Table saw electrical question

[Dick Holt]

I am waiting for my new Shop Fox 8" jointer to come in. Because it is 220V, I have to put in a 220V outlet in the basement. I was thinking, since I have to put in a new outlet, why not convert my Delta contractor saw from 110V to 220V ? I can pick up an extra 1/2 HP by doing this. I know I have to rewire the motor, but what about the power cord ? It is 14-3 wire. The motor draws 12.8A at 110V and 8.6 on 220V. Do I have to replace it or can I just cut the plug off and put on a new one for 220V ? TIA,
Dick

[Ken Fitzgerald]

Dick,

Unless your motor has something special, you will not gain one iota of horsepower by converting your motor to 220.

There might be some special motors made with separate windings for 220 vs 110 but a huge majority of motors use the same set of windings and there is NO increase in hp by rewiring for 220vac.

This is a misconception, a rumor that has no validity.

P = IxE..... doubling the voltage while decreasing the current by a factor of 2 has no change in the resulant power.

IIRC....there might be some argument about a shortened time to reach normal speed due to applied voltage so a motor will spin up faster or recover faster if bogged down but without any increase in HP. It's been over 45 years since I studied this stuff. Some of the engineers here......correct me if I'm wrong.....

[Dick Holt]

Ken,
I was just reading an article in a past issue of Wood magazine. It said what you just did. It went on to say that in a few motors there are extra windings that come into play only on 220V. If there were no difference in HP ratings, then the amperage on 220V would be exactly 1/2 the amperage on 110V. One half of 12.8 would be 6.4A. The label lists amperage on 220V as 8.6A, not 6.4. The label also lists the HP as 1.5/2 HP, with the 2 being HP at 220V. If there were no difference in HP, then I would not bother converting. It would not be worth the time or money.
Dick

[Rod Sheridan]

Dick, you are correct, in this case (it's the only one I know of) the manufacturer derated the motor on the nameplate so it could pass approval for the 120 volt rating.

You will obtain 1/2 more HP in this case.

Ken is also correct that normally a motor has the same performance on any voltage it's rated for, as long as the supply circuit is adequately designed..........Regards, Rod.

P.S. The power cord is larger than required for 240 volt operation so you're just fine.

[John Aspinall]

I did this exact conversion 2 years ago (Delta contractors saw, 1980's vintage), so let me add my $0.02 here.

I might be getting a little extra power, based on the de-rating at 110V mentioned above. But the big perceived difference is in startup time. On 110V, I could count to five while I waited for the motor to spin up. On 220V, it's at full speed by the time I've lifted my finger from the start button. I like that. Plus I'm decreasing the I-squared-R losses in my house wiring.

Do it. I should have done it years earlier.

[Dick Holt]

John,
Glad to know it was worth converting. Did you just put a different plug on the power cord or did you replace it? Rod said the existing cord would be fine, but I was thinking of replacing it in order to get a longer one. What did you do?
Dick

[Chip Lindley]

Theoretically, there should be no difference in a motor run on high or low voltage. If a 15A 115v saw can be run on it's own dedicated 20A circuit, there will never be a problem. But, otherwise, the factors affecting motor operation are in the wiring before it ever reaches the motor.

From personal experience, I got much better operation of my Rockwell 1.5hp, 15A contractor's saw after switching to 230v. For too long I suffered with the saw tripping my 115v garage circuit during heavy cuts. The problem was that my garage circuit was shared with other amperage draws which could not be avoided; overhead lighting, outdoor yard lighting, and anything else plugged into a garage outlet.

As soon as I had a 100A sub-panel installed in the garage shop, the 15A saw motor was switched to 230v and I never ever looked back. No more lights dimming, and much faster start-up. The old Rockwell would rip 2" white oak without complaining. Now I run every machine in my shop on 230v if possible. That frees up the single 115v wall circuit, still shared with lighting.

Keep your 14ga. cord on the saw and just replace the plug. Your saw will draw only 7.5A on 230v rather than 15A on 115v.

~~Chip~~

[Rick Christopherson]

Dick, you are correct, in this case (it's the only one I know of) the manufacturer derated the motor on the nameplate so it could pass approval for the 120 volt rating.

