Electrical Advice

[Tom-D]

When I built my work shop 3 years ago, I hired a Electrical contractor to come wire the shop correctly, and It was inspected by the state electrical inspector and stamped off with the little sticker they placed in the main circuit breaker box.

Last Thursday I had a major failure of my brand new welder the ground lead to the welding bench became a high resistance connection, So the welder found a ground of least resistance thru my big belt sander neutral ground, which smoked the cords of the sander and the welder.

OK moving, on we repaired those with new cords, and every thing worked good again until yesterday when my drill press decided to smoke its cord, and pop a breaker for the circuit its on.

I then unplugged the drill press and reset the circuit breaker and nothing in the shop worked, nothing, all three circuits were dead. I then tripped the circuit breaker in the master breaker panel in the house that feeds the shop, and removed all the C/Bs in the shop panel.
This is what I found. The advice I need is simple, do I need a whole new panel in the shop? or can this one be repaired?

 

[jsstevens]

If it were me, I'd buy a new panel of the same model and swap the guts. That way you don't have to redo the conduit and wire. You will need all new breakers.

Having said that, what's actually going on with the electric? I've seen damage like that in one breaker with something loose and arcing (arcs make heat without necessarily drawing enough current to overload the breaker) but never a whole panel. And the breaker protecting the shop panel should have kicked long before there was that much damage from over current.

 

[Art Rose]

Where does the power for that panel come from? Is it sized to handle the additional current load of that new panel? How far did you pull the wire to reach the new panel? What supply voltage did you have before your overcurrent meltdown? Were all of the wire terminations correct and tight? Were the wires for your new welder terminated correctly? Are the breakers in that panel properly sized for the load you subjected them to? Were the breakers properly seated in the panel? Was there corrosion in the panel? Did the panel somehow get wet? Did you find evidence of fire ants, rodents, or reptiles inside the panel?

 

[Tom-D]

Where does the power for that panel come from? Is it sized to handle the additional current load of that new panel? How far did you pull the wire to reach the new panel? What supply voltage did you have before your overcurrent meltdown? Were all of the wire terminations correct and tight? Were the wires for your new welder terminated correctly? Are the breakers in that panel properly sized for the load you subjected them to? Were the breakers properly seated in the panel? Was there corrosion in the panel? Did the panel somehow get wet? Did you find evidence of fire ants, rodents, or reptiles inside the panel?

The power comes from a 50 AMP breaker in the house master breaker panel.
It is 3 # 6 solid copper wires run 122' total to a 50 AMP breaker in this box.
The rest of your questions are best answered by the state inspector's sign off, it all met code when installed.
The only connection that fried, was a breaker and we can't tighten those.
My max load in the shop is 25 amps, I can not run all my equipment at one time, I'm just one person. Plus the total amp drawn by all the machines I have in the shop would be under 50 AMPS.

I had to prove that for the state, or they would require a separate meter, and separate master box for the shop.

and no, about the critters, water and rot, did you look at the pictures. the panel is only 3 years old. on a brand new building.

 

[Tom-D]

If it were me, I'd buy a new panel of the same model and swap the guts. That way you don't have to redo the conduit and wire. You will need all new breakers.

Having said that, what's actually going on with the electric? I've seen damage like that in one breaker with something loose and arcing (arcs make heat without necessarily drawing enough current to overload the breaker) but never a whole panel. And the breaker protecting the shop panel should have kicked long before there was that much damage from over current.

If it were me, I'd buy a new panel of the same model and swap the guts. That way you don't have to redo the conduit and wire. You will need all new breakers

That was my question could the guts be changed, after reading your post I checked, and yes they can be, they are held in by two screws. So that's what will happen.

Having said that, what's actually going on with the electric? I've seen damage like that in one breaker with something loose and arcing (arcs make heat without necessarily drawing enough current to overload the breaker) but never a whole panel. And the breaker protecting the shop panel should have kicked long before there was that much damage from over current.

I don't understand it either, I don't know why the 50 AMP breaker didn't trip, but it wasn't tripped when I pulled it this morning, and can't be tripped by hand now.
I am back feeding this breaker, I don't know if that makes any difference or not.
Anyway, we're off to get a new box, to see IF we can get the lights back on by dark.

