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Topic: Share your worst electrical nightmare!

Tony Bandiera Jr
Film God

Posts: 3067
From: Moreland Idaho
Registered: Apr 2004

posted 08-13-2004 04:24 PM

quote: Randy Stankey
Nobody else has the balls to even go into the electrical vault by themselves. That just leaves little ol' me.

Yeah, it's amazing how many people are deathly afraid of electricity. As long as you watch what you're doing and what you touch you can work live equipment safely.

I would imagine for safety's sake you at least let someone else know when you're going into the vault, just in case...in the military we had to have at least two people present even when changing fuses/replacing breakers.

Camlocks when used properly are the safest and best way to make temporary power hookups.

I have seen some temporaries done with battery jumper cables [Eek!]

and oversized alligator clips! And one case where they loosened the main lugs on a 400 amp panel UNDER LOAD to jam their temps in with the feeder!

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Bob Healey
Film Handler

Posts: 93
From: Milford, CT
Registered: Sep 2001

posted 08-13-2004 08:54 PM

quote: John Hawkinson
Bob Healey writes, "The dimmer rack was designed to be run off of camlocks or a pair of 30A 3phases lines in parallel...It turns out that the electrician crossed the black and the blue phases when he hooked up the second outlet."

Is there a requirement that L14 connectors have the phasing in any particular order? I was under the impression that it was not safe for devices to assume any particular order at all.

--jhawk

The phasing does matter when you're using two lines with those style connectors wired in parallel. And, the connector in question's an L-21 (5 wire).

edited to include quote left out first time around

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Richard Fowler
Film God

Posts: 2392
From: Ft. Lauderdale, FL, USA
Registered: Jun 2001

posted 08-13-2004 09:04 PM

My first memory as a small tyke was sticking bobby pins in a wall socket as a two year old [Smile]

In the summer of 1968 / 69 I worked as a stage electrician and followspot operator for a musical revue. We traveled through the USA and Western Canada. A creaky 50KW CAT generator was used for locations without power and weatherproof tie boxes where city power was available. Frequency would occaisionally drift and adjusting rpms to the Hammond B-2 organ in the band was a quick fix in a pinch. Black "tweaks", requiring rubber gloves, especially on a damp day, where more common than Cam Locks. My travel trailer had an electrical tap kit of "Mueller" insulated clips so I could tap off a service line if plug in power was not available...some of the [bs]

I did in my late teens and early 20's it is amazing I am still here [uhoh]

Cinema servicing....using car D.C. jumpers to run an Ashcraft Corelight at a drive-in...getting zapped through a wrist bracelet from a Christie ignitor ( no more jewelery ). Enduring power issues in Latin America such as exposed ballast resistors, ground buss bar in one point of a building to home run connections....concrete rebar in a building roof for ground in Mexico....fused neutrals instead of hot....a "floating" ground in Argentina from a 1930's corroded connection dangling in the air from the still connected building lead [uhoh]

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Randy Stankey
Film God

Posts: 6539
From: Erie, Pennsylvania
Registered: Jun 99

posted 08-14-2004 08:53 AM

There's nothing in our electrical hookup that's the least bit tricky. Once you pull the disconnect and open the cover there's nothing that can bite you unless you reach behind the safety cover that goes over the live feeders. You know. The one that says, "DO NOT REMOVE THIS COVER - ELECTROCUTION HAZARD" in big black letters. [Big Grin]

Actually, I prefer to be the only one who does the tie-ins. There's less chance of having to decode somebody else's screwy work when I have to do a job.

I always take somebody with me when I go into the vault. Even if they can only yell for help or something. It's funny to see the looks on their faces when I tell them, "If I get electrocuted, don't try to touch me or else YOU will get electrocuted too!" Then I show them where the main disconnect for the building is. "If there's trouble, pull that big black handle over there and you'll shut the whole building down."

By this time, they are usually heading for the exit and I'm sitting in the corner, doubled over with laugnter. [Big Grin]

My standard line is to tell people that they don't have to work on electricity if they are afraid to. I'd rather let the person go than have them make a mistake because they are too afraid to think straight.

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John Hawkinson
Film God

Posts: 2273
From: Cambridge, MA, USA
Registered: Feb 2002

posted 08-14-2004 05:58 PM

Bob: I understand the phasing matters!

What I was suggesting was that any device that assumes the phasing might be the same on two receptacles is asking for it. [uhoh]

I assumed you meant L14, but the same should go for L21...

(I don't see anything in the NEC either way on this question.)

--jhawk

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Bob Healey
Film Handler

Posts: 93
From: Milford, CT
Registered: Sep 2001

posted 08-15-2004 11:05 PM

quote: John Hawkinson
Bob: I understand the phasing matters!

