Buying a used air compressor: tips?

[bud--]

Far as I know they all unload when the motor stops I wouldn't bet on starting against high head pressure.

I think the answer is closer to what clare wrote. In looking around, the motors I saw on compressors were capacitor start, capacitor run. Those motors, in general, have relatively high starting torque and relatively low starting current for that torque. I have seen no reason to believe "special compressor motors" are anything but standard cap start, cap run motors.

The problem I have is Jon's 3HP SPL motor. It is a scam rating. Just like the scam ratings that resulted in the class action lawsuit, which the manufacturers settled. If Jon knew it was not a real number then why post it? (And then there was Jon's 2.3HP miscalculated value.)

A scam "peak" 3HP motor has a peak (near stall) torque that is equal to the normal running torque of a 3HP motor. It is not the starting torque of a 3HP motor.

For many of its smaller compressors, Grainger gives both the scam "peak" HP (competitive with Jon's scam rating) and a real HP.

I haven't seen any reason to believe that the "real" HP is not the appropriate rating. Because there are plenty of scam ratings, you can't compare compressors based on HP rating (as many people here have said). Even with real HP ratings you need to compare the air you need with what a compressor provides (also as many people here have said).

============= This is similar to joule ratings on surge suppressors. In that case there is not a defined way to measure the joule rating. So some manufacturers use deceptive ratings. As a result, some major manufacturers no longer give a joule rating.

[Vic Smith]

Yep. Gift selection is important!

--Vic

[Vic Smith]

I used to blast parts with glass beads when I was a heat treater. But I didn't pay attention to the compressor. Looks like I'll buy a wire brush for that instead.

--Vic

[Vic Smith]

No. I just butted in on this thread..

Yeah, had that happen, but not often at all. Always managed with a breaker, even it I had to add 6 feet of persuader to it. My kid is a truck suspension mechanic. Does it all, including fire trucks, loaders, etc. He NEEDS his air stuff.

--Vic

[gfretwell]

Air just makes things happen faster. The best example is my assortment of nail guns. There are things you can do with a nail gun that you can't do with a hammer.

[Vic Smith]

About ten years ago I added a couple joists to my garages. Maybe 12 nails. Big ones, with a hammer. I've made a number of work benches, using drywall screws. Want to be able to take them apart if needed. Never needed to yet. If I did framing, I'd get an air nailer for it. The small compressor/brad nailer I bought when I put up new woodwork was maybe the smartest tool investment I ever made. Now I can't imagine ever using a hammer with brads again. I guess that's how you feel about your nail guns.

--Vic

[gfretwell]

Brad nailers are the low end of my gun assortment but when I was putting the extra framing in my attic to meet the hurricane code, I can't imagine doing it without a framing gun. To start with, I wasn't banging with a hammer and cracking the drywall ceiling below. I also put on 7 squares of shingles on my addition without hitting my thumb once and that was a first for me in roofing. ;-)

I use my brad nailers on a regular Bevco CO2 tank sometimes when I don't feel like dragging a hose out.

[Tony Miklos]

That doesn't sound so great anymore, power for the compressor but no 120 for everything else. I'd be checking to see if the wire can be pulled or not through the old conduit. If so then install a legal/code/safe run with 240 and a neutral. But if he just wants to inflate tires why bother. On the other hand he mentions sandblasting, either a tiny blaster, way too much patience, or go with the 240.

[krw]

He said,

"Yes, the motor on my compressor is not a 3HP motor, it is a 3HP SPL 15A/115V motor. That's about 2.3HP Continuous, which is more than the 1HP you and gfretwell" claim is the absolute limit for air compressors."

Implying that it was a 2.3HP motor and that gfretwell's 1HP "limit" was wrong by a factor of 2.3. At *best* he's a troll.

[Tony Miklos]

Oh my more setbacks. Trying to compare my 25+ year old 1hp Sears compressor to the one in the link. My 1 horsepower puts out 5.8 SCFM @

90PSI. Yours is rated different, it puts out 5.2 CFM @ 90PSI. So we need to convert SCFM to CFM or vise versa. I want to see how my old 1HP compares to the new 2HP.

[Steve B]

There is absolutely nothing on this earth that smells worse than rotten shrimp. If you ever want to get even with someone, a few pounds of raw fresh shrimp left to age for a few days in a sealed bag will do it. A friend of mine jilted a girlfriend. While he was offshore for two weeks, she went to where his car was parked, dumped about five pounds of shrimp inside it and closed the door. He set fire to the car. Lucky, it was a beater anyway. We could smell the car when we got on the dock.

Hell hath no fury like a creative woman who has been scorned.

Steve

Heart surgery pending? Read up and prepare. Download the book $10