Says it pulls 15 amp at 115v. Aside from probably tripping many a 15amp breaker, the formula states it's a 1.85 hp motor.
115 (volts) x 15(amps) x .8(power factor) divided by 746 (watts per hp) = 1.85
m
While your math is fine, it starts off with an erroneous assumption. The 15 Amps refers to the required breaker size since compressor makers are too embarrassed to actually put the true motor HP rating onto the nameplate. All this still goes on despite a class action lawsuit several years ago in which the manufacturers got a mild slap on the wrist and the plaintiffs got a few cheesy trinkets and an empty promise.
I can assure you that if the motor can start and run on a 15 A circuit that it is no larger than one horsepower. The peak value of the initial starting current on this type induction motor typically runs 4 to 6 times the steady-state running current. The breaker can handle a momentary overload so it is able to absorb some of this initial surge, but NEC rules would limit the FLC to less than 12 Amps at any rate. Practical considerations necessitate that it be even less than that in order to minimize nuisance trips of the breaker.
You also used a power factor term which is not correct. The proper factor to use here is efficiency which is not related to PF. For this type motor, the efficiency is nominally 60 to 65 percent, so to be safe, plug 0.6 into your equation. Efficiency is the ratio of how much mechanical power is produced to how much electrical power is consumed. The difference between the two is how much of the power that gets converted into heat. If you put your hand on a compressor motor, you will know "right quick like" how really inefficient it is.
Gee, attaching the photo was more work than taking it apart. If you don't mind take a look. Looks like the ring cap or something similar is bent. In you guys estimation is this fixable or is there something else that may have caused it and I may be throwing good money after bad?
It's only $38 for the kit but maybe there's a reason for the the mess up.
Mike
Hey Mark,
It's the only visible damage. The cylinder is light aluminum and I guess it did have some scoring although not deep (my only comparison would be brake rotors). I believe the kit comes with the rod and all of the pieces pictured. It will probably be worth the money to see if it works. I'm not much of a mechanic but I'm guessing the loudness comes from the additonal air passage by the valve in the cylinder.
Thanks,
Mike
These oilless compressors are really simple little machines and doing an overhaul is easy. There is no scoring of cylinder walls to even worry about because the rebuild kit comes with new reed valves, piston, and kevlar cylinder wall. You will see that the aluminum block is just a mounting fixture for the parts and is unlikely to have any problems. The most likely cause of the sudden change in loudness is almost certainly due to a fatigue crack in the intake reed valve. If you wait long enough, it will break off and be ingested into the cylinder at which point there will be another sound change. Just don't ask me how I happen to know this. Anyway, the piston, cylinder wall, and valves were all toast in my compressor -- I installed the kit and it took less than an hour and I was back in business. Your next compressor needs to be oil type with real pistons and steel sleeve cylinders in a cast iron or aluminum block. Your ears will thank you and in the long run it will cost less.
If the cylinder is scored, you're going to have a tough time getting a seal and any real CFM out of that pump. I think you should call PC and ask before you buy any parts. Also ask if you can use a cylinder hone to reduce the scoring yet still maintain a sufficient piston seal for worthwhile operation.
mm
See above. It is not a problem.
Thanks for the input. I checked and the kit comes with the cylinder sleeve, rod, o-ring, compression ring and cap for approximately $38.00 That's not too bad considering the replacement cost of the compressor. My only concern now is what caused it (may never know) and is there an underlying problem that needs repair also. I emailed PC and I am waiting on a reply.
Thanks,
Mike
Yep, that sounds like the kit that I got.
