Small compressors are cheap ... $3-5000 new. Most are not designed to run continuously so can't be run to a bank with out a lot of fooling around for the initial fill. Constant run compressors start at about $5000 and go up from there.
Drive choices for a home system can be 110/115 VAC, 220/230 VAC, gasoline or diesel. Of course, gas or diesel need to exhaust outside away from the intake. Nobody is stupid enough to run a gas or diesel engine directly inside a closed garage. 110/115 compressors draw a
LOT of amperage and will require (in many areas) installation to a switch box or to a Turnlok plug and receptacle (depending on your codes). Ours draws 29 amps and, while some of our customers have satisfactorily run them on standard plugs and outlets, you and/or your electrician have to be certain of your circuitry for safe installation. We do not ship them with plugs for that reason.
Auto shutdown is a real nice feature. It allows you to walk away from the machine when filling your banks and it shuts the compressor off when it reaches it's pre-set pressure. However, they don't function on the small 115VAC compressors without a separate start circuit because of the high amperage draw of that little motor.
Auto drains can be added to just about any compressor for $5-900. They just require some sort of power for the timing device.
Oil is an area where there is a lot of argument. I am a big believer in clean, synthetic oil. Some people tell me that they switched to synthetic so they could extend the time between changes. Not me!! I actually cut my suggested times in half and have never had a mechanical problem! Clean oil lubricates, cleans and cools the internal parts and is a small price to pay compared to repair parts. Plus, if you are pumping Nitrox, it shortens the effective life of the oil anyway so change away. I suggest using the 751 for standard air and the 455 if pumping Nitrox. However, the 455 has an affinity for water so it needs to be fully heated up regularly to cook off the moisture and changed at first sign of any condensate in the sump. In any case, oil should not sit in your sump for more than a month without being run up to temperature.
Pumping Nitrox is just fine for up to 40% at no more than 3000 PSI. Is that a magic number that, if exceeded will blow up the world? No ... just a base safety point that no compressor manufacturer feels comfortable exceeding based on research done so far.
Nitrox is made before going into the compressor in a couple of ways.
- The cheapest is to make your self a mixing stick. Of course, you have to buy/rent a tank and regulator for the oxygen and you have to pay attention to what you are doing. You can buy or download The Oxygen Hacker's Companion for instructions on how to put one together.
- The safest and easiest way is also the most expensive ... Membrane system. A membrane for 3-6 CFM personal sized compressors is $5450 while one for the larger 6-10 CFM machines is $7900.
I hope that has helped.
