Air Compressor 101

[Dartswinger70]

I have an old air compressor, that I picked up cheap,the tank is 15-20 gallon upright.I put a harbor freight pump on it and it works fine,but it bogs the pump down at approximately 30 psi,is there a check valve or a missing peice that will keep the pump isolated from the pressure in the tank?When i disconnect the outlet line it will pump all day,it seems to be working against itself like a car with a clogged cat.Also, if there is something out there,where can I get the part?Can anyone post a simple diagram of how to plumb a air compressor?Thanks for any feedback

 

[64dartwagon]

There is a check valve sometimes between the pump head and tank. You might have a larger pump head than what that motor is setup for. If it's output is higher than the one before then most likely the drive motor is to small, and won't last long or just overheat alot.

 

[SRT_DSTRHOLC]

Whats good good enough compressor for holding the valves in the head durinng spring changing?

 

[DARTLARRY]

what size motor do you have? It sounds like the motor cant turn the pump once it builds up backpressure. Go to a bigger motor and it should be ok.

 

[RedFish]

Just thinking out loud again... If the motor is wound for both 110V and 220 V , there may be a problem in those connections.

 

[Prine]

I know one thing about compressors, a 1.1hp, 17 gallon cannot keep up with a DA sander!!

I should have got a 5hp!!

 

[dgc333]

I know one thing about compressors, a 1.1hp, 17 gallon cannot keep up with a DA sander!!

I should have got a 5hp!!

Don't pay any attention to horsepower ratings on compressors. The numbers they advertise are not true representations of the capability of the motor or the compressor. The only important thing to use for comparison is the cfm rating and the pressure that it's rated at.

For example a 5 HP electric motor that runs on typical 120 volt household current would require a 35 amp service. Your common plug is only rated for 15 amps and the wiring in your house is typically only rated for 20 amps. So if you see a compressor with a 5 HP rating and it has a regular NEMA 5-15P plug on it then you know the rating is bogus. You could have a 5 HP rating if it was a 220 volt motor but would you would need a 220 volt circuit.

The way they get away with this is in order to get a UL safety certification one of the test that must be run on an electric motor is what is called a locked rotor test. What they do is lock the motor so it can't turn and let it draw what ever current the motor wants regardless of any fuses (curretn or thermal) or the wiring external to the motor. What they are trying to determine is if the motor will catch fire or do anything else that would be dangerous to the user. If the motor happens to draw 31 amps at 120 volts that converts to 5 HP. The whole compressor system will have thermal overload as was well as over current protection that limits the motor 2 HP before tripping.

 

[Dartswinger70]

I think the motor is ok, it spins when the pump bogs, and starts to burn the belt,anyone know where I can get a 1 way valve for the circuit between the pump and tank?

 

[64dartwagon]

If your belt is slipping then that's no good either. Putting a check valve in won't lower the pressure that the pump has to overcome to get more in. As the pump goes to a higher pressure it has to work harder, what good is a 9oohp smallblock and a Dana 60 if your using a 300,000 mile burnt up 904. It just ain't gonna work right, and your not going to be happy with the results.