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220 and TS3612

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  • #16

    It boils down to simple Ohms Law, E = I * R (Voltage = Current * Resistance). When wired for 120V the motor has an internal resistance of approximately 9 ohms and draws 13 amps. When wired for 240V it has an internal resistance of approximately 37 ohms and draws 6.5 amps. It is a single-phase motor; hence there are not multiple legs and it draws a total of 6.5 amps when wired in this configuration as stated on the manufactures plate affixed to the motor. You are correct, the higher the current draw the lower the gage of wire (larger diameter) is needed.

    Hope this helps clarify it.



    • #17
      I'll take the second half:
      Also, if my understanding is correct, (based on what I learned in the past)one would run 220 because motors that draw 15 or more amps usually require bigger wire, the motor will start faster, and recovery would be faster due to the lower amp draw at initial start up. Am I correct in tating this?

      Functionally, you are correct enough. Technically, a bit off.

      The more amps, the larger the wire. Fifteen is not a magic number in this regard. What 15 is, is the most common size for a household 120v circuit. Note early on where Jake commented that 13 amps is close to the maximum for a 15 amp circuit. You should not run a circuit at it's maximum, it is bad for the breaker and you are running right at the design edge. Like running your car at red-line all the time, you wouldn't expect the engine to last long.

      If you are lucky enough (like I am), your house may have 20 amp wiring. If it doesn't, what you -may- -not- -do- is replace the breaker. Because, the higher amps requires a larger wire inside the wall. Fifteen amp circuits use 14 gauge wire, 20 amp uses 12 gauge.

      There are 120 volt circuits available above 20 amps, but they are unusual and may not be allowed in a specific location. They may also require special connectors. For example, a NEMA 5-30R 120 volt 30 amp plug looks like this:

      Think about those when you look at some companies equipment which is 2 horsepower running at 120 volts. One that comes to mind has a 24 amp draw.

      Trying to come back to the question , it obviously can become inconvenient to run 120 volt equipment at more than about 15 amps, so 240 volt becomes an attractive option. It is very rare to find a house in the United States that doesn't have a 240 volt feed.



      • #18
        Thanks guys. My main question was on the amp draw @220 v. Still kind of confuses me, but I'll go by the nameplates. I do understand the difference in amp draw as it relates to wire size, but just wanted to be clear that a 220 motor will start fater and run better because of the amount of current needed vs. amount available.

        Right now, I have 110 in my garage and as soon as this darn snow melts, I plan on running some new wire for 220. I was thinking 8ga. (becaue I thought 220 wa 6.5 x2 vs just 6.5 total), but now I think 10 would be plenty. Then again, larger wire never hurts and it only costs a few cents more a foot. Better to plan for the future.


        • #19
          At the risk of going on forever, with 120 volt household wiring, the current goes "out" on one wire, and "back" on the neutral. We measure the out, but not the back. 13 amps in the discussion. When hooked to the 240 volt single phase in most homes, The current goes "out" on one wire, and "back" on the other hot wire. Twice as much pressure (voltage) but only half as much current flowing through the wire.

          The rule of thumb for wiring is, as Dave says, 15 amps requires 14 gauge wire, 20 amps requires 12 gauge wire (the basic house wiring in all the newer electrical codes), and 30 amps requires 10 gauge wire. So if Mike runs 10 gauge wire, he can run 30 amps at 240 volts, or could run two sets of 120 volt equipment at 30 amps, half on each "side".

          The catch in the electrical code is this: If you have a 30 amp breaker, with proper wire, you should also have only heavy duty 30 amp plugs, and wire suitable for 30 amps all the way to each appliance, since 25 amps should never blow the breaker. A normal plug and appliance cord will overheat carrying 25 amps, so you have a dangerous situation. The solution: bring the 10 gauge (or 8 gauge or whatever) wire to a distribution panel. Everything up to the panel is protected by that big breaker. But from the panel out to the outlets, multiple standard breakers with standard wiring. (If you wire your own distribution panel, remember that the neutral is NOT connected to the ground at a distribution panel, only at the main panel.)

          At the risk of starting still another debate, keep in mind that a circuit breaker must carry more than the rated load for short periods of time - it takes a huge current (for a fraction of a second) to start a single phase motor or turn on an incandescent light bulb. The "how long before it blows" design curve for a normal circuit breaker is something like 20 minutes at full rated current before a circuit breaker is supposed to pop. But a short circuit ("infinite" current) should make it pop in a fraction of a second.

          Because of the possibility of old house wiring, and lamps that share the same circuit, etc., UL won't approve anything for home use that requires more than about 13 amps.


          • #20
            "If you have a 30 amp breaker, with proper wire, you should also have only heavy duty 30 amp plugs, and wire suitable for 30 amps all the way to each appliance, since 25 amps should never blow the breaker."

            No, this isn't quite right. Let's take a much more common example.

