Should I convert my Dewalt 746 TS to 240v?

[Alex Jacobson]

I'm redoing the wiring in my new studio, which has tons of 3phase, but little 110 or 220 easily accessible. I'm going to split up several of the three phase plugs, and am wonder whether I should leave myself a 220 circuit and convert my Dewalt 746 TS? Am I going to get a noticeable power or performance increase? Is it work the time/$ when I could have one more 110 circuit. Any thoughts?

Thanks

[jack forsberg]

when you say you have lots of 3 phase what do you mean?at what voltage? is the saw 3 phase or single phase.

Or you you mean you have 3 wire 240 single phase house hold power?

jack
English machines

[peter gagliardi]

Assuming you are at 110v single phase, and want to know about going to 240v single phase, no it won't give you more power. What it will do, is lower your amp draw for that particular machine in half, and allow you to run lighter wire to the outlet. As a rule, you always try to run your equipment at highest possible voltage when it is an option. Machines run better and cooler, thus lasting longer.

[Alex Jacobson]

when you say you have lots of 3 phase what do you mean?at what voltage? is the saw 3 phase or single phase.

Or you you mean you have 3 wire 240 single phase house hold power?

jack
English machines

I've got lots of receptacles of three phase at various combinations of voltages and Amp circuits. I'm thinking about converting one to 220 single phase, in addition to some 110 single phase.

Saw is 120/240 single phase, right now set up as 120.

[jack forsberg]

I've got lots of receptacles of three phase at various combinations of voltages and Amp circuits. I'm thinking about converting one to 220 single phase, in addition to some 110 single phase.

Saw is 120/240 single phase, right now set up as 120.


Alex

how much experience do you have with 3 phase power? Your not making sense is why i ask . If you have 3 phase what is the primarily voltage entering the building?

There are ways to get single phase power from 3 phase . Do you have transformers and what are they.
How are you running the saw now?

jack
English machines

[Wade Lippman]

You probably can't get 240v from your 3phase, but only 208v. Your saw might work on 208v, but not as well as it does on 120v.
Even if you do have 240v, there is no good reason to use it for your saw. It is only 15a and will work just fine on a 20a line that doesn't have other stuff on it.

[Peter Quinn]

If you really have native 3 phase in the studio I'd be more inclined to shop for a good 3 phase saw than get into any backwards conversions.

[Howard Acheson]

>>>> As a rule, you always try to run your equipment at highest possible voltage when it is an option. Machines run better and cooler, thus lasting longer.

No, that's not a rule. All convertible 120/240 motors always run on 120 volts internally. There are two coils each running 120 volts and using 1/2 the 120 volt amperage (The coils act as a resistance and split the amperage). All you do when you re-wire the motor to run on 240 is change the wiring connecting of the coils from parallel to series. When wired for 240 volt operation, one 120 volt leg and its associated amperage is routed to each individual coil rather than a single 120 volt line providing 120 volts to both coils. The same voltage and amperage runs through the individual coils no matter how it it wired. It is amperage that creates heat, and because the amperage in each coil is the same for both wiring configurations, there is no difference in the heat produced by either wiring configuration. The motor is perfectly happy with either voltage and doesn't even know you made the change.

[peter gagliardi]

Howie, not being an electrical engineer, I am having a little trouble following what you said. If the motor converts 240 to 120, then it is in effect a transformer?? And if it is amperage that creates heat, how is it that a motor wired at 240v and supplied with 1/2 the amperage of the 120v motor doesn't run cooler? I'm not connecting the dots? I'm sure you have much more experience than I do, I'm only a woodworker in real life, but .... So in essence if you supply 240v to a convertible motor, it transforms it to two legs of 120 and turns it into a heater of sorts?, and in doing so acts like a boost transformer?
Seems like that defeats the purpose of higher voltage motors.

[Chris Fournier]

Agreed! Three phase is pretty sweet and opens up a lot of equipment options.

