizes? Getting 3phase mains is not an option here unfortunately (rented house, landlord not keen on the idea).
Any other options that people can think of?
Many thanks for your help. Cheers

 

[Erie Fred]

What I did with a 10 hp Quincy for many years.
Go with a smaller pulley (75%) and use a start box on the original 3-phase motor.
You'll only get 75% of the rated HP from the motor, but reducing the pulley
will allow it to work.
Make sure you don't go too slow, or the lube system won't work (I'm sure google will find you the t-30's RPM limits)

 

[Jason Copland]

Many thanks Fred, that sounds like an option. One question though, what did you mean by "use a start box"? (just to clarify again, the most my RPC will put out is 7.5hp and the minimum the compressor motor has is 10hp)
You're right, Google did give me the minimum speed on the compressor - 800rpm.

 

[Erie Fred]

Many thanks Fred, that sounds like an option. One question though, what did you mean by "use a start box"? (just to clarify again, the most my RPC will put out is 7.5hp and the minimum the compressor motor has is 10hp)
You're right, Google did give me the minimum speed on the compressor - 800rpm.

It's just a voltage sensing switch and start capacitor.
Once up to speed, the 3 phase motor simply runs on single phase (much like your RPC does) you could add some run caps to balance things a little bit.

https://cedarberg.com/files/cedarberg/ckfinder/files/PhaseConvCatWeb.pdf

 

[Jason Copland]

Just back with another thought - I have another compressor with a dud pump (that's why I'm keen to get the IR up and running) The old compressor has a 4.4kw single phase motor fitted - I'm wondering if I can use that motor to run the IR. I know I'll need to down size the motor pulley and I think I'll have to drop the maximum psi as otherwise I think the motor will struggle once the pressure is getting high. The IR is designed to run up to 175psi - way beyond what I ever use, so far the most I've ever needed was 120psi and I set the pressure switch to turn off at 120psi - I could do the same on the IR.
Would this solution work? It would be a simple swap over for me to do as I have nearly everything already here.
Thanks

 

[Erie Fred]

One of the ideas for running 175 psi, is the more air the receiver holds.
Yes. you regulate it down to 125 psi, but by running up to 175 psi, your storing that much more.
As with most of these problems, your limited by electrical service, no easy way around it.

 

[Jason Copland]

Thanks Fred, you're right, it will be less air but with a 500ltr tank that doesn't bother me much - my old compressor had a 270ltr tank so I'd still be better off.
The problem is as you say, electrical supply.
Cheers

 

[awemawson]

When I wanted to run a very large compressor for my NC machine (Moog Hydrapoint 1000) years back and my Transwave rotary converter wasn't big enough I removed the reed valves from one of the three cylinders (it was a Prestcold Freezer room compressor) and ran it on two. Ran happily like that for several years.

 

[not done it yet]

Andrew,

I just looked up that compressor. Appears to be a two-stage jobbie, so disconnecting anything seems to be out of the question.

There are reasons why they sell cheap…..

 

[Popcorn]

https://www.portlandcompressor.com/docs/compressors/datasheets/IR-7100-datasheet.pdf

 

[not done it yet]

You're right, Google did give me the minimum speed on the compressor - 800rpm.

Jason,

Do you have a link for that? I only found different specs (800 and 1100rpm) but nothing which stated the minimum operating speed for the pump. It may depend on whether the crank bearings are fed through the dipper or simply by splash.