Sub-panel breakers keep tripping

[Kid B]

A few months ago, with the help of my neighbor, I ran a 60a sub panel out to the garage. In the sub panel, there are three 50a 240v outlets (never to be used at the same time), and four 20a 120v outlets for LED lights and power tools.

Today, I opened a drawer of a metal tool box and it bumped the drill press table (drill press was plugged into 220v outlet) and it arced and tripped a breaker. However, the drill press stayed on. The breaker it tripped was for outlets in another part of the shop. The toolbox had no electrical components on or near it. Rubber casters too.

Another time, while using my metal cutting bandsaw (110v) to cut a long piece of stock, the workpiece touched my welding table, which had a welding positioner on top and plugged into another outlet. Another arc and breaker trip.

Finally, a few days ago while TIG welding on a low amperage inverter machine plugged into 220v, the breaker kept tripping. The welder stayed on and continued working, the breakers that tripped were the dedicated light circuits.

Any ideas what the heck is going on?

 

[mm08822]

Pull cover off sub and clear take pic.

Edit your post explaining exactly which cb tripped and when. Too vague.

Even Pic of main panel open could help.

Measure sub panel voltages: l1-l2, l1-n, l2-n, l1-grd, l2- grd, n - grd ?

 

[chinboys]

Make sure the new sub panel's neutral and ground bus bars Are Not Bonded to each other. As well as each circuits neutral and ground are tied to their own respective bus bars
The NEC code requires this for safety dedicated grounding to new grounding rods and not to the extended neutral.
Current flows on both legs of the 240v circuits when in use. The ground on this circuit is the path the current will take should a potential short occur and it through you or another less resistive conductor.
On the 120v circuit, the hot and neutral are used for AC current flow. The ground is again used for a more safe current flow should a short occur.
On the main panel, both the ground and neutral are bonded and this path is tied to earth or ground. But on subpanels, this must not happen and requires a new ground to be referenced for both 240 and 120 v.

 

[MovingAlong]

A few months ago, with the help of my neighbor, I ran a 60a sub panel out to the garage. In the sub panel, there are three 50a 240v outlets (never to be used at the same time), and four 20a 120v outlets for LED lights and power tools.
...
Any ideas what the heck is going on?

Not without seeing the wiring in complete detail: the connection at the main panel, the sub-panel input feed, the breakers and the 240v outlets. And as mentioned, heavy focus on the grounds & neutrals. Meanwhile, I'd shutdown the sub-panel before resetting another breaker... it's not done correctly.

Would also be curious about the sub-panel itself and how it is supporting 3 x 50a circuits in a 60a panel. Wondering about how the 120v outlets are balanced too. Ensure you're not overloaded on one leg..

 

[American Locomotive]

It sounds to me like you have two problems at once:
1) The panel is not connected to a working ground feed coming from your home
2) You have a 120v circuit that's is shorted to metal somewhere in your shop (be it inside a box, or a piece of equipment).

So most likely everything in your shop that has a ground connection is actually floating at around 120v. I'd start by getting a multimeter and checking the voltage between the ground pin of an outlet in your garage and the neutral connection of an outlet. It should be near 0 volts. I'd then check the voltage between the ground pin and the concrete floor of the garage - it should also be about zero volts.

 

[MovingAlong]

... I'd then check the voltage between the ground pin and the concrete floor of the garage - it should also be about zero volts.

Shoot, I'd forgotten about an odd one I chased down decades ago - was getting a shock cleaning out a goldfish pond next to a house using a metal poled pool skimmer. Drove a large screwdriver into the ground about 4-5' away from the pond, put one lead on the screwdriver and one lead in the pond. Yep, AC voltage!

Turned out to be a disconnected ground on a water heater inside the house...

 

[wyliesdiesels]

wow post a bunch of pics of the subpanel, main panel (with covers removed), receptacle wiring, etc

 

[Lassen Forge]

We just chased one like this down before we wired my shed-shop. We were having really strange breakers throw - like the kitchen and the heater, or the bathroom lights and the outlets in one room. Turns out someone had been futzing with the room lights in my wife's office (the old living toom) and they had the wiring screwey, and it was backfeeding supply voltage into a floating ground... but only when certain light switches were on, in a certain order. Fun times. Had to hire someone to start chasing and slinging wires around (here, EVERYTHING runs in flexible conduit, into common junction boxes, and, wel, yeah, loads of fun when you have 4 stories of house....)...
Thats when I figured I best learn something about EU wiring... at least it's not those "loop stsyems" they have in the UK, where your fuses are in the plugs of the appliance.

 

[Norcal]

We just chased one like this down before we wired my shed-shop. We were having really strange breakers throw - like the kitchen and the heater, or the bathroom lights and the outlets in one room. Turns out someone had been futzing with the room lights in my wife's office (the old living toom) and they had the wiring screwey, and it was backfeeding supply voltage into a floating ground... but only when certain light switches were on, in a certain order. Fun times. Had to hire someone to start chasing and slinging wires around (here, EVERYTHING runs in flexible conduit, into common junction boxes, and, wel, yeah, loads of fun when you have 4 stories of house....)...
Thats when I figured I best learn something about EU wiring... at least it's not those "loop stsyems" they have in the UK, where your fuses are in the plugs of the appliance.

What they have in the UK is a 32A ring circuit, which is why the plugs are fused, like the formerly allowed NEC allowed practice of allowing the frames of certain appliances to be grounded to the neutral, are just archaic.

 

[Lassen Forge]

What they have in the UK is a 32A ring circuit, which is why the plugs are fused, like the formerly allowed NEC allowed practice of allowing the frames of certain appliances to be grounded to the neutral, are just archaic.

Thanks! I have looked at diagrams of these and while I can logic out MOST electrics, ring circuits (I forgot what they were called) throw me for a loss!

 

[dogdog]

maybe some sort of electromachicken exorcist needed ?

I wonder if electricians still use Megohmmeter or Megger now a days to trace for potential shorts. or you just have a bad breaker.