Rewiring A Tool for 220V?

[crokett]

I was always taught that 220V was preferable to 110 because it was slightly more efficient - llower amperage means ess electricity was lost to heat. However, in a post on another forum it was posited that this is not true. The motor will still draw the same total amperage and therefore would have the same inefficiencies. So then this begs the question, if there is no advantage to 220V, then why are some tools sold that way and why do others have the option to be wired like that?

[JR]

By definition, a motor configured for 220v draws half the amperage than the same motor configured for 110v. It's the power that's the same, not the current draw.

There is therefore an advantage for 220v operation in lower current consumption, meaning probably lower heat generated, therefore longer life for the motor.

JR

[Tom Slick]

a 120v 20a circuit could* handle 2400w or about 3hp max. A 220v 20a circuit could* handle 4400w or about 5.5hp max. Both would use the same wires and circuit breakers. You can install a larger machine with the same wiring with 220v.

It also means smaller wire sizes, conduits... not a big deal for homeowner stuff but when you are buying 400' of 12awg vs 400' of 6awg and matching conduits to install a machine it becomes a cost of installation issue.

220v motors also don't require a starter circuit like 120v


*note: that's a straight volts*amps=watts calc, in reality you wouldn't want to run it at max constantly.

[LCHIEN]

a 120v 20a circuit could* handle 2400w or about 3hp max. A 220v 20a circuit could* handle 4400w or about 5.5hp max. Both would use the same wires and circuit breakers. You can install a larger machine with the same wiring with 220v.

...

220v motors also don't require a starter circuit like 120v


*note: that's a straight volts*amps=watts calc, in reality you wouldn't want to run it at max constantly.

no starter circuit, i think you are confusing 1 phase vs three phase. 3-phase needs no starter caps, but all one phase induction motors regardless of 110/120 or 220/240 V need starter circuits.

[LCHIEN]

regarding Crocketts post, I think there's confusion regarding efficiency.

Assuming the wires are proportionatly sized, and power is delivered to the motor without measurable line drops, then the power consumed for the same load is the same, using twice the current at 120V than for 240V but exactly the same amount of power (measured in watts).

Now arguably there's some power lost due to line voltage drops due to wire resistance.
Assuming the same branch circuit wiring gauge (say 12 ga for a 20-A circuit) is used for both installations then the voltage lost in the wiring will be twice as much for the higher current 120V installation than at the 240 volt installation. But at fulll load we're only talking 2-4 volts times 7 amps difference so about 15-20 watts extra is wasted in the 120V installation heating up wires. With 2HP machines drawing 1800 watts we are talking about power differences of about 1% - not much. So it could be said there is an efficiency gain under certain cirumstances but only around a percent or so.

Theoretically we can also save money wiring with smaller branch wiring - but in all practicality, you are not going to install a 10A 220V circuit for the 2HP machine we mentioned above... the electrician will laugh and you probably can't even find a 10A breaker. You're going to go ahead and install 12 ga, 20A circuit since most of the cost is pulling the wire.

So practically speaking there's not much incentive to upgrade to 220V UNLESS you need more amperes than the existing 120V circuit can provide (e.g. greater than 2 HP, but less than 4 HP) or perhaps your wiring is just undersized.

[Tom Slick]

I phrased (phased?) it wrong. no start caps needed for 220v, just a phase "splitting" circuit.

[crokett]

[QUOTE=LCHIEN;423350
So practically speaking there's not much incentive to upgrade to 220V UNLESS you need more amperes than the existing 120V circuit can provide (e.g. greater than 2 HP, but less than 4 HP) or perhaps your wiring is just undersized.[/QUOTE]

Aha. So... I have a planer that is already at 220V. I have (or will have) a PM66 likewise. I have a jointer that could be at 220 if I wanted it to be. So since the planer is already at 220 and I have to pull the circuit anyway, is it worth replacing the power cord on the jointer to rewire for 220? Also, assuming I am not going for the DC that can create black holes, is there a signifgant advantage to a 110 vs 220V rated collector? It doesn't sound like it.

[Knottscott]

Crokett - Discussions about 110 vs 220v (aka 120v/240v) are among the most highly debated and misconstrued of any I see on the wwing forums. Unfortunately, I'm no where near informed enough to set things straight!

There are advantages to 220v, but it's not the panecea many want it to be. If I understand correctly, the motor windings do see the same current regardless of the configuration, as they're either in series in one configuration, or parallel in the other, but with 220v, the individual legs of the supply circuit see half the amperage that a single hot leg of 110v sees, which means that you can either use thinner wire to save money with 220v, or the existing wire used in a 110v tends to have lower voltage loss if you switch the same wire to 220v, which tends to equate to the motor running the way it should....especially true of long runs. A good 110v circuit can do all the things a 220v circuit tends to do, but if you're going to rewire a bad 110v circuit, you might as well run the 220v line.

