120V vs 240V electric motors

[Partsman2]

Most motors such as those used on compressors can be wired for either 110 or 220. If you are going to be moving it around I would think the 110 would be preferred. If it's stationary I think 220 is a no brainer.

 

[HGM]

Bird,
I'll second most of what was said already.

I chose 220 for my shop so I wouldnt be limited, I do some auto work periodicly and would like to do a little painting and sanding. These tools use quite a bit of air. With my 80gal tank and an air ratchet or die grinder running, the compresser comes on often. Check the CFM of any tools you might use. I have found that with tools like this bigger is always better. I didnt want to have to wait for the comp to cycle so I could get that pice of metal cut.. Like dave said about the 4cyl vs 8cyl, my compressor doesnt have to work as hard. The electric bill for the shop alone is about $20mo with no activity and when I have done a major job or two lasting a several days with alot of air consumed, it has yet to go over $25.

The deciding factor for you would be, is it portable?

If you go portable, 110 would be prefered. I would not think twice about 220 if its going to be stationary. I have the big one in the shop and a small portable cheapy for nail guns and stuff away from the shop. you can pick one up at the local pawn shop cheap.

 

[TonyV]

This may be drifting a bit away from the original question, but it does apply to compressor motors so here goes. When you multiply volts times amps for inductive loads like motors, you do NOT get watts...this is a common misconception. What you actually get, and again, this is for inductive loads, is VOLT-AMPS, or VA for short. The volt-amps represents the amount of "apparent power", rather than the true power in watts. This is going to get a little technical now so bare with me here. Apparent power (VA) is actually composed of two different things and they are reactive power and true power (watts). Reactive power represents the amount of electrical energy that is needed to produce the magnetic fields within the motor. Edison does not charge you for reactive power since it winds up going right back to the power lines. True power (watts), which we do pay for is really the amount of electrical energy thats converted to heat energy. (end of real technical stuff /forums/images/graemlins/smile.gif ) Its not easily determined exactly how much true power any given motor may draw without knowing the efficiency of the motor. One thing that can be done is to look at the HP rating. This can still be unreliable because various manufacturers play some games with this number. If you trust the HP rating, then multiply it by 746 to get the amount of OUTPUT watts. In other words theres about 746 watts per HP, and remember, watts represent 'true power'. If the motors efficiency is published, you can then divide your output power by the efficiency in order to get true INPUT power.

As it turns out, as a general rule 220V motors will be more efficient than 120V motors. This means basically that 220V motors, for a given HP, will run cooler than their 120V counterparts. Running cooler means using less 'true power', and therefore less expensive to operate.

I now return you to your regularly scheduled program. /forums/images/graemlins/grin.gif

...Tony

 

[_RaT_]

Tony, a most excellent job!

 

[Bird]

I appreciate all the information. Of course I've owned a few compressors over the years, even disassembled some for repairs, and there are lots of good brands available. On TBN, there's been lots of discussion about a tractor dealer being more important than the brand. Of course, I can do any of my own repairs, so I guess the air-compressor dealer might not be too important at this time, but I do feel some degree of loyalty to Industrial Air of Texas in Arlington for a couple of reasons. Quite a few years ago, when I had a Craftsman, built by DeVilbiss, it broke while it was still in warranty. At that time, Industrial Air was closer than the Sears service center and Industrial Air was a factory authorized service facility for DeVilbiss, so I went there. I should have known that Sears buys in quantity and agrees to do all warranty work, so the guy at Industrial Air said he could fix it, but not under warranty. However, he disassembled it, showed me what was broken, and reassembled it at no charge. So when I bought a stationary, larger compressor, that's where I bought my Puma, 60 gallon tank, 230 volt, V-twin cast iron, 6 hp. Of course he said they called it an "imitation 6 hp" showing me a monster that he said was a true 5 hp motor. That Puma was very good and I was quite happy with it, but I sold it when I moved back to town.

So now I know that I'm not going to buy a direct drive, I'm not going to buy an oilless, I'm not going to buy an aluminum crankcase, and while the compressor will be seldom, if ever, moved, I am going to buy one with wheels that I can move around if I want to. And for any of my foreseeable uses, 7 CFM is all I'll need, but I do want one that I'm not afraid of damaging by keeping it running for extended periods of time.

Nothing is definite yet, and I may or may not buy from Northern Tool, but this compressor by Industrial Air is the forerunner at this time. /forums/images/graemlins/wink.gif Of course you might notice the small misprint on the part of Northern Tool since they call it a single stage one place and a two stage another place. /forums/images/graemlins/wink.gif

 

[Steve_Miller]

I'll second Tony here and also state that anything rated 1.5 HP or more is starting to push any 15 amp breakers, especially if there are frequent starts as in a compressor application. It's much easier on the motor for starting on 220-240 volt as well as the contacts on switches. Another non related issue, I converted my water pump in my house to 240 volt so that it is easier on my generator if and when I have to use it because of the surge of starting.

Steve

 

[_RaT_]

Good point. While my well pump is only 1/2HP but the distance from my circuit breaker panel is about 500'. Going 240V saves on wire size and when necessary to use, my generator hardly knows it when it calls for power. Again though in Birds case with intermittant use and conveniance, its hard not to recommend 120V. I recall a compressor manufactuer that made conversion from 120 to 240V very simple, flip a switch and adapt a cord.