 

[ebetancourt]

I would spend some time inspecting the ground, all the way to the ground. No pun intended. I would also get one of those gadgets with the lights that verifies that neutral, ground and hot are all properly placed. I have seen a major renovation of a commercial building with lot's of electrical equipment pass inspection. Then the "ground" was discovered to not have been actually connected to the ground!

 

[JOhnH]

I had an old FPE box that did that while also burning up my air conditioner. But I don't think there are very many of them around any more, especially none that have been installed with the past 3 years.

That problem put FPE out of business. I hope this isn't a rerun of that fiasco.

 

[Art Rose]

After you've installed the new panel, make sure you check panel line voltage to neutral, and to ground, for each hot leg. Then check voltage across your hot legs. Make sure that line voltage is balanced and within 10% of your equipment label voltage. Make sure all connections are mechanically sound and not corroded. (including your bonding and grounding connections) (Assuming it's a 230volt single phase welder?) Turn on your equipment, weld a bead while you check amp draw for each hot leg. Lacking answers for several of those questions previously asked, it's difficult to accurately shoot from the hip. Good luck. By the way.......Electrical inspections are like Annual inspections. Trust....but Verify.

 

[Tom-D]

After you've installed the new panel, make sure you check panel line voltage to neutral, and to ground, for each hot leg. Then check voltage across your hot legs. Make sure that line voltage is balanced and within 10% of your equipment label voltage. Make sure all connections are mechanically sound and not corroded. (including your bonding and grounding connections) (Assuming it's a 230volt single phase welder?) Turn on your equipment, weld a bead while you check amp draw for each hot leg. Lacking answers for several of those questions previously asked, it's difficult to accurately shoot from the hip. Good luck. By the way.......Electrical inspections are like Annual inspections. Trust....but Verify.

I have cured the welders ground problem, by sanding a clean spot on the corner of the welding bench and drilling a hole and thread it to take a bolt. the (-) lead is now bolted to the bench. no more clamp.
Every thing is back together, with new internal C/B holder, (that thingy that the CBs snap into) and all new C/Bs. Line voltage is about 119 volts, as it was to start 3 years ago.
I did buy a new box the get the parts I needed.
There were two other C/B that looked burned, they are in the trash.

 

[Tom-D]

Going back together I found that my 8 foot florescent light balast was bad, it tripped the C/B when I turned on the lights, (it's now in the trash) replaced with 2, 2500 lumen LED lights.
All circuits are good to go, working as they should.

 

[Let'sgoflying!]

Am I understanding there has not yet been a smoking gun found? Or is the original problem solved (the ground from the welder)?

 

[Tom-D]

Am I understanding there has not yet been a smoking gun found? Or is the original problem solved (the ground from the welder)?

Pretty much.. still wondering what the cause was.
The welder never popped a breaker, it just smoked the neutral ground wires ruining the sander and welder cords. The drill press was a simple wire short, popped a 15 amp breaker. China made crossed a ground with a hot, then bolted a guard over it, finally shorted out.
The Florissant ballast was on a 15 amp breaker, never popped it until today.

 

[Let'sgoflying!]

Pretty much.. still wondering what the cause was.

jeez, hate to rewire everything only to have it happen again

 

[JOhnH]

I have cured the welders ground problem, by sanding a clean spot on the corner of the welding bench and drilling a hole and thread it to take a bolt. the (-) lead is now bolted to the bench. no more clamp.

This may be a stupid question since I am neither a welder or an electrician, but what is the bench grounded to?

 

[Art Rose]

Absolute total shot from hip..... Something caused arcing there at the breaker clip connection. Might have been corrosion, not seated properly, faulty breaker, or any number of other causes. At any rate, there was very high resistance to current flow at that point. As you have learned, a 50 amp breaker is pretty stout, and it takes quite a bit of current flow before it will trip. Circuit protection needs to be properly sized for your equipment. Is this possibly a typical overkill installation? (fire hazard) Who knows? Did you check actual operating amps yet?

