Hi Bill,
My 2 cents,
AIR COMPRESSOR BASICS.
Rule number one..................... it's all about air draw/air consumption.
Rule two ...................... domestic /industrial. (single phase/three phase)
Rule three ...........................oil or oil less.
Rule four .....................electric or petrol driven motors.
Rule five ....................air compressor noise.
TARGET EXAMPLE.
You're a home jock on single phase power supply, and you want a compressor to carry out various tasks around the home.They might be for example using an air blower gun, a spray paint gun, any air driven power tool such as a sand blasting gun, air grinders, air sanders, air nibblers, air die grinders, air ratchets, tire inflators, air hack saws, air chisels, air rattle guns, air nailing/staple guns etc,etc.
Rule 1. Air draw. (This is what it's all about.) No matter what air tool you're using, it will have it's own particular air draw or air consumption (air volume) to properly operate or drive the tool you are using.The tools listed above have a wide variety of air consumption requirements. When buying or choosing any air compressor for home use (single phase), the most important thing to consider is how much air the compressor can produce or deliver. This is a standard measurement and is measured in cubic feet/ liters per minute. Most compressor brand manufactures will or should quote two measurements. A. An overall restricted air delivery of cubic feet per minute, and B. (a free unrestricted air delivery) of cubic feet per minute. The free air delivery is the measurement that you need to go by when choosing the air production/output of the compressor you want to own. What's FAD? Free air delivery is tested and measured in cubic feet per minute, with the ability of any compressor to deliver unrestricted, continuous air flow output and at maximum pressure around 100 to 120psi with the machine running full duty cycle. (no compressor motor cut in/ cut out) That is the true output measurement to go by, as any air tool you will be using will have it's own air draw/ air consumption spec in an FAD readout context.
For Example, lets take auto spray guns. They come in a great variety of air draw consumptions. Let's say your spray gun has an air draw of 12 to 14 cubic feet per minute (that's air volume, not air pressure we are looking at here). That will mean that your compressor should have the ability of at least matching that same air production (12 to 14 cfm) of air needed to run that spray gun continuously with trigger pulled. If it doesn't, then your compressor will not be able to keep up the air consumption the gun needs to operate properly. You will get pressure drop problems, (the tank starts running out of enough stored compresseed air) and the compressor will keep on running with little or no motor cut in/cut out cycles. That will lead to overheating and eventual burn out of the electric motor. Tank size does play a part in the FAD equasion to some extent. If you have a large capacity tank, that is an advantage, but what really matters is when the compressed air built up in the tank runs out, you will still need to totally depend on the pump, pistons and motor to keep up the air draw requirement coming through no matter. This is where FAD is the only spec that really matters and what you should go on when choosing your compressor.
So bottom line here is work out what air tools you want to end up using, and establish what the biggest air draw will be in your collection of tools. It pays to buy a compressor with more FAD then you will need for obvious reasons. There are limitations of maximum FAD output range you can buy on single phase power supply motors. Usually it peaks out with a single phase, 3 horse electric motor with 10 or 15 running amps capacity. Some 3 horse motor compressors require a 15 amp dedicated circuit line going back to the main power board with a separate fuse/ breaker installed. Some don't.
Rule 2. Single phase for home /domestic applications. Getting three phase power supplied to your home means big bucks to set up.
Rule 3. If you have fairly large air consumption needs, then going three piston with oil crank is the only way to go. Small oil less compressors are ok for small air draw demands such as running nail guns or any air tool that doesn't need a continuous big air draw. (for example, trying to run air sanders , grinders or buffs are useless as you run out of air very fast) However, there are companies like Chicago Air out there that are producing medium to large air output, single phased spec compressors that are running oil free pump systems, and are rated at low db specs.
Rule 4. For domestic usage, you can buy petrol driven compressors as well as electric driven ones. I would stick to buying electric driven compressors,as petrol ones have drawbacks such as running noisy, petrol fumes and potential explosions etc. There is one advantage of going petrol, and that is you can buy a model that has a greater air production FAD output than the maximum output of a single phased, 3 horse electric motor model. More FAD happening there.
Rule 5. Domestic single phased compressors are slowly getting quieter as time goes on. Some are coming down to as low as 71db, which is pretty good for keeping the neighbors happy. However, most still run at around between 90 to 100 decibels. The small cheapie FAD oil less models are usually the noisey ones coming in at around 100 to 120 dbs . Youch!
CONCLUSION.
Buy the biggest single phased compressor you can afford, but most importantly, be sure to match the FAD delivery of the compressor up with the biggest air draw air tool you will be using. Also, buy quality if you can. Quality brand compressors always last longer than the cheapies do. Take into account the extra cost involved with setting up dedicated 15amp circuits. Go oiled comps and go for a quiet running db spec if you can. What did i end up doing for my home setup? Here in Australia, we run 240 volt/10 amp domestic circuits. The biggest, (quality) compressor i can buy here has an FAD spec of 12.5 cfm. (3 horse, 10 amp, with a price tag of around $2,400. Aus) I'm running production type gravity feed guns (non HVLP) with an air draw of between 12 and 14 cfm. To get out of jail, i bought a second compressor with a 2.5 horse 10amp spec that delivers an FAD of 8 cfm. When needed, i run the two compressors in unisen to deliver the required FAD i need. (20.5CFM) I did go to the trouble and expense of setting up a dedicated heavy duty power cable line with both compressors linked up, and the circuit going back to the power board running a dedicated 32 amp breaker fuse to handle the total 5.5 horse power draw. All good! So hope all that helps.
Greg. (pro auto spray painter.)
