Motor wiring help needed

Patrice Lemée

Patrice Lemée

Joined
Aug 13, 2002
Messages
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I wanted to rewire my drillpress cause the wiring is at least 25 years old and was badly done. So here are the pics of what I did. Well it went poof and tripped the breaker in the panel. Any idea what I did wrong?

Pad
 

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you have the switch going to ground(green wire), take the green wires
off and tie them together. the two black are the onlys ones that should be on that switch.
at least thats what it looks like from the pics.
usualy its like this.
Green is for ground fault.
white neutral
black hot wire.
 
Last edited:
Well this switch was already wired. I took it apart and the green wire was exposed and connected somewhere on the switch. Is this possible or did I imagine it?I knew I should have taken pics before disassembling. :(

Pad
 
Don't know if this helps, but I took my OHM meter and sat down and learned how the switch worked. Do some quick tests. I also concur with the above. Is the replacement switch of the same type?
 
I wouldn't be surprised if the switch was grounded. I'd need to see the back of the switch to see if the green is supposed to ground to that lug. Try taking the ground off that point and just tape it off for now. If it works that's not a proper grounding lug. If it doesn't there is something else wrong and it's very hard to tell without seeing a lot more.
 
Ok, there is one black nut on the bottom marked "common". The two gold nuts at the top show continuity with the black nut in either position. Is this of any help?

Pad
 
Well it works without the ground so I guess it'll stay ungrouded. I was sure it was grounded somewhere. :confused:

Thanks for your help.

Pad
 
Padrig said:
The two gold nuts at the top show continuity with the black nut in either position.
Pad
Click to expand...

I assume from this that you have a multimeter and know how to test for continuity. You need to find the 2 screws on the switch that are 'switched'. Put your tester on continuity and hold a lead on each screw while switching the switch. Repeat until you find the ones where the connection is switching on and off. You probably have a common (hook your hot wire from your breaker to this one) and 2 switched lines...one on when the other is off.

Caution: If that is a simple household light switch, it is probably only rated for 1/4-1/3HP loads and if you have a big drill press, you may have fried it. Motors pull a large amount of current until they get up to speed (called inrush) and motor switching devices are extra+++ heavy duty to handle it. A light switch is not.
 
common is the hot wire comming in to the unit, from the plug should be a black wire.
You are shorting the Common to(black wire) to ground(green wire) you can connect the green wires to the case to ground the whole unit. they shouldnt be on that switch.
 
Oh, it was likely grounded to a screw attached to the metal frame previously.
 
Now that you mention it Rusty it was attached to the box. It's amazing that I get dressed by myself in the morning. ;)

CDH. the motor is only 1/4HP so I guess I am alright but it is a good thing to know since I wanted to put a bigger motor on the someday.

Thanks again guys.

Pad
 
That switch should be fine on that with a 1/4 or even a 1/2 hp motor, shouldn't pull more that 20a even at start up, and most of those switches are either 15 or 20-25 amp rated. I use one on my air compressor and its a 1.5 hp motor.
 
That's good. 1/2 HP or even 1HP was what I was looking at but for now 1/4 seems just fine. The Drill press is an old Rockwell 15" by the way.

Pad
 
This should be a good learning experience.

Next time you rewire a switch and you aren't 100% sure you did it correctly, you can ohm it out with your DMM before plugging it in. Check the continuity with the switch on and off and make sure none of the wires short when the switch is thrown.
 
Make dure that you hook the ground (green) wires back to the grounding screw(or frame) on the motor.
From a safety stand point, it is important---could keep you alive.

-Mike-
 
Actually the ground is what got me started on this. My nephew-in-law bought me one of those electrician pens that shows you if a wire is live. Well it was fun so like a kid I went around the shop checking everything. Well on the drill press everything made the pen glow. I took a look at the wire and there was only 2. The person who had it before had snipped the 3 strand wire and connected a 2 strand wire to it. I don't know anything about this but suspected that the ground might have something to do with it. Hence the rewiring of the whole thing.

Thanks for the warning.

Pad
 
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