[Jeff Duncan]

My understanding is the only reason to run dual voltage tools at the higher voltage is to be able to run smaller circuits and gauge wire as the motor is pulling less amps. Other than that they should run the same way.

As far as pulling 110 or 220 single phase from a 3 phase outlet, I wouldn't try it unless you have a really good handle on electricity. I know there are at least 2 types of 3 phase power and the one I have has different voltages in different wires. There's also no neutral wire in 3 phase which would make a 110 single phase outlet tricky, I'm not sure multiple 110 outlets from a single line would even be possible? I'm not saying it can't be done, just that if it can it's probably best handled by an electrician;)

good luck,
JeffD

[Art Mann]

Peter,

Howard's explanation is exactly correct. Unfortunately, to understand it, you will have to understand a little about the nature of AC power and phase angles. If you measure the voltage between one hot leg of a 240V plug and neutral, you will read 120V nominal. The same is true if you measure the voltage between the other hot leg and neutral. The 240V is measured between one hot leg and the other because they are 180 degrees out of phase. With 3-phase power, the story gets even more complicated because the voltages of the three legs are 120 degrees out of phase with each other. Don't worry if that doesn't make any sense. It is probably not worth the effort to learn what it means. Suffice it to say that the current running through the two coils of a single phase motor added together is the same whether they are connected in parallel (120V) or series (240V).

I need to add that there is more to consider than the current in the windings of the motor. There is also the amount of current in the wires feeding your breaker box. In my case, the wires going to my shop are just barely adequate. A motor running on 240V will require half the current of a motor running on 120V. Therefore, I run all the equipment I can on 240V to avoid the voltage drop in the feed wires.

[glenn bradley]

Am I going to get a noticeable power or performance increase?

Just my experience but, in a word, no. There are lots of minutia that folks cling to to justify running higher voltage but, for a tool that runs correctly on 110v, the user experience at 220v is the same. Reports of moving from a poorly provisioned, shared, overworked 110v circuit to a dedicated, properly provisioned 220v circuit perpetuate the stories. Minutia aside, watts is watts.

[Glenn Bird]

Art has given the best explanation along with Howie. The only reason to run 220 is to lessen the voltage drop on the wiring or to be able to use lighter wiring than running 120v.

[peter gagliardi]

Well, the other reason to run higher voltage- at least where I am, is that as a business, I pay commercial rate which is higher. Also, along with a higher rate for your power, we are on a demand meter which bases your rate on your amp draw!
The more amps you draw the higher your rate for what you use. So I run high voltage everywhere I can.

[scott spencer]

...I need to add that there is more to consider than the current in the windings of the motor. There is also the amount of current in the wires feeding your breaker box. In my case, the wires going to my shop are just barely adequate. A motor running on 240V will require half the current of a motor running on 120V. Therefore, I run all the equipment I can on 240V to avoid the voltage drop in the feed wires.

Thank you Art. The motor wiring and supply circuit are two different aspects in this equation, which is a significant point, and possibly one of the reasons these arguments go in endless circles. It's more common for a fully loaded 120v circuit to suffer some voltage loss than it is for a 220v that splits the same load across two hot legs. The 220v circuit is simply less likely to get near it's max load, so is less likely to suffer voltage loss during peak demand, and is one of the more compelling reasons to switch a motor that may draw loads that approach max circuit load to 220v if possible.

[Wade Lippman]

Howie, not being an electrical engineer, I am having a little trouble following what you said. If the motor converts 240 to 120, then it is in effect a transformer?? And if it is amperage that creates heat, how is it that a motor wired at 240v and supplied with 1/2 the amperage of the 120v motor doesn't run cooler? I'm not connecting the dots? I'm sure you have much more experience than I do, I'm only a woodworker in real life, but .... So in essence if you supply 240v to a convertible motor, it transforms it to two legs of 120 and turns it into a heater of sorts?, and in doing so acts like a boost transformer?
Seems like that defeats the purpose of higher voltage motors.

