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Make sure the wire is still attached!
-
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Electrical peeps, cypher this one for me.
- Thread starter RaisedByWolves
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Ok, took my multi meter and checked the outlet where everything is plugged in.
Between the two spades I get 122V, from one spade to ground I get the same and on the other spade it starts out at .3 and immediately goes down to .03 and then settles and bounces around .002, so I think that checks out.
Same result on both power strips so I know Im grounded there also. Then I checked the drill press at the plug with it unplugged and it was showing 24v which I don't understand other than that LEDs do weird **** sometimes, and there's that regulator in the mix also so Im dismissing that as continuity seemed good all around..
For diagnosis sake or because power strips are da debbil? I need the power strip for several reasons and it is a quality unit.
Between the two spades I get 122V, from one spade to ground I get the same and on the other spade it starts out at .3 and immediately goes down to .03 and then settles and bounces around .002, so I think that checks out.
Same result on both power strips so I know Im grounded there also. Then I checked the drill press at the plug with it unplugged and it was showing 24v which I don't understand other than that LEDs do weird **** sometimes, and there's that regulator in the mix also so Im dismissing that as continuity seemed good all around..
Why dat?
For diagnosis sake or because power strips are da debbil? I need the power strip for several reasons and it is a quality unit.
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Diagnostics, it's best to rule out things. Nothing is good, unless proven so. I had a power strip that was weird, it was leaking to the case. That LED thing is suspect. Shouldn't do that.
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Gotcha.
I was wondering about eliminating factors or just some peoples hatred of strips.
I looked long and hard to find one that was A: high quality and #2 had the features I needed to set up the shop the way I want it.
These having switched outlets and an always on socket fit the bill. Hit the main switch and everything gets power for it to then be switched on and the always on is for the dehumidifier.
I only mentioned the LED thing as my ring light for the mill will retain power and give a brief flash if I hit the switch without having that power strip turned on. This occasionally makes me thing my light blew up, but they just store a little power somehow.
Ghost LED I think its called.
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www.unitopledstrip.com
The safety ground should carry no current, ever!
Unless something is WRONG...
when you moved the wires to where both were on same screw, you may have fixed a poor connection.
Something is leaking...
We have an antique all-metal hair drier, used for bench work.
Has wood handle, and sometimes would get a surprise.
Plug is old 2 prong, both same size and the power switch has internal leak to case.
Looking for replacement, temp repair was a 3 prong plug to force consistent connection and placed that wire on the neutral side
For your machine, you need to troubleshoot, and do it live.
You will need to use an extension cord plugged into a different outlet, hopefully distant location to help insure it may be correct.
Plug in the power strip and measure voltage from the safety ground on extension cord to all holes on the plug strip.
Should only be on the small vertical holes.
Next, place voltmeter in the small hole on the cord, this is the hot side.
Measure voltage to all holes on the plug strip.
The large vertical and safety ground should all measure 120 vac.
The small vertical should read either 0 vac if on same leg of lines, or 240 vac if on opposite side, either is fine.
Plug in your machine and move voltmeter to safety ground on the cord then measure the holes on a different outlet on the strip.
Turn on machine and repeat.
Unplug machine and disconnect the 2 wires mentioned above.
BE CAREFULL NOW!
Turn off strip and plug in cord.
Make sure nothing touching machine and it is not sitting on a rounded bench, place on wood.
Turn machine off and strip on.
With voltmeter still in the ground on the cord, measure voltage to any bare metal on the machine, should be 0 vac.
Turn strip off, machine on, strip on.
Repeat measure.
Should be 0 vac.
If not, turn off strip then unplug.
Mark and remove one wire at a time and repeat above until test shows 0 vac.
Replace each wire before next test.
Report back as needed.
Sent from my SM-G781V using Tapatalk
Unless something is WRONG...
when you moved the wires to where both were on same screw, you may have fixed a poor connection.
Something is leaking...
We have an antique all-metal hair drier, used for bench work.
Has wood handle, and sometimes would get a surprise.
Plug is old 2 prong, both same size and the power switch has internal leak to case.
Looking for replacement, temp repair was a 3 prong plug to force consistent connection and placed that wire on the neutral side
For your machine, you need to troubleshoot, and do it live.
You will need to use an extension cord plugged into a different outlet, hopefully distant location to help insure it may be correct.
Plug in the power strip and measure voltage from the safety ground on extension cord to all holes on the plug strip.
