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Logan 820 wiring issues

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vincent52100

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#1
Well, got a weird problem with the power on my 820 lathe. It has a 110v motor and Dayton drum switch. With the motor and switch on the bench it works fine. If I put it on the machine without mounting the switch it works. If I mount it to the machine it trips the breaker. The odd thing is that it worked when I picked it up (but I don’t know how it was wired at the outlet). I assumed it was probably a wire shorted to the switch or frame. I checked for that and found no problem, pinched wire etc. But before I replace all the wiring to and from the switch I thought it might be a good idea to see if someone sees something I did wrong. There are no markings on the motor and it has two red and two black wires coming from the motor, not labeled at all. Do the the two sets of wires need matched up, a certain red and a certain black? It has a single capacitor. The switch itself is a Dayton. I don’t know which wires should be paired or if it matters. Hopefully the wiring diagram makes sense.
Thanks!
 

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markba633csi

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#2
Sometimes the switch cover causes a short to one or more wires which then causes a short to ground when you mount everything up. Check for that.
mark
ps be careful you have a potential shock hazard there, take all precautions
 
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Bi11Hudson

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#3
There are a couple of things I question about your drawing. I should say "that make me nervous".

The most significant is the jumper across two points. The switch, if I am seeing it correctly, has two lugs (jumpers, bars, whatever) that switch between straight across and crossed. FWD is one way, REV the other. The lugs? will change shorts from FWD to REV.

Now, without actually seeing how the switch moves, I will proceed through what is necessary. The first thing is to determine which wires are which at the motor. A multi-meter is the most well known tester, there are many ways to check continuity. Use the "ohms" scale, Rx10 or Rx100, to ring out the wires. There will be two distinct windings, one of a relative fixed resistance, one with a tapering over time. The former, the run winding. The latter, the start winding.

The wire colours are relatively meaningless. As in, they will vary from motor to motor. I am going to assume the black pair to be the run winding and the red pair to be the start winding. This may or may not be the case. But will do for my explanation. As long as one winding is reversed relative to the other, it will reverse. So, make the continuity test and determine for sure which pair is a winding. Do that first, by whatever method.

Once that is done, connect one black wire to the neutral. The WHITE wire in the line cord. This connection is not connected to the switch at this time. It is a stand alone connection. The other black wire connects to the terminal of the switch that closes only straight through. An ON-OFF switch. The other side of that switch connects to the LINE side, the BLACK wire of the line cord. This will leave an X-II connection on the switch.

The four connections left will be on the diagonal. In REV, they make up one way. In FWD, they make up the other. Connect the RED pair to half of this. The other half connects to the line cord. This will reverse the winding, depending on which way the switch is thrown.

UPDATE

Sorry for the interruption....
The enclosed photo is from a plastic, Chinese made drum switch. It does not match the Grainger switch but will illustrate the connections. The important issue here is to reverse one winding relative to the other. And to open both windings in the OFF position.
##DrumSwHookup.jpg
 
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vincent52100

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#4
Thanks for the info guys! Will try all the suggestions.
 

vincent52100

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#5
I took your advice and rechecked everything. There is nothing shorting out against the cover. I checked for any cross flow in the power cord, like two wires that are contacting each other ( the cord is old and I will replace it) but didn’t find any problems. Could not find a similar problem with the wiring going to the motor. I’ve attached a diagram of the switch both without the jumper wire and with it installed. This is with it completely disconnected. I can’t see what the purpose of the jumper is but then I’m don’t really know how it works. Also I’ve listed the Ohm readings from the windings.
Thanks again for any help
 

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markba633csi

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#6
You shouldn't be seeing low ohms readings to earth- sounds like the motor has an internal defect
When you made those tests was the motor completely disconnected from the switch and power cord?
mark
 

vincent52100

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#7
Yes, completely but with the cable attached to motor but not the switch. I’ll remove anything attached to the motor and check it again.
 

vincent52100

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#8
Have looked at everything again. My numbers and switch positions were correct on the drawing. Took readings from each blade of the power plug. I had continuity from each blade, except from the mechanical ground, to each post of the drum switch, both forward and reverse. This is not the the case when the switch is out of the circuit as in the diagram. Could it be a bad motor?
Thanks
 

Bi11Hudson

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#9
I'm baaccckkkk.

It seems the switch is faulty. At least that's what it looks like from your tabulation. What's missing is the second connection in the REV position. There was a "work around" made in the wiring so that the machine would run, although not correctly. My suggestion is to replace the switch. And wire it correctly. That's my suggestion to the problem. There are a few "git bys" that will work, but when dealing with line power, my first instinct is safety. Do it right, then you don't have to do it over.

