[OP]
Member
I'm new to woodworking and I recently purchased a a table saw and jointer that can be operated on 110 or 220 VAC single phase. My shop has both available. I'm trying to think thru the advantages of running on 220. It seems like there should be no HP, or performance difference(in theory). Am i missing something? Thanks in advance for any guidance.
Contributor
Matt,
In most cases, there is no practical advantage.
Ken
So much to learn, so little time.....
Contributor
At 110, the saw will draw twice the current as at 220. If your circuit feeding the motor can supply the current without excessive voltage drop, then there's absolutely no difference in operating the motor at 110 or 220.
The motor will have the same power, it will generate the same heat, and it will last as long. No difference at all.
That said, there are practical reasons for running large motors on 220/240, primarily because the wires in the supply circuit would have to be quite large.
Mike
Go into the world and do well. But more importantly, go into the world and do good.
Member
One thing I noticed in my shop is that my dust collector (110V) generated enough inrush current on startup that it constantly tripped the breaker. It's a 1.5 HP motor on a 20 amp circuit, which should have been enough to supply the motor. Switching the motor over to 220V mode took care of this problem, since the current draw was now less.
My wife also notices that the lights in the rest of the house don't flicker like they used to when I turn the dust collector on.
Member
As others have said, the difference between running 240 vs 120 is largely theoretical with little practical difference as long as the circuit is capable of providing the required current with acceptable voltage drop.
240v operation requires half the amperage to produce the same power as 120v. In a marginal circuit, you might see the motor coming up to rated speed at startup or recovering from near stalled condition noticably faster when running on 240v. But, in normal operation with a circuit properly sized for the load, you're unlikely to notice any real difference.
With that said, if 240v is readily available, my practice is to use the higher voltage to run dual voltage motors. That's strictly a personal preference. It's not a big deal, IMO, to swap a couple of leads in the motor. But, if it requires running a new circuit to supply 240v when an existing 120v circuit could carry the load, it's very doubtful that the theoretical benefit would outweigh the cost.
Wilbur indicated he saw an appreciable difference with his DC on startup. The reason is that a DC with a high inertia impeller is significantly harder to start that a tablesaw with it's low inertia sawblade. The DC's startup transient has a much longer duration during which there may be as much as 4 to 6 times as much current being drawn than under normal full load conditions. That longer high current startup period is more likely to trip a breaker than the short startup period of a tablesaw.
Last edited by Tom Veatch; 05-06-2009 at 1:07 PM.
Tom Veatch
Wichita, KS
USA
Member
Well from a cost standpoint it should be a wash. You use the same number of watts either way. I would think that if you are worried about electrical capacity out of your breaker box then 220 is the way to go. You have a set number of amps after the primary breaker (in lots of cases this is 200 amps). Using the motors in 220 mode would lower the number of amps flowing through the box and therefore allowing more electrical devices to be running at the same time.
Member
If you intend to run a cyclone or even a Shop vac on the same line... I would go 220 V on the saw. You will pull about 11 A after intial start-up and if you use a cyclone another 15 A so.. you will need #10 gauge wiring and a 30 A breaker.
You run into the same thing sometimes with 220 V. I have a 5 HP TS that pulls about 18 A with 220 V. The cyclone pulls about 15-16 A and it runs the same time as my large machines so... I added a second 220 A just for the cyclone.
In your case I think it just depends with the 220 V using a bit less electricity but maybe electricity is cheap where yor are?
Good luck...
Sarge..
Contributor
That's incorrect, a 200 ampere single phase service for a house would allow 200 amperes at 240 volts, or 2X200 ampere loads at 120 volts.Originally Posted by Marty Paulus
You could have 400 amperes at 120V, or 200 amperes at 240V.
You are limited to 48KVA regardless of the voltage......Rod.
Contributor
John, if you use a 30 ampere breaker, you can only have 30 ampere receptacles on the circuit. You wouldn't be able to plug a shop vacuum into a 30 ampere receptacle...Rod.
[OP]
Member
That gives me some good points to mull over.
Member
Another practical consideration is that if your saw is portable you might want to take it to a job site or a neighbors or something where 220V might not be available. Obviously you could always rewire the saw again, but if you expect to do this fairly often it might be a hassle.
Brian Walter
Member
Aside from the "220 vs. 110 volt controversy", it might be just as important to have a dedicated line to some machines. Some of the problem running certain machines on 110v circuits is that it's sharing that circuits' power with something else like lights etc. In that case when you switch over to a dedicated 220 line you just might see a difference. I know my table saw comes on with a bang and comes up to speed much faster once I switched to 220.
Alan T. Thank God for every pain free day you live.
Member
Current ShopNotes issue has an article on this, but everyone here has done a nice job covering it.
http://www.shopnotes.com/issues/105/
"In The Shop 40 / Motor Wiring
Is there an advantage to wiring for 240v vs. 120v? Here’s what you need to know."
The best solution is if you've got 220 then use it, since it frees up your 110.
Member
Just one small extension on Rod's statement. While you could have a total of 400 amps flowing you'd still be limited to 200 amps maximum in each leg. So only if the load were nearly perfectly balanced between the two legs would you be able to get 400 amps through 120v loads without tripping the breaker.
Tom Veatch
Wichita, KS
USA
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