# Is this compressor big enough?



## ZBigKahuna

Hey all, i'm new to the forums and i have a couple questions for you guys.

Let me just start by saying that i am only 15, so keep in mind i'm on a budget.
Now, down to business. Within the next few months i plan on purchasing an air compressor to power a 1/2 inch. impact wrench (Ingersoll Rand 231g) and 3/8 inch air ratchet (Ingersoll Rand 170g). I won't be using the tools daily and I won't need the impact for much more than pulling a couple tires here and there and the ratchet for using on misc. bolts, nuts, etc. My main question is will a 15 gallon air compressor be enough to power the tools for what i need them for. It's 1.5 running hp, 3360 RPM, oil-lubed, cast iron cylinder, 5 CFM @ 90 psi, and has a thermal overload. 
Any and all input is appreciated.


----------



## briankmizell

Easiest way to tell is to look at the specs on each tool and see what CFM it uses at said air pressure.

You may be able to get away with using it, but I am willing to be it will be close. Chances are you will run out of air.


----------



## ZBigKahuna

Thanks for the reply. Now i have another question. Would it be better to get the 15 gallon oil-lubed unit, or a 33 gallon oil-free unit with the same CFM?


----------



## tractornut

oil lubed will be much quieter than the oil-less unit but neither one will be able to keep up with the impact and barely capable of running the air ratchet i would suggest looking for a better unit if its not in the budget to go new then try looking on craigslist or just save up to buy new. although if you have your heart set on getting one now go with the oil lubed compressor it will recover from the high air usage of the tools quicker


----------



## ZBigKahuna

Ok Thanks.

These are the 2 that its come down to.

SPEEDWAY Start to Finish™ 15 Gallon Vertical Air Compressor - 7678 - Tools - Air Compressors & Air Tools - Air Compressors

Craftsman 33 Gallon Air Compressor: Power Countless Tools with Equipment from Sears

Maybe i should wait until black friday and see if i can get a good deal on a nice 30-ish gallon, oil lubed, belt drive?


----------



## jow

ZBigKahuna,


Do you have local sources to explore various compressors? I had my challenge in 1972 on what compressor would work best for my needs. After attempting to build a larger and purchasing a smaller used interim, I settled on the attached compressor. It has met 95% of my needs related to automotive work and general handyman use. Exceptions that required more compressor vs waiting a few minutes for the compressor to catch-up (otherwise it has been perfect for my need):
High 200 + ft lbs VWs required (flywheel and rear axles)
Painting a complete car vs panels (an experienced painter needing to flow vs waiting).
These exceptions were so seldom that I had friends that loaned me larger compressors 2-3 times since 1972. Or! I took VW needs to their shops or used extended cheaters and torque wrenches.

Good Luck! (I admire your desire to work and researching "todays quality")


----------



## ZBigKahuna

I have a few stores near me (Sears, Lowe's Home Depot) but not many. I think im probably going to end up getting the 33 gallon craftsman compressor and buy a 2 year warranty on it, then in a couple years when i have the money, if the compressor is dead, i'll buy a nicer oil-lubed unit. And as i said before, i wouldn't be using it to often nor would i mind having to wait a couple minutes for the tank to fill, but i think 33 gallons should be plenty for my needs.


----------



## ZBigKahuna

Ok, i've been researching the specs. on the 33 gal. Craftsman and a couple things. 

(1). IF i buy that compressor, i'll get a 2 year warranty with it, covering it until i have the money to buy a new one in a few years.

(2). The cut-in pressure of the tank is 120 p.s.i. which means it will start re-charging before the pressure is too low to run the tools (90 p.s.i.)

(3). Oil-free engines seem extremely easy to rebuild, and i wouldn't mind having to do so if i need to, actually, i'd kind of enjoy it 

Not sure any of these count for anything, but i just thought i'd throw them out there.


----------



## ZBigKahuna

I think i've decided to go with a Craftsman Professional 27 gallon twin cylinder oil lubed, belt driven model. CFM rated at almost 6.0 @ 90 p.s.i. Hopefully this will fulfill my needs.


----------



## briankmizell

ZBigKahuna said:


> Ok, i've been researching the specs. on the 33 gal. Craftsman and a couple things.
> 
> (1). IF i buy that compressor, i'll get a 2 year warranty with it, covering it until i have the money to buy a new one in a few years.
> 
> (2). The cut-in pressure of the tank is 120 p.s.i. which means it will start re-charging before the pressure is too low to run the tools (90 p.s.i.)
> 
> (3). Oil-free engines seem extremely easy to rebuild, and i wouldn't mind having to do so if i need to, actually, i'd kind of enjoy it
> 
> Not sure any of these count for anything, but i just thought i'd throw them out there.


Even if it cuts in at 120 LBS, if it only makes say 6 SCFM @ 90LBS and your tool uses more than 6 SCFM @ 90 LBS then the compressor wont be able to keep up. 

If it uses 6.5 or 7 SCFM the tool will continue to run at optimum speed for a short while, but once the pressure falls below 90 lbs the pump wont be able to produce the same amount of air that the tool is using, and the compressor will continuously run until the tool is shut off. The longer you run that tool, the longer it will take the compressor to refill. In the long run the compressor will be prematurely worn out.

The ideal scenario would be to get a compressor that produces 33% more SCFM @ 90 LBS than the most air demanding tool you have needs @ 90 LBS.

So if you have a impact that uses 14 SCFM @ 90 LBS then you will need a compressor that produces 18.62 SCFM @ 90 LBS.

These numbers are just scenario's, not exact figures of any tool per say.


----------



## jow

*Added Air Compressor Drain Water Access Reservoir*

Please tell me what I’m missing about making a new post and excuse me for butting in but I almost fit here. LOL. My little Sears Compressor has been all I could have ever wanted for the space it needs and variety of jobs over the years.

My recent maintenance is what I wanted to post: 

An Added Air Compressor Drain Water Access Reservoir is 40 yrs late with a new 39 yr old tank in the attic stored. The compressor was not leveled with the drain at the lowest point w/o adding?? Fun Stuff! I must say I believe the oil in the condensation water in the tank helps to protect it. That also presents a problem if the ports are not large enough to remove the grease mixed in the water. 

I hope the galvanized pipe holds the water and wear between draining which will be more often now. In the attachment you will see my next goal of increasing the valve. I stepped up the reservoir's joints shown to rem grease faster vs (larger valve being adapted next) thinking the drain was complete. There Is No End To Maintenance In The Next 40 Years!


----------

