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Switch wiring on old unisaw

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Forum topic by Toolhoarder86 posted 08-17-2019 10:35 PM 178 views 0 times favorited 5 replies Add to Favorites Watch
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Toolhoarder86

4 posts in 239 days


08-17-2019 10:35 PM

Topic tags/keywords: unisaw wiring plug tool

Hello,
I just bought an old Unisaw that appeared to be wired for 220v, but the way it was wired was extremely confusing to me. At the switch, there are two wire coming out the top feeding the motor, one black, one white. In the bottom of the switch coming from the power cord are a black wire and a green wire, both hooked to the switch. There is a white wire hooked to the metal switch case, where ordinarily I would think the ground would go. The power cord is 10/4. The red wire is not utilized in the switch box, but is connected in the plug to a hot lead. The green wire is hanging loose at the plug. Black wire is connected to hot. White wire connected to neutral. It is an old fashioned 3 prong dryer plug. The cord was very damaged and frayed, but the saw turned on when plugged in. To me, it must’ve only been getting 120v in this configuration, but the plate on the motor shows this setup. Help!

-- There’s always a bigger tool.


5 replies so far

View MrUnix's profile

MrUnix

7468 posts in 2676 days


#1 posted 08-17-2019 10:41 PM

Given the condition of the wiring, I’d rip it all out and start with some fresh wire and a new plug.

Cheers,
Brad

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

View Toolhoarder86's profile

Toolhoarder86

4 posts in 239 days


#2 posted 08-18-2019 02:58 AM

Yeah, already doing that. Just trying to figure out the correct way to wire it up.

-- There’s always a bigger tool.

View MrUnix's profile

MrUnix

7468 posts in 2676 days


#3 posted 08-18-2019 04:04 AM

Yeah, already doing that. Just trying to figure out the correct way to wire it up.
- Toolhoarder86

That’s pretty simple… it’s only two wires + ground. I’m guessing from your description that you have a DPDT switch instead of a magnetic starter like on the newer models, so it’s just line in to the switch, and then to the motor. If you are asking how to wire up the motor for the proper voltage, then that depends on if you want to run at 120v or 240v – but the wiring from the wall is still the same.

Cheers,
Brad

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

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Toolhoarder86

4 posts in 239 days


#4 posted 08-18-2019 04:29 AM

Ok, thank you. I’ll give that a try. Just weirded me out the way the previous owner had it.

-- There’s always a bigger tool.

View CaptainKlutz's profile

CaptainKlutz

1746 posts in 1971 days


#5 posted 08-18-2019 07:35 AM

+1 Brad’s comments, reasonably simple 2 wire + ground.
+1 Get new wire and plug to make sure all is well.

IMHO – Hardest part about the wiring inside the old RI motor hook up is determining wire colors for two voltage configurations. Those motors are from 50+ years ago, and wire colors fade, or all turn various brown shades over time. The Vintage Machinery/OWWM site has posts and wiring diagrams if need more information on the old bullet motors.

BTW – If wired for 240v, the most common 1hp single phase bullet motors draw about 6 amps. Can safely use even 200 foot of 14AWG power cord and save some $$ over previous owners use of 10AWG.
If wired for 120v, suggest use of 12 gauge; but it is still only 12A FLA and < 50 foot 14 gauge cord still wouldn’t create any serious voltage loss.

Best Luck.

-- I'm an engineer not a woodworker, but I can randomly find useful tools and furniture inside a pile of lumber!

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