Conventional Fixtures HELP! Source 4 sparks at yoke

The extension cord trouble is not caused by a short, but a poor connection somewhere at that point: either the extension cord's connection to the socket where it's molded in, or the spotlight's plug connection to its cord, or the interface between the two (dirt, looseness in the socket so it doesn't grip the prongs of the plug well, etc.) The poor connection leads to higher resistance or arcing, both of which dissipate power and that creates heat that melts stuff.

A hot shorted to a neutral would cause the breaker to trip (very nearly) instantly. If it doesn't, the breaker is dangerously bad and needs to be replaced. Standard household circuit breakers are "thermal-magnetic" circuit breakers and have two mechanisms by which they trip when there's too much current: first, the thermal part, which responds relatively slowly to small overcurrent situations, and is basically a bimetallic strip similar to that in a thermostat or thermometer that the electric current passes through. More current passing through it means it heats up more and bends more, and eventually it bends enough to trip the breaker mechanism and shut off the power. This allows a modest overcurrent for a short period of time without a nuisance trip, such as might be expected from a motor starting up. The other trip mechanism is the magnetic trip, which responds instantly at a higher current and consists of a little electromagnet triggering the trip mechanism. More current through the electromagnet means a stronger magnetic field, and at some point it's enough and the current gets shut off.

Theatrical dimmers often have on their outputs just magnetic breakers, which don't suffer from different response characteristics as they get warm. The little breakers on power strips are often thermal only (and often are of slightly dubious reliability, though that's not as much of a worry since the circuit the power strip is plugged into is presumably protected properly by a proper breaker or fuse).

Please make sure the system does not get used at all until thoroughly inspected and repaired as needed by a qualified electrician. I hope it's not the case, but I would not be surprised if there are further issues that need to be addressed, hopefully just simple things like snugging up connections that have worked loose over the years. Your life, your cast and crew's lives, and possibly your audience's lives in case a fire should start are worth any inconvenience it might cause.
 
DrewE said:
Please make sure the system does not get used at all until thoroughly inspected and repaired as needed by a qualified electrician. I hope it's not the case, but I would not be surprised if there are further issues that need to be addressed, hopefully just simple things like snugging up connections that have worked loose over the years. Your life, your cast and crew's lives, and possibly your audience's lives in case a fire should start are worth any inconvenience it might cause.
Click to expand...


yes, that's the plan.
 
You don't actually say that this is a school, but if it is, it needs to call in its electrician ASAP.

Otherwise, whomever is responsibility for the facility does.

It's not just a question of whether there's danger; it's a question of whether *you knew about it and didn't yell for help*; if it kills someone...
 
Jay Ashworth said:
You don't actually say that this is a school, but if it is, it needs to call in its electrician ASAP.

Otherwise, whomever is responsibility for the facility does.

It's not just a question of whether there's danger; it's a question of whether *you knew about it and didn't yell for help*; if it kills someone...
Click to expand...
Yep, we’re not touching it until the electrician clears it. It is a school.
 
so glad you are still alive. IMHO, the entire theater needs to be red-tagged (no one in there, not even work lights) til this is diagnosed and solved. You have some bad voltages running around where they do not belong. The melting thing ... eithe something is over-fused, or (worse) you have 220 or 240 backflowing into a 110v circuit. I discovered one of those the hard way in my HS years (1970s) ... rolled a trusty Allied Electronics tube mixer-amp in for an event, plugged it into the same outlet as always, and was treated to the nasty smell of burning transformer windings. Cause - in this ancient part of the school, some genius had installed a fuse (this was before breakers, sonny) in the NEUTRAL line. When something blew the fuse, there was 220 across the 110 outlet. Could have been fatal.

That's only 1 of many "by the grace of God" moments. If you aren't comfortable telling your head of school that a lighting / safety professional said "shut that room down til its competently diagnosed and repaired", I am happy to make a call. This is not stuff to mess around with. We are not in the physics lab, and lives are at stake.

Ben

PS - come over for a chat sometime when you're not at 150% with school ... I'm in Rockridge area of Oakland
 
Yes ... way too much going wrong here. If it's a problem caused upstream of the grid system, outlets, switch plates, stuff you expect to be at safe ground potential ... could provide a nasty surprise. It's no fun to be the boy who cried wolf. But better safe than sorry.
 