            I have my desk lamp here. It says right on it, 60 watt maximum bulb. It has an 18 gauge cord, which has a 5 amp capacity (if the source I find is trustworthy, I don't have anything around on wire this small). This is perfectly adequate and legal, even though it is attached to a circuit whose breaker is 20 amp capacity.

            Divide the wiring of a particular circuit into two parts, divided at the outlet (also called "in wall", "out of wall"). The circuit breaker's job is to protect the "in wall" wiring, right up to and including the outlet. This is why a 30 amp circuit needs a 30 amp outlet. But, the wiring out of the wall is sized and protected by the device that uses it.

            So, my lamp is just fine with its 18 gauge cord. In fact, that cord will handle tem times the maximum allowed bulb, which probably has something to do with the rudimentary protection afforded by a lamp. In the case of an induction motor, the motor should have a built-in circuit breaker that protects it and its wiring.

            Oh, a note regarding oversizing of wire. It can be overdone. Principally, ensure that the equipment you are using (breaker, outlet) is intended to handle the gauge you are using. It could be worse than just using the intended size, if a larger wire won't properly attach.

            Eight gauge is 40 amp wire, that's enormous. A five horsepower tablesaw (real 5) runs well on 30.



            • #21
              In fear of the impending slew of rebuttals I am very slowly venturing into the pool on this one.

              OK the big toe is in and here we go.....

              Dave I'm ashamed of you, you have been involved in this before and I know that you know the correct answers, but you seem to be leaving me in a confussed state, and yes I know that is easy to do but...

              Each of the following points has been touched on by others here however I'm not in the mood to give credit where credit is due, so it's a blanket statement with this disclaimer.

              I learned the following the hard way so you must trust me on this. I too thought that a motor wired for 220 drew 1/2 the amps it did at 120, but after being corrected on the forums after shooting my keyboard off, and then seeking the advice of a friend of mine that is an electrical engineer I offer the following.

              Now how to explain this as it was explained to me.

              At 120 volts your saw draws 15 amps, when measured on the current carrying leg, the black wire tied to the single pole breaker, you will not see any current on the white/neutral wire as it is effectively ground.
              At 220 volt you measure 7.5 amps on each leg, both wires tied to the 2 pole breaker drawing current from both legs of your panel, you still will not see any current on the neutral/ground leg. So 15 amps at 120 or a total of 15amps at 220/7.5 amps on each leg.

              Sorry folks as far as the POWER COMPANY is concerned your still using 15 amps, 7.5 amps on each leg, if you don't believe me call your power company.

              Now the bottom line, since I'm really not trying to write a book here the net benefit of wiring your saw for 220 is that it will run better. As stated it should run cooler, and it should run up faster, and it should not have a problem ripping some big old piece of hardwood that would most likely bog it down and trip the breaker if wired for 120.

              So with that I'm jumping out of the pool and running...............

              It\'s not the quantity or quality of your tools that matters....<br />It\'s all in the firewood that\'s left over.....


              • #22
                I believe power companies charge by the watt not the amp. 220V 7.5A = 110V 15A, watts the same, unfortunately bill the same.

                Dave can pick up the rest, and as I've mentioned before, there's too many Dave's in WW'ing, just makes for confusion...



                • #23
                  I couldn't resist throwing a touch more confusion in the pot.

                  Of course, power (watts) is the voltage x current. For DC circuits, it is unchanging (unless the voltage or load changes). On AC circuits, because the voltage (and thus the current) is continuously cycling, the power is either an instantaneous measurement or an equivalent (compared to DC) power.

                  The power or watts that you are paying for may get a get more confusing. If your typical loads are very inductive (coils, motors) or capacitive, there is a phase shift in the current (it will lag or lead the voltage). This means to get the same instantenous power, you need to draw more current. I'm not exactly sure if the standard residential electric meters compensate for this. Of course, with the amount of power most residences use it is really not an issue. However, I think power companies often add a surcharge to companies (they consume alot more power) based on the "power factor" which is a measurement of how much the current is out of phase with the voltage. In those cases, the companies try to bring their usually inductive loads (motors) back into phase with the current by adding capacitive loads.


                  • #24
                    Originally posted by DCH:
                    Sorry folks as far as the POWER COMPANY is concerned your still using 15 amps, 7.5 amps on each leg, if you don't believe me call your power company.
                    I'm going to have to disagree with you on this one. Since at a very basic level what determines your power usage is wattage (or work done) lets look at it this way. If a 1 1/2 hp motor is wired for 120v drawing 13 amps, it will be using 1560 watts of power. I convert the saw to 240 v drawing 6.5 amps, it is once again using 1560 watts of power. If it was still drawing 13 amps, that means it would be using 3120 watts of power! That energy would have to be going somewhere, either as doubled power output from the motor or dramaticly increased heat from the motor. I can say that neither of these are true.

                    I am by no means an electrical engineer, but this is simply what I have observed.



                    • #25
                      What he said was that the saw will be drawing 7.5 x 2 which is still only 15 amps, not double as you have posted.

