Air Compressor cfm.

[EFPaisley]

I recently purchased a brand new Kobalt air compressor, 26 gallons. And have been having issues with cfm. I had an old Porter-Cable 6 gallon .8 hp pancake compressor that was supposed to provide 2.3 cfm. I had picked up a set of tools and knew the cfm in them was too high for the P-C and was frustrated that some tools only ran a few seconds then had to refresh before using again. I was looking for a bigger compressor. I bought a brand new Kobalt air compressor, 26 gallons with 1.8 hp and 4.5 cfm @ 90psi. The old Porter-cable does a better job running the tools than the new Kobalt. Do I have a defective unit? A misunderstanding of cfm? I have Trades pro and Central pneumatic and the manuals say cfm requirements are 4-5 cfm. What can be wrong? I do like how quiet it is. I can carry on a conversation around it. It is quieter than my Porter-Cable but I would rather have one that functioned properly rather than one that is quiet.

 

[Stedlin]

Use a calculator like this one to determine if it is putting out the rated CFM.
https://www.airgastech.com/resources/calculators.html#cfm-calculator

 

[dnschmidt]

And the answer is: THEY LIE. Every power tool manufacturer, especially the cheap ones like Harbor Freight, GROSSLEY understate the amount of air needed to power their air tools. For example a die grinder uses about 15 SCFM and an air sander like a Dynabrade uses 17 SCFM. My SATA, Iwata and DeVilbiss pro level spray guns use 17 SCFM. I have an 80 gallon 5HP two stage Quincy and it runs damn near constantly when I do a lot of sanding with my air sanders and it puts out 17 SCFM. This is why when the daily question is posted on this forum about which compressor he or she should buy my standard answer is the biggest one that will fit into your garage.

 

[PoorUB]

Residential grade compressors make me crazy with their ratings. 12 amps and 120 volts? That compressor is a bit over 1 HP, not the 1.8 HP advertised. You didn't gain much over the compressor you had, except a larger tank that takes longer to fill when it runs down which is probably your frustration. your pancake compressor fills 3-4 times as fast do to the smaller tank.

Also watch the ratings on air tools. They often rate them with an average CFM, not the actual CFM. The actual CFM is what the tools will draw running full on for minutes. The average CFM is something like on 25% of the time and off 75% of the time so the CFM needed might be 3- 4 times of the average.

 

[PoorUB]

Here is some info from a air tool manual.

They state 4CFM average and actual CFM is 29!

And people wonder why their 1 or 2HP compressor doesn't cut it!

 

[nbpt100]

Any air tool or compressor I have ever owned had the CFM rated at a certain pressure. To get the stated CFM you need to be at the stated pressure. Look at your lines and fitting and make sure they are big enough. They may be causing a pressure drop. also what is the top tank pressure where the compressor shuts down at? It may be lower on the new unit than the old one.

 

[rancherbill]

Do I have a defective unit? A misunderstanding of cfm? I have Trades pro and Central pneumatic and the manuals say cfm requirements are 4-5 cfm. What can be wrong? I do like how quiet it is. I

Curious. CFM is only part of the problem

You have a much larger tank on the new unit. You have lots of stored air to run an impact for example, because they are just bursts. To run tools that run for a while, like a sander, you need compressor capacity.

All consider the 'infrastructure' of your air setup. Do you have new smaller ID hose, are they longer etc. All of these will decrease available air at the tool.

As somebody stated there are lies, damn lies, and compressor specs.

 

[EFPaisley]

Residential grade compressors make me crazy with their ratings. 12 amps and 120 volts? That compressor is a bit over 1 HP, not the 1.8 HP advertised. You didn't gain much over the compressor you had, except a larger tank that takes longer to fill when it runs down which is probably your frustration. your pancake compressor fills 3-4 times as fast do to the smaller tank.

Also watch the ratings on air tools. They often rate them with an average CFM, not the actual CFM. The actual CFM is what the tools will draw running full on for minutes. The average CFM is something like on 25% of the time and off 75% of the time so the CFM needed might be 3- 4 times of the average.

