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A large Single Phase motor, which is better 230 or 115 volts?

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  • A large Single Phase motor, which is better 230 or 115 volts?

    For a large say 2 hp single phase motor doesn't it start and run better on 230 volts vs 115 volts?
    Retired - Journeyman Refrigeration Pipefitter - Master Electrician - Fine Line Automation CNC 4x4 Router

  • #2
    Yes, generally speaking its better to run it on the higher voltage. The current drawn is half on the higher voltage which means the various voltage drops are half. Considering the average motor takes a surge of roughly 3X its operating current when starting, that decreased voltage drop makes it start easier. Another point is that with decreased voltage drop there is also less heat generated.

    It does not matter much for small motors (under 1hp) but becomes more important as the size increases. This is one of the reasons why you don't see motors 5hp and up rated for 115V (exceptions are very rare).

    2hp on 115V isn't too bad but 230 is much preferred if its not a lot of trouble.

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    • #3
      Another vote for 230v if you can manage. I've had 2hp 115v milling machine motors produce random breaker trips even on dedicated circuits.
      I just need one more tool,just one!

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      • #4
        A 2 hp motor will draw about 26 amps on 120 volts. That alone will pop circuit breakers often at a mediocre load. I'd switch it to 220.

        For example I have a true 2hp on an air compressor. Not one of these cheap cap start and run designs and initially I set it up out of convenience on 120 volt. It ran ok but got sluggish as tank pressure built up. I changed it over to 220 and wow what a difference. It starts instantly and sometimes will chirp the belt. It'll restart at full pressure like the tank was empty.

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        • #5
          Originally posted by wmgeorge View Post
          For a large say 2 hp single phase motor doesn't it start and run better on 230 volts vs 115 volts?
          I couldn't help but notice in your signature line you list yourself as "Master Electrician".
          Location: Saskatoon, Saskatchewan, Canada

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          • #6
            Originally posted by Arcane View Post

            I couldn't help but notice in your signature line you list yourself as "Master Electrician".
            I saw that also.

            The windings are either in series for 230 or parallel for 120v.
            The motor windings get the same voltage no matter what.
            It is just a factor of line resistance leading to voltage drop
            and what is convenient to run to the motor.

            -Doozer
            DZER

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            • #7
              Originally posted by wierdscience View Post
              Another vote for 230v if you can manage. I've had 2hp 115v milling machine motors produce random breaker trips even on dedicated circuits.
              No such thing as a "random trip".
              If you fall on your azz, it could be a clumsy trip.

              -D
              DZER

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              • #8
                Originally posted by Arcane View Post

                I couldn't help but notice in your signature line you list yourself as "Master Electrician".
                I posted because on another Forum I posted the statement... larger (single phase) motors start and run better on 230 volts vs 115. Wow I had a lot of non technical people posting I was completely wrong and in spite of over 50 years in the field and with masters license (retired) 115 would be their choice!! Since I posted no calculations to prove my point I was Wrong. Just thought maybe I was loosing it in my old age but I would never run a larger 2 Hp and above on 115 volts if 230 was available.
                Retired - Journeyman Refrigeration Pipefitter - Master Electrician - Fine Line Automation CNC 4x4 Router

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                • #9
                  Ahh! That explains the question!
                  Location: Saskatoon, Saskatchewan, Canada

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                  • #10
                    Arcane I was in your fine city a few years ago on our trip to Alaska. I headed south because our map was kind of vague and looking for a short cut. I thought that lake must have a road headed south.... wrong. It was a long rewind and got back on the real highway!!
                    Retired - Journeyman Refrigeration Pipefitter - Master Electrician - Fine Line Automation CNC 4x4 Router

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                    • #11
                      Originally posted by wmgeorge View Post
                      Arcane I was in your fine city a few years ago on our trip to Alaska. I headed south because our map was kind of vague and looking for a short cut. I thought that lake must have a road headed south.... wrong. It was a long rewind and got back on the real highway!!
                      Yeah, I don't like driving around our city. It seems like the last thing they care about or think of is decent traffic flow. It's really easy to go down the wrong road if you aren't familiar with everything.
                      Location: Saskatoon, Saskatchewan, Canada

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                      • #12
                        You are 100% correct. I have no clue why anyone would argue against that. What on earth were their reasons?

                        As you would know very well, the full load current exceeds the breaker rating and the wire ampacity for standard branch circuits at 120V. That's a first point.

                        If 240V is available, it would obviously be the best approach for all the reasons mentioned.



                        Originally posted by Doozer View Post

                        No such thing as a "random trip".
                        .........

                        -D
                        Well, there kinda is, since that motor may not trip breakers every time on that slight overload, and probably would not open a standard 20A breaker even at full 120V load current for quite a long time, if ever. Household circuit breakers have trip points that can depend on temperature, the surge current depends on exact timing of switching on the load, etc, and they have a "trip curve" of current vs duration of the current.

                        If it was a 5 HP load, then I'd expect it to trip every time.
                        3751 6193 2700 3517

                        Keep eye on ball.
                        Hashim Khan

                        If you look closely at a digital signal, you find out it is really analog......

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                        • #13
                          I just upgraded my wood bandsaw from a 1 HP to a 2 HP motor. Since the new motor would not work with the existing 15A 110v plug by the saw, I needed to run a new plug to power the saw. I could have extended on of the 20A 110v circuits and just barely meet the 19A power draw of the saw or what I chose to do which was run another 220v plug from the table saw outlet which is a 20A 220v circuit. On 220v, the motor is rated to draw around 9A.

                          I'm not a master electrician, but that just seemed to be the sensible thing to do, can't imagine why someone would say it's wrong. Whether it runs/starts better or not I can't say, but I could guess that it probably would given the much larger margin of error for current supply capacity vs actual draw.

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                          • #14
                            With a saw, it probably bogs less, and starts faster. If that is "better" or not, is the user's choice and opinion.
                            3751 6193 2700 3517

                            Keep eye on ball.
                            Hashim Khan

                            If you look closely at a digital signal, you find out it is really analog......

                            Comment


                            • #15
                              I used to have a big GE tri-clad motor that was 3hp, 110v or 220v. I was told it came out of a bowling alley and the tag said something like 36 amp at 110v, but it would start off a 20 amp 110v circuit. It came on a camelback drill press I bought years ago.

                              If you wire it for 110v, there is a chance you will trip the breaker and you can't run anything else off that circuit. If you wire it 220v you need to have it by a 220v outlet, but it should run a little better. If it was me, I would try it out on 110v and if I kept having problems tripping the breaker, I'd move it to a 220v outlet.

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