Sanity check on 240v outlet...

[Don1357]

This should be a quicky for anybody that knows what they are doing

I'm wiring a 30amp breaker for my compressor. The 10 gauge wire is black, white, and bare ground. Obviously black and white go into the 30 amp breaker but do I put the bare to the neutral bar or the ground bar?

 

[mike93lx]

ground bar. it is a EGC (equipment grounding conductor), not a neutral

 

[wyliesdiesels]

This should be a quicky for anybody that knows what they are doing

I'm wiring a 30amp breaker for my compressor. The 10 gauge wire is black, white, and bare ground. Obviously black and white go into the 30 amp breaker but do I put the bare to the neutral bar or the ground bar?

Thats a loaded question

First off, whats the HP rating on the motor? If more than about 3Hp, it will need to be hardwired.

Second, the answer to your question depends on what type of panel youre connecting it to. If its the main service panel, then the neutral bar is usually also the ground bar since its bonded to the enclosure.

However, if this is in a subpanel with a 4-wire feeder, then the EGC from the compressor circuit needs to go to the ground bar.

 

[Wrench97]

Put black tape on the exposed ends of the white wire to ID it as hot.

 

[Don1357]

Sub panel, non bonded ground (I should have said that). I'm wiring it to ground then.

The compressor 'claims' 7hp. but that's the usual peak power shenanigans. The plate states 17.3 amps at 240v, which is a smidgen less than the 2hp motor on my grizzly dust collector pulling 18 amps @ 240v. It is rated for 100% duty cycle so it should make me happy.

 

[wyliesdiesels]

Sub panel, non bonded neutral (I should have said that). I'm wiring it to ground then.

The compressor 'claims' 7hp. but that's the usual peak power shenanigans. The plate states 17.3 amps at 240v, which is a smidgen less than the 2hp motor on my grizzly dust collector pulling 18 amps @ 240v. It is rated for 100% duty cycle so it should make me happy.

Fixed it for ya

and 17.3a would be way more than a 2HP motor. It would be at least 3Hp if not closer to 3.5hp.

The NEC FLC lists 2hp as 12a and 3HP as 17a....

both your motors are at least 3HP. make sure whatever receptacle and plug you use is rated for at least 3HP

 

[ezzzzzzz]

I installed dedicated 50amp and 30 amp outlets to feed my mill, lathe, band saw, welders, lift and compressor. Nothing is hardwired but every plug and cable is sized appropriately.

 

[mike93lx]

I installed dedicated 50amp and 30 amp outlets to feed my mill, lathe, band saw, welders, lift and compressor. Nothing is hardwired but every plug and cable is sized appropriately.

You bought HP-rated plugs? Amp rating and HP rating aren't the same thing

 

[u2slow]

I installed dedicated 50amp and 30 amp outlets to feed my mill, lathe, band saw, welders, lift and compressor. Nothing is hardwired but every plug and cable is sized appropriately.

The important thing to know is that its unsafe to 'pull the plug' on a running machine of significant HP due to arc-flash. IMHO, your plugs/receptacles will handle the nominal current otherwise, but are likely a Code violation - because most things electrical have to be idiot-proofed. HP-rated plugs/receptacles (usually with interlocked disconnects, and/or arc-shielding/quenching ability) will cost you large. That's why hard-wiring takes over.

The other thing is motor table current values found in the Code books. These are historical values derived from very basic/standard motor designs. Modern motors (i.e. your actual motor) may use capacitors, or be slightly more efficient, to reduce the full-load current requirement. Thus begins the argument of whether to size a circuit per the equipment on-hand, or the generic xHP motor in a book. (Different Codes do things differently.)

What's safe enough for you?

 

[Don1357]

The important thing to know is that its unsafe to 'pull the plug' on a running machine of significant HP due to arc-flash. IMHO, your plugs/receptacles will handle the nominal current otherwise, but are likely a Code violation - because most things electrical have to be idiot-proofed. HP-rated plugs/receptacles (usually with interlocked disconnects, and/or arc-shielding/quenching ability) will cost you large. That's why hard-wiring takes over.

The other thing is motor table current values found in the Code books. These are historical values derived from very basic/standard motor designs. Modern motors (i.e. your actual motor) may use capacitors, or be slightly more efficient, to reduce the full-load current requirement. Thus begins the argument of whether to size a circuit per the equipment on-hand, or the generic xHP motor in a book. (Different Codes do things differently.)

What's safe enough for you?

Gosh, you were reading my mind... I was about to ask how in the hell a plug designed to handle the amperage was not designed to, I don't know... handle the amperage?

I mean when my electrical ignorant mind thinks about it you have to wonder, why on earth would you have a 240v 30 amp plug when you are not supposed to connect a 240v machine pulling 18 amps? Based on what you are saying I can see how having something arc-flashing on the confined spaced under the stairs, shared by the dust collector atomizing very fine dust, can be a very-very-very bad idea.

 

[u2slow]

No problem.

FWIW, my portable compressor is one of the largest that comes cord/plug connected. Its rated 15A @ 240V, 2.98kW (very close to 4HP) with a factory 6-20P.

 

[wyliesdiesels]

No problem.

FWIW, my portable compressor is one of the largest that comes cord/plug connected. Its rated 15A @ 240V, 2.98kW (very close to 4HP) with a factory 6-20P.

the factory 6-20P is fine but good luck finding a 6-20R with that high of a HP rating...

 

[u2slow]

the factory 6-20P is fine but good luck finding a 6-20R with that high of a HP rating...

I believe that's one of the reasons it's HP is listed as 'SPL' instead of an actual number. The machine is manufactured as a complete consumer product meant to plug into any std 6-20R general-use circuit.

 

[wyliesdiesels]

I believe that's one of the reasons it's HP is listed as 'SPL' instead of an actual number. The machine is manufactured as a complete consumer product meant to plug into any std 6-20R general-use circuit.

whoops i didnt see the 15a FLA.

no way is that 4HP.

3HP is 17a FLC

you can't use the wattage to determine HP because no motor is 100% efficient.

your motor is about 3HP

 

[theoldwizard1]

Put black tape on the exposed ends of the white wire to ID it as hot.

Red would be better !

 

[Jim greengo]

ground bar. it is a EGC (equipment grounding conductor), not a neutral

It doesnt matter if the panel is a main and not a sub.

 

[Don1357]

What does it entails to hard wire this thing? Is it basically to run a metal shielded wire from a wall box to the compressor itself? The compressor doesn't have an on/off switch. I see Home Depot has this switch:

https://www.homedepot.com/p/GE-30-Amp-240-Volt-Non-Fuse-Indoor-Safety-Switch-TGN3321CP/100674081

So wire to this on/off switch, then wire the compressor on metal conduit to it?

 

[wyliesdiesels]

yes you would run some FMC/flex from a wall j box or disconnect (required if further than 50' from and not within sight of, the breaker panel), to the termination point on the compressor.

 

[u2slow]

whoops i didnt see the 15a FLA.

no way is that 4HP.

3HP is 17a FLC

you can't use the wattage to determine HP because no motor is 100% efficient.

your motor is about 3HP

Its a capacitor-run motor, so the (running) line current is lower than table values.

You may be right on the watts. I rarely see a kW rating on 60Hz motors.... and there's no HP marking to compare to.

3HP still beats the 2HP receptacle rating... so once again we see there's one set of rules for installers, and another for the manufacturers.

 

[sberry]

I think one thing about mfg is the stuff has a switch on it. My pressure washer has real 5 hp and comes with 30A cord and plug.