guys with air compressors come in please

220 is 110 doubbled up in the breaker pannel with a 220 breaker and a thicker wire ran to the comp

Buy a 110 electric motor and put a bigger pully on it so it's easier to turn the motor. And sell the current motor and probly make money. Some electric shops would trade you and maby through in a bit of cash for you.

Any good electrician should be able to run you a 220 in your garage for a few hundred.

If your compressor is curently wired for 220 then it will NOT run on 110. 220V power in this country is dual phase power. You'll have to pardon me if you already understand that, I had some difficulty following the initial post.

If your buddy ran it through a 110 outlet at his house then it's wired for 110. His blowoing a circuit breaker or fuse can indicate lots of things. It doesn't necessarily mean it will do the same at your place. Don't use extention cords. Plug it in and see if it works before making rash changes.

If there is a breaker box in your garage (often there is if it's an original attached garage) then putting a 220V outlet in is cake and won't cost you much. You can rewire the motor to run 220 (if able) and toss an outlet in.

Most motors with more that 1HP will run on either 110 or 220 volts. Many of them will have a wiring diagram on the motor showing what wire to move/use for 110 or 220.

The problem is that if you run the motor on 110 volts it uses up twice the current that it would on 220. A 220 volt motor uses 15 amps, but the same motor running 110 volts uses 30 amps. Your 3 HP motor figures out to be 20 amps and some change when using 110 volts. One HP = 746 watts, so 3 HP x 746 = 2238 watts, divide 2238 watts by 110 volts to get 20.34 amps.

That means it has to be the only thing on that circuit. No lights, refrigerators, fans or anything else but the compressor. Turn the breaker off or remove the fuse for the circuit that the compressor uses and see what goes off.

Compressors need either a slow blow fuse or a circuit breaker. Use a regular fuse and it will blow just before the automatic pressure shutoff turns the motor off - I found that one out the hard way.

Daggar said:

If your compressor is curently wired for 220 then it will NOT run on 110. 220V power in this country is dual phase power. You'll have to pardon me if you already understand that, I had some difficulty following the initial post.

If your buddy ran it through a 110 outlet at his house then it's wired for 110. His blowoing a circuit breaker or fuse can indicate lots of things. It doesn't necessarily mean it will do the same at your place. Don't use extention cords. Plug it in and see if it works before making rash changes.

If there is a breaker box in your garage (often there is if it's an original attached garage) then putting a 220V outlet in is cake and won't cost you much. You can rewire the motor to run 220 (if able) and toss an outlet in.

Click to expand...

Daggar is right. Make sure you connect electric motors to the voltage they are designed for.

I might be able to help since my job is electrical engineering . Excuse me if this is a little long or if I offfend anybody. But here it goes..........

The voltage to the typical residence in the US is 120v/240v, single phase. You probably hear 110v, 115v, and 120v often used in conversation. For all intents and purposes, the are the same. Actually, the measured voltage should be close 120 volts for phase-to-ground (hot to ground). 240 volts, single phase is what you get when you measure phase-to-phase (hot to hot). It sounds wrong, but 240 volts is what you get when you have 2 hots supplying a load. This voltage is commonly refered to as "220". A majority of single phase 240v motors are labelled 230 volts. This is done because some electric company's voltage quality is not that great and might be a little lower than 240 volts, especially way back when. The motor is designed to operate, or see, a voltage in the 220v-240v range. If you connect a 230v motor to a 240v supply, there is no problem. This is actually good because there is a little less current, or ampacity draw. (voltage x ampacity = wattage) Higher voltage equals less current draw. However, if the voltage "dips" too low, say down to 200 volts, the same motor will draw more current and can overheat, or overload and will/should "trip" the circuit breaker, or fuse. The load on the motor (such as a frozen pulley) can also cause problems, but that is beyond the focus of this. The bottom line is that 220 motors and 230 motors (single phase) are one in the same.

So, if the 3hp, 230v motor is single phase, it will draw approx 17 full load amps. You will need a 30amp/2-pole circuit breaker in your panelboard (aka: breakerbox or fuse box). This will protect your motor and circuit conductors as per the NEC. Also, you should run 2 #10 awg copper (preferred) conductors for the "hots" or phase conductors and 1 #12 awg grounding conductor in a minimum 1/2" conduit from the circuit breaker, or fuse, to the compressor. You can also run Romex, or another type of multi-conductor cable. A proper means of disconnection should be there as well, such as a plug/cord setup with a receptacle (on the wall adjacent to the compressor). You can "hard-wire" the compressor, eliminating the receptacle (aka: plug) as long as the load (the compressor) is in the line-of-sight of the panelboard.

Whatever you do BE CAREFUL. Electricity can mess you up, or kill you, if you're not careful. If you don't feel comfortable with doing this type of work, or haven't done this before, get somebody with some experience to help you. Or, just get an electrician to help you.