                      Also, this goes against what I had questioned earlier. As I was explained to earlier, the saw will draw a total of 6.5 amps on 220, instead of 6.5x2. (6.5 total, which seems to be about a quarter of what it was at 110v) That totally confused me! What also confused me was the statement that when wired to 220, the current is only drawn from one hot and goes back on the other.

                      BTW, why do we keep saying 110/220 when the normal voltage is about 120/240?


                      • #26
                        Sorry folks as far as the POWER COMPANY is concerned your still using 15 amps, 7.5 amps on each leg, if you don't believe me call your power company.

                        No, no, no, no, no. As several gentlemen pointed out, your power company charges you for watts. Residential service, the billing increment is kilowatt hours (there has to be a time factor).

                        The billing conclusion you came to is correct however, either voltage costs you the same amount (within reason). Occasionally, someone gets the crazy concept that their power company charges them by the ampere, and that running on 240v will halve their electric bill. At that point, I offer the person fifty bucks for a copy of a residential electric bill showing billing of amperes. You see, I work next to the TXU (Texas Utilities) building in Dallas, and I could make a fortune selling peeks at such a bill to the folks that work there.

                        What also confused me was the statement that when wired to 220, the current is only drawn from one hot and goes back on the other.

                        My suggestion is to not beat yourself up too much trying to understand AC power mechanics. But if you really want to see how it works, go to the library and look at books on the subject. It's too long for this forum, and pictures are essential. If you just forget the whole split-line thing and think of 120V as 120V and 240V as 240V, you'll be easier off.

                        BTW, why do we keep saying 110/220 when the normal voltage is about 120/240?

                        They are nominal (nominal, in name only) voltages. The three common nominal systems I see are 110/220, 120/240, and 125/250 (which I think is what the electrical code uses). What actually comes out the wall is something around there, usually. If you want to hear someone chuckle, call the power company's customer service and ask them what voltage levels are guaranteed to you.



                        • #27
                          Hopefully, after opening this, I can help those who could care less about the electrical engineering [img]smile.gif[/img]

                          Wiring for 220V=good!

                          Wire size for 220V on a 20 amp circuit for the wattage of my Ridgid TS is 12 gauge where I live (the building inspector signed off on it- and was interested in checking out my TS, a fellow WW [img]smile.gif[/img] )

                          Running much larger wire may or may not be a benefit (if you never higher wattage). Trust me, running big wire is a pain because of drilling bigger holes,the wire doesn't bend as much, and the wire won't connect easily.

                          Thanks for everyone for replying to the posts.


                          • #28
                            running big wire is a pain

                            Amen! [img]smile.gif[/img]



                            • #29
                              Hi gang,
                              First off, the serious stuff. I've been following this thread with interest. I'll likely wind up starting out in my shop with 110, and eventually updgrade to 220 a month or so. (phased construction budget).

                              That being said:
                              My Real Name is Dave, I just use Ned because there are so many darned Daves out there...

                              LOLOL Only kidding.
                              Thanks again for the tips/advice.
                              Ned<br /><br />Madison Woodsmith<br /><br />Masonry: 2B1ASK1


                              • #30
                                I too have been following this tread. And I didn't know squat when I wired my shop. I learned alot then, and learned alot from this thread.
                                When I wired my shop, the walls and ceiling were up and painted. Above the truss's were sheeted for storage. Code here is that exposed wire has to be covered. I didn't want to tear down all that painted sheeting to run Romax. Solution: Conduit and spooled strand wire.

                                I used 12 guage for the 110's, and 10 for the 220's. Overkill I'm sure. But if I want to change a circuit to 220, all I do is pull another 12 and change the receptacle at the box.
                                On another note, I used 20 amp breakers on the 110's, but the recepticles are 15 amp rated. Stupid, but at the time construction was over a grand over budget and the difference between 15 and 20 amp recepticals was 3 bucks each. I used 30 plus recepticles. But if I change them all to 20 amp, I meet commercial code, except for a 2 hour fire rated wall between the house and garage, that's attached to the house.

                                But each machine is on it's own circuit, and no Ridgid, or any other machine on 110 pulls more than 15 amps. So if it's a dead short, it will blow the breaker anyway. And being in conduit I don't have to worry about wire damage, and the conduit makes nice hangers for small items

                                When I was setting up the budget about this time last year, I figured 500 for service, and 500 for electric. I worked with the power company rep, and he got me service, including a pole for zip. He origanlly quoted me 1500! Nice guy aye? Bet he was a woodworker too. But the electric went just under 2k. OUCH.

                                All in all, I was 2500 over budget on everything when all said and done. So no furnace or A/C unit was installed

                                But I'll be darned if I'll suffer the summer without A/C after cooking putting things together last summer. 11 or 12k BTU is getting installed. I got a sears card and can pick up cans on the road to make the $10 payment a month for it! Affording the electric will be another thing

                                What really boggles my mind now is I want to add on a 32x24 addition, and where the money is going to come from for that! (Donations accepted)
                                John E. Adams<br /><a href=\"\" target=\"_blank\"></a>