Recommendations http://www.billpentz.com/Woodworking/Aircompressor/temp.cfm
Based upon my set of tools, my friends said I had two choices. I could buy at least a 60-gallon tank with not less than a real 5 HP motor powering a two-stage compressor that will deliver at least 11 CFM at 90 PSI. Alternatively, I could buy a smaller unit and keep using patience as I did with my Craftsman while waiting for recovery and make sure I gave it time to cool down after use. The cost difference is about double, I decided on a quality smaller unit, but not too small.
Here is the list of things they told me and that I already knew to consider in my air compressor purchase:
Buy an oil bath unit because the oil-less tend to have heating problems that would not be good for the amount of spraying and sanding that I do, plus they are much more noisy.
They said there are two compressor preferences. Many prefer big slow pumps as they will wear forever. Others prefer midsized units with a fast motor to permit quick recovery. My friend with the air compressor shop prefers the slow movers. He recommends using top quality synthetic oil that you change as needed, depending on use, but not less than once a year. He uses the Ingersoll Rand synthetic oil because it is readily available at Home Depot.
I also needed to decide if I wanted a stationary compressor or one that I could move around. For portability most like a horizontal under 40 gallon tank or one with a short squat vertical tank and wheels. The tall ones were reported in the forums as having too high of a center of gravity so are dangerous for one person to try to move alone. We need two people to move or install the larger vertical tank air compressors. Many like the vertical tanks because they use less floor space. The horizontal tanks often will fit nicely under a bench or work table. The big ones should be moved in and left in place because they are so heavy. All need access and plenty of airflow so they can stay cool.
Buy one with a motor rated for continuous duty, preferably a good American made motor with 100% duty cycle rating. My sanding and painting makes me an infrequent hard user, which is something many inexpensive imported limited duty motors were never meant to handle.
Get one with at least a 30 gallon tank, anything less is going to not have enough reserve to let me run either my HVLP or larger air tools for very long before having to wait for recovery.
Find a unit with an easily accessible drain line and replace it with a cable pull drain. Apparently, until you get in the hundred plus dollar range, the automatic drains are not worth bothering with.
Buy one with an oil sight gauge that makes it easy to check the oil every time the unit is used, then make sure you check it each time!
Buy one that makes it easy to change the oil. Many have the drain plugs setup so all you can do is make a huge mess draining your oil all over your compressor. He said he often replaced drain plugs with an oil drain line that he made up with a valve. This let the end of the oil drain go into a bucket for an oil change without giving the compressor an oil bath.
Buy one with a built in muffler or that can add one later.
If I buy an upright, go to an air compressor store and buy four of the rubber or neoprene and cork vibration pads to set that unit on to significantly reduce the noise level.
Make sure the unit has or buy a dual set of gauges, one for the tank pressure, and the other for the line pressure. Put another gauge on fittings so it can sit right before my paint spray guns, especially the HVLP unit.
Make sure to get one with or add a line turnoff valve at the tank and use it, as it is bad news to leave the hoses pressurized. Always let the line pressure out of the hose after use.
Buy all my air fittings at once from the same maker as mixing and matching always leads to leaks and frustration. They and many others said don't buy them from my Tools By the Pound store. Sticking with a popular brand name helps, as fittings can be added later and generally work without leaking.
Install a water filter with built in drain to protect my spraying. The size of that filter depends on how humid each area is. In my area, a tiny one is ample except in the wet winters.
Although there are many ways to plumb a shop for air, both of my experts recommended the same thing. Start with a heavy flex hose that connects the air compressor to wall mounted copper pipe. That flex hose takes care of the vibration of the compressor. Run the copper pipe up (or in) the wall and across the ceiling to a pull down self winding air hose reel located in the center of my shop. One recommended also running a line to my workbench and using one of those self winding curled little 6' hoses. Here is a site that gives a good idea on how to setup your air compressor lines and avoid water problems.
Copper pipe comes as either flexible tubing or rigid pipe. The flexible tubing is not suitable for an air line. The heaver "L" gauge rigid pipe is what I recommend but you can get by with the lighter "M" gauge. David Craig pointed out to me that the authority on copper pipe is
http://www.copper.org/publications/pub_list/pdf/copper_tube_handbook.pdf and their Table 3 shows either the "L" or "M" rigid pipe in 1/2" diameter will work fine. My air compressor expert agrees. For sure use 1/2" pipe, as the smaller diameter pipe adds a huge amount of resistance and reduces airflow.
My friends recommended using sweated fittings to plumb the airlines and feed the hose reel. Don't forget particle and water traps at every service drop. You might want to look at this Copper Soldering Website for information on copper piping and how to solder.
Both said PVC works and is plenty strong, but not something either would use. When this stuff gets old or cold enough it becomes so brittle it can easily explode.
Install your air lines so that they drain any water to your vertical run(s). At the bottom of each vertical run, put in an inexpensive finger operated drain to get rid of any condensation, then regularly drain those pipes (the box stores sell the inexpensive CH units).
Buy a nice self-winding hose reel and mount it centrally on the shop or garage ceiling. The hose reel is not just a convenience it is also an important safety item as it keeps the hose under control if it should rupture.
Always buy a good quality air hose of at least 3/8" interior diameter with at least a 300 PSI rating. Make sure you limit your air hose to about 25 feet as longer lengths really degrade the airflow. If you really do need a long hose, seriously consider moving up to 1/2".
which compressor would you choose?