Replies

1. 
   saschafer | Apr 18, 2008 08:11pm | #1

   The benefit is lighter-gauge wiring: All else being equal, you can power twice as large a piece of equipment with 240V than you can with 120V. So, for example, you can run up to a 1-1/2 HP motor from a 20A 120V circuit, but you can run up to a 3 HP motor from a 20A 240V circuit. The physical wiring would be the same in either case, the only differences would be in the circuit breaker (double-pole rather than single-pole) and the outlet.

   -Steve

    

2. 
   brad805 | Apr 19, 2008 01:57am | #2

   You will be limited to 1.5hp or 2hp with 110v and you may find that machines of that size will not suffice.  I started with 110V and now none of my machines are 110.  Many of my machines are 4hp. 

   Brad

   
   

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   Edited 4/18/2008 6:58 pm ET by brad805

1. 
   N9157J | Apr 19, 2008 05:33am | #3

   Is that the issue then? Limits on HP?

1. 
   benhasajeep | Apr 19, 2008 08:48pm | #4

   You can get motors higher that 2 hp on 110v.  But you can't use "normal" household circuits.  It is not common to have 110v motors higher than 20amps but they are made.  Alot of tools are sold at 110v because thats what "most" homeowners have in their garages / houses.  I know of 1 tool in particular that comes with a 2.8 hp 110v motor and that is Hitachi's resaw band saw.  They say will operate on 20amp 110v circuit.   There is no noticeable power difference on running a dual voltage motor on 110v vs. 220v.  There is also no energy savings either.

   Basically any savings would be, being able to install thinner guage wiring.  But most people who install 220v noramlly install 20 or 30 amp breakers anyway.  So you end up using the same gauge wire anyway. 

1. 
   Tinkerer3 | Apr 20, 2008 05:47am | #5

   According to my calculations, a 2.8HP motor running at 100‰ efficiency would take 19 amps.  As you know, motors do not run at 100‰ efficiency.  Further more, no more that 16 amps should be drawn from a 20 amp circuit.  I don't think it is not possible to develop 2.8 HP with only twenty amps at 120 volts.  Also, on given circuit on a long line, there is twice the voltage drop with 120 volts as there is with the 240 volt circuit.

1. 
   benhasajeep | Apr 20, 2008 06:53am | #6

   Everything I have read about the saw is it is under powered.  So I would think its not actually a 2.8 hp motor (more like 1.5 actual).  The manual does state 115v 2.8 hp though.  But I also have a craftsman 16 gallon vac that says 5 hp, and it runs on a 15 amp 110v circuit.  So most likely its probably a numbers game like some others use to sell their stuff.

   BTW Amazon was selling the Hitachi for $1,760 yesterday.  Thats a good $500 less than anywhere else.   Still not low enough for my wallet though.  The price has been comming down the last month (from $2,300).  Maybe they are dumping them?? 

2. 
   saschafer | Apr 20, 2008 03:17pm | #7

   "But I also have a craftsman 16 gallon vac that says 5 hp, and it runs on a 15 amp 110v circuit."

   That's a different situation. Your vac has a universal motor, and there is no agreed-upon standard for rating universal motors, so the manufacturers come up with all kinds of imaginative ways to rate their equipment, none of which bear any relationship to reality. The same goes for routers and other portable hand tools.

   Induction motors are a different story. There are standards for rating those, and induction motor ratings are generally pretty accurate.

   If your bandsaw has a universal motor, that would explain the anomalously high rating. But most bandsaws have induction motors. If that were the case, the motor's nameplate would specify the current draw as well as the output power rating.

   -Steve

    

3. 
   benhasajeep | Apr 20, 2008 05:31pm | #8

   I do not have the Hitachi, just had been looking at it for the last month or so.  And I did find out yesterday that it comes with a universal motor, not an induction motor.

4. 
   Tinkerer3 | Apr 20, 2008 11:20pm | #9

   All said and done, I have a MM16 with a motor rated 4.8 HP.  In the manual it says you can probably run it with 20 amp circuit.  I imagine that is right - the situation being that with such a large motor for the application that it would probably rarely draw on the full 4.8 HP that it is capable of.  I think I would shy away from a universal motor on a bench or floor model machine.  As good as some of them are, they are just not made for continuous running

   Edited 4/21/2008 11:01 pm ET by Tinkerer3

5. 
   WillGeorge | Apr 21, 2008 05:13pm | #10

   GOOD ANSWER! I have worked with all kinds of motors in my service days.. The HIGH VOLTAGE, HIGH AMPS, NEVER BROKE DOWN!  Ok so hardly ever!

   As in.. Remember that heat is made by amps (WATTS!) and when you're at a higher voltage there are less amps running. For this exact reason, electricity is transmitted over long distances at extremely high voltages.  Just my opinion from a old service man that MAY or NOT know what he is talkin' about! Sometime I do!

   I have no idea how it changes your utility bill!

2. 
   brad805 | Apr 21, 2008 07:21pm | #12

   High amp single phase motors above 2hp usually are more expensive and far less common than their 220V counterpart.  220V single phase takes you to about 7.5hp or so and then you pretty much start looking at three phase.  Most commercial shops run 3phase machines, but then many of them run 25hp wide belt sanders or other power pigs.

   Brad

3. 
   michaellc | Apr 21, 2008 07:18pm | #11

   I'll try to help.  I'll not get into electrical theory as I'm blissfully ingorant,  but if you want advice of what to put in your shop I might be of some use to you.  Most table saws will need 220.  Most 8" jointers will use 220.  Most bandsaws above 14" will use 220.  A planer larger than a lunchbox style will use 220 and most dust collectors above 1hp will use 220.  It kinda depends on what you are going to do in this hobby.  How big are the machines you plan to buy.  I have a 220 ts, 110 jointer, 14" bandsaw, luchbox planer and a shop vac, so I'm kinda mixed.  I have 1 220 outlet and 1 110v 20 amp circuit and a bunch of 110 15amp outlets.  At minimum you should have 2 110 20amp circuits and a 220 circuit and most of your needs will be met unless you go into full production.   Hope  I have told you something you already know.    Good luck.

   mike........

1. 
   WillGeorge | Apr 21, 2008 07:56pm | #13

   Another good answer!

1. 
   ndmatt | Apr 22, 2008 06:38am | #14

   The HP rating on universal motors is akin to HP ratings of cars.  For example, a car might be rated 325HP at 3,800 RPM.  How often do you actually get to that number, and when is it for more than a few seconds?  The bottom line is, the motor is only outputting a fraction of the rated HP most of the time.