Sizing the Air Compressor for a Small Shop

      Horsepower and tank size aren't the best measures of whether a compressor can keep up with the work you're giving it. Here's a closer look at the specs that matter. January 25, 2013

Question
I have a very small custom shop where I do small furniture projects. I'm looking to upgrade to a bigger compressor. I run your typical nail guns, orbital sander, spray guns, etc. My 30 gallon will not keep up. I'm considering going to an 80 gallon but want to make sure that is big enough.

Forum Responses
(Cabinetmaking Forum)
From contributor M:
I am a one-man shop and have a two-stage compressor with an eighty gallon tank and it never really works hard at all, even if I am spraying. It has a 3 HP 220V single phase motor. I don't know the CFM. As I think you are implying, it's much better to go oversize on a compressor over the long run, since it will last much longer if it isn't running constantly.



From contributor W:
I've had a 60 gallon, 3 hp 220 Husky for 4 years this week. I know that because the warranty is almost up. I had to rebuild the pistons last week and Campbell Hausfield didn't have any problem sending me the parts for free. The warranty is 4 years.

I have a 1 man shop and as such, never really use more than one tool at a time. I always have enough air. The biggest user of air is my palm sander. It does make the compressor work. Everything else, not so much.



From contributor I:
When I was in your situation I kept upgrading my compressor every year. I started with a pancake type compressor and after 6 years or so, I ended up with a used 5 HP vertical IR. I think it was 80 gallon. That was enough to power the Dynabrade and spray booth (not at the same time). I did not have to get a bigger compressor until I hired more people.


From contributor A:
The 3 hp or 5 hp 80 gallon will cover you until you get multiple users on sanders. It will provide plenty of air for spraying. 60 gallon is the minimum for spraying. It will work, but you won't be able to use anything else while spraying. The compressor will run almost nonstop. I would encourage you to get the 5hp 80. If needed later on, you can add another 80 gallon tank and it will keep you going for next to nothing.


From contributor L:
The tank size only decreases the number of on/off cycles when the compressor is not fully loaded. There are a lot of cheater 5hp units out there, but if you check the current draw against what a true 5hp requires, you will find they are not really 5hp. That is unless they are magically generating electricity. Don't measure a compressor by tank or hp. Use the rated cfm @ 90 lb. Reciprocating compressors should not be run continuously. Some will list the duty cycle. A random orbit sander on less than a real 5hp compressor will not allow the compressor enough rest time between its start/stop cycles. Electric motors will overheat when subject to frequent cycling and that will wreck the insulation/motor. The service factor on the motor name tag indicates how much reserve the motor has. If it is 1.0 it has none. 1.15 is better. Compressors will need to have an actual motor starter, not just a pressure switch. The function of the starter is to not only start and stop the motor via the contactor, but also the electrical draw limit and thereby help protect the motor from burn out. You're never get more than what you pay for in a compressor (or anything else, for that matter.)

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