You will obtain 1/2 more HP in this case.

You are correct that Delta derated this motor, but not correct in what that actually means. Derating the motor simply means they lowered the numbers printed on the nameplate. If connected to a 20 amp 120 volt circuit, the motor would still produce the full rated power. This motor is no different than any other dual voltage motor.

[Rod Sheridan]

Thanks Rick, didn't mean to leave the impression that the HP rating was different at 120/240 volts.

It was a strange marketing effort............Rod.

[Dick Holt]

OK, now I'm confused!
Dick

[Rod Sheridan]

OK, now I'm confused!
Dick

Hi Dick, when you plug the saw into a conventional 120 volt 15 ampere circuit you can run it up to 1.5 HP load. (12.8 Amp rating)

On a 120 volt 20 ampere circuit you can run it up to 2 HP load. (It would be 17.2 amperes rating)

Same for 240 volts, you can run it up to 2 HP (8.6 amperes rating).

It's the same HP motor at either voltage.

What the marketing people have done is re-badge it as a 1.5HP motor so it can be sold to run on a conventional 15 ampere circuit.

Regards, Rod.

[John Aspinall]

Glad to know it was worth converting. Did you just put a different plug on the power cord or did you replace it? Rod said the existing cord would be fine, but I was thinking of replacing it in order to get a longer one. What did you do?

Dick,
I used the original cord (with a new NEMA 6-15 plug). I was pulling a 220V circuit to several places in the workshop, so I had the freedom to put the outlets exactly where I wanted them, and hence no need for a longer cord.

I did also take the opportunity to replace the original (inadequate) toggle switch, with a big aftermarket paddle switch. The switch is mounted proud of the front face of the saw, in its own electrical box. It looks like crap, frankly, but I can now turn the saw off with a nudge from my knee, should an emergency arise.

[Anthony Whitesell]

Hi Dick, when you plug the saw into a conventional 120 volt 15 ampere circuit you can run it up to 1.5 HP load. (12.8 Amp rating)

On a 120 volt 20 ampere circuit you can run it up to 2 HP load. (It would be 17.2 amperes rating)

Same for 240 volts, you can run it up to 2 HP (8.6 amperes rating).

It's the same HP motor at either voltage.

What the marketing people have done is re-badge it as a 1.5HP motor so it can be sold to run on a conventional 15 ampere circuit.

Regards, Rod.

Curious but serious, how do you prevent the motor from running at 17.2A when on a 15A circuit?

[Rod Sheridan]

Anthony, obviously you cannot.

That's why they list it as 1 1/2HP 12.8A, if you exceed that you're overloading it.

Of course running it at 17.2A for a moment or two on a 15A circuit isn't a problem as long as the load pattern allows the wire, breaker, receptacle etc to stay within thermal limits.

This is like any motor, it can be overloaded for a short time period, then run at reduced load to cool, then the cycle can repeat.

Regards, Rod.

P.S. Duty cycle rating is often used for motors, I have a 4HP saw/shaper with an S6 40% rating (IEC). This means it can be run at full load for 4 minutes, then 6 minutes no load, then repeat.

Obviously it's going to be darn near impossible to run it at 4HP for more than 4 minutes in a home shop, so the IEC motor ratings make a lot of sense. You get a compact motor that can run at high outputs with a time profile that matches hand fed wood working machinery fairly closely.

[Curt Harms]

.............
P.S. Duty cycle rating is often used for motors, I have a 4HP saw/shaper with an S6 40% rating (IEC). This means it can be run at full load for 4 minutes, then 6 minutes no load, then repeat.

Obviously it's going to be darn near impossible to run it at 4HP for more than 4 minutes in a home shop, so the IEC motor ratings make a lot of sense. You get a compact motor that can run at high outputs with a time profile that matches hand fed wood working machinery fairly closely.

Interesting. I wonder if that partially explains the Jet JJP-12 motor overheating situation. That seems like one small motor compared to a 3 h.p. Marathon or Baldor. But if it has a fairly low duty cycle, it would produce 3 h.p. But then someone who has a couple hundred board feet stacked up and sends it through one board right after another would easily exceed that duty cycle.