Air compressor controls

[Mike OMelia]

I have a Kobalt 60 gallon, 3hp compressor. I bought it off craigslist one year ago... It was about a year old when I got it. Performs well, no problems. But I have no idea what the pressure cutoff point is. I've had it up to 110 psi and it was still rolling. As if now, I have no requirement above 100 psi. As far as I can tell, the max pressure set point is not adjustable. Questions are, what is the setpoint, can I modify it, and is there an add-on device I can purchase to make it modifiable (given that the OEM stuff cannot be adjusted?) yes, I am aware if pressure regulators, but I would like it to run at a lower duty cycle.

Thanks!

Mike

[Michael Flores]

Mike, Im not sure exactly what you are asking but im sure some can come in and correct me. The question is why would you want to change the cut off point? I have an IR compressor that cuts off at 150 psi's. The higher the psi's in the tank means the longer you can run your tools with out the pump kickin in. As far as the duty cycle is concerned. The duty cycle is set by the manufacturer when they design the machine that deals with the heat generated. If the compressor is rated at a 30% duty cycle, it means for every 3 minutes off run time, it needs 7 minutes to cool down. I had a little 20 gallon than would not shut off for nothing when i was using any kind of sanders. I was lucky i didn't burn it out. Now i have the big IR and it only goes on for a little while to refill the tank while im using the sanders.

[Rick Lizek]

It is adjustable but for single stage compressors is preset at the factory to shut off around 120 lbs and cycle on at 90 lbs. Having the 120 cutoff give you some reserve or your compressor will be working more which is the opposite of what you are truying to do. I would suspect they don't tell people how to adjust things is they don't want folks to adjust them. The fact that you don't even know at what pressure it stops gives me concern...just look at the gauge when it shuts off.

[Frederick Rowe]

Mike - As Michael and Rick mentioned, having your compressor run to it's max - say 150 PSI- gives you a reserve of air for your tools so that the compressor is not running whenever the demand exists. The motor uses a lot more amps to start up than when its running. Therefore it is more efficient to have the compressor running for a longer period of time rather than cycling on and off to keep the tank in a narrow PSIrange for the tool you are using.

Your max PSI as well as cut in and cut out pressure should be indicated somewhere on your tank. Where you can make an adjustment, is lowering your cut in pressure.

For example. A compressor has a cut off pressure of 150 PSI and a cut in pressure of 120 PSI. Your air tool only requires 50 PSI(a spray gun), you can lower your cut in pressure to 60 or 70 PSI. This would reduce the number of times the compressor cycles (the total run time would be the same) to store the same volume of air. This will reduce electrical use and some wear and tear on the motor, albeit by a very small amount.

If you reduce the cut in pressure to the minimum required by the tool, your compressor will need to have the capability to produce the minimum SCFM needed by the tool - and while doing this it may not be adding to the pressure of the tank. For example, if your spray gun requires 13 SCFM and your compressor only produces 10 SCFM, you'll need the compressor to cut in before the PSI level drops to the minimum level otherwise the compressor won't be able to keep up with the tool.

Air tools vary with respect to psi and SCFM requirements. An HVLP spray gun and a nailer have much different requirements. If you decide to change any settings on your compressor, make sure it will produce sufficient PSI for all your tools.

The cut in and cut out pressures can be adjusted by a small amount via screws in the pressure switch. The pressure switch is a small plastic box with power leads. Attached are photos of a typical pressure switch and internal set screws. One screw adjusts cut in pressure, the other cut out pressure. To change, run the compressor to max PSI then open dump valve and watch pressure gauge to see when the compressor kicks in. That is your cut in pressure (cut out pressure is when the compressor shuts off). Note the position of the set screws and turn one of them a 1/4 turn. Repeat compressor start up and note cut off pressure. If it changes from your first cycle, then that screw controls the cut off pressure. If the cut off pressure remains the same, then open the dump valve and note when the compressor kicks in. If that pressure changes, then you know that set screw controls cut in pressure. Make adjustments accordingly.

