farmbag72 Posted July 15, 2014 Report Share Posted July 15, 2014 I recently replaced my old compressor (motor croaked) with a new Kobalt compressor & have been happy with the purchase. Its fairly quiet and easy to drain water from (what else can you say about a compressor?). It is a 5 gallon unit so its fairly small & runs quite a bit when I'm "banging" nails with my framing nail gun. If I piped from the new compressor to my old compressor tank, then to my nail gun, I could expand my tank capacity to 16 gallons and keep the new compressor from kicking on so frequently. Does anyone know if there might be any harmful "side effects" for my new compressor if I did this? I can't think of anything other than the compressor having to run longer to pressurize the larger tank capacity when I turn it on. Are there any benefits to having a larger tank capacity besides keeping the compressor from cycling so often? Also, can anyone tell me what component/factor the x cfm @ y psi is a description of? This 5gal compressor says 5cfm @ 90 psi but a 20gal compressor said 4cfm @ 90psi so I don't see it as a function of tank size necessarily. Guess I should have asked while I was doing my research to make this recent purchase but I was SOL with a croaked compressor in the middle of a complete renovation & a baby deadline screaming at us and I just couldn't take any more time picking a compressor. Quote Link to comment Share on other sites More sharing options...
Tom King Posted July 15, 2014 Report Share Posted July 15, 2014 The larger the tank capacity, the longer the intervals between the compressor kicking on and off, but of course it will have to run longer at the time. cfm not much of a factor of tank size, but rather the "keep up with" rate of the compressor. Quote Link to comment Share on other sites More sharing options...
Tpt life Posted July 15, 2014 Report Share Posted July 15, 2014 Duty cycle rating is how this is expressed. Tank size will not matter with a continuous duty rating. Might need to dig for a spec sheet. I took my compressors duty rating from the wear in procedure. They shipped it dry and said after filling with oil to run the compressor with a line open for twenty minutes. Quote Link to comment Share on other sites More sharing options...
wtnhighlander Posted July 16, 2014 Report Share Posted July 16, 2014 Compressors are rated by the amount of intake air they consume, that's where the CFM rating originates. I believe the psi rating is the pressure available at the discharge port of the compressor, and has nothing to do with the tank. The CFM out of the tank is a function of tank capacity, regulated pressure, and outlet area. Quote Link to comment Share on other sites More sharing options...
Tpt life Posted July 16, 2014 Report Share Posted July 16, 2014 True and not all at the same time. Compressors are marketed based on CFM Recovery Rate. This helps to pair the compressor with the demand. There is still a Duty Cycle rating. My compressor is rated at around 4.5 CFM Recovery. I can run a framing gun, fire twenty nails, the compressor cycles for three minutes then cycles off for three. At this rate, the compressor is operating 50% of its use and for only three minutes at a time. If I bought an air sander that uses six CFM, my compressor will run continuously and the tool will not operate properly. If I perfectly balanced my tool with the recovery rate, say a sander that only requires 4.5 CFM, I can still have problems if the compressor is not made to run continuously. At some point the compressor could overheat. The recovery rate is one piece of a two part puzzle. This got really wordy, maybe someone has a better way to present this. Quote Link to comment Share on other sites More sharing options...
wdwerker Posted July 16, 2014 Report Share Posted July 16, 2014 So the long and short of it is a bigger tank will give you more time before the motor starts running but it will ultimately hurt the motor with long run times to fill the larger tank. Plus the line between the 2 tanks will be under high pressure! If it blows in the middle of the night the motor will run all night and cook itself ! I had a hose fail in my shop a few months ago sometime in the night. Compressor was boiling hot and sounded awful when I got there in the morning. Shut it down and waited hours for it to cool off. Changed the oil and found out a couple of days later that the valves in the head were shot. 3 days and $100 to get a replacement head, I had to do the repairs and use a little job site compressor in the shop until I got it fixed. If it hadn't been a commercial cast iron pump it wouldn't have been worth fixing. We now unplug the hoses each night . Quote Link to comment Share on other sites More sharing options...
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