220 vs 110

[cg 2005]

I knew that eventually a EE would respond with an answer a CE could understand. I will convert to 220 on the 9x20 and any others when possible because it's just cool to say you got 220 machinery.

 

[RWL]

Your motor will come up to speed faster at 220 than at 110. I'm not familiar with your lathe, but if it starts quickly, let it alone. If on the higher speeds the lathe takes a few seconds to come up to speed, 220 will improve that.

 

[Jeephead]

This question comes up all the time. There were many good answers but lets get real. Technically it is cheaper to run on 240 volt. This has to do with wiring resistance. For motor operation resistance is just s waste of energy in the form of heat. 240 volts require half the current that 120 volt require. So less heat is generated which means it is more efficient. there are many other factors to efficiencies like wire sizing, material, and windings. Unless you are a factory with lots of motors, don't worry about it.

So what does 220 volts buy you? Maybe nothing unless you have a large load. First let me say I as a rule of thumb of 7.5 amps per horse power (HP) at 120 volts. This is a good number for a good motor with its inefficiencies. Lets use my table saw as an example. It has a 2 HP motor. Under normal load, that means it will draw 15 amps (W=I*E). It is normal to exceed that 15 amps calculation when you load the motor.

When I ran oak through the saw it was not unusual to trip the 20 amp breaker. 20 amps - 15 amps only leave a 5 amp head room. If the breaker didn't trip, the thermal over load on the motor did. Now what about 220 volts. If you double the voltage the current is cut in half. So when I convert my table saw to 220 volts, the current required is 7.5 amps instead of 15. Now with the same 20 amp breaker, I have 12.5 amps to spare before tripping. After changing to 220 volts on my table saw, I have never tripped the circuit breaker or thermal over load.

My feeling is this, if your motor is over 1 HP switch to 220 volt. You won't save any real money but your motor will be happier.

Sorry for the long winded response. Like anything else there is a lot more to this but for the home hobbiest, it doesn't amount to a hill of beans.

Watts cost the same 120 or 240 vac. The losses show up as copper losses in the wiring which is expressed as IxR squared with wire resistance doubling every 3 ga so, 10 ga is 1 ohm per 1000 ft. and halving less than 10 each 3 ga. So doing the math shows the heat loss with smaller wire and more current at lower voltage. Voltage loss is easy too with ohms times current showing volts loss. Again because of lower volts resulting in more current to get hp. Hp = 748 watts no matter volts which is what you pay for.

 

[OrangeAlpine]

Bill, I am not sure I am following your question - what do you mean by that?

See post #6. I had to lower the operating pressure. The motor was obviously overloaded when restarting on 110.

Bill

 

[stern]

Its probabaly a combination of things. Running on 110 the motor will start a bit slower, and when driving a pump head (compressor cylinder) this can present as a momentary larger load on the motor. Second, at 110 the current draw will be about twice that of 220, which means the "line loss" will be far more dramatic. With the current now about twice that of 220 over the same lines (from breaker to motor which includes all wiring), the voltage loss over that wire will double. Depending on the wire size and motor draw, this can reduce the voltage and make it harder for the motor to turn the pump head. I have seen it where the voltage drop can be as much at 10V.
I had this with one of my compressors, worked fine until it tried to turn on when there was pressure in the tank (start up with empty tank was no problem), then it would stall. the only way to get it run was to bleed more air out of the tank.

 

[PurpLev]

See post #6. I had to lower the operating pressure. The motor was obviously overloaded when restarting on 110.

Bill

Ok - yes in RE to that post you are correct - the length and gauge of wires does play a role in this. the problem is not that the motor was overloaded - the problem more likely is that the motor was drawing too much Amperage for the wires to be able to provide it and the line was overloaded - hence the requirement for lower gauge wires (thicker) and shorter runs otherwise when you overload the wires (not the motor) they can overheat and cause a fire hazard. That's why you have Amp rated breakers in your electrical box - to protect the wires in the walls from burning the house, not for the safety of your motors.

A 2HP motor should be run on a 30Amp 110v rated line at a minimum (40amp would be better considering start-up draws) - and is REALLY pushing the envelope with 110v...

 

[Tony Wells]

If you guys are having compressor starting problems on voltages the pump is designed for, then you have unloader problems that need to be addressed. You will eventually kill the motor if you don't tend to it.

 

[refinery Mike]

i am an electrician with 40 years experience. Leave the 110 motor alone. the only reason to go to 220 is when you get into larger horse power motors. then you will find that the wire size and breaker size starts to make a difference. Like try to find a 50 amp single pole 110 breaker. For a 9-20 lathe 110 will run just the same as 220. In fact the actual windings of the motor will not see any difference at all at 110 or 220 each winding sees 110 volts regardless. Low voltage has two 110 paths and high voltage has one 220 volt path sharing half of the voltage on each winding. If you put a volt meter on the motor windings both ways the windings will show the same voltage and current. The only advantage would be if you were running the electricity 100 yards out to a barn from your house. Then the higher voltage would be better because it would have less line loss going out to the barn.

 

[cdhknives]

Don't forget that you need an extra hot conductor to run US 220 (euro 230V is different) so if your wiring is not already set up for 3+G (typically red+black for hot, white for neutral, and bare or green for ground) it is NOT worth the effort to change 1Hp and below to 220V. The line loss savings is trivial and as mentioned the motor only runs cooler because it gets slightly higher voltages at the terminals (not double because of the serial vs. parallel windings, just less line loss).

If you are having the shop lights dim when your 1Hp motor starts, yeah, that MIGHT be fixed by switching to 220V to distribute starting amperage across 2 conductors (yes, that is the long and short of it, you are splitting the load between the 2 hot lines with US 220V)

If your motor is stalling at 110V it MIGHT be fixed by switching to 220 but you are PROBABLY masking a bigger problem causing larger starting effort requirements...dragging bearing, sticky pistons, bad starting capacitor, corroded wiring connections, etc.

 

[stern]

You can easily check if the problem is the compressor or lines by connecting the compressor directly to the the 110V on the breaker panel.If the problem persists then its a compressor issue, if not is simply line loss over the wiring. While the motor doesn't care either way (110 or 220) the voltage drop due to load current over the lines WILL change going to 220. When lights dim its a clear indication the "line voltage" is dropping.