Never set the cut out pressure above the max PSI rating of your unit.

You will likely only be able to change the range of cut out and cut in by 20-40 PSI. They are designed to work in defined ranges - not be infinitely adjustable. If you really need a different range of air PSI, you can replace your pressure switch with one of a different range. Here is link to General Air Products. They sell replacement pressure switches.
http://generalairproducts.thomasnet.com/viewitems/pressure-switches/69j-series-pressure-switches?

[John Coloccia]

I have a Kobalt 60 gallon, 3hp compressor. I bought it off craigslist one year ago... It was about a year old when I got it. Performs well, no problems. But I have no idea what the pressure cutoff point is. I've had it up to 110 psi and it was still rolling. As if now, I have no requirement above 100 psi. As far as I can tell, the max pressure set point is not adjustable. Questions are, what is the setpoint, can I modify it, and is there an add-on device I can purchase to make it modifiable (given that the OEM stuff cannot be adjusted?) yes, I am aware if pressure regulators, but I would like it to run at a lower duty cycle.

Thanks!

Mike

If it's the one I think it is, I think it's set to 135PSI. As others have said, a max should be listed on the tank. Also, there should be a relief valve on the tank. You should check that periodically anyway.

[Julian Wong]

I have a Kobalt 60 gallon, 3hp compressor. I bought it off craigslist one year ago... It was about a year old when I got it. Performs well, no problems. But I have no idea what the pressure cutoff point is. I've had it up to 110 psi and it was still rolling. As if now, I have no requirement above 100 psi. As far as I can tell, the max pressure set point is not adjustable. Questions are, what is the setpoint, can I modify it, and is there an add-on device I can purchase to make it modifiable (given that the OEM stuff cannot be adjusted?) yes, I am aware if pressure regulators, but I would like it to run at a lower duty cycle.

Thanks!

Mike

Mike, if yours is like my Kolbalt (depends on year of manufacture - diff manufacturer produce the kobalt line), the cut off pressure should be at 135psi, and cut in @ 110psi. I have a Condor brand pressure switch, both the cut in and out pressure can be adjusted. Google Condor pressure switch to find your exact model. But I wouldn't adjust it if I were you. Like other have said, it will hold more air before you run out/refill, especially if you use sanders, die grinders or spray guns.

[Josiah Bartlett]

There's another reason why you might not want to mess with this... single phase induction motors are usually rated so they shouldn't be started more than 6 times an hour. For this reason, some continuous duty rated compressors (like Quincy) have dual controls. My Quincy has an air operated unloader system that I can turn on that regulates the pressure on the tank without starting and stopping the motor, by unloading the intake valves to keep the compressor from compressing. Its very useful when painting or running a DA sander- it keeps the system happy.

By lowering the max pressure on your tank, you are lowering the storage capacity of the tank. For a given amount of air consumption, the compressor will have to cycle more often, even if the motor doesn't have to run as long per cycle.

[Mike OMelia]

OK, thanks. I don't know why I fear the thing... guess I should just let it run till it cuts off. Now, I did buy a pressure regulator once (from Lowes) but for some reason, I never got it to work right...again, I am exposing my ignorance. I put a guage on the end of the line, set the pressure at the regulator, but the pressure on the end of line gauge never seemed to be the same.

Mike

[Julian Wong]

OK, thanks. I don't know why I fear the thing... guess I should just let it run till it cuts off. Now, I did buy a pressure regulator once (from Lowes) but for some reason, I never got it to work right...again, I am exposing my ignorance. I put a guage on the end of the line, set the pressure at the regulator, but the pressure on the end of line gauge never seemed to be the same.

Mike


If your air line run is long, you may experience pressure drop during high usage if your end pressure is close to the tank pressure. When you use the tool (especially high volume tools), the air pressure in the air line drops, that's why the line gauge pressure may fluctuate.

To minimize pressure loss, you will want to maintain as high as possible tank pressure and regulate the pressure at the tool end.

