Magnetic switch disconnect question

[Todd.Brock]

I acquired two Champion compressors over the weekend. One is a 5hp 3 phase set up. The other is a single phase setup I am considering keeping. My end goal is to not leave the compressor powered on. I don’t want a small leak to cycle the compressor at 3 am. How is the best way to go about that? I verified that it was wired up consistent with some posts by GA Hybrid (I searched! ) so I connected it temporarily, and when I switched the panel breaker on, the compressor started. I expected to have to press a button on the mag starter. The square in the center of the mag switch depressed as soon as power was applied. I assumed that was a start button. I understand that b/c there was no tank pressure, the pressure switch did what it was supposed to do.. but raised the question of where should a disconnect go?





Also, the covers are missing. Is there somewhere that I can replace the enclosure or at least find a cover ? I may have to buy a whole new switch to get the cover. If I have to get a new pressure switch, should I get one with an on/off switch?

Edit... Wires that are wrapped in painters tape are from the low oil shut down switch. I don't know where to wire these in in the mag switch. I'm not super concerned with a sight glass showing oil level

For clarity, it is a 3 HP 1740rpm motor, so the receptacle and plug have not been exceeded. It is rated at something like 16 or 18 amps. I have a 30 circuit powering it.

 

[G_P]

You can put a switch on the wires from the pressure switch to the mag starter. Just get a toggle switch and drill a hole in the side of the mag starter enclosure and mount it there.

Post up a pic of the mag starter and its enclosure. I have some empty enclosures left over from old starters that were burned up and may have a cover that will fit yours.

 

[Todd.Brock]

Thanks GP. Pics added!

 

[Stuart in MN]

I agree, putting a switch in line with the pressure switch is probably the simplest thing. Those enclosures look pretty generic, if you can't find a cover I'd just get a new empty box and put the existing starter in it.

 

[Charles (in GA)]

When you install it, you will need to add a disconnect switch on the power circuit that supplies the compressor. Most likely wall mounted, adjacent to the compressor. Throw this switch off and the power to the compressor is cut off. For hard wired equipment like this, a disconnect is required for equipment that is more than 50 ft from the circuit breaker panel, or if the breaker panel is not in the line of sight from the equipment.

When you powered the compressor it did just what it was supposed to do. The pressure switch was calling for pressure, and making the circuit to close the magnetic starter.

The square button in the middle is part of the movable contact mechanism. It simply allows you to force the contacts together manually and make the motor run, when the relay is not commanded to by the pressure switch. Not needed on a compressor, but useful on some other types of equipment or machinery.

Charles

 

[rockwithjason]

Usually there is a switch on the pressure switch enclosure that locks out the auto start feature. If not just add one as stated by others

 

[Todd.Brock]

Since I may have to get a new pressure switch to get the cover, I will get one with the on / off / auto switch. The panel is about 15 feet away on the same panel. I will wire it in correct, I just wantes to make sure the compressor ran as it should. It does! Thanks again...

 

[Todd.Brock]

I meant to ask, what amp or HP should the pressure switch be rated for? I am using a 30 a circuit and a 3 HP motor. B

 

[Stuart in MN]

Since you have motor starters, they are supplying the current for the compressor motor. All the pressure switch has to do is supply current to energize the starter, and that's pretty miniscule - probably 100 milliamps or so, in any case less than an amp.

 

[Todd.Brock]

I just wasn't sure what info was needed. So it won't matter about hp , I just need 145-175 psi range with an off and auto switch.

 

[malibu101]

You can put a switch on the wires from the pressure switch to the mag starter. Just get a toggle switch and drill a hole in the side of the mag starter enclosure and mount it there.
.

That's exactly what I did to solve this same problem.

 

[Todd.Brock]

Well, all cleaned up and rewired. I didn't use the low oil switch. I used 10-3 soow until I can figure out exactly where the compressor will live in the garage. It's a 3 HP motor so I'm cool as far as a plug. Thanks for the input!