As Howard said, there are two coils in a 120/240 motor.
If you set it up for 240v you put them in series; one after the other, putting the same current through both so the total current is X.
If you set it up for 120v you put them in series; two separate circuits, putting separate currents (two X currents) through both so the total current is 2X.
However, either way each coil sees X current and 120v (when run through two coils in series, each coil sees half the voltage; in parallel each coil sees the full voltage). So internally they are identical.

No transformers, no difference in the heat, no difference in the efficiency. Perhaps a difference in start up due to voltage drop if the wiring is marginal. But that's all.

[glenn bradley]

Well, the other reason to run higher voltage- at least where I am, is that as a business, I pay commercial rate which is higher. Also, along with a higher rate for your power, we are on a demand meter which bases your rate on your amp draw!
The more amps you draw the higher your rate for what you use. So I run high voltage everywhere I can.

This is interesting. Are there other places in the country, or zoning definitions for demand metering, where power is billed by amps? I could see this as a real incentive to convert to higher voltages.

[jack forsberg]

don't mater what voltage your shop is feed its watts not amps you pay for. Watts= voltage x amps. I hp draws the same watts no mater the voltage. Meters read watts.

jack
English machines



Well, the other reason to run higher voltage- at least where I am, is that as a business, I pay commercial rate which is higher. Also, along with a higher rate for your power, we are on a demand meter which bases your rate on your amp draw!
The more amps you draw the higher your rate for what you use. So I run high voltage everywhere I can.

[Michael W. Clark]

don't mater what voltage your shop is feed its watts not amps you pay for. Watts= voltage x amps. I hp draws the same watts no mater the voltage. Meters read watts.

jack
English machines

That's my experience too. Demand is KW, not amps. The industrials I have been involved with pay much less per kWh than the homeowner in the same area. Not sure about commercial customers, maybe the utility is gouging them?

[jack forsberg]

I know there are at least 2 types of 3 phase power and the one I have has different voltages in different wires. There's also no neutral wire in 3 phase which would make a 110 single phase

JeffD
Jeff there are many 4 wire 3 phase systems and even if you only have a 3 wire delta you can use a transformer to derive a ground/common(4 wire Y).

jack
English machines

[Alex Jacobson]

Thanks for all the thorough responses! Looks like I'll stick with the current setup, and forget about the 240, maybe down the road look into getting a more powerful saw.

[Michael W. Clark]

This is interesting. Are there other places in the country, or zoning definitions for demand metering, where power is billed by amps? I could see this as a real incentive to convert to higher voltages.

Glenn,
I used to work for a company that had a manufacturing division in Van Nuys. The eletrical rates were crazy high compared to the rates at our other facilites. Demand metering (kW) and power factor penalties are common for industrials. Regarding demand, the utility has to have the infrastructure/grid to supply the maxium KW draw of the facility, even if the facility does not draw that much power all the time. The meter is on the feed, like at your house. In a simple example, a facility may set it's monthly max kW at 7AM every morning when they start up all the electrical equipment at once. If you stagger the start-up by a period of time (sometimes only 15 minutes), you can cut the max demand set and therefore, the electrical bill. The demand charge is a component of the bill, still charged for energy (kWh), cost riders, power factor, rate adjustments, etc. Just have to look at the particulare rate structure or talk to the utility about optional rate structures depending on usage.

Mike

[Pat Barry]

Some basic facts need to be understood. First whether you use 220V or 110V for your electrical source, the combination of the voltage and the current (V*I) equate to power consumption. Thus a 220V circuit will only require 1/2 the current of a 110V circuit to do the same job (provide the same power). The power company provides 220V to my home and that's measured by the meter in terms of kilowatts supplied. Do you really think the meter spins at a different rate if you are using the same amount of power at 110V vs 220V? Do you think you are outsmarting the power company by using 220V at half the apparent current draw?.