Electrical problem with stage pin/adapter

dpak

Active Member
High school drama teacher here. A student plugged in a fixture (S4 Jr) with stage pins into an adapter cord with an Edison plug to test the light before bringing it up to the catwalk. There was a spark, she said she felt a shock, and there was a puff of smoke. Below are pictures of the pin and the adapter. I've checked the wiring on each and everything seems to be correct (though there could be a problem with the wiring under the sheath). The student is also claiming that inhaling the smoke may have made her sick, even though flu is spreading around the school. Any thoughts on what may have happened?

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SteveB

Well-Known Member
You've got 2 connectors and plugs here. The male looks like some arc flash when it was plugged in, the female as well, though we cannot tell if the flash was caused by the female hot terminal being located in the wrong slot inside the connector. The female is as BTW, incorrectly wired. There should not be that much bare copper showing off the insulation, as well the copper is supposed to fit into a silver aluminum crimp connector (not seeing those, bad photo angle), that goes under the screw terminal and held in place by the brass screw.
 

RonHebbard

Well-Known Member
Premium Member
High school drama teacher here. A student plugged in a fixture (S4 Jr) with stage pins into an adapter cord with an Edison plug to test the light before bringing it up to the catwalk. There was a spark, she said she felt a shock, and there was a puff of smoke. Below are pictures of the pin and the adapter. I've checked the wiring on each and everything seems to be correct (though there could be a problem with the wiring under the sheath). The student is also claiming that inhaling the smoke may have made her sick, even though flu is spreading around the school. Any thoughts on what may have happened?

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High school drama teacher here. A student plugged in a fixture (S4 Jr) with stage pins into an adapter cord with an Edison plug to test the light before bringing it up to the catwalk. There was a spark, she said she felt a shock, and there was a puff of smoke. Below are pictures of the pin and the adapter. I've checked the wiring on each and everything seems to be correct (though there could be a problem with the wiring under the sheath). The student is also claiming that inhaling the smoke may have made her sick, even though flu is spreading around the school. Any thoughts on what may have happened?

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@dpak Thoughts in random order.
Ground is not always in the middle, only on 20 & 30 Amp 2P&G's, it's one of the outer contacts on 60's & 100's..
Are your contacts designed for crimped installation?
Toodleoo!
Ron Hebbard
 

Colin

Well-Known Member
I theorize the student was plugging into a hot stage pin connector, judging by where the arc damage is, and maybe doing so with all the crooked, straining, wiggling, slipping, huffing and puffing that high schoolers often bring to that task, and that commonly enough results in an arc that could nip whatever flesh is adjacent (because the straining and huffing and puffing) at the time.

So I’d replace the damaged pins and re-wire that connector like Steve said, with correct strip length and ferrules. The fuzzy stuff n1ist notes just looks like standard issue ETC stuff to me, which can get a little hairy looking. It’d be pretty unusual to find asbestos inside a fiberglass jacket on a S4jr, but I suppose one never knows…

And I’d do a mandatory, non-blamey (re)training for everyone doing this work, to include how best to mate every type of connector in your facility (including hand position and what motions work best), what a correct and incorrect connection looks like, how to get help if they need it so they don’t abandon a poor connection that might for instance have a gap big enough for an arc to jump out or a safety cable to get in, and also how to do that particular task of a lamp check without that hazard arising. Buy a stage pin lamp checker, or any continuity tester. When you do really need to energize one like for a bench focus, plug into a switched outlet or power strip so nothing’s energized until connections are made, or at least mate the stage pins first and then plug the Edison into power; I think that’s considerably less risky, especially in student hands.

Sounds like the student is okay but appropriately spooked. Help her feel okay about it by working with her nonjudgementally to figure out exactly what causes may have been, and use this to teach some safety to everyone.
 
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JonCarter

Well-Known Member
Plugging anything "hot" is never a good idea--turn circuits off before making connections. Plugging anything "hot" will result in some amount of arcing when the pins mate. The larger the load on the circuit, the more the arcing. Also, mating the plug and connector s-l-o-w-l-y and not POSITIVELY and QUICKLY will generate more arcing, and if the operator wiggles the connectors the least little bit while trying to get them together, the more the arcinc. (Wanna make your own arc light? Hot-plug in a 2K instrumet slowly and then hold one of the pins 1/16" apart after you make the first contact. Guaranteed to need a new connector.)
 

TimMc

Well-Known Member
Premium Member
With apologies to Prince, "this is what it sounds like, when sparks fly". :cool:

Little story, optional-

One of the things we do in our shop is an annual "tighten all the screws and test" electrical inspection of everything we can find in the shop or in pre-packs on trucks. Lots of Edisons, L14-30 and L21-30, motor control pickles, even distros get this love.