[Tom Slick]

to simplify
(maybe)
1 hp is 750w by definition, always, regardless of whatever powers it, steam, water, diesel fuel, horses, magic fairies, etc. Its a measurement of power, not electricity specifically. Losses (resistance) in a electric motor make it consume more than 750w, lets say 800w consumed to put out 1hp (750w) just for round numbers.

Watts = Amps * Volts, by definition, always.
so
800w = 6.6a * 120v
800w = 3.6a * 220v
800w = 3.8a * 208v
800w = 1.6a * 480v
800w = 1.3a * 600v

notice a constant? how is electricity consumption measured/metered? (1000) Watts per hour. no matter what voltage you are using, you are paying for watts consumed, and they stay the same at any home/industrial voltage.
There are some efficiencies at higher voltages but nothing a home or even moderate sized shop will notice.

[LCHIEN]

Aha. So... I have a planer that is already at 220V. I have (or will have) a PM66 likewise. I have a jointer that could be at 220 if I wanted it to be. So since the planer is already at 220 and I have to pull the circuit anyway, is it worth replacing the power cord on the jointer to rewire for 220? Also, assuming I am not going for the DC that can create black holes, is there a signifgant advantage to a 110 vs 220V rated collector? It doesn't sound like it.

in your case a tossup or maybe even leaning towards 220V. If the current is more than 15A at 120 then I'd go 220. (that's any tool rated more than 1.5 HP, in reality).
If you already have some 220V wiring and tools, then that would be a good reason to run the rest the same way. You can get more power (twice as much) on one 220V 20A circuit than 2 120V 15A circuits, this is useful if you have more than one 220V tool, as you do.

[jackellis]

If you have some 220V tools and another you can convert, I'd run 220V circuits for all three. I'd put a DC on its own branch and allow the others to share since you can only use one of them at a time but the DC will always be running.

[3thumbs]

[I was always taught that 220V was preferable to 110 because it was slightly more efficient - lower amperage means ess electricity was lost to heat. However, in a post on another forum it was posited that this is not true. The motor will still draw the same total amperage and therefore would have the same inefficiencies. So then this begs the question, if there is no advantage to 220V, then why are some tools sold that way and why do others have the option to be wired like that?]

If I rewire my 15 amp Delta tablesaw to run on 220 volts, then it would draw only 7.5 amps. That means it will drain my wallet at half the rate than it did before.

[pelligrini]

Your Delta would still drain your wallet the same. It still uses the same amount of watts.

[BobSch]

[I was always taught that 220V was preferable to 110 because it was slightly more efficient - lower amperage means less electricity was lost to heat. However, in a post on another forum it was posited that this is not true. The motor will still draw the same total amperage and therefore would have the same inefficiencies. So then this begs the question, if there is no advantage to 220V, then why are some tools sold that way and why do others have the option to be wired like that?]

If I rewire my 15 amp Delta tablesaw to run on 220 volts, then it would draw only 7.5 amps. That means it will drain my wallet at half the rate than it did before.

Rewiring a tool for 220 will draw half the amperage, and since line loss is the wire's resistance time the current SQUARED, halving the current means 1/4 the loss. (That's why bulk power distribution is done at high voltages. Up to 500,000 volts or better.)

As far as your wallet goes, your out of luck, since electric rates are based on power used and that won't change since halving the current by doubling the voltage give the same POWER draw. Sorry.

[LCHIEN]

[I was always taught that 220V was preferable to 110 because it was slightly more efficient - lower amperage means ess electricity was lost to heat. However, in a post on another forum it was posited that this is not true. The motor will still draw the same total amperage and therefore would have the same inefficiencies. So then this begs the question, if there is no advantage to 220V, then why are some tools sold that way and why do others have the option to be wired like that?]

If I rewire my 15 amp Delta tablesaw to run on 220 volts, then it would draw only 7.5 amps. That means it will drain my wallet at half the rate than it did before.

That's a case of knowing a general rule but not understanding the science.

The motors no more efficient, you pay for power, not amps and the power (amps times volts) required to do the same work is identical.

as explained before there are slight efficiencies and cost savings in power lost in wiring, on the order of 1-2 or 3 percent - usually not enough to cause you to pay an electrician $500 to rewire your shop. YOu can save a small amount on wiring if you plan ahead and put in 220V, but again, not enough to make it worth calling an electrician for changing existing wiring in shops.

The main reason for some tools being offered in both is that its a very low cost increment to do so (one standard configurable motor is cheaper than stocking two motor types and supporting two separate models) and many locations offer one or not the other voltage. If the tool power requirement exceeds 2 HP, then 220V is almost surely called for in most places.

if forced to give a yes/no answer to "is 220V better than 110 for tools", I'd hem and haw and then say yes, 220 is better. But there's a lot of caveats and the other part of the answer I'd be thinking is just barely and not all the time.