I agree. What ultimately needs to happen is a baseline measurement of the grid with all circuits disabled. Assuming it's at 0 volts potential to ground (where it should be), an electrician can then bring circuits online one at a time until they see a change. Then the problem circuit/fixture is isolated and can be properly diagnosed. I also agree with @Ben Stiegler that you've shown us some other issues which are probably unrelated to your arcing - but potentially dangerous on their own. I would pull down each cable/fixture and do a service call on everything. Too many loose connections and poorly-fit connections in one place for my liking. Makes one wonder what other issues exist that have yet to rear their ugly head.
 
Broken record here but..... Ezra, as a student at the school, why are you the one flipping breakers and diagnosing and red flagging and putting yourself at risk? You sound like you're very involved and enthusiastic and knowledgeable about the venue but, as a student, you shouldn't be hands-on in a potentially lethal scenario. I'm the qualified adult (tech teacher) and I can't imagine a scenario in which I would let students handle a situation the second something started sparking like that.
Sure, they could observe and be involved in hands-off troubleshooting and it would be a great learning experience but I would never put or allow a student to put their hands on a rig that I knew to be questionable. I'm glad you're safe and you've learned some valuable info in this thread - you have a bright future ahead of you. I have no problem with that and I'm not finger wagging at you. I do, though, wag my finger at whatever adults are involved there.
 
And -- and the electricians should know this, but you'd be amazed -- I wouldn't do this particular thing with less than 2 licensed electricians, with walkies, and a cellphone. Good if smart, interested students like you are observing safely, but you are not their safety man, either.
 
and I'm the slightly intrusive adult techie in the neighborhood who talked to the school maintenance/safety administrator today ... they understand the gravity of this, tho not all the details.

Ezra, if you haven't provided them with a printout of all the info you shared here, please do so - you have a lot of excellent observations, and the breaker-holding-it-on thing is definitely something they need to hear about.

Please do keep us posted on what all is found - you have a lot of interested folks around the globe paying attention!
 
Ezra Newman said:
Hey guys, our show opened last night and I had a problem I've never seen before.

Some context: we have Source 4 19 degree 750 watt conventional spots. Our grid that the spots are mounted on is metal pipe with a thin, easily scratched coat of paint on it. I think its not unreasonable to say that the C clamps cut through that everywhere on the grid and so any/all lights could be making an electrical connection (although there shouldn't be any power flowing through the grid, obviously).

One of our spot ops noticed a spark where the yoke bolts to the C lamp, so I turned off the light and had our spot op (carefully) unplug it. We replaced our entire lamp housing and cable assembly (plug all the way to the lamp) with a different one and turned the light back on. A little later there was another spark.

My spot op thinks it might be static or caused by metal grinding on metal but that seems somewhat unlikely to me because it's all metal parts (not static) and the light isn't that heavy or moving that fast. We've never seen this before. I cut power to all the lights in the grid at the circuit breaker when the audience left so it couldn't spark overnight.

I was thinking that its possible that a light is shorting through the grid and sparking there for some reason.

Have you ever had this problem?


Thanks.

Also posting this on safety.
Click to expand...
Sparking at the yoke is usually a very simple thing to check and fix
The fixtures plug is wired wrong, the neutral and ground are swapped. Electricity takes the path of least resistance. A grid that must be grounded is a far better conductor than the outlet ground. In a conduit system a break in the conduit (that is the grounding conductor) and often happens in theater situations as people see it as a good place to tie things to.
I see burned outlet and you had a pic of a melted molded Edison cable.
Edison connectors are the absolutely worst connectors to use for lighting. Particularly in a place like a school were students and even staff have absolutely no knowledge of even the most basic electrical skills, like putting a new plug on anything. Let alone understanding why figuring load (even though it’s just simple addition) is even nessary.
That melted Edison cable is not even approved for use in a theater! Another reason Edison’s should never be used as people just go and purchase things at a hardware or home center. They ALL say “heavy duty”.even the 16gauge ones!! then let’s just add a cube tap and run 2 or 3 lights on it. Your lucky all it did was melt.
If it’s not a miswired plug causing the sparking
the place has a serious problem that can’t be diagnosed by an adult, not even most electricians. An experienced industrial electrician licensed with trouble shooting ability (not just new work) and experience in theater wiring (as it is different than a factory, a lot different) that person also need to be able to troubleshoot incoming electrical services and all the various 3 phase services used in this country as god forbid a 3 phase corner grounded delta has had a failure either in the building (would be on a separate meter)
or even a service like that in another building or even down the street could cause grid electrification
 
