Air Compressor Wisdom

[bigdee]

I do have another question though.........In replacing the pressure switch, I noticed that who ever installed it had it wired backwards according to the labeling on the switch. They had the supply line wired to the motor side and the motor wired to the line side......how much did that matter? l

It will make no difference at all.

 

[ehenry]

Bonz, its a 3hp. The pressure switch was a very common rectangular Funas/Hubbell switch. I have another compressor with the same type switch and the instructions in the cover are the same.as the old switch that burned up and the new switch I just purchased.

I have another problem now that I need help with. Both the old pressure switch and the new pressure switch have a place for a small 1/4 line. The old switch didn't have a line running to it and it worked fine until it burned up. When I installed the new switch I decided to run the 1/4 inch line to it thinking it would allow the switch to function like it should. Well, when the compressor reaches the shut off point, it shuts down and then air bleeds from a small bleed hole in the fitting where the 1/4 inch line connects and continues to bleed until the cut-in point is reached. Any ideas on this one?? Cut-out is 140lbs cut-in is 115lbs. The switch came preset at this setting.

 

[ehenry]

Disregard ya'll......Google and youtube are wonderful things.

 

[bonz_d]

So why is it that you think you need such heavy wire for a high voltage 3 hp motor? It shouldn't be pulling more than 10 amps. We wire 5 and 10hp 480v with 10 or 12 ga. wire. That 4ga is good up to 85.amps 12ga up to 25 amps. Which is one of the reasons for going to high voltage 220/240.

 

[bonz_d]

Disregard ya'll......Google and youtube are wonderful things.

Unloader valve?

 

[bigdee]

So why is it that you think you need such heavy wire for a high voltage 3 hp motor? It shouldn't be pulling more than 10 amps. We wire 5 and 10hp 480v with 10 or 12 ga. wire. That 4ga is good up to 85.amps 12ga up to 25 amps. Which is one of the reasons for going to high voltage 220/240.

Correct. For a 3hp 240 volt motor 12-2 is adequate. You may have to use a 30 amp breaker to handle the starting current though.

 

[ehenry]

Well its not that I think or thought I needed that heavy of a line. The reason for the #4 wire is that it was already in place for an old Lincoln cracker box welder that I very seldom ever used. All I had to do was reroute line to where I'm placing the compressor, wire in the shutoff and I'm ready to go.

Does anyone know anything about the centrifugal unloader on this compressor? I don't believe its working like it should since it bleeds air the entire time the compressor is running then quits when it reaches the cutout set point.

 

[bonz_d]

Sounds like a terrific reason to me to use it!
Try looking at this site, might find your answer to the unloader.
http://www.about-air-compressors.com/compressor-repair.html