Wiring Help Needed... 240volt 15amp Compressor??

[Ozsum2]

See my last post for an answer to that... You don't need any 120V line in a compressor, just 240V, so it sounds like they ditched the center-tap line... When we're talking about voltage, we're talkign about the DIFFERENCE in potential. So if you were to measure the voltage from the 240V line to the 120V line, it would read 120V, as would 120V to ground. Sounds like you just need the 240V hot, ground, and common.

White should never be hot in a situation like this... Its dangerous... It would put a potential on the chassis of the compressor.

OK, I'm confused. What is the solution?

 

[WORTH]

OK, if your generator has RED/Black/White/Green

and your compressor has black/white/green and is a 240 volt unit

connect red/generator to White/compressor
connect black/generator to black/compressor
connect white/generator to green/compressor

and if you feel so inclined you can connect green/generator to the sub panel case for ground.

now if you need to tap 110 volts off the sub for lights or whatever, you can use either the RED and White, or the Black and white for your 2 leads, and use the green for your ground.

EDIT; to clarify what someone already said. If you check the generator, you will get

120 across the black and white
120 across the red and white
240 across the red and black

the green is a ground to the case.

 

[nosaj122081]

OK, if your generator has RED/Black/White/Green

and your compressor has black/white/green and is a 240 volt unit

connect red/generator to White/compressor
connect black/generator to black/compressor
connect white/generator to green/compressor

and if you feel so inclined you can connect green/generator to the sub panel case for ground.

now if you need to tap 110 volts off the sub for lights or whatever, you can use either the RED and White, or the Black and white for your 2 leads, and use the green for your ground.

EDIT; to clarify what someone already said. If you check the generator, you will get

120 across the black and white
120 across the red and white
240 across the red and black

the green is a ground to the case.

Right... I agree. And I'd ground it just to be safe, you can't overground something.

If you visualize a transformer (just imagine the low side, just picture 1 long coil of wire around a magnet), the red wire comes off one end of the coil, the black off the other end, and the white line would come out the middle. If you were to put a voltmeter on any 2 lines, you measure the DIFFERENCE between the 2. Just like you'd measure 120 from hot to ground and 0 from hot to hot on a regular 120V outlet.

 

[JB66]

Thanks for the replies.. this should explain better.

My house has the main circuit breaker panel in the basement. All the breakers are used up. It also has a sub-panel installed right next to it. The sub-panel is an INPUT PANEL for our generator in case we lose power in the winter. The INPUT sub-panel doesn't have the garage on any of the breakers, just main ammenities.

My garage isn't wired for 240V, only 120V.

Is this INPUT PANEL hard wired to the main panel with a cutoff switch in between (I hope!)?

Last I knew, all the electric companies I've questioned and all the various electric codes in NY anyway, prohibit electrical generation equipment being directly connected to their system without their approval (which is based on the proper switching equipment [either manual or automatic] being installed between the lines). Correct me if I'm wrong, but you have the potential of connecting two sources of power to one line (which might solve your problem completely). All the single phase 240v wiring I've ever done has the Black and Red as the two hot leads and the white as the neutral. ie. you get 120v between black & white or red & white and 240v between red & black. The green wire is the ground wire always. It grounds the appliance or tool for the sake of safety. Liability insurance with their corresponding "laws" have pretty much mandated that this type of equipment be wired this way.

Bottom Line... If you're planning on using this compressor off your generator, install the box in your garage and run the cord directly to the generator.

 

[JB66]

BTW, does the motor say 120/240 volts on it? If so, it can be wired for EITHER, but internal wiring has to be changed! This is why they recommend a professional. I would wire it normally (120v) first, unless it specifically says 240v only, and see if it starts. If it's really 240v only, the starting capacitor won't build enough of a charge to start it. You'll know within 2-3 seconds.

 

[67bluestang]

I bought a 60 gal at Costco and used a 3 prong dryer cord and plugged it in to my outlet for the welder. White, Black for power and green for ground.
I looked at the compressor and from the way it's worded, it's 240v only. Most will say 120/240v if it will handle both.

 

[limey66]

OK guys, I've checked the books and the two pics below best show what you guys have over there. There is an error on the pics below - the dryer and cooker outlets (30A & 50A) have been switched between the drawing and the write-up, but you guys will know which is which, but beacuse of the green terminal I think you need the third option shown as an air conditioner outlet.

You need the two phases, and you say that you have one other terminal which is green. That can only be ground. Test it to see if there is continuity between the green terminal and the compressor casing. If there is, ONLY CONNECT IT TO GROUND. It seems odd that you have a white as a phase (normally neutral) but I'm sure that is the only way it can be:

green and that is the ground wire.
black and that is the hot wire.
white and that is the other hot wire.

That is the best I can offer from a few thousand miles away, and it will be the safest option if you don't know for definite what the terminals on the compressor are. If it's a 240V machine this is not the only way it could work with three wires, but the green one, surely, has to be grounded.

Let us know how you get on.

 

[Ozsum2]

OK guys, I've checked the books and the two pics below best show what you guys have over there. There is an error on the pics below - the dryer and cooker outlets (30A & 50A) have been switched between the drawing and the write-up, but you guys will know which is which, but beacuse of the green terminal I think you need the third option shown as an air conditioner outlet.

You need the two phases, and you say that you have one other terminal which is green. That can only be ground. Test it to see if there is continuity between the green terminal and the compressor casing. If there is, ONLY CONNECT IT TO GROUND. It seems odd that you have a white as a phase (normally neutral) but I'm sure that is the only way it can be:

green and that is the ground wire.
black and that is the hot wire.
white and that is the other hot wire.

That is the best I can offer from a few thousand miles away, and it will be the safest option if you don't know for definite what the terminals on the compressor are. If it's a 240V machine this is not the only way it could work with three wires, but the green one, surely, has to be grounded.

Let us know how you get on.

That's what we thought, but needed the go ahead from an expert. So, in some rare cases, white can be hot.

 

[1320stang]

Too tired to type a long reply (I came into work at 10pm Sunday and I'm just now leaving, got about 5.5 hours sleep in that amount of time), but my Craftsman had the diagram on the inside of the box that you have to take off to hook the wires up.