 

[jsstevens]

Absolute total shot from hip..... Something caused arcing there at the breaker clip connection. Might have been corrosion, not seated properly, faulty breaker, or any number of other causes. At any rate, there was very high resistance to current flow at that point. As you have learned, a 50 amp breaker is pretty stout, and it takes quite a bit of current flow before it will trip. Circuit protection needs to be properly sized for your equipment. Is this possibly a typical overkill installation? (fire hazard) Who knows? Did you check actual operating amps yet?

If it was arcing, it probably never came close to exceeding the 50Amps. Arcs make heat and when I was doing electrical work, I replaced multiple, reputable (not FPE or Zinsco) breakers that had melted because of a loose wire. I think you're correct that the breaker was arcing to the bus (based on the pictures). As the carbon builds up it gets worse and worse. It's a good idea to run the back of your hand down the front of the panel occasionally and feel for heat. If you can feel it, somethings not right. Check it out.

And an inspector is highly unlikely to find a loose wire, so it can easily pass inspection and still have a problem.

John

 

[Art Rose]

This reminds me a little of the day I was walking thru a penthouse chiller plant on the way to look at a cooling tower issue. As I was walking past the chiller starter panel, something didn't feel right. I thought I felt heat on the side of my face, weird. Stopped, turned back to the panel, and started to place my hand on the panel to figure out what was so hot. Glad I didn't actually touch the panel, it would have burned my hand. We immediately opened the panel and found two wire lugs that were literally glowing yellow hot, ready to blow. Killed the power immediately. Why the glow? Simple, poor maintenance.

As a current flows through a conductor, there's a certain amount of thermal induced expansion and contraction, or other, in the conductor, and a part of a chillers annual inspection requires that all electrical connections be checked for proper torque. The higher the voltage, the higher potential current flow, and any form of resistance to flow will tend to create lots of heat as those electrons are forced thru the resistance. In this case it wasn't going to be a simple meltdown like in this little single phase breaker panel that we've been talking about. This chiller starter was an explosion ready to go off. All because some dipweed didn't do their job.

 

[Let'sgoflying!]

two wire lugs that were literally glowing yellow hot

Do such lugs need to be replaced after an event that alters their metallurgy?

 

[Tom-D]

jeez, hate to rewire everything only to have it happen again

me too

 

[Checkout_my_Six]

so....what would cause the back feeding (smoking) to the external circuits (devices)....drill press, belt sander, lights, and other items? I'm thinking the only item in "common" is the Main white common lead. If that were bad or faulty to the Main panel, from the house....current would seek another path to ground thru those devices.

Go to your main panel in the house and make sure....1. the white wire is the correct size to handle 240V 50 amps and length. 2. the lug is tight and has lube on the conductor. 3. and make sure the leads are not damaged .....4. remote, but, possible damage to the white conductors between your house and shop. This would prevent full rated current flow from the main source.

 

[Tom-D]

This may be a stupid question since I am neither a welder or an electrician, but what is the bench grounded to?

Nothing, It is part of the welder's + and - circuit. My 6X48 belt sander sets on it too, so when the welder lost its welding ground it found a ground thru the frame ground of the sander. Just remember all circuits on any shop have this common ground. that is what the bare copper wire is.

 

[Tom-D]

so....what would cause the back feeding (smoking) to the external circuits (devices)....drill press, lights, and other items? I'm thinking the only item in "common" is the Main white common lead. If that were bad or faulty to the Main panel, from the house....current would seek another path to ground thru those devices.

Go to your main panel in the house and make sure....1. the white wire is the correct size to handle 240V 50 amps and length. 2. the lug is tight and has lube on the conductor. 3. and make sure the leads are not damaged .....4. remote, but, possible damage to the white conductors between your house and shop. This would prevent full rated current flow from the main source.

I don't believe the drill press was the cause of the main breaker failure. the drill press simply had a short circuit, due to the black and green wire being crushed together, and popped the breaker as it should have.
All wire connections have been checked and are tight, none were loose.
The wire size for the run from the house master panel to the shop sub panel requires a #8, for 50 AMPS, we ran a #6. voltage loss is nil.

