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I just purchased a band saw and I have the option of running it at 120 V or, by opening the cover on the motor and swapping around a couple of wires, running it at 240 V.

In general, I understand that running it on 240 V is "better", but what are the actual advantages that make it "better"?

NOTE: I'm building a new shop to put it in, so I'll be able to (and am actually planning to) run a couple of 240 V circuits with several receptacles per circuit, so that is not a concern for me at this time.

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    OK, some unsolicited advice (which is always dangerous (LOL)), but 2 things: 1) Go big on your panel (and or-sub-panel) When I build out my shop (attached to my house, even though it was a sub-panel in the shop I went with a 42 space 200 amp panel, feed by 125 amp circuit from the house's main panel. 2) I have found that shops are constantly evolving with new tools , changes in layout etc. So to future proof my shop I went with Wiremold 4000 raceways connected directly to the main sub-panel...which also provides a good ground path. This may seem like over-kill in your situation. Apr 29, 2023 at 20:58
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    ..., a bit more: While it may seem like over-kill, large panels are not expensive, but a total PITA to change out later. and while product recommendations are OT here, I'm going to bend the rules a bit and attach a link to the product I used: wiremoldproducts.com/catalog/… Apr 29, 2023 at 21:00
  • Too late, @GeorgeAnderson. I've already got a 40/40 panel installed in addition to a new meter main and the fully stuffed 26 space panel that the house came with. ;) Not only will the new panel pick up all the new circuits for the 2 new construction projects, but I'll be adding (much needed) additional circuits for the kitchen and other areas of the house. One step ahead of you, my friend!
    – FreeMan
    Apr 30, 2023 at 11:14
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    Tim Allen's character on Tool Time (Home Improvement) would have loved this! May 1, 2023 at 12:49
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    @GeorgeAnderson Note that asking for product recommendations is what is not allowed; giving them as supplementary information is allowed, unless it is spam (you get some kickbacks or advertising fees) May 2, 2023 at 22:20

7 Answers 7

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As alread mentioned by others, Half the current, which makes 1/4 the resistive losses (if the wire was the same size, which it probably won't be.)

The more subtle follow-on effect is that what resistive losses there are, particularly the ones that bite you on startup surges, will be half the percentage of the overall voltage. Resulting observation - starts easier, less prone to stalling. Likewise, less resistive heating in the motor windings means it will run cooler.

Basically, unless you need to drag the saw around to sites where a convenient source of 240V isn't something you can depend on, there's no reason to wire it 120V. If it lives in your shop, that does not apply, because you'll have convenient sources of 240V there.

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    When I've heard/read advice to use 240 for table saws, the reason given was that it was less likely to bind up and shoot the piece you are cutting back at you. That would fall under 'stalling', right?
    – JimmyJames
    May 2, 2023 at 20:26
  • actually they would be 1/4 the percent of the overall voltage May 2, 2023 at 22:21
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IMHO it's always better to run at 240v than 120 if possible. For one thing you can run smaller, less expensive wire and get the same amount of power.

Next, even if you keep the same wire size for 120v you get a LOT less voltage drop from the panel to the tool. I have a hobby wood shop with a table saw, band saw, jointer, compressor, dust collector, planer and drum sander. All of them run at 240v.

Next, next (LOL) running everything possible at 240v puts virtually no load on the neutral, which I feel is a good thing.

So my humble advice is to run everything possible at 240v.

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    4x less voltage drop, to be exact. (resistive loss is proportional to current squared, so half current is one quarter the resistive loss)
    – Alexander
    Apr 30, 2023 at 15:54
  • @Alexander Thanks for the math. I didn't know the details but did know you get a lot less voltage drop at 240 vs 120. Thanks again. Apr 30, 2023 at 16:04
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    Isn't it half the current, and half the voltage drop, resulting in one quarter of the resistive power loss? Apr 30, 2023 at 21:33
  • @TannerSwett Ah yes, correct.
    – Alexander
    May 1, 2023 at 22:56
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You get around the 1500 watt limit. 120V plug-in appliances won't get UL approved if they take more than 1500 watts (or 1800 watts in rare cases). In fact drawing more than 1800 watts will trip a 15A breaker.