What I was suggesting was that any device that assumes the phasing might be the same on two receptacles is asking for it.

I assumed you meant L14, but the same should go for L21...

(I don't see anything in the NEC either way on this question.)

Sorry, I should have been more clear earlier. The L21 connectors were never intended to be used for general hookups, but to piggy back this rack off a much larger rack with a bigger supply if an additional 12 channels were needed in a venue. Since both racks were built at the same time, it the phasing issue was taken care of when the receptacles were installed in the larger rack. Its been a few months since school let out for the summer, and I forgot that little detail, since the larger rack has since been retired. That was a one-off hookup and I didn't have the tools to check phasings and the electrician didn't even though i told him several times both feeds were in parallel.

On left is the rack in question and on right is the rack it was designed to connect to. The plugs on the bottom are covers in case someone connects the L21s to the power feed while running off of the cams.

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Tony Bandiera Jr
Film God

Posts: 3067
From: Moreland Idaho
Registered: Apr 2004

posted 08-16-2004 03:02 PM

Bob: Nice racks!! [Big Grin]

jhawk: You're absolutely correct, the NEC doesn't specify any phasing standard for "polyphase" devices. The only reference is to certain 3-phase systems with a "stinger" or "wild" leg. (A leg of the service where phase-to-neutral voltage is not a constant 120v, but varies from aprox. 175-285 volts.) It is supposed to be the "B" phase in those panels and presumably devices.

A very simple tester can be built to help avoid the problems Bob has experienced.:

You'll need two pigtails with the proper connector plugs wired correctly, (3) 240 volt pilot lamps (neon or Incand.)and a suitable box to mount them in. (I think neons would be better and more durable)

Simply wire one terminal of each lamp to the SAME phase of each pigtail, (lamp one wires to A on tail 1 and A on tail two, etc.) and you're done!

How does it work? Easy. If both pigtails are connected to correctly phased plugs, the lamps WILL NOT light! (Because the lamp has both wires connected to the same phase, no current flows.) If either receptacle is miswired, TWO of the lamps will light on the affected phases. (Example: Lamps A and C lit, means that one of the recptacles has A and C phases crossed.)

This will not of course tell you which one is backwards, but you can at least make corrections as needed.

My shop up North had one of these, built into a rack panel so we could check phasing on camlocks as well.

I can email a schematic to anyone who wants one.

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John Hawkinson
Film God

Posts: 2273
From: Cambridge, MA, USA
Registered: Feb 2002

posted 08-16-2004 03:33 PM

OK, everyone else can skip this one. [sleep]

Tony: "The only reference is to certain 3-phase systems with a "stinger" or "wild" leg. (A leg of the service where phase-to-neutral voltage is not a constant 120v, but varies from aprox. 175-285 volts.) It is supposed to be the "B" phase in those panels and presumably devices."

Well, that's not the only reference.

Article 408 (Switches and Panelboards), I. General, 408.3 Support and Arrangement of Busbars and Conductors, (E) states:

quote: National Electric Code, 2003 draft, 408.3(E)

(E) Phase Arrangement. The phase arrangement on 3-phase buses shall be A, B, C from front to back, top to bottom, or left to right, as viewed from the front of the switchboard or panelboard. The B phase shall be that phase having the higher voltage to ground on 3-phase, 4-wire, delta-connected systems. Other busbar arrangements shall be permitted for additions to existing installations and shall be marked.

Exception: Equipment within the same single section or multisection switchboard or panelboard as the meter on 3-phase, 4-wire, delta-connected systems shall be permitted to have the same phase configuration as the metering equipment.

FPN: See 110.15 for requirements on marking the busbar or phase conductor having the higher voltage to ground where supplied from a 4-wire, delta-connected system.

I believe that clearly indicates that for a 120/208-Wye system (which is surely what Bob has), all panels need to have the same arrangement of A, B, and C phases. Those need not be a priori referenced to something, i.e. no equipment could predict the phase rotation between them, but all panels in the installation should agree on which phase is A.

The constraint for the "wild leg," of course, simply means that it must be the B phase.

The problem is that there is no requirement that receptacles be wired with the A, B, and C phases in any particular order.

--jhawk

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Tony Bandiera Jr
Film God

Posts: 3067
From: Moreland Idaho
Registered: Apr 2004

posted 08-16-2004 07:11 PM

jhawk: Thanks for the correction. [thumbsup]

I should have not said "only reference" in that context. My bad! I was focused on the recepticle issue.... [Smile]

The NEC is an interesting and somewhat confusing document, it has to try to cover all possible contingencies...and it can be misread or misinterpreted. Also, mutiple sections of the Code can address multiple issues!

I'm wondering if any local codes have set a standard for phase sequence of devices?

