Replies

1. 
   DouglasABaker | Jan 10, 2003 06:03pm | #1

   Unless you have to run new wiring in either case (ie you don't have 120 or 240 outlets), there is no compelling reason either way.  You may hear the argument that 240V is less wear on the motor, but to my knowledge this has not actually been supported by any studies - it is just theory.

   If you _are_ running new wires, then 240V can be cheaper since you use smaller gauge wire.  It also is a better choice for long runs since you get a lower voltage drop, making it easier to start the motor (you also get to use a smaller gauge wire since you are only carrying 1/2 the amps per leg, making pulling the wire a LOT easier).  However, for short runs, the cost and voltage difference tends to be negligible.

   So really, the question is, do you want new outlets in your shop?  If you need them anyway, go for 220.  If you don't, and have 110 available, then there is no compelling reason to spend money that could otherwise buy you a new tool of some sort ;)

   Doug

2. 
   TKanzler | Jan 10, 2003 07:39pm | #2

   I can think of a few reasons NOT to use 240V power, if you don't need to.

   1. Portability is reduced or eliminated.  Not an issue for stationary tools.
   2. Takes more panel space than 120V.  Not an issue if sharing the circuit with the saw, but the DC should have it's own circuit.
   3. Plugs must be changed to 250V styles, either straight blade or locking.
   4. Switches must be double-pole.  Again, may not be an issue, especially if machines have magnetic starters.
   5. GFCI protection, though not required for 240V, is more costly if used.  If using the duplex receptacles with both 120V on top and 240V on the bottom, the 120V part at least must be GFCI, and I don't know how you could do that without using a 2-pole GFCI breaker, or some inefficient wiring scheme.  Better to keep them separate, or use 2-pole GFCI's, IMO.  I've only seen those dual voltage duplex receptacles in 15A versions, although I suppose they can be found in 20A.
   6. If these things work well now, the labor is a waste, besides the cost of the parts.

   None of these negatives are terribly compelling, but you asked for reasons, so those are some that come to mind. 

   Be seeing you...

1. 
   ccampbell | Jan 10, 2003 11:22pm | #3

   Thanks for the replies.  I don't currently have a 240 outlet (or 220 or 230 or whatever - I don't get the differences) but I need one for my new planer.  I'm also short on 110's and have been running extension cords across my basement.  Our plan is to take an unused old 220 that was for an air conditioner that doesn't exist any longer and run it over to my power tool "alley".  We're going to put in a junction box and run three lines out of it to three different places on the wall.  Each of these new outlets will have a 220 plug and two 110's.  Our theory is that no two of my 110 tools would be running simultaneously, and the 220 tools draw so much less amperage that it won't matter for them to share a circuit.

1. 
   TKanzler | Jan 11, 2003 12:17am | #4

   The nominal voltage in the US (per the NEC definition) is 120V, 240V, 480V, and so on), and is used so that everyone can refer to the same thing with the same nomenclature, especially codes and standards.  Devices are usually rated at 125V, 250V, and so on (look at a receptacle or wall switch yoke; it has to be rated at or above what it's handling), and induction motors made to the NEMA MG-1 standard (just about any induction motor you'll ever see on WW machines or in industry) are designed for and nameplated 115V, 230V, etc, in recognition of the inherent lower voltage under load due to branch circuit losses.  I have no knowledge of where 110/220V comes from (I even have an old motor nameplated 117V), except that many moons ago a lot of motors and equipment was labelled as such.  I think current standards have done away with creative voltages for the most part.  But in the end, everyone's talking about the same thing.  

   So, when you buy a plug (rated 125V), and plug it into a receptacle on the wall (also rated 125V), which is on a 120V (nominal) branch circuit, which is delivering 117V (no-load) through a cord with 300V (or better, 600V) insulation to a machine with a motor designed for 115V, it may only get 110V or less if the machine is worked too hard or the wire run is too long.  I hope that clears up any confusion.Be seeing you...

1. 
   noone51 | Jan 12, 2003 01:32am | #8

   Just FYI - the nameplate voltages are the minimum voltages specified by the manufacturer for proper operation of the motor. There is usually a maximum also but they rarely put that on the nameplate.

1. 
   TKanzler | Jan 12, 2003 08:53am | #11

   Just FYI - the nameplate voltages are the minimum voltages specified by the manufacturer for proper operation of the motor. There is usually a maximum also but they rarely put that on the nameplate

   Respectfully disagree.  ANSI/NEMA MG 1-1998 (governs small and medium induction motors) states, under Variations from Rated Voltage and Rated Frequency, Running:

   "Alternating-current motors shall operate successfully under running conditions at rated load with a variation in the voltage or the frequency up to the following:

   a. Plus or minus 10 percent of rated voltage, with rated frequency for induction motors

   b. Plus or minus 5 percent of rated frequency, with rated voltage.

   c. A combined variation in voltage and frequency of 10 percent (sum of absolute values) of the rated values, provided the frequency variation does not exceed plus or minus 5 percent of rated frequency."

