quincy qt 5 80 gallon air compressor ground wiring

hello fellow enthusiasts. ..need help asap wiring my compressor. i am stumped as to the grounding :/ where exactly would i connect ground cable to compressor? have the breaker/panel part figured out using 3 wire. any and all input is appreciated.noticed two green screws inside compressor electrical box. the motor is grounded to one, the other does not have anything connected to it so im ***uming would ground there?? thanks

 

If it's green, should be ground. If the motor ground is green and also elctrically conductive to the other, unused green when checked w/VOM, unused terminal is a ground.
Dave

 

two hot wires usually one is black and one is red and a white neutral wire, there may also be a green screw or screws to attach a green bonding wire

 

I have an IR 80 gal 220V and have the 2 green screws in the pressure switch box also but only 1 ground wire attached to 1 screw, other screw is not used.

 

thanks fellas...sounds good. chaos, so did your ground comming from panel/breaker connect to green screw?

 

***uming you are using 3phase yes that would be the ground location or sometimes they will have copper lug screwed to the back of the box. If you are running single phase make sure the wire you "ground" is actually the ground before you do it though.( I ***ume 3phase because you described a 3 wire breaker panel)

 

It would be rare to have 3 phase in a home, I think the 3 wires are 2 hot and one ground or neutral, and yes the green lug would be the ground wire. Not needed but for safety if something fails.

 

the unused green screw is most likely bonded to the other one with the ground wire on it threw the can or a bar. definately ground your compressor.
not just throwing out suggestions without been doing electrical for 23 yrs.

 

thanks again to all. ..its a single phase, so yes two hot and one ground. just picked up all i need to finish installation from the local hardware so i can get "big blue" blowin this weekend. you guys are awesome.
alex