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Rockwell band saw motor tripping GFI

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Happy Labor Day,
I am working on this 1947 Delta 14” band saw.
I am getting close, just need one more bearing and I thought I was ready to go.
I replaced the electrical source 14/3 wire. Plugged it in and the GFI tripped immediately.
I checked my work, all looked good.
I removed the end shield and cleaned the points. They were pretty bad. I also discovered a chaffed wire. One of 3, there are two sets of 3 wires. See pic.
I taped the damaged insulation assuming that was it. Blew all the saw dust out of the motor etc.
I plugged it and it ran perfect, for about ten seconds, then tripped the GFI.
I haven’t checked amp load yet.
This is a 115/230 ac motor. 1/2 HP, frame is 56. Rated at 7.7 amps at 115 v which is how it is wired now.
Please excuse the improper names I applied to the components, I really am an idiot when working on anything electrical.
I would like to save this motor. I’ll look for more shorts in the mean time.
Do you think it can be saved?
 

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#2
GFCI can be overly sensitive, particularly with older motors and such. You may not have anything wrong really, just an older motor. Try connecting it to a non-GFCI outlet. If it runs for a short time, I doubt it is a short, though there could be a problem with the centrifugal switch and/or run capacitor.
 
#3
The contacts are as good as I can get them. They made contact over about half the diameter/mismatched. I filed and bent it straight.
I’ll try a different outlet.
What is the best way to measure amp load/draw. I know how on a 3 phase but......
Thanks
 
#4
I had an electric an opener that regularly tripped the GFCI. Switching to a different out, no problem. I replaced the GFCI socket which solved the problem.
However, the purpose for a GFCI is to detect small leakage currents to ground which could mean that you could have an intermittent or high resistance short to the motor frame. I would suggest connecting to another GFCI outlet. If the outlet trips, you would most likely have a problem with the motor. If it runs fine, replace your suspect outlet.
 
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#5
I tried a non GFI outlet and it works!,
Ah, it changes direction though. Clockwise, then counter clockwise. It seems to struggle a bit then takes off.
Ideas?
 
#6
I measure current draw with a clamp on ammeter. It works on single phase or three phase. They are very reasonably priced at HF.
 
#7
I noticed a wiring diagram on the side plate. I’ll check to see if it is wired according to the plate for 115.
 
#8
I have the tools to measure draw I just don’t know which wire?
 
#9
If you have a clamp on ammeter, place the clamp around one of the wires coming into the motor, preferably the load wire. It can be anywhere in the circuit as long as it is a single wire. If you have an inline meter, you will have to disconnect the load wire at some point and rewire through the ammeter.

An easy way to do either is to wire up a duplex socket with a plug ( an old computer cable is a good candidate). for the clamp on, place the clamp around one of the leads, preferably the load wire, and for an in line meter connect the load wire to the meter and another wire from the meter to the outlet.

BE CAREFUL! 120 volts has a bite at best and can be lethal at worst. Make all your connections and stand back before you apply power. If youo are by any measure uncomfortable with doing this , it would probably be best to take the motor into a motor repair shop.
 
#10
Couldn't he Ck the wires for short , by touching each one while searching for continuity . Wires each one and the probe to one and motor . If there's continuity there's short . Bad wire found
 
#11
Continuity testing is a good place to start. The connection being wired for the right voltage is also important. With it reversing itself, something isn't right and that could very easily be the reason why it trips a GFCI.

For testing amp/watt draw on smaller loads, a kill-a-watt meter is about $20 at HF and others. It includes a pass through outlet, so no need to mess with wires or worry about shocking yourself.
 
#12
I suspect the start capacitor or centrifugal switch if the motor is randomly reversing on start up-
Check the wiring is correct according to the diagram on the nameplate also
Test all motor wires with an ohm meter to the motor case- all readings should be very high resistance (250,000 ohms or more)
Mark
 
#13
GFIs can trip for several reasons. I've seen them go when shutting off a small motor - the shaded pole type, no start winding. When you shut off the power to anything with a coil of wire, there can be a spark at the switch. That can be enough to trip an overly sensitive GFI. Could the 'ten seconds' have coincided with the centrifugal switch tripping as the motor came up to speed? The spark from that could have tripped it. Replacing the GFI might solve it.

Another sure tripper is if the neutral connection comes into contact with the ground. An intermittent contact could allow the motor to run until contact is made. The ground is connected to the neutral back at the service, but contact near the load creates a separate path.
 
#14
Photo looks like white and green are together.

Check that.

Green needs to only connect to frame.

Check plug with ohm meter.

Safety ground needs to show as open to both line connections.

Sent from my SAMSUNG-SM-G930A using Tapatalk
 
#15
Ok guys, thanks. I have the test equipment, I’ll have to relearn how to use them to test the ideas that have been shared.
It is a dual voltage, single can, single phase motor FYI.
 