   Nameplate voltages are the design value for that motor, and all performance parameters will vary from reported and/or nameplated values.  Things like efficiency, power factor, locked-rotor torque, pull-up torque, breakdown torque, all current values including start-up (or locked-rotor), etc. will change, and usually not for the better, even at higher voltage.  Full-load efficiency and power factor both decrease with an increase in voltage above rated, due to saturation of the iron, resulting in increased heating.  The key word is "Rated".

   Be seeing you...

   Edited 1/12/2003 6:52:35 PM ET by TDKPE

2. 
   RW | Jan 12, 2003 10:42pm | #12

   Are we barking up the wrong tree? I think what they heard was more likely that efficiency increased when you moved to 3ph. That would make more of a difference in how the motor performed than 110 vs 220. No?" Exult O shores, and ring O bells!  / But I with mournful tread,  / Walk the deck my Captain lies,  / Fallen cold and dead" - Whitman

3. 
   TKanzler | Jan 13, 2003 09:09am | #13

   Um, I'm not sure what you mean, or to whom you are responding.  Looking at 3-phase motors only, efficiency goes from the mid 60's at 1/4 hp up to the high 90's above 500 hp.  Single-phase motors follow a similar trend, and of course only up to about 10 hp.Be seeing you...

4. 
   noone51 | Jan 13, 2003 09:20am | #14

   So, I was wrong ? Read your material again. Your technical explanation is exactly what I said. I guess it's a matter of interpretation.

2. 
   johnhardy | Jan 11, 2003 02:28am | #5

   I'm not sure it's code to have multiple 220 volt devices running simultaneously from the same circuit. In any event, it's theoretical that you could have 220 volt devices that each use up more than half the available capacity, and running two would trip the breaker.

   I'd be conservative and have dedicated 220 volt outlets, one per device. And only one receptacle per circuit so there is no confusion. I personally use the locking type receptacles/plugs for my 220 volt devices. They cannot easily become dislodged, and I like that.

   John

3. 
   TKanzler | Jan 11, 2003 06:51pm | #6

   If you intend to connect both 120V and 240V receptacles to a single branch circuit, you need 4 conductors in that cable (2 hot, 1 neutral, 1 ground).  I doubt that the old AC branch circuit has more than 2 hots and a ground.  You also can't go over 20A regardless of cable size, since you're connecting 120V receptacles for small stationary and hand tools, though 15A receptacles are OK (I'd use spec. grade 20A anyway, for their heavier construction).  

   I've done almost exactly what you're proposing, a couple of garages ago, with an unused Jenn-Air branch circuit (10/3-G), dropping to 20A 120/240V and running conduit along the kitchen/garage wall.  I only use one machine or tool at a time anyway, and these receptacles were for that purpose only.  Lights, radios, etc. were on a pre-existing garage circuit (you don't want lights on the same circuit as machines; it stinks when the lights go out during a cut).  It would have been extremely difficult to add more circuits (tiny partial basement, and really long way from panel to garage), so this was a good way out.  But if I had intended to stay in that house for a long time, I would have taken the trouble to add several circuits, possibly from a new subpanel.Be seeing you...

1. 
   PlaneWood | Jan 11, 2003 07:11pm | #7

   My 'rule of thumb' is to use 220V for any tool over 1.5HP.   The cost of wiring 220 will negate any savings advantage for 1.5HP or less.  Right now, my planer and my ac/dc welder are the only 220V machines I have and they share one outlet.

   PlaneWood by Mike_in_KatyPlaneWood

1. 
   noone51 | Jan 12, 2003 01:35am | #9

   Mike, I completely agree. My rule of thumb is to never change a 120v machine to 220v if it is portable. Most of those are 1.5hp or less so your rule also applies.

2. 
   mitch | Jan 12, 2003 02:04am | #10

   in my own practical experience:

   any machine that must handle a large increased load in its usage (for example- table saw or band saw ripping thick and/or hard stock, jointer or planer with wide and/or hard wood, compressor near its peak pressure) will run noticeably better on the higher voltage.

   any machine that runs under a more or less constant load (drill press with average size bits, dust collector) will not benefit from the upgrade.

   i don't have any fancy testing, etc to prove my position- only my personal experience with my own equipment.  the table saw and air compressor were like night and day- i couldn't believe how much better they ran.  the saw (2hp baldor) would bog down and throw a 20A breaker on 115v.  on 230v it was like having a much bigger motor!  the compressor would labor for 30 seconds to a minute getting the last few pounds of air to shut-off pressure on 115v-  on 230v it zooms right up with no struggle whatsoever.  on the other hand, my 3/4hp drill press made no difference at all.

   mitch