Richard Young said:
Sparking at the yoke is usually a very simple thing to check and fix
The fixtures plug is wired wrong, the neutral and ground are swapped. Electricity takes the path of least resistance. A grid that must be grounded is a far better conductor than the outlet ground. In a conduit system a break in the conduit (that is the grounding conductor) and often happens in theater situations as people see it as a good place to tie things to.
I see burned outlet and you had a pic of a melted molded Edison cable.
Edison connectors are the absolutely worst connectors to use for lighting. Particularly in a place like a school were students and even staff have absolutely no knowledge of even the most basic electrical skills, like putting a new plug on anything. Let alone understanding why figuring load (even though it’s just simple addition) is even nessary.
That melted Edison cable is not even approved for use in a theater! Another reason Edison’s should never be used as people just go and purchase things at a hardware or home center. They ALL say “heavy duty”.even the 16gauge ones!! then let’s just add a cube tap and run 2 or 3 lights on it. Your lucky all it did was melt.
If it’s not a miswired plug causing the sparking
the place has a serious problem that can’t be diagnosed by an adult, not even most electricians. An experienced industrial electrician licensed with trouble shooting ability (not just new work) and experience in theater wiring (as it is different than a factory, a lot different) that person also need to be able to troubleshoot incoming electrical services and all the various 3 phase services used in this country as god forbid a 3 phase corner grounded delta has had a failure either in the building (would be on a separate meter)
or even a service like that in another building or even down the street could cause grid electrification
Click to expand...
what he said! these are great examples of the "you can't imagine how messy a root cause there could be" that I was struggling to describe. Keep us posted - worst case, we can all come over with some insulated sticks and a bag of marshmallows to toast.
 
"Edison connectors are the absolutely worst connectors to use for lighting. Particularly in a place like a school were students and even staff have absolutely no knowledge of even the most basic electrical skills, like putting a new plug on anything. Let alone understanding why figuring load (even though it’s just simple addition) is even nessary.
That melted Edison cable is not even approved for use in a theater! Another reason Edison’s should never be used as people just go and purchase things at a hardware or home center. They ALL say “heavy duty”.even the 16gauge ones!! then let’s just add a cube tap and run 2 or 3 lights on it. Your lucky all it did was melt."

I guess you had better send your concerns about Edison connectors to ETC and all the other manufacturers of LED stage lighting fixtures who regularly supply Edison connectors on the fixture whips as well as supply connector strips with Edison connectors.
 
microstar said:
"Edison connectors are the absolutely worst connectors to use for lighting. Particularly in a place like a school were students and even staff have absolutely no knowledge of even the most basic electrical skills, like putting a new plug on anything. Let alone understanding why figuring load (even though it’s just simple addition) is even nessary.
That melted Edison cable is not even approved for use in a theater! Another reason Edison’s should never be used as people just go and purchase things at a hardware or home center. They ALL say “heavy duty”.even the 16gauge ones!! then let’s just add a cube tap and run 2 or 3 lights on it. Your lucky all it did was melt."

I guess you had better send your concerns about Edison connectors to ETC and all the other manufacturers of LED stage lighting fixtures who regularly supply Edison connectors on the fixture whips as well as supply connector strips with Edison connectors.
Click to expand...
They know but don’t have to care as it’s all on the end users to know what’s what
 
Wow, Ezra, you are one lucky young man! You could have so easily killed yourself, no kidding! No one here’s wagging fingers at you, but please respect that electricity can eat you up in half a heartbeat. Safety needs to be the number one goal when you walk into that theater. And if you have peers helping, you need to watch out for and mentor your team in the safe way to do things. You sound like a sharp guy, you could do well in the industry! Best wishes to you for a fruitful and long life. 😉
 
