120V vs 240V electric motors

[Bird]

I may be buying a new air-compressor in the near future. I know what I want in a compressor, but am undecided as to whether to go with the 120 volt motor or the 240 volt. I like the idea of being able to plug one in almost anywhere, but the fact is that I'll very likely not move it around. The place it will be used has both 120 volt and 240 volt receptacles already in place. I understand the 240 is more efficient, but need someone to convince me which way to go, and why.

 

[kenmac]

I have a portable air compressor. 2 hp 20 gal. tank. This motor can be wired either for 220 or 110. I chose to keep it on 110 because if I want to take it somewhere else to use it, 220 maynot be available.

 

[PineRidge]

Bird a 220 volt unit will run for approx. half as much money (electricity usage) over the life of the unit than a 110 volt counterpart.

 

[Cliff_Johns]

</font><font color="blue" class="small">( Bird a 220 volt unit will run for approx. half as much money (electricity usage) over the life of the unit than a 110 volt counterpart. )</font>

I wonder how that works. They use about half the amps, but at twice the volts that makes about the same watts so the cost should be about the same, maybe a little less since 220 may be a bit more efficient.

Mostly, I use 220 when I need more torque like on a table saw. 220 motors don't bog down as easily. For a compressor, I wouldn't think it would make all that much difference, but the same motor wired 220 may last a bit longer.

Cliff

 

[Junkman]

More information is needed to make a proper evaluation. If you are going with a small compressor, there is no reason to use a 220 volt motor. If you are planning on having a larger unit, such as a 5 HP 2 stage compressor, then the 220 volt motor is the better choice. The higher voltage motors are more efficient in the way that they work. They have more torque and the ability to run for longer periods with less effort. The savings is like living in a very mountainous region of the country. A 4 cylinder car will use more gas to get up the mountain than its 8 cylinder counterpart, since the 8 cylinder car will have more power and be able to climb the hill with less effort. Like the 4 cylinder car vs. the 8 cylinder car, you need to know what environment that it is going to be working in. If this is a home workshop that you occasionally will be using a limited amount of air, then the 110 volt motor will be fine. If you are going to be using air powered tools in your workshop for any length of time, then the 220 volt motor will be better suited for your needs. Also, keep in mind that some HP ratings are not true to the advertised numbers. Not all motors are created equal.... /forums/images/graemlins/grin.gif

 

[v8dave]

A 120 V unit of substantial capacity will likely max out the breaker on that feed circuit. Typical full size air compressors on 120 V will draw 15 amps, so any other devices also on the same circuit may cause the breaker to trip.

Some times construction sized 120 V units units are rated to draw 20 amps which is supposed to be a special socket and heavier wiring although the plug will fit into a standard 15 amp socket.

Ever grasp the plug connectors of a 120 V compressor after it's been running a while? Kinda warm aren't they? Makes me uneasy, and the decision for a 240 V compressor a lot easier.

Now having said all this, if you get a light weight lower HP compressor, like used for a nail gun, then a 120 V unit makes a lot of sense. But, if you're going for a big tank unit get the 240 V one.

 

[deereman63]

i grew up with 240 volts. Machinery works a lot more efficiently ...just dont stick yours fingers into the conectors.

 

[Cityboyfarmer]

For power usage, a 120 volt motor does not necessarily use more energy than a 240. Multiply volts times amps and that will give you the VA rating of the motor. For example, a 120 volt motor that pulls 15 amps uses 1800 VA (Volt/Amps) A 240 volt motor that pulls 7.5 amps also consumes 1800 VA. Efficiency calculation comes in when VA is converted to wattage. an 1800 VA motor that produces 1440 watts of usable energy is 80% efficient. Motor quality varies. Better quality = more $$$

Now that I have glazed your eyes over with stats, I like 240 volt motors for the higher VA applications. If the compressor you like pulls over 15 amps at 120 volts, I would choose the 240 volt motor. If it pulls under 15 amps at 120 volts, I would choose the 120 for the flexibility.

 

[_RaT_]

Bird, look at the nameplate amperage draw at 120V and then 240V on switchable voltage motors. For example, if a compressor motor that is 120V/240V draws 12 amps at 120V, it will draw 6 at 240V. Whether its 12 X 120 or 6 X 240, the wattage is the same excluding efficiencies. As you know, once you take into account the run of wire from the electrical panel to the servicing outlet, through whatever cord you may add to the compressor, it will have a voltage drop. That drop will be higher as the current through it increases but minimized when larger condcutors are used. Is it a concern? Only if it gets excessive. Most devices can easily handle swings either way of about 5 volts. So for a 120V outlet that drops to 115V as a result of the air compressor turning on, you will be fine. I have found on my small Emglo direct drive that I will frequently pop the built in breaker on a cold morning. The solution, let the compressor run with zero head pressure until the oil warmed up or even better, use synthetic oil, problem solved. I now have 3 compressors. 1 Emglo 1.5HP direct drive 120V, one SpeedAire 1.5 HP beltdrive 120V and a IR 5HP 240V 80 gallon beltdrive. As much as I like the IR 5 HP 80 gallon, my potential new place won't accomodate it, its for sale and almost brand new. /forums/images/graemlins/frown.gif

 

[wroughtn_harv]

I have both. They each have their place and purpose.

If I could only have one and it was for stuff around the house I'd go with a contractor style belt drive like the Emglo.

I can't stand the racket from the direct drives.

Just me.