So, Black Friday is approaching. In my experience, Home Depot is a great place to go because they have very good specials and they are damned near empty in the morning.
Anyways, I’ve got an air compressor right now that’s only a two gallon unit. It’s just a cheap little one from last year, but it’s been very good for me. The only problem with it is that it’s just too small. I just finished painting a coffee table I just built, and it basically took two days because I could spray for a good 20 seconds before the compressor kicked in, and another 10 to 15 seconds before the pressure was too low for my sprayer to work.
I’m planning on painting cabinets, and I’m going to be using my sprayer. With Black Friday I’ve got two options I’m considering. One is a huge 26 gallon compressor that comes with some crappy accessories. The other one is only a 5 gallon compressor that comes with a set of decent-quality nail guns.
How do I know if the 5 gallon is big enough? Is there some calculation I can run based on the information from my sprayer’s manual?
Most pneumatic tools I’ve used have an airflow specification (e.g. 10SCFM@90psi).
Most air compressors I’ve seen have a supply rating (e.g. 7SFCM@40psi, 4SCFM@90psi).
You’re pretty much guaranteed that any tool is going to be using air faster than the compressor can keep up. With hand tools, though, you use it for a few seconds at a time and the compressor has a change to catch up.
A sprayer is used in a completely different way with long continuous working periods. You probably want to go with a larger tank if that’s your primary use.
Also, note that spray guns usually work at 20-25psi. A compressor made to work at +100psi will have much lower flowrates just by virtue of design. You might be able to find a high-flowrate low-pressure compressor made to keep up with a spraygun.
A lot of the compressors that I have seen at places like Home Depot have a label on them that tells you for what purposes they are adequate. It’s about a 5 step differential. What you need for a nail gun is a lot different than what you need for a sander. Go to the store and look at the display models and the boxes. Decide what your needs are then go one better.
I’d like to point out that for spraying cabinets you might be better off with a high volume low pressure unit. These are usually not actually compressors that can run air tools and fill tires, but a trubine unit that only produces 4-10 PSI, but lots of volume.
I wouldn’t pay too much attention to the size of the tank. Under continuous tool operation, if you don’t have the power you could still be faced continuous compressor operation.
My recomendation for you is to get a 5 horse power oiless compressor.
I have never seen a real 5 HP oilless compressor offered for sale. A real 5 HP motor will draw a little over 20 amps from a 230V circuit. With great care you can just run a 2 HP motor from a 115V outlet. Such a machine may well be marked with a meaningless “5 HP peak” and will run most spray guns continuously.
Oilless pumps may be a good idea for fussy paint work, but you still have to filter the water condensation out, so oil contamination is not a huge worry. I know several people who do lots of finish work on aircraft, and all use 2 stage oiled compressors. Additionally, all the oilless machines I have used and seen for sale were direct driven, making the noise from them quite obnoxious. Belt driven compressors are much more pleasant to share a workshop with, and oiled pumps used by hobbyists tend to have lifetimes measured in generations rather than years like oilless pumps.
Get the bigger one you mentioned. Go for volume, because you are burning through a heap load of air when you spray. The small and medium sized one’s are fine for shooting nails and such, because that is not constant use and happens in bursts, and they are designed for such use. A recycle of the motor to keep the tank up to par isn’t an issue either for a nailer.
Larger spray projects require more volume and a motor that can replace that volume quickly. Small craft-type projects could be do-able with a small/medium scale compressor/tank, but not what you are talking about.
I am used to running heavy automotive equipment, like air ratchets and a sandblaster, but from all my experience, I say always go with a bigger compressor than you think you will need. A 3hp unit with a 20+ gallon tank will handle most anything that doesn’t require a lot of air for an extended amount of time, but if you have the electrical hookup for it, a 5hp doesn’t cost much more but can deliver a lot more air.
Most of my friends use a compressor a lot, so few of them go with an oil-less unit, but everyone of them that has an oil-less complains about the excess noise, and within a year or so, the compressor blows up.