With 240V, you have a 3000 watt practical limit and a 3600 watt hard max. That's twice as much. At half the current, the breaker is far less likely to "nuisance trip".

In a 3-phase shop, it's easier to balance the panel. Many shops in 3-phase country are wired 120/240V "wild-leg delta" - which looks like normal split-phase, but with a third phase 208V away from neutral and 240V away from the other hots. However, 120V loads all wind up on the same phase, which annoys the power company and they may charge you for the phase imbalance. Going 240V lets you plug the saw into the other phases.

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    The 1500 watt limit is already in play here, is it not? This saw can be (and is currently) configured to run on a 120v circuit and, therefore, is subject to all the design limitations of a 120v circuit, no?
    – FreeMan
    Apr 30, 2023 at 11:15
  • re: "1500 watt limit", does that mean that, e.g., plug-in electric kettles are all limited to 1500W?
    – njzk2
    Apr 30, 2023 at 12:22
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    @njzk2 yes, which is why Americans don’t use electric kettles! Apr 30, 2023 at 14:23
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    @Jacob +1 for linking a Technology Connections video. It's the "mouse-drawn red arrow" of DIY stackexchange! (the real reason is, we don't drink a lot of tea... we have Mountain Dew :) Apr 30, 2023 at 21:51
  • @Freeman depends what's happening inside that jumper box. Apr 30, 2023 at 21:51
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Depending on the exact implementation of the 120/240 wiring of the motor, the benefits of 240 range from small ones like

  • energy efficiency gain (2-5%),
  • less light dimming on motor startup,
  • less interference with the other appliances (you don't want your old-ish workshop computer restarting each time you turn on this tool, do you?)

... all the way to e.g. twice the usable power of the tool. Yes, the motor has its power rating and also yes, its practical performance depends a lot on the power fed to it.

As a proud citizen of a 240-only country I always noted how hesitant and sluggish are 120V motors and how careful people need to be when plugging multiple appliances into a single circuit.

Go 240 whenever you are sure you won't need to plug the same thing in a 120-only place.

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    if you do need to plug it in a 120-only place occasionally, of course you can just change the jumpers again May 2, 2023 at 22:24
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The 240 volt wiring will use half the current as the 120 volt wiring so maybe it will be a reduction in the wire size since these saws can have large motors. 240 volt wiring is "better" because it automatically balances the loading in the panel when you have many 240 volt appliances hooked up.

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It will be more efficient. For the same amount of power your current will be half as much. There will be less energy loss due to resistive heating. Also running at 240v you will have more torque and it will perform better under heavy load.

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Does your tool use a switchmode PSU ?

Many data centers make both 208V and 220V available in customer racks. Switchmode power supplies are slightly more efficient at higher voltages, with the difference being 1-3%.
Source https://www.servethehome.com/120v-208v-power-consumption/

There is also slightly less heat produced, and therefore less cooling power is needed.

This saving can also apply to computers and devices at home, though 3% of the power cost for one computer is a few cents a month, and will likely never repay the cost of running a 240V circuit and outlet and breaker. For bitcoin miners though, it does add up.

US homes might have a 240V drier and hot water cylinder because these are high-power-usage devices. 2% saving there is worth it.

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    For the dryer and water heater wire size is a factor too. 240v 30A 10 AWG dryer would be 120V 60A 6 AWG. Wouldn't matter for me - my dryer receptacle is attached to the side of my panel. But if it is in another room the wire cost is important. May 2, 2023 at 4:24
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    I don't think my bandsaw has a PSU beyond "receptacle on the wall".
    – FreeMan
    May 2, 2023 at 14:50
  • @FreeMan sounds like my bandsaw - a wall plug, a switch, and a mains voltage AC motor. Nothing fancy. The motor's name plate might have wattage info that could be relevant here ?
    – Criggie
    May 2, 2023 at 21:47
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    I don't think any bandsaws have switch-mode PSUs. That sounds like a programmer-centric idea :) May 2, 2023 at 22:24
  • @user253751 "efficiency-centric" perhaps ?
    – Criggie
    May 2, 2023 at 23:42

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