The top two poles are the reversing switch. The bottom pole is the ON-OFF switch. The RUN winding. That's the way it looks, anyway. When the middle pole failed, a "jerry-rig" was produced to power the machine, likely in the FWD position. With the switch isolated from the machine, it likely worked. Poorly, but worked.

There is a possibility that the motor is grounded. The way to test this is to remove all connections to the motor and use an instrument called a MEGGER. A meg-ohm meter. Lacking this(probably), a multi-meter on a high range, 10K or better will (sorta) work, as it's only about 9 volts. The reading should be a very high number from any wire to ground. The megger is a standard test device for motors, putting some 500 volts on the winding(s) to ground. Big motors use the same device with a higher voltage for motors up to 7200 volts and up. 7200 is the largest I have ever worked on. Above 500 volts, a HI-POT tester is generally used, rather than a megger.

As an aside, when I need a line cord, I generally go to a home center and buy a short extension cord. Usually a Nr 14. And cut off the female end, a foot or so long. 'Cas'n I ever need a female cap. Ya never know... ...

The proper replacement for the switch will be Grainger, Sq. D, Eaton, somebody like that. But they are right proud of their products. I found the switch as Chinese made for 10 bux on FleaBay. Yeah, it's plastic. But I ordered one to check out. It isn't here yet, but might be worth following up on if you're working on the cheap.

Bill Hudson​
 

markba633csi

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#10
If you are getting low ohms readings from ANY motor wires to ground/case then the motor probably has a fault (bad capacitor, shorted winding, etc.)
All motor wires should read at least 100,000 ohms or more to the case housing (ground)
mark
 
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wa5cab

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#11
Vincent,

I would assume, as others have, that the two black wires go to the run winding. And that the two red wires go to the start circuit, which consists of the start winding, the centrifugal switch, and the start capacitor all connected internally in series. And I also have to assume that you made the resistance readings with the motor completely disconnected from the switch and the line cord. If the latter assumption is true, then the run winding is shorted to the field poles or to the motor frame, something in the start circuit is shorted to either the field poles or the frame, and the start capacitor is leaky (bad).
The reading that you should have gotten with the analog (not digital, which is almost useless for this purpose) multimeter set on any resistance scale is that the needle should have kicked towards zero momentarily the first time that you connected the leads to the red wires and then quickly or slowly gone back to infinity. With a good capacitor in the start circuit, the second time that you connected the meter to the red wires, there should have been little if any needle movement, as the capacitor was already charged up to the internal battery voltage. To take a second reading with a good capacitor, first connect the two red wires together for several seconds.

Anyway, if your readings are valid (meaning that the caveats that I listed above were met), you need both a new motor and a new switch.
 

vincent52100

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#12
I may have found the problem. One of the black wires had worn through the insulation where it comes through the motor housing to the connection box. I put heat shrink on it, and the other wires, where they come through the motor housing. I'm going to put rubber grommets where the wires come through the housing and a strain relief where the wires from the switch to the box. I really should have noticed that there was no protection for the wire. Any way, there grounding problem with the black field is gone. I looked at the switch again closely and I think it is fine. The mfd on the capacitor is within the range printed on it. I won't get a chance to put it back together until this weekend and I will also replace all the wiring. I also think the leads from the winding are too long so I think I might shorten them. Thanks again for all the help, really got me looking in the right area.
Can't tell you how much help I've received from this forum on my whole lathe project. Soon be making chips!
 

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wa5cab

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#13
Well, perhaps in was a testing error instead. But I will repeat that if you have a steady state relatively low resistance reading through the Start circuit, regardless of what else might be wrong, the capacitor is bad regardless of what its value is.

I assume that after you found and repaired the shorted black wire, that measuring the resistance to ground of the black circuit now shows a reading of at least sever megohms. What about the red circuit? Your notes said that it also had a short to ground.
 

markba633csi

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#14
Sounds like you found the problem- your switch connects like this inside:
drumDiag1LG.jpeg
And the diagram in your first post is correct
Mark
 

vincent52100

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#15
It works! The problem was the wire rubbing against the case. I wrote the wrong numbers for the red wires, it wasn’t 0.0ohms, it was 0.L. Old age and bad eyesight. I installed rubber grommets where the wires come through the motor housing and replaced the power cord and used flexible conduit from the switch to the motor. I found the wiring diagram on industrial-electronics. com for the switch. Runs great and everything’s works! Thanks for all the help. I’d still be thinking I needed a new circuit installed in the basement.
 

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