Curious. CFM is only part of the problem

You have a much larger tank on the new unit. You have lots of stored air to run an impact for example, because they are just bursts. To run tools that run for a while, like a sander, you need compressor capacity.

All consider the 'infrastructure' of your air setup. Do you have new smaller ID hose, are they longer etc. All of these will decrease available air at the tool.

As somebody stated there are lies, damn lies, and compressor specs.

My frustration is that in less than 2 seconds the tool runs down, quits, then hisses. I let it rest for 5-10 seconds and it runs again for less than 2 seconds. The tank pressure drop is very small but I can't get much work done in less than two seconds. I moved the 25 ft hose from the 6 gallon to the 26 gallon and expected better performance.

 

[American Locomotive]

There isn't a single consumer air-tool in the world that will run down a 26 gallon tank in 2 seconds. It sounds like your hoses are too small, or the pressure regulator on the compressor is not turned up.

There should be a big blue knob on the compressor, if it's the 26 gallon "Quiet Tech". Turn the knob up as much as it will go and see if that helps.

 

[fsae0607]

My frustration is that in less than 2 seconds the tool runs down, quits, then hisses. I let it rest for 5-10 seconds and it runs again for less than 2 seconds. The tank pressure drop is very small but I can't get much work done in less than two seconds. I moved the 25 ft hose from the 6 gallon to the 26 gallon and expected better performance.

I had a similar problem with the regulator that come installed on my Husky 30 gallon. The regulator was ****. I removed it and used a good external regulator. Problem solved.

 

[PoorUB]

My frustration is that in less than 2 seconds the tool runs down, quits, then hisses. I let it rest for 5-10 seconds and it runs again for less than 2 seconds. The tank pressure drop is very small but I can't get much work done in less than two seconds. I moved the 25 ft hose from the 6 gallon to the 26 gallon and expected better performance.

You have some sort of restriction in the air lines at the compressor. I agree with the other posts that the regulator is suspect. If you have some spare fittings and a air pressure gauge, cobble up a tee fitting with the gauge right at the air tool and see what happnes, My bet the air pressure at the tool drops like a rock and stays down until you stop for a couple seconds, then it refills the air hose and you go another couple seconds. That indicates a restriction some where. The pressure gauge at the tool should maybe drop 10 PSI at the most.

 

[Downwindtracker 2]

15 amps ( horse and a half) at 110 will give you about 5 SCFM . More likely less. Consumer grade air tools have looser tolerances which means more air required .

 

[toyotadriver]

I agree check your compressor. It should run those tools without issue. I used air tools for years (ratchets and impacts) on a 20 gallon compressor without a problem. I did have to let it catch up from time to time but it could do it. I now have a 60 gallon 240v compressor and it does everything I need it to and then some. But, your new compressor should be working just fine for your needs.

 

[u2slow]

Small lines/fittings, low-flow regulator, low tank pressure all contribute.

My first compressor (still have it) is a 3hp/10cfm/240 v portable unit. Presses up to 135-140psi or so. Very grateful I didn't start with less.

EDIT: Many portables have a small size tank fitting, and a restrictive regulator.

 

[racecougar]

My frustration is that in less than 2 seconds the tool runs down, quits, then hisses. I let it rest for 5-10 seconds and it runs again for less than 2 seconds. The tank pressure drop is very small but I can't get much work done in less than two seconds. I moved the 25 ft hose from the 6 gallon to the 26 gallon and expected better performance.

What size is this 25' hose? What tool are you trying to operate?

 

[Stillgottimefor1]

I was given a small portable compressor new, and there was a sintered metal filter in the outlet from the regulator that VASTLY reduced flow volume. Removed /replaced that.

 

[rancherbill]

I agree with the pressure regulator suggestion. Turn it back and forth between 10 psi and 120 psi., while there's a blow gun attached that you can hear. Maybe its just sticky or there's factory stuff stuck inside.

 

[Jland]

Many air tool specs recommend a 1/2” hose which makes a huge difference in tool performance and from my experience simply adding a high flow coupling helps too.. of course this doesn’t address your problem but just FYI

 

[MacMcMacmac]

I see a lot of small print where cfm requirements for a tool are based on a 25% duty cycle.

 

[PoorUB]

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