Should only be on the small vertical holes.
Next, place voltmeter in the small hole on the cord, this is the hot side.
Measure voltage to all holes on the plug strip.
The large vertical and safety ground should all measure 120 vac.
The small vertical should read either 0 vac if on same leg of lines, or 240 vac if on opposite side, either is fine.
Plug in your machine and move voltmeter to safety ground on the cord then measure the holes on a different outlet on the strip.
Turn on machine and repeat.
Unplug machine and disconnect the 2 wires mentioned above.
BE CAREFULL NOW!
Turn off strip and plug in cord.
Make sure nothing touching machine and it is not sitting on a rounded bench, place on wood.
Turn machine off and strip on.
With voltmeter still in the ground on the cord, measure voltage to any bare metal on the machine, should be 0 vac.
Turn strip off, machine on, strip on.
Repeat measure.
Should be 0 vac.
If not, turn off strip then unplug.
Mark and remove one wire at a time and repeat above until test shows 0 vac.
Replace each wire before next test.
Report back as needed.
Sent from my SM-G781V using Tapatalk
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Take an ohm meter and put one lead on the ground terminal of the plug, put the other meter lead on the chassis ground and measure resistance, it should be very low.
The only reason you got hit is that there’s current leak somewhere, the resistance going through you was less than the resistance of the ground circuit. It could be rusted or otherwise highly resistive.
When in doubt establish a common ground.
Examine visible power wiring and components. look for wires or other components that are in close proximity to castings or other potential points of contact with the frame.
The only reason you got hit is that there’s current leak somewhere, the resistance going through you was less than the resistance of the ground circuit. It could be rusted or otherwise highly resistive.
When in doubt establish a common ground.
Examine visible power wiring and components. look for wires or other components that are in close proximity to castings or other potential points of contact with the frame.
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- Jan 5, 2014
- Messages
- 1,009
Sorry for the long-winded answer here. These things are hard to describe in few words...
TLDR: Figure out ground AND leakage problem and fix both as needed.
Going on recollection, you can start to feel the tingle at about 2-3mA or so. 50mA can kill you and that is not much current. With a moderate (and likely getting worse over time) leakage cause, those two values are very close in the scheme of things. 3mA today could get to 30mA a few weeks or months from now and sneak up on you.
Is the circuit a GFCI circuit? If not, I suggest you make it one. Since there is no VFD, any GFCI trips will often be for a valid reason. These can be a nuisance sometimes but also better than being hurt or dead.
Because your machines are isolated from ground by the wooden bench, the leakage current would prefer you to the bench to get to ground. Because your grounding situation appears to have improved for some reason, the current prefers the ground wire so you no longer feel it.
Here's what I would do. (Granted I have the equipment and experience. If you don't, maybe find someone local that can help you or hire a good electrician.) Simple tests, like some mentioned above by several others can work and often do. The problems can be subtle though. You can easily measure a "good" ground with an ohmmeter when the ground bond isn't really good at all, for example. The ohm meter only uses a tiny voltage and current for the measurement and it can find the really bad connections.
You have two problems I think. Leakage because nothing was done to fix that and grounding because you don't know for sure how that got improved or if that improvement is permanent.
Grounding/Bonding:
Turn off the power at your panel breaker and inspect all the screw connections of each receptacle in the circuit leading from your equipment to the panel that feeds the circuit. Make sure all are tight. The receptacles are usually daisy-chained with several in a branch circuit. Inspect any wire-nuts or crimps within the outlet boxes and be sure they are all still tight, especially the grounds. Make sure all metal and the metal tabs of any receptacle are bonded well to ground.
Inspect the ground connections of at least this circuit within your panel to be sure they are tight.
Inspect your panel. Is there a solid connection to a ground rod? If this is a sub-panel, the ground rod may be at your service panel instead. Depends.
With the shop equipment unplugged, start wiggling and tugging on ground bond wires in the equipment. You might find one that looks fine but pulls out of a crimp connector easily. You may see some corrosion at a connector. Fix anything you find wrong. Check, eliminate or replace the power strip too.
Leakage:
You need to determine what device(s) are leaking and how much. There are methods to do this. The megger is a simple way to narrow down a problem but you can do it with a regular DMM and a procedure that requires you to take some care when doing it. Basically you interrupt the ground with an ammeter in series (or better yet use a clamp-on leakage current meter) and measure the leakage of each piece of the puzzle using the 120VAC as a current source. Start at a high range and move down. The problem with a series-connected ammeter is that you can blow the fuse in the ammeter and then it reads zero (and the equipment is no longer grounded). You always check for that. BTW, the megger I listed above is a DC one. It won't detect capacitive leakage. It is more of an insulation test.
