I bought a 220v air compressor a few weeks ago, which the previous owner had hard wired in his shop. instead of cutting the wires cleanly he disconnected them. it's taken me a while to wrap my head around it but if i understand correctly, 220v doesn't need a ground although it's not a bad idea to install. That being the case, should i just ground the "green" wire to the frame of the air compressor? what's the safest / recommended way to proceed?
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adding a ground to my 220v air compressor?
- Thread starter upjeeper
- Start date
The ground is for safety. It is not needed for normal function. All equipment should be grounded. The ground just needs to connect to the metal body of the motor or controller.I bought a 220v air compressor a few weeks ago, which the previous owner had hard wired in his shop. instead of cutting the wires cleanly he disconnected them. it's taken me a while to wrap my head around it but if i understand correctly, 220v doesn't need a ground although it's not a bad idea to install. That being the case, should i just ground the "green" wire to the frame of the air compressor? what's the safest / recommended way to proceed?
theoldwizard1
Well-known member
240V motors do not need a NEUTRAL. They should have a GROUND !
Duke74
Well-known member
Theoldwizard. I was going to say that but ya beat me to it.
wyliesdiesels
Well-known member
Its 240v and it most certainly does need an EGC. Every circuit should have an EGC. It is for safety. Perhpas you confused EGC for neutral?I bought a 220v air compressor a few weeks ago, which the previous owner had hard wired in his shop. instead of cutting the wires cleanly he disconnected them. it's taken me a while to wrap my head around it but if i understand correctly, 220v doesn't need a ground although it's not a bad idea to install. That being the case, should i just ground the "green" wire to the frame of the air compressor? what's the safest / recommended way to proceed?
Its 240v and it most certainly does need an EGC. Every circuit should have an EGC. It is for safety. Perhpas you confused EGC for neutral?
thanks. not sure, that's why i'm asking. it is an older unit, and current pressure switches (like you see on your water pump) have a ground point on the switch itself, but neither the motor nor the pressure switch have a point that looks like it would have a ground.
i'm familiar with 220v / 240v not requiring a neutral.
220 volts has a neutral but is 50 Hertz 208V or 240V does not.thanks. not sure, that's why i'm asking. it is an older unit, and current pressure switches (like you see on your water pump) have a ground point on the switch itself, but neither the motor nor the pressure switch have a point that looks like it would have a ground.
i'm familiar with 220v / 240v not requiring a neutral.
the ground is there so that if a hot leg touches the frame, it will trip your breaker from the dead short. the alternative is your compressor is now live at 120V above ground potential, and when you touch it and something else, YOU are now the ground path.I bought a 220v air compressor a few weeks ago, which the previous owner had hard wired in his shop. instead of cutting the wires cleanly he disconnected them. it's taken me a while to wrap my head around it but if i understand correctly, 220v doesn't need a ground although it's not a bad idea to install. That being the case, should i just ground the "green" wire to the frame of the air compressor? what's the safest / recommended way to proceed?
The former is clearly the preferable choice. the ground doesn't really make the machine "safer", it just lowers the risk to you significantly by preventing this one single condition from continuing. call it semantics if you want. this is why the ground wire must be big enough to carry the fault current without burning up or being too small to trip the breaker. The machine will happily run without the ground connected.
I won't speak for all models but at least for the ones I've seen without a magnetic starter (ie the motor is directly switched by the pressure switch) the ground connects in the pressure switch. That ground lug is connected to the metal body of the pressure switch. The metal body of the pressure switch connects to the tank via the short pipe it's threaded onto. That grounds the tank. The motor is bolted to a metal plate which is welded to the tank. So the motor is grounded via the tank and the pipe to the pressure switch.thanks. not sure, that's why i'm asking. it is an older unit, and current pressure switches (like you see on your water pump) have a ground point on the switch itself, but neither the motor nor the pressure switch have a point that looks like it would have a ground.
i'm familiar with 220v / 240v not requiring a neutral.
Wrench97
Well-known member
Pressure switch is metal screwed into a metal tank with a metal motor bolted to it, 1 ground wire to the switch grounds them all.thanks. not sure, that's why i'm asking. it is an older unit, and current pressure switches (like you see on your water pump) have a ground point on the switch itself, but neither the motor nor the pressure switch have a point that looks like it would have a ground.
i'm familiar with 220v / 240v not requiring a neutral.
wyliesdiesels
Well-known member
grab a multi-meter or ohmmeter and test from bare metal on the motor frame or tank to the bare metal on the pressure switch. if you dont have continuity then something is wrongthanks. not sure, that's why i'm asking. it is an older unit, and current pressure switches (like you see on your water pump) have a ground point on the switch itself, but neither the motor nor the pressure switch have a point that looks like it would have a ground.
i'm familiar with 220v / 240v not requiring a neutral.