#16
Photo looks like white and green are together.

Check that.

Green needs to only connect to frame.

Check plug with ohm meter.

Safety ground needs to show as open to both line connections.

Sent from my SAMSUNG-SM-G930A using Tapatalk
Please NOTE this post. It is very important that the green power supply cable lead should only be connected to the frame and not the neutral.

The green provides the safety protection when not using a GFCI protected branch circuit.

David
 
#17
I will take a picture of the wiring diagram and a detailed pic of the current wiring scheme.
I do see a green wire tied in with the yellow and blue/white on #4.
There is a green wire soldered to the board. It was one of the damaged wires.
I will check it out this evening.
Thank you
 
#18
Sometimes manufacturers will use green wires for inside winding connections (they really shouldn't)
The only green wire outside the motor should be the ground (earth) wire
M
 
#19
I checked the capacitor when I got home. This motor is done.
The wires have hard cracked insulation, every thing I check just tells me it’s time to let it go unfortunately.
I found one from Grainger for $115.
I didn’t want to spend the money but at least I can say it has new tires, new bearings and a new heart.
 
#20
I don't know and you guys seem to know what you are doing, but another thought - we know GFCI outlets are sensitive to inductive loads, like motors with capacitive start so plugging into a non GFCI outlet works. Old appliances did not have polarized plugs. Maybe the ground pole indexes the polarity correctly? I have an old fluorescent light that, if you plug it in backward (just double prong) will zap you if you touch the housing, turn the plug over and it doesn't (yeah, nice, and I haven't used it since). If no ground, is that why it reverses direction?
 
#21
Was the capacitor bad? Or you just didn't want to repair the wiring? Perfectly understandable, but many motors can be spiffed up and put back in service as long as the windings are not shorted, open, or shorted to the case. Some odd sized square capacitors are no longer available, which necessitates fitting a substitute. Centrifugal switches are sometimes too far gone. Very seldom that a USA motor can't be saved; can't say the same about import ones tho
m
 
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#22
My two cents. I made up a six inch male and female extension cord with open twn wires so that I could use my clamp on ammeter. It just goes with me in my electrical bucket. Yes color coded wires with the correct polarity. I plug in the extension cord into the outlet and plug in the appliance to check the current flow. easy peazy
 
#23
My two cents. I made up a six inch male and female extension cord with open twn wires so that I could use my clamp on ammeter. It just goes with me in my electrical bucket. Yes color coded wires with the correct polarity. I plug in the extension cord into the outlet and plug in the appliance to check the current flow. easy peazy
I built this version of your idea about a brazillian years ago. Because my ancient analog meter doesn't have very sensitive scales, I made a "coil" of 10 turns, so that I can get a 10X current reading.
kHPIM5507.jpg kHPIM5509.jpg
 
#24
hman, I like your jig. I used to have the same Amprobe. Lost it in the house fire. I did make a similar adapter, but my newer clamp meters don't usually need the boost. I did do the ten-wraps thing back in the day, though.
 
#25
GFI's have no place in a shop imho. My place has a 2 car attached and a 2-1/2 car detached garage that is now my shop. The previous owner of the place had GFI's everywhere. Why? I have no clue. It's certainly not required by code. I couldn't even plug in and use a shop vac without tripping a GFI. They're all replaced now with standard outlets and all is good.
 
#26
Some areas require GFCI in attached garages. It's all up to the inspector.

If you think those are annoying, don't try an AFCI. Those things suck.
 
#27
Some areas require GFCI in attached garages. It's all up to the inspector.

If you think those are annoying, don't try an AFCI. Those things suck.
From what I could gather from the NEC, GFCI's are required in garages that are built at or below grade. Makes sense, just like in a basement that may take on water.
 
#28
All of the 110V outlets circuits in my shop are on GFCI breakers. I'm not a big fan of the GFCI outlets, they seem to have a much higher failure rate than GFCI breakers. My shop is basically a ground level detached garage on a slab. I had one older Craftsman motor that would trip the GFCI. It had a bad starting capacitor that had a high resistance short to the case. The GFCI was doing it's job.
 
#29
Was the capacitor bad? Or you just didn't want to repair the wiring? Perfectly understandable, but many motors can be spiffed up and put back in service as long as the windings are not shorted, open, or shorted to the case. Some odd sized square capacitors are no longer available, which necessitates fitting a substitute. Centrifugal switches are sometimes too far gone. Very seldom that a USA motor can't be saved; can't say the same about import ones tho
m
I have been thinking this through, I may try to fix it. The capacitor is bad, I figured out how to test it and that has got to be a good place to start.
Meanwhile, I installed a new motor and its going up for sale when I get one more part.
PLUS, I am learning a bunch of stuff!!
 
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