[Jeff Monson]

Mike, When using a regulator I have a psi gage after the regulator, otherwise you are just reading tank pressure, to do it right you will have to put in another psi gage right after the regulator. To set the regulator (mine anyways) you turn the adjusting knob counterclockwise to reduce pressure and clockwise to increase pressure. I always hook up a blow gun or my spray gun and turn them on while setting pressure with the regulator, you will hear the pressure change and with the second gage you can dial it into any pressure you want, then just tighten the lock nut and you are ready. I have always sprayed at 22lbs of pressure, with the use of a good quality regulator, just have to remember to increase pressure when filling tires, or cleaning the shop :)

[Mike OMelia]

Mike, When using a regulator I have a psi gage after the regulator, otherwise you are just reading tank pressure, to do it right you will have to put in another psi gage right after the regulator. To set the regulator (mine anyways) you turn the adjusting knob counterclockwise to reduce pressure and clockwise to increase pressure. I always hook up a blow gun or my spray gun and turn them on while setting pressure with the regulator, you will hear the pressure change and with the second gage you can dial it into any pressure you want, then just tighten the lock nut and you are ready. I have always sprayed at 22lbs of pressure, with the use of a good quality regulator, just have to remember to increase pressure when filling tires, or cleaning the shop :)

Aha! Running the tool while making the setting makes sense! I went and studied diagrams on how pressure regulators work and could not see how you could do it unless air was flowing through the device. Thanks! Is the regulator you can get at lowes OK?

[Jeff Monson]

Aha! Running the tool while making the setting makes sense! I went and studied diagrams on how pressure regulators work and could not see how you could do it unless air was flowing through the device. Thanks! Is the regulator you can get at lowes OK?

Not sure on the lowes brand Mike, but I have had a couple of very cheap regulators over time, my finding is a regulator without a locknut will stray from its original setting. I dont find this too annoying unless you are using spray equipment like an hvlp, mine is finicky on pressure. The one I use now came from an auto parts store that also sold alot of paint products, I paid $33.00 for it. I'd recemmond trying the one you have and see how it works for you.

[Greg Bender]

Mike,
I can't speak about your specific unit but in working at Ingersoll Rand the units we build have pressure cutoff values that are in tune with the various components related to holding the air pressure safely.I would think that whoever builds the Cobalt unit would rather nobody adjusted the cutoff pressure.Our (homeowner) type of units do not have a real blowdown,and like everybody has said the unit is designed to operate within a 25 to 35 psi range without over running that induction motor.If you had a compressor that had a continuos duty motor and controls you would have more leeway in your adjustmants. There should be a tag with all the applicable info for your model on the tank somewhere.We build compressors that go to 609 psi but the components,especially the tank and overpressure safety valve are built to that level of performance.

By the way,have you dumped the petcock at the botom of your tank to clean out the moisture.Rust inside the tank is something you want to avoid.If you ever suspect that the compressor is charging beyond what the manufacturer claims is the normal value ,shut it off and call Kobalt.They are very aware of what a tank failure will do to there bottom line.If you have any questions PM me and I will do my best to answer them.
Thanx,Greg

[Mike OMelia]

Mike,
I can't speak about your specific unit but in working at Ingersoll Rand the units we build have pressure cutoff values that are in tune with the

By the way,have you dumped the petcock at the botom of your tank to clean out the moisture.Rust inside the tank is something you want to avoid.If you ever suspect that the compressor is charging beyond what the manufacturer claims is the normal value ,shut it off and call Kobalt.They are very aware of what a tank failure will do to there bottom line.If you have any questions PM me and I will do my best to answer them.
Thanx,Greg

I do drain the tank regularily. I now better understand the concepts behind operating range, duty cycle, and pressure regulators. I just have not had the time to address this issue. I really appreciate you all educating me and doing it in a way that did not say "RTFM!". I don't have one. ;) But I will try to find one online. I will not tamper with any settings, but I will work on the regulator side of the problem. - Mike