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Running a 3-phase 230V table saw on single phase 110V.

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Forum topic by david_t posted 04-13-2021 11:16 AM 652 views 0 times favorited 11 replies Add to Favorites Watch
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david_t

2 posts in 35 days


04-13-2021 11:16 AM

Topic tags/keywords: tablesaw motor voltage electrics

Hey all, I recently was given my grandfather’s Unisaw and it came with a 3-phase 230V 3HP motor. I’m in a rental so adding a 230V plug is unfortunately out of the question, and Delta has confirmed that there’s no way to rewire it for 115V, unlike newer Unisaw motors.

My question is this, and I’m pretty sure the answer is “no”: Is there any combination of phase converters/VFD’s/etc. that will allow me to run this saw on 110V single-phase wall power?


11 replies so far

View Mosquito's profile

Mosquito

11128 posts in 3379 days


#1 posted 04-13-2021 11:56 AM

I doubt it. If you can’t install a 220v circuit, I’d say no for the same reason.

Even if you found a VFD to push 3HP with 110v, you’d probably also have to be able to add a higher Amp non-gfci 110v circuit, depending on what the VFD required. Don’t know what the VFD would want exactly, but usually a 3HP 110v motor is around 27 Amp (which is why they’re not as common).

-- Mos - Twin Cities, MN - http://www.youtube.com/MosquitoMods - http://www.TheModsquito.com

View Fred Hargis's profile

Fred Hargis

6991 posts in 3580 days


#2 posted 04-13-2021 11:57 AM

There is probably some really complicated way to use 2 wall outlets if they’re on different circuits (and differeant legs in the panel) but the basic answer is no. 3 phase motors can’t be rewired to single phase (120V) even on the new Unisaws.

-- Our village hasn't lost it's idiot, he was elected to congress.

View MrUnix's profile

MrUnix

8566 posts in 3286 days


#3 posted 04-13-2021 02:07 PM

Quick answer: No.

Got a clothes dryer? Those are typically 30 amp 240 volt, which would be sufficient for your saw.

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

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LesB

2990 posts in 4530 days


#4 posted 04-13-2021 05:39 PM

Three phase is not a common service for residential locations and especially rentals. I actually had 3 phase at my place but then the utility company put in new wire and transformers that were only single phase. Fewer problems for them having tree limbs fall across the two wires and mess things up.. Fortunately my tools were not 3 phase anyway.

Your best option is to replace the motor but then the saw will only preform marginally with a 120v motor. However investing in a dual voltage motor would prepare for a future time when you do have a 240 hook up. This is assuming the saw in in good condition to begin with because new motors are not inexpensive. How much do you want to invest in an old saw?

-- Les B, Oregon

View HokieKen's profile

HokieKen

17554 posts in 2225 days


#5 posted 04-13-2021 05:44 PM

Like Brad said, you may have a clothes dryer circuit? And like Fred said, if you can tap two 115V circuits that are on opposite legs of the panel, you can pull 230V to power a VFD but I imagine that is frowned upon by electricians…

-- I collect hobbies. There is no sense in limiting yourself (Don W) - - - - - - - - Kenny in SW VA

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david_t

2 posts in 35 days


#6 posted 04-13-2021 06:16 PM

Thanks everyone, this is a huge help and the confirmation I needed that I should just go get a new motor. The saw and current motor are in excellent condition and I think a local shop will buy the current motor which should offset the new motor’s cost a bit.

To those asking about the clothes dryer outlet, I checked and it looks like it’s running on 115V with a gas hookup for heat. Pulling 115V from two circuits feels like one of those things that’s technically possible but far beyond my limited electrical skills.

Thanks again for the responses!

View LesB's profile

LesB

2990 posts in 4530 days


#7 posted 04-13-2021 06:58 PM

Check this web site for an explanation of the difference between single phase and 3 phase.

Don’t mess with trying to pull 120v from two different circuit outlets. 240v circuits have split breakers that are mechanically connected at the service box and if one breaker shorts it trips both breakers. If you used two separate outlets this would not happen and the motor could overheat and start a fire.

-- Les B, Oregon

View tvrgeek's profile

tvrgeek

1872 posts in 2736 days


#8 posted 04-13-2021 07:20 PM

Yea, new motor, but you are not likely to go past 2 HP with 110. Might check the size of your breakers and wires. Even so, you would need a 30A 110, 10 gauge wire for 2 HP.

You could get a single phase 220 3 HP motor and run it off the dryer plug as it only needs a 20A 220 line. Good motors are not cheap, so be ready.

View MrUnix's profile

MrUnix

8566 posts in 3286 days


#9 posted 04-13-2021 07:23 PM

Thanks everyone, this is a huge help and the confirmation I needed that I should just go get a new motor. The saw and current motor are in excellent condition and I think a local shop will buy the current motor which should offset the new motor s cost a bit.
- david_t

Be warned… there is more to it than just swapping motors, and doing so (to 120v) would noticeably degrade the machines performance. You may be better off selling (or storing) that saw and getting one that will work for you now on 120v. Just my 2c

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

View Bill1974's profile

Bill1974

172 posts in 4072 days


#10 posted 04-13-2021 09:00 PM

A 3 hp 110 VAC motor is going to need a good size circuit to run it, like a 40A circuit. I am guessing there is not a suitable 40A 110 VAC outlet in your place. Easiest thing is to check the breaker panel and see if you have one or two 110 VAC lines feeding it. If you do it’s a matter of having an appropriate circuit added to it that you can plug a vfd into to take single phase 240 VAC and output 3 phase 240 for your table saw. You could replace the motor, but it’s likely a replacement motor is more than a vfd.

If you are unable to have a 240 circuit put in you are SOL. With the popularity of electric cars and the chargers they need, there is a good chance to be able to install a new circuit and maybe have the landlord okay it and maybe chip in as it would be an improvement to the property.

View Fred Hargis's profile

Fred Hargis

6991 posts in 3580 days


#11 posted 04-13-2021 09:39 PM


Be warned… there is more to it than just swapping motors, and doing so (to 120v) would noticeably degrade the machines performance. You may be better off selling (or storing) that saw and getting one that will work for you now on 120v. Just my 2c

Cheers,
Brad

- MrUnix

That’s where I shake out on this. Either store the saw for use when you’re set up a little better, or sell it and get something you can use where you’re at.

-- Our village hasn't lost it's idiot, he was elected to congress.

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