 

[Checkout_my_Six]

any device that has that third prong....ground wire....does not flow current thru that conductor. The ground wire, third prong, is there as an alternate path, to provide a "safety" path to earth ground so that the operator does not become that path. The ground should never flow current....unless there is a short inside the device.

All return current will flow in the return path thru the common lead (white wire)....

Now....I wonder what kind of ground clamp the welder has? Was it making good contact to the welding table? If not, the welding circuit could be returning (arcing) thru those nearest internally grounded devices.

 

[Tom-D]

any device that has that third prong....ground wire....does not flow current thru that conductor. The ground wire, third prong, is there as an alternate path, to provide a "safety" path to earth ground so that the operator does not become that path. The ground should never flow current....unless there is a short inside the device.

All return current will flow in the return path thru the common lead (white wire)....

Now....I wonder what kind of ground clamp the welder has? Was it making good contact to the welding table? If not, the welding circuit could be returning (arcing) thru those nearest internally grounded devices.

I depended upon the new welder's ground clamp to make a good path for the welding, it didn't. (That smoked the sander cord). That has been re-wired with new 3 wire cord and a new 3 wire plug. the welder negative lead is now bolted to the welding bench.

When the sander cord was destroyed, only the Green wire over heated, the white and black were not involved.
The sander has been totally rewired, and was working as it should when the master breaker smoked. It was not running when the drill press decided to short out.

 

[jsstevens]

so....what would cause the back feeding (smoking) to the external circuits (devices)....drill press, belt sander, lights, and other items? I'm thinking the only item in "common" is the Main white common lead. If that were bad or faulty to the Main panel, from the house....current would seek another path to ground thru those devices.

Go to your main panel in the house and make sure....1. the white wire is the correct size to handle 240V 50 amps and length. 2. the lug is tight and has lube on the conductor. 3. and make sure the leads are not damaged .....4. remote, but, possible damage to the white conductors between your house and shop. This would prevent full rated current flow from the main source.

Just a note, if the wire is not aluminum (I'm pretty sure Tom said copper) no lube required. If it's aluminum, it need de-ox compound on it. And do make sure the lugs are all tight. But that's not what burned up his breaker. That was arcing at the bus bar where the breaker plugs onto it.

John

 

[cowman]

I'd open up every one of the outlet boxes and look. It's very common for wires to come from together after being hooked up when the cover/outlet/wires get smooshed into the box.

 

[Checkout_my_Six]

Just a note, if the wire is not aluminum (I'm pretty sure Tom said copper) no lube required. If it's aluminum, it need de-ox compound on it. And do make sure the lugs are all tight. But that's not what burned up his breaker. That was arcing at the bus bar where the breaker plugs onto it.

John

more I think about this....I'm going with a bad welder ground clamp connection....where the welder found an alternate path to ground thru the nearest grounded devices.

 

[Art Rose]

"two wire lugs that were literally glowing yellow hot"
"Do such lugs need to be replaced after an event that alters their metallurgy?"

Yes, when they get that hot, definitely replace the lugs. Also perform a full inspection of the wiring and starter panel. Anything even suspect should be replaced. Sounds simple, but depending on the facility, screwing up can result in tens of thousands of dollars worth of equipment damage, not to mention the potential loss from out of service equipment.

 

[redtail]

Absolute total shot from hip..... Something caused arcing there at the breaker clip connection. Might have been corrosion, not seated properly, faulty breaker, or any number of other causes. At any rate, there was very high resistance to current flow at that point. As you have learned, a 50 amp breaker is pretty stout, and it takes quite a bit of current flow before it will trip. Circuit protection needs to be properly sized for your equipment. Is this possibly a typical overkill installation? (fire hazard) Who knows? Did you check actual operating amps yet?

If it was arcing, it probably never came close to exceeding the 50Amps. Arcs make heat and when I was doing electrical work, I replaced multiple, reputable (not FPE or Zinsco) breakers that had melted because of a loose wire. I think you're correct that the breaker was arcing to the bus (based on the pictures). As the carbon builds up it gets worse and worse. It's a good idea to run the back of your hand down the front of the panel occasionally and feel for heat. If you can feel it, somethings not right. Check it out.

