What is a good size compressor?

[Campy]

Regarding that used dual stage air compressor that I bought, it has a Century 220 volt, 22.0 amp, 5 h.p. electric motor. I've mounted the power box and the Furnas magnetic starter on the wall next to it. The top of the air compressor had hit the starter box (the door was off) when it was laid down on the bed of a truck when I was picking it up and, today, I noticed that the front plastic piece that was attached to the base behind it is broken clear across.
Is it necessary to use a magnetic starter with a 22 amp, 5 h.p. electric motor, or can I get rid of it and have the three wires go directly from the power box to the little air regulator box on top of the air tank?

[johnshenry]

[reasley]

Campy

The magnetic starter provides two services to the motor on your compressor. It has contacts large enough to take the full amperage load on start up and it provides overload protection. You could probably get the pressure switch to work for a few cycles, but it would soon burn up the contacts. A replacement starter should be around $60.

[AJ Quick]

[Bugs'n'Pugs]

What is the biggest (by cfm) compressor on the market that can be used with 110-volt?
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[reasley]

This is a difficult question to answer. There are so many different manufacturers out there. No one could know them all. There' s no free lunch. Its always a trade off between amperage and cfm. That's the reason for moving up to 220 volts. it drops the amperage by 50%.

I've seen up to 7.5 cfm at 100 psi on a 110 circut. They draw around 20 amps and would have to be on a 25 amp circuit at a minimum. You can't just plug these into an outlet as it usually uses a different plug. A 6 to 6.5 cfm will draw about 15 amps and will run on a 20 amp circuit. Any compressor manufacturer that sells into the consumer market will have one of this size. Re-read John Henry's post on page 2 and shop around.

[Campy]

Regarding my dual stage air compressor, I need some help with the wiring: the three wires from the electric motor go up to the magnetic starter, and black, white, and green wires go down from the magnetic starter to the small air regulator unit on top of the tank. The plastic piece in it has four connections for wires: I have the black wire connected to the right one, which is marked 'line"; to the left of it, the connection is marked "motor," the one to the left of it is the same, and the connection at the far left is marked "line." Should the white wire go to the connection marked "line"? When I first got the air compressor, an electrician had wired it and he the black wire going to "line" and the other wire going to "motor", which didn't make sense to me. There is a screw in the metal case for grounding a wire, so I have the green wire going directly to it.

[reasley]

Campy
The black and white wires from the magnetic starter connect to the terminals marked "motor". The terminals marked "line" connect to your incoming power leads. The white wire is not a common. In a 220 circuit both leads are hot and need to be switched. It is also absolutely required that you attach the green ground leads from the power source as well as from the starter.

If you are at all uncomfortable or unsure hooking these up seek help.

[Campy]

Thanks for the information, reasley. I have the power box, which came with the air compressor, on the wall and the wires go from it to the magnetic starter. Its on/off lever is what he used to turn the air compressor on and off. The three wires coming out of the starter go to the air regulator unit on the air tank. The electrician he had set it up had the black wire at the "line" terminal and the other wire at the "motor" terminal next to it. Yesterday, I connected the white line to that "motor" terminal and the air compressor worked. Should I leave it that way or try it with both wires connected to the "motor" terminals?
The oil drain bolt is in the typical spot at the base of the pump, with flat metal in front of it, so there is no way to get a funnel next to it. With my smaller horizontal air compressor, I used to lean the unit toward the side so the oil would drain out through a funnel and not on the air compressor, something which I can not obviously do with a vertical tank mounted on the garage floor. Does anyone have a suggestion for getting the oil out of the pump without making a mess?

[reasley]

The oil drain is easy. The plug is most likely 1/4" npt (could be 3/8"npt). Just buy a pipe nipple long enough to reach over the edge of the platform and a 90 degree elbow. The existing plug will screw into the elbow to seal it off.

As for your wiring issue. It won't usually matter whether you attach the mag starter on the line side or the motor side of the switch. But... do it right, be consistant. Hook both hot wires from the starter to terminals in the pressure switch marked "motor". Hook the 2 hot leads from the power source to the terminals marked "line". Both green wires should be grounded to the pressure switch body. The wiring of this beast is critical to your safety. Do it right.

[AJ Quick]

[skatepopwar182]

I bought my 25 gallon 1.8 hp craftsman for loke $360 it does 6.8 cfm at 90 psi. I wish I would of gone bigger but it gets the done and it was right in my price range.

[clinkfield]

Anyone have any experience with the 80 gallon Kobalt compressor that is sold at Lowes?
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[DarinNDebra1961VW]

I know that we're all compelled to look at the relatively inexpensive compressors that are available from Sears, Lowes, Home Depot, Sams Club...places like that.

If you're looking at a 5hp compressor...be aware. A real 5hp 1 phase electric motor weighs almost 100lbs.. and the shaft is 1 1/8" diameter and these big boys turn 1800rpms. Dont be in the mindset that the 3600rpm motors are what you need. All these are doing is slinging a cheaply built aircompressor to pieces.

A real air compressor has cast iron (finned cylinders) just like the ones on our vw's. And they can be rebuilt later down the road. If you buy the cheap one, sure you'll get some use out of it. When it breaks, you have a piece of junk that is worthless. In the long run it would be better to stick with a good heavy compressor with a cast iron pump. Champion, Ingersoll Rand, something like that. Does it cost more? sure does. It will last you for decades if well maintained and serviced.....

A dead give away...if the motor on the 5hp compressor is the size of a coffee can? or says SPL on the data plate where HP is normally listed....just walk away. Its not what you're expecting.

[DarinNDebra1961VW]

Another point I forgot to mention. Dont look for longevity from the direct drive air compressors. Look for one thats belt drive. Otherwise you have something you have to go back to the OEM to get a replacement motor for. You can rest assured that they will thoroughly spank your wallet. If your belt driven, you can buy the motor at any reputable electric motor repair shop, or industrial supply company.

Im in the electric motor repair business. Not looking to plug for business, just want to share with my friends what works and doesnt work. I get these small homeowner type compressors in my shop all the time for repair (this should be a sign) and 99% of the time, they are toast and have to be replaced.

If you can afford to go with the higher quality, then for god's sake please do so. You wont regret it. If you cant? then buy the homeowner style machine, but just dont expect a long life from it.

Thanks friends !!!!!!!

[vdubyah73]

Define long life. If you buy a homeowners compressor and use it as a homeowner/hobbyist it ought to last while. 5 years ago I bought a Husky Pro, 7hp peak, single phase 220v, 60 gallon, 10.3 cfm @90 psi, cast iron, 100% duty cycle. $400 dollars and absolutely no problems. Built my Buggy and repaired my Bus. It almost keeps up with a cut off grinder some times called a whizzer. I don't give it much of a break, when using it, when the lack of air slows a tool to where it doesn't want to work, I'll stop until the compressor stops and start right back up. Probably should have gone up a size or two, but I spent what I could afford. Did I say I haven't had a single problem with it. It was, at the time, the smallest 220V they had at Home Depot.

Bill
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[AJ Quick]

[bill may]

my "big red" (snap-on) is a 10hp 120 gallon 220 volt. it is quiet and puts out good air.
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