An alternative (and better I think) way to measure leakage current is to isolate the chassis of the item you are testing from ground (dry wood bench etc.) Place a 1000 ohm resistor in series with the ground wire and power it up. Never touch the equipment you are measuring. Measure the AC voltage across the 1000 ohm resistor. I usually use a 10 Watt one because 100mA of current would be 10 Watts. Each volt you measure equals 1mA. I made a short extension cord / plastic box outfit with a resistor in the ground line for this purpose. It has a 100mA fuse in each of the power wires too. If the equipment has a dead short, say good-by to the fuse(s). In either case, unplug it right away.
If you are interested, I can sketch the setup I have used and post it.
TLDR: Figure out ground AND leakage problem and fix both as needed.
Going on recollection, you can start to feel the tingle at about 2-3mA or so. 50mA can kill you and that is not much current. With a moderate (and likely getting worse over time) leakage cause, those two values are very close in the scheme of things. 3mA today could get to 30mA a few weeks or months from now and sneak up on you.
Is the circuit a GFCI circuit? If not, I suggest you make it one. Since there is no VFD, any GFCI trips will often be for a valid reason. These can be a nuisance sometimes but also better than being hurt or dead.
Because your machines are isolated from ground by the wooden bench, the leakage current would prefer you to the bench to get to ground. Because your grounding situation appears to have improved for some reason, the current prefers the ground wire so you no longer feel it.
Here's what I would do. (Granted I have the equipment and experience. If you don't, maybe find someone local that can help you or hire a good electrician.) Simple tests, like some mentioned above by several others can work and often do. The problems can be subtle though. You can easily measure a "good" ground with an ohmmeter when the ground bond isn't really good at all, for example. The ohm meter only uses a tiny voltage and current for the measurement and it can find the really bad connections.
You have two problems I think. Leakage because nothing was done to fix that and grounding because you don't know for sure how that got improved or if that improvement is permanent.
Grounding/Bonding:
Turn off the power at your panel breaker and inspect all the screw connections of each receptacle in the circuit leading from your equipment to the panel that feeds the circuit. Make sure all are tight. The receptacles are usually daisy-chained with several in a branch circuit. Inspect any wire-nuts or crimps within the outlet boxes and be sure they are all still tight, especially the grounds. Make sure all metal and the metal tabs of any receptacle are bonded well to ground.
Inspect the ground connections of at least this circuit within your panel to be sure they are tight.
Inspect your panel. Is there a solid connection to a ground rod? If this is a sub-panel, the ground rod may be at your service panel instead. Depends.
With the shop equipment unplugged, start wiggling and tugging on ground bond wires in the equipment. You might find one that looks fine but pulls out of a crimp connector easily. You may see some corrosion at a connector. Fix anything you find wrong. Check, eliminate or replace the power strip too.
Leakage:
You need to determine what device(s) are leaking and how much. There are methods to do this. The megger is a simple way to narrow down a problem but you can do it with a regular DMM and a procedure that requires you to take some care when doing it. Basically you interrupt the ground with an ammeter in series (or better yet use a clamp-on leakage current meter) and measure the leakage of each piece of the puzzle using the 120VAC as a current source. Start at a high range and move down. The problem with a series-connected ammeter is that you can blow the fuse in the ammeter and then it reads zero (and the equipment is no longer grounded). You always check for that. BTW, the megger I listed above is a DC one. It won't detect capacitive leakage. It is more of an insulation test.
An alternative (and better I think) way to measure leakage current is to isolate the chassis of the item you are testing from ground (dry wood bench etc.) Place a 1000 ohm resistor in series with the ground wire and power it up. Never touch the equipment you are measuring. Measure the AC voltage across the 1000 ohm resistor. I usually use a 10 Watt one because 100mA of current would be 10 Watts. Each volt you measure equals 1mA. I made a short extension cord / plastic box outfit with a resistor in the ground line for this purpose. It has a 100mA fuse in each of the power wires too. If the equipment has a dead short, say good-by to the fuse(s). In either case, unplug it right away.
If you are interested, I can sketch the setup I have used and post it.
Last edited:
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