Richard Young said:
Sparking at the yoke is usually a very simple thing to check and fix
The fixtures plug is wired wrong, the neutral and ground are swapped. Electricity takes the path of least resistance. A grid that must be grounded is a far better conductor than the outlet ground. In a conduit system a break in the conduit (that is the grounding conductor) and often happens in theater situations as people see it as a good place to tie things to.
I see burned outlet and you had a pic of a melted molded Edison cable.
Edison connectors are the absolutely worst connectors to use for lighting. Particularly in a place like a school were students and even staff have absolutely no knowledge of even the most basic electrical skills, like putting a new plug on anything. Let alone understanding why figuring load (even though it’s just simple addition) is even nessary.
That melted Edison cable is not even approved for use in a theater! Another reason Edison’s should never be used as people just go and purchase things at a hardware or home center. They ALL say “heavy duty”.even the 16gauge ones!! then let’s just add a cube tap and run 2 or 3 lights on it. Your lucky all it did was melt.
If it’s not a miswired plug causing the sparking
the place has a serious problem that can’t be diagnosed by an adult, not even most electricians. An experienced industrial electrician licensed with trouble shooting ability (not just new work) and experience in theater wiring (as it is different than a factory, a lot different) that person also need to be able to troubleshoot incoming electrical services and all the various 3 phase services used in this country as god forbid a 3 phase corner grounded delta has had a failure either in the building (would be on a separate meter)
or even a service like that in another building or even down the street could cause grid electrification
Click to expand...
@Richard Young Posting in FULL SUPPORT: The three phase 120 / 208 distribution throughout the condo' I lived in for 35 years was all underground in a combination of "Fibre Duct" (think molded paper and tar as installed in Canada in the mid 50's and deemed Carcinogenic less than a decade later in the mid 60's) Every few lawns had a ~12" diameter cover with strange (to everyone outside the small world of electrical distribution) FIVE sided [non] hex bolts incapable of being gripped by the majority of our world's pliers, wrenches, sockets et al.
The covers were cast iron built to withstand foot traffic, lawn mowing, snow shovelling. kids playing, yada, yada.
The covers were affixed via bolts into ~1/4 galvanized metal anchored to the inside circumference of an open-bottomed ~ 36" length of ~12" diameter Fibre Duct whose sides carried on down to ~ 3' below finished grade.

Within the cute little pseudo manholes, 3 phase 4 conductor distribution wiring connected via Burndy 'split bolt style' approved connectors branching out in five or six directions to carry what (to most residents) appeared to be the 'normal' single phase 120 volts typically derived from a single center-tapped transformer winding with its center tap bonded to your incoming traditionally threaded iron water pipe.

I'm sure you can see this coming.
Above grade and within each of our 85 units all appeared "normal"; everybody's unit had a meter base and meter outside on a exterior wall fed via rigid conduit rising from below grade and exiting out its rear directly into the rear of our "sealed" FUSE boxes (from the days before those new trendy breaker thingies became common place) Out of the fuse panel within your unit, bonded to the incoming cast iron water pipe ahead of your water heater and our condo's world was peaceful and serene until, over the decades:
Graded lawns sank in various locations, landscaping contractors added soil topped with sod to again restore our lawns to the pristine look we were all paying for.
Mowing lawns by hand became contractors with large, heavier, ride-on mowers.
Sidewalks settled with paving contracts being let every decade or so to contractors who merely overlaid ever more asphalt 'til all walkways again appeared perfect and pistine.

IMAGINE THE HADES that began being reported sporadically with vastly differing symptoms from each of the 85 unit owners when underground cables became tensioned like bow strings 3' + below grade and neutral junctions began failing in their below grade Burndy 'split bolt style' connectors:
My lights are REALLY bright and they're burning out every two weeks.
My clothes drier's not drying as quickly as it used to.
My furnace isn't running right.
Two of the burners on my electric stove are TOO hot yet the other two are hardly getting hot at all.

@Richard Young You can all too well imagine the chaos and varieties of logic applied by the various unit inhabitants, their relatives, friends, acquaintances, "home inspectors", licensed and non-licensed electrical contractors, plumbing contractors replacing iron incoming water lines with plastic et all: Add seasonal rains, the melting snows of winter then toss in a condo wide system of professionally installed lawn and garden sprinklers, add contractors upgrading below grade natural gas distribution and blend to taste.

Your post Sir is understood and appreciated. (even more so by this young whipper snapper who spent the entire first year of his IBEW Installation and Maintenance apprenticeship, to the day, installing literally miles of 4" and 2.5" I.D. fibre duct ~6' below grade to carry 13.8 and 27.6 KV 3 phase 3 wire (in the 4" ducts) and and POT (Plain Old Telephone) and synchronous clock data (in the 2.5" ducts) between 11 duplex manholes (with two access covers per hole to segregate the "REAL MEN" electricians from their wussy brethren in their communications divisions) throughout several acres of largely undisturbed soil destined to become the new west campus of our local university.

Reading your post stirred many memories of several of my journeymen who, as electricians, were better suited to carpentry and plumbing.
Thanks again for your post and the memories it's rekindled.
Toodleoo!
Ron Hebbard
 
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