Sorry for the long response. Let me know if I can be more confusing.

Bottom line is you should be able to use this compressor, so be

Mike

jrichker said:

Most motors with more that 1HP will run on either 110 or 220 volts. Many of them will have a wiring diagram on the motor showing what wire to move/use for 110 or 220.

The problem is that if you run the motor on 110 volts it uses up twice the current that it would on 220. A 220 volt motor uses 15 amps, but the same motor running 110 volts uses 30 amps. Your 3 HP motor figures out to be 20 amps and some change when using 110 volts. One HP = 746 watts, so 3 HP x 746 = 2238 watts, divide 2238 watts by 110 volts to get 20.34 amps.

That means it has to be the only thing on that circuit. No lights, refrigerators, fans or anything else but the compressor. Turn the breaker off or remove the fuse for the circuit that the compressor uses and see what goes off.

Compressors need either a slow blow fuse or a circuit breaker. Use a regular fuse and it will blow just before the automatic pressure shutoff turns the motor off - I found that one out the hard way.

Click to expand...

jrichker is also right. Make sure NOTHING else is on the compressor circuit, just to be safe, and not to complicate the situation.

btw the reason my amps are diff is that I used the NEC table 250-95 which indicates 17 amps at 230 volts. So if you're at 220 volts it will be a little more.

mike50sa said:

So, if the 3hp, 220v motor is single phase, it will draw approx 17 full load amps.

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Your amps and my amps don't jive - 3 Hp comes out to 2238 watts + a small fudge factor for the inefficiency of the motor. The 2238 watts works out to be 20.34 amps at 110 volts and 10.17 amps at 220 volts. That's a lot of difference. I think one of us missed something along the way.

Hey Mike...


I gotta get some clarity on your post so bare with me.

You say that 220V wiring in a home here in the U.S. is single phase? I know that that's often what it's referred to but isn't it actually dual?

Each leg of 120V to neutral in A/C current (pushing and pulling electrons) would be a single phase while combining 2 of those legs to make 220V would show a double sine wave. The 220V would be the difference peak to peak between each phase (one phase pushing while the other pulls). Isn't that correct?

Daggar said:

Hey Mike...


I gotta get some clarity on your post so bare with me.

You say that 220V wiring in a home here in the U.S. is single phase? I know that that's often what it's referred to but isn't it actually dual?

Each leg of 120V to neutral in A/C current (pushing and pulling electrons) would be a single phase while combining 2 of those legs to make 220V would show a double sine wave. The 220V would be the difference peak to peak between each phase (one phase pushing while the other pulls). Isn't that correct?

Click to expand...

No problem. You're right in what you are saying. However, "single phase" 240 volt is achieved with 2 phase conductors, but still referred to as single phase. Essentially you have a "two phase", or dual phase distribution. The measured voltage is as you state, peak-to-peak. To elaborate, 240 cannot be achieved with only one phase (or hot) conductor and a ground. So I can see where the terminology is misleading. It's a phase-to-phase measurement but it's referred to as "single-phase 240v". The industry doesn't refer to it as two phase. A 240v service is comprised of 2 hot conductors (one per phase) and a ground. A 120 volt feed is measured phase-to-ground as is comprised of a hot, a neutral, and a ground.

jrichker said:

Your amps and my amps don't jive - 3 Hp comes out to 2238 watts + a small fudge factor for the inefficiency of the motor. The 2238 watts works out to be 20.34 amps at 110 volts and 10.17 amps at 220 volts. That's a lot of difference. I think one of us missed something along the way.

Click to expand...

It's cool. I was just using the National Electrical Code, Section 430 "motors, motor circuits, and controllers", Table 430-148.

I was looking at something else earlier when I quoted Table 250-95, that was incorrect. Section 250 is for grounding.

The best way to find out how many amps the motor draws is to look a the motor itself. It will have a name plate on it that will give the voltage ratings, amperage draw and other pertinent informations.

Since it is a dual winding motor it should say something like

Voltage
110/220

Amp
???/???

The numbers should be respective, i.e. in the voltage section if the 110 is first the first # in the amp section will be what the motor draws. The motor will draw more amperage at 110 than it would if wired up for 220.

For a safety factor you should try not load a breaker in excess of 80% of its rating. So if you have 20 amp breaker it is best to keep the load under 16 amps.

Unfortunately the straight HP-watts-amps conversion doesn't really work well since a motor is an inductive load. If it were a resistive load, i.e. heater or incandescent light it would work fine but with a motor the amperage and voltage are not "in phase" with each other and depending on how efficient the motor is determines to what degree they are out of phase with each other. Kinda complicated and lots of math.

10 years as an electrician pays off every now and again.

220/221, whatever it takes