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Tony Bandiera Jr
Film God

Posts: 3067
From: Moreland Idaho
Registered: Apr 2004

posted 10-15-2004 03:14 AM

Bumping this up...

Recently did some repairs at a local theatre with various strange problems with the lamp (odd flicker at random), light dimmer and automation....called in electrician to find one of the main feed wires to the booth subpanel badly burned at the lug, which was loose.

While repairing this problem, suggested the sparky take a look at the theatere's main switchgear, where he found 14! of the 18 breaker lugs loose!! [Eek!]

We were amazed as it had been that way for at least 10 years!! Somebody was watching over that place for sure!

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Rick Raskin
Phenomenal Film Handler

Posts: 1100
From: Manassas Virginia
Registered: Jan 2003

posted 10-15-2004 04:03 PM

Had this experience at a TELCO central office some years ago. We were testing the backup generator which required we switch the loads from commercial power. The procedure was to go down the main switchboard and operate breakers in the trip (commercial)-close (generator)sequence. A tech went down the board going trip-close, trip-close, trip-close, close-trip. At that point a huge flame shot out from under the switchboard causing a small fire that was quickly extinguished. Subsequent upgrades automated the switchgear to eliminate any operator error.

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Barry Floyd
Phenomenal Film Handler

Posts: 1079
From: Lebanon, Tennessee, USA
Registered: Mar 2000

posted 10-16-2004 01:54 AM

After reading some of yalls posts... I feel a little bit better about the electrical guys that were here at our drive-in for a concert a couple of weeks ago.

We had a huge classic car show and live concert at the theatre on the 3rd of October. The trucks for the stage crew arrived at 10:00 a.m. that morning to start setting up for a 3:30 p.m. show. They kept building and building and building this monstrosety of a stage. By the time they were done, there was a wall of speakers, lighting gear, etc. that was taller than the concessions building. I looked at one of the guys and asked, "Where do you think your gonna plug all of that into?"

They ran these HUGE thick cables behind the stage, behind the building and in thru the projection port hole. Once inside, the removed the cover off of our main 3 Phase 600 amp power panel, and removed the breakers to the restroom heaters. I thought they were total nuts as they wired directly into the main panel while it was HOT.

I thought they were crazy, but it sounds like you guys do this kind of stuff all the time. [Eek!]

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Thomas King
Expert Film Handler

Posts: 119
From: Sheffield, Yorkshire, England
Registered: Oct 2004

posted 11-05-2004 01:32 AM

Our booth is carpeted. Yes, isn't that silly? This carpet and my big manly walking boots interact in such a way that just by walking around for a bit, I can accumulate a considerable potential, which gets earthed whenever I touch something big and metal like, say, the projector, or the platter, or the rack. Bzzt. "Ow!" *swears*.

I know it's pathetic and minimal, but I'm quite happy with it. It's enough for me.

Shocking.

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John Pytlak
Film God

Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000

posted 11-05-2004 09:24 AM

quote: Thomas King
Our booth is carpeted. Yes, isn't that silly? This carpet and my big manly walking boots interact in such a way that just by walking around for a bit, I can accumulate a considerable potential, which gets earthed whenever I touch something big and metal like, say, the projector, or the platter, or the rack. Bzzt. "Ow!" *swears*.

Static charge generated by walking across carpeting can be controlled by maintaining a higher relative humidity in the projection box (ideally 50 to 60 percent RH). You can also treat the carpeting with a conductive topical antistat like Static Guard, Neutrostat, Staticide, etc.:

http://www.aclstaticide.com/01/index.html

quote:

--------------------------------------------------------------------------------

History
Definitions
Examples of static electricity & ESD
Facts about static electricity
Electrical characteristics of materials
Five basic rules for ESD control
Conclusion

Most of these antistats use quaternary ammonium compounds which conduct electicity in the presence of moisture from normal humidity. Using conductive footware also helps.

In addition to the annoying shocks you get when touching grounded objects, charge buildup can also "zap" sensitive electronic components. There is a wide variety of static control companies, including Simco, Meech, etc. who provide static control technology to the plastics and electronics industries.

http://www.meech.com

http://www.simco-static.com/data/index.shtml

http://www.kinetronics.com

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Phil Hill
I love my cootie bug

Posts: 7595
From: Hollywood, CA USA
Registered: Mar 2000

posted 11-05-2004 07:25 PM

One of the things that helps take the "sting" outta that static spark to your finger, or other body parts, is to use a metallic lock-key or a coin to complete the spark.

While you'll still get the jolt, you wont get the burn from the arc end directly to your skin or pinkie. [beer]

It's soooo much better and hurts less and very soothing! Sorta like "Tastes good, but less filling". [Wink]

>>> Phil

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