A situation not dissimilar to @dpak 's led us to find a mis-wired connector on one of our cables, that, when mated with a venue's mis-wired receptacle, produced a 'near-soiling event.' :oops:

Our cable had either passed, or did not attend, the inspection over the course of several consecutive years. How that happened is the puzzlement, and there is the possibility of a field repair done incorrectly. Either way it was embarrassing and potentially dangerous. It also helped me understand the required testing and *tracking* of electrical assemblies used in production by other countries and/or jurisdictions.
 

Van

CBMod
CB Mods
Premium Member
The "Shock" may very well simply have been the nervous reaction to the arc flash. While it IS possible to shock oneself when plugging in a stage pin connector, or an Edison or L5/20 it is very difficult to do. I truly detest the English BS1363 plug it was specifically designed to make it impossible to shock oneself when plugging or unplugging. The problem is, it is stupid looking and bulky.
As far as the "feeling sick" from the Magic Blue Smoke, <which is what makes electricity work, you know>, it is Acrid but not terribly toxic in the amount you would inhale from a short arc flash. Given the little amount of carbon scoring I'd say this little feller has seen some action.... Wait, I went to a galaxy far, far, away. Given the little amount of carbon and melty bits I'd have to say this was a teeny tiny flash which was much more scary than dangerous. The Feeling sick probably came from the Adrenaline rush and the icky smelling smoke.
I will agree with everyone else on that first plug there should not be any exposed copper when the plug is properly wired. the "crimp connector" everyone is talking about is called a Ferrule. you can order them from almost any electrical distributor and they should be a dime a dozen. <Figuratively> They often get lost, not installed, or forgotten. They keep the screw from cutting the copper when someone gets overly aggressive with a screwdriver, but even they can't resist the power of a Makita. I once got an entire order of Fresnels from a company whose name rhymes with Colortran, in which well over half the wire inside the GSP's were cut even though they had ferrules. It added almost a day on my install.
 

almorton

Well-Known Member
BS1363 and BS546 have their drawbacks, but they do have the advantage that the cable doesn't stick out when the plug is mated, it lies flat against the surface. The drawback is that the pins tend to stick up and there are few things more annoying than stepping on a three pin plug barefoot at night. I guess it's what you're used to; I know plenty of people who think of Edison plugs as toy connectors.

A 125A 415V 3 phase Ceeform is a bit of a bulky connector, but of course there are always bigger contenders ;-)
 
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almorton

Well-Known Member
Good luck. The British (not English) "3-pin square" BS1363 plug was around just after WWII but there are still BS546 "3-pin round" (mainly 15A but still some 5A, too) widely in use in theatres all around the UK.
 

Van

CBMod
CB Mods
Premium Member
Edison plugs are terrible. They're just what we have until someone is willing to change a more than nationwide standard.
we'll change right after we go Metric....
 

DELO72

Well-Known Member
I thoroughly agree with anyone who said the insulation needs to be going right up to the entrance of the pin. The exposed wire on each of the leads should be safely inside of each Pin, with only the silicone and braded wire insulation showing outside of it. All those bare, frayed wires lead to an electrical hazard risk. The likely problem is that the plugs were not fully connected when the power was applied, causing the electricity to arc across the two pins (male/female) instead of flow smoothly between them. the smoke was a result of the carbon scoring/charring. It's not going to make the student sick. Never plug in a fixture to a live circuit if you can help it. Make sure it is first fully plugged in securely and then switch on the power. Also any dust or dirt residue that is in the connectors or on the pins could also cause the electrical resistance and arcing as well. You are always better off going with the Marinco or Leviton Bates stage pin connectors with the clear covers (IMHO), so you can see the wire situation inside and make sure they are wired correctly and securely.
 
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dpak

Active Member
Thank you for all the responses! I had thought the ferrules were just for convivence - I will be buying a set and putting them on all stage pins, along with trimming the wires down. I'll also review with the students how to plug in. As for plugging in live, is there any alternative? We do that when using the lights in the room and to test the lights before bringing them up to the catwalk. Is it possible to put a switch on the adapter? Possible, that is for someone who has little experience?
 

techieman33

Well-Known Member
Thank you for all the responses! I had thought the ferrules were just for convivence - I will be buying a set and putting them on all stage pins, along with trimming the wires down. I'll also review with the students how to plug in. As for plugging in live, is there any alternative? We do that when using the lights in the room and to test the lights before bringing them up to the catwalk. Is it possible to put a switch on the adapter? Possible, that is for someone who has little experience?

To test the lights just use something like this. It'll check that there is continuity which would indicate that the lamp is still good. It sounds like you might also be using them in the classroom sometimes? For that I would probably get a little shoebox dimmer and cheap dj console.
 

tjrobb

Well-Known Member
Good luck. The British (not English) "3-pin square" BS1363 plug was around just after WWII but there are still BS546 "3-pin round" (mainly 15A but still some 5A, too) widely in use in theatres all around the UK.
I stayed in a hotel with the 546 everywhere. Fortunately they had an adapter for my CPAP, which I'd already switched to 1363 (as I'm from Edison land).
 

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