And an inspector is highly unlikely to find a loose wire, so it can easily pass inspection and still have a problem.

John

I concur. As soon as I saw the pictures that was my conclusion as well. Arcing due to loose connections/contact at the bus. Could have been bad breakers. I've seen this happen on a few occasions myself.

 

[redtail]

I have cured the welders ground problem, by sanding a clean spot on the corner of the welding bench and drilling a hole and thread it to take a bolt. the (-) lead is now bolted to the bench. no more clamp.
Every thing is back together, with new internal C/B holder, (that thingy that the CBs snap into) and all new C/Bs. Line voltage is about 119 volts, as it was to start 3 years ago.
I did buy a new box the get the parts I needed.
There were two other C/B that looked burned, they are in the trash.

You might want to inspect the new panel periodically to make sure it's not happening again. Just a visual inspection with the cover removed, not taking everything apart. Use your nose as well. If it's arcing, you will probably smell it.

 

[Tom-D]

Could a brown out cause this?
I ask because today I find that the shop have been having electrical problems too, all about the same time.
I know the cause of the welder failure.
I know why the drill press failed, but I don't know why the Main breaker arced like it did.

 

[J4000]

I've had the back-plane on a 3 phase panel do this same thing -- a breaker which failed to seat properly just sat there making more heat, more resistance, etc. until a catastrophic meltdown occurred, just like these pictures. The root cause was the loose breaker; nothing more. I now try to periodically run around with one of those Harbor Freight thermal readout guns and aim it at my panels when they're heavily loaded, looking for hotspots. This action has cause me to tighten some lugs on occasion.

 

[Tom-D]

I've had the back-plane on a 3 phase panel do this same thing -- a breaker which failed to seat properly just sat there making more heat, more resistance, etc. until a catastrophic meltdown occurred, just like these pictures. The root cause was the loose breaker; nothing more. I now try to periodically run around with one of those Harbor Freight thermal readout guns and aim it at my panels when they're heavily loaded, looking for hotspots. This action has cause me to tighten some lugs on occasion.

Good suggestion, I have a IR thermometer

 

[redtail]

Could a brown out cause this?
I ask because today I find that the shop have been having electrical problems too, all about the same time.
I know the cause of the welder failure.
I know why the drill press failed, but I don't know why the Main breaker arced like it did.

Not likely. A momentary drop in voltage shouldn't cause that kind of damage, nor a momentary spike. That looks like long term arcing/heat. It's one of the reasons we have routing inspection work orders for our 480v 3-phase motor controls and ACBs (air circuit breakers), which includes tightening wire terminals and lugs.

 

[Tom-D]

Not likely.

Oh Well, back to watching temps.

 

[redtail]

On the other hand, brownouts (low voltage) can wreak havoc on induction motors due to higher current flow through their windings, causing them to overheat and burn up. Here at the tunnel, we have a total of (84) 480V 3-phase motors driving our ventilation fans. Our incoming high tension is stepped down from 13.2KV to 480/277. 480 for the motors and 277 for tunnel lighting. Six high tension feeders (3 from two different power suppliers for redundancy). A series of protective relays will actually trip the 13KV ACBs during a significant under-voltage condition, killing the 480 to the motors on that particular bus. So we're not only protected against over-current, but also under-voltage.

 

[jsstevens]

Could a brown out cause this?
I ask because today I find that the shop have been having electrical problems too, all about the same time.
I know the cause of the welder failure.
I know why the drill press failed, but I don't know why the Main breaker arced like it did.

I don’t see how. A brown out can cause a motor to draw excessive current and might kick the breaker or burn the motor up but the damage in your pictures was from way too much heat.

 

[wilkersk]

The cheap aisle at Home Depot has all kind of switches and breakers I wouldn't put in my house. The house I sold last year originally had HD cheap service panel with breakers that literally rattled inside the panel. The conduit that brought electrical service to the mains from the street wasn't properly aligned with the bottom of the panel, and just about every outlet and switch in the house were so cheap that they outright failed, or developed intermediate "no work" positions that you could actually see arcing from in a dark house. I replace all that crap. It had supposedly passed inspection too.