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Air Compressors, how much is too much?

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TomMull

TomMull

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I'm moving into my shop this Spring and have decided to leave my old 80 gal 3.5 horse single stage compressor in the old shop which is in the basement. My shop is totally non-commercial. While I've always been able to make this small compressor do, I've never really had enough air. Initially I'd thought of getting a 5hp two stage, which can be had for $1000 or so. If I read the specs correctly, that would improve my capacity by about 50%. Since I've been able to get by with my smaller one I could certainly get by with that.
However going to the next level, 7.5hp two stage will double my capacity at least. (It's hard to make a direct comparison because the capacity of the bigger commercial units is given at the compressors max of 175 lbs rather that the home units which are given at 45 and 90 psi.) Down side is that the cost is more than $2000. Budget is kinda stretched anyway but it would be really nice to worry not about running out of air. Also easier to keep water out of the paint as it would run cooler.
Any thoughts/ opinions will be appreciated.
Tom
 
More air is always better in my opinion. IE: my media blaster takes more air than it specifies, so the compressor can't keep up. When I painted cars, same situation. you can throttle it down, but you can't pull more out of a weak machine. I think a 5 hp would do for me. I currently have a 3.5HP.
 
Jerry said:
More air is always better in my opinion. IE: my media blaster takes more air than it specifies, so the compressor can't keep up. When I painted cars, same situation. you can throttle it down, but you can't pull more out of a weak machine. I think a 5 hp would do for me. I currently have a 3.5HP.
Click to expand...
Thanks, Same here. Blaster operates only with smallest nozzle, I paint with cheap LVLP gun instead of my top of line HVLP, and I occasionally have to wait on the impact wrench. I would be disappointed to have the same restraints with the 5hp.
Tom
 
I run a 5 hp, it will run tools just fine. When I sand blast or spray a big car I connect another tank into the system and let it build before starting. It extends my usable time. For the blaster, I usually run out of sand by the time pressure drops. Not a problem for painting.
Marv
 
Marvin Gruber said:
I run a 5 hp, it will run tools just fine. When I sand blast or spray a big car I connect another tank into the system and let it build before starting. It extends my usable time. For the blaster, I usually run out of sand by the time pressure drops. Not a problem for painting.
Marv
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Thanks for the input, Marv, 2 votes for the five and 0 for the bigger one. I'd given some thought to hooking the old tank (and compressor) with the new one but they will be 600+ feet apart. (I suppose the hose would add to the volume). I'd like to be talked out of the 7.5 but thinking that in addition to volume, I think it will be quieter and run cooler (less moisture) than the 5. Just wonder if that will justify the cost.
Tom
 
I have a 7hp standup with a twin cylinder 2 stage compressor. I can run the pressure down with an exterior sand blasting unit, but with careful monitoring I can go a long way before the pressure drops too much. Heavy blasting takes a lot of air. PJ
 
I am using a 3.7hp 60 gallon compressor from Lowes, it is rated at 11.5cfm @ 90psi. Works fine in my shop using HVLP paint gun, angle die grinder, palm sander. No problems. I occasionally use a HF hand held abrasive blaster, keeps up. It will not keep up with larger blasters.
 
TomMull said:
...a 5hp two stage, which can be had for $1000 or so. ... 7.5hp two stage will double my capacity at least ... the cost is more than $2000.
Click to expand...

Sounds like you would be better off going with two of the $1000 units vs. one $2000 unit....?

Start with one $1000 unit. If / when you run out of air, get a second one. Your outlay is 2k, same as it would be for the bigger model. And you get the bonus of only having to run one when your air needs are less - at $0.10 / kw-hr, a 5 horse compressor costs about 30 cents per hour to run, vs. 50 cents / hour for the 7.5 horse. You could even get fancy with the piping and use both compressor storage tanks with only one airhead running.

This assumes you have the available space for two units...

Regardless, a cheap solenoid drain trap is a worthwhile add-on. Wet tanks rust, rusty tanks can leak or worse, blow up. https://www.grainger.com/product/ASCO-Brass-Solenoid-Valve-WP109001/_/N-ri3?s_pp=false&picUrl=//static.grainger.com/rp/s/is/image/Grainger/4EKY2_AS01?$smthumb$, for example.
 
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