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Author Topic: Event hall fun  (Read 8205 times)

TJ (Tom) Cornish

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Event hall fun
« on: November 19, 2017, 10:37:35 pm »

I had an event yesterday in a room that I have been in before - a fairly large event center.  There are 14-50Rs around the room, and I had used this particular receptacle before.  I resisted the urge to plug in and go, and instead took my own advice and tested it.

Boy am I glad I did.  The room had a recent renovation, and this receptacle was apparently touched, and in the process of whatever they did, ended up being miswired as a H-H-H-G instead of a H-H-N-G.  In other words, the neutral terminal was connected to the third phase hot leg, which caused both legs of my distro to be 208v instead of 120v. 

I avoided release of the magic smoke, but only barely.  As I mentioned, I had used this exact receptacle previously, and at the time it was fine.  I was able to find a different 14-50R that was correctly wired and I notified the venue to tag and repair this receptacle, but this was a good reminder to me and hopefully to others to never assume anything.
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Mike Sokol

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Re: Event hall fun
« Reply #1 on: November 20, 2017, 08:22:08 am »

The room had a recent renovation, and this receptacle was apparently touched, and in the process of whatever they did, ended up being miswired as a H-H-H-G instead of a H-H-N-G.  In other words, the neutral terminal was connected to the third phase hot leg, which caused both legs of my distro to be 208v instead of 120v.

Good catch. This could have gone sideways in a hurry.
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Mike Sokol
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TJ (Tom) Cornish

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Re: Event hall fun
« Reply #2 on: November 20, 2017, 08:55:47 am »

Good catch. This could have gone sideways in a hurry.
After the fact, I thought about what gear I had onsite that day that was intolerant of 208v and the only things I could come up with were my dimmers and conventional lighting, and possibly the video projectors.  As far as I know, everything else - amps, mixer, stage boxes, wireless equipment, LED and discharge lighting, all could take the higher voltage without damage.

Obviously there are significant life safety and liability issues and there is no excuse for this moron electrician that can't tell the difference between a neutral wire and a hot wire, but it is interesting that the gear damage potential is significantly reduced compared to a few years ago.
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Adam Kane

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Re: Event hall fun
« Reply #3 on: November 20, 2017, 12:01:11 pm »

Obviously there are significant life safety and liability issues and there is no excuse for this moron electrician that can't tell the difference between a neutral wire and a hot wire, but it is interesting that the gear damage potential is significantly reduced compared to a few years ago.

I noticed the plate is labeled 32-34-36...so at least he got that part right.

We were setting up outside for an event about 10 years ago, and the electrician was connecting our tails into one of the portable "doghouse" panels (which has a transformer to step 480/277 down to 208/120). Our tails are clearly labeled/color coded for a 120/240 (or 208) single phase system (Black, Red, White, Green). Not to mention only four conductors. He told me all was set and took off. I went to meter a couple of recepts like I always do before I connected anything, and was getting 277-ish from each leg AND neutral to ground. Dork put the black/red/white on a 3-pole breaker in the 480 panel.

Never saw him at that event again in subsequent years.
« Last Edit: November 20, 2017, 12:04:40 pm by Adam Kane »
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Stephen Swaffer

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Re: Event hall fun
« Reply #4 on: November 20, 2017, 01:09:12 pm »

It could be that that plate was there from the original install and was originally wired three phase then someone converted the receptacle to a 14-50R moving one phase to the neutral.  It wouldn't be the first time an electrician was tripped up by someone elses failure to follow code-especially confusing at the panel end, if they left the 3 pole breaker in place and just abandoned one pole.  Of course, it should still have been tested before they left the property. 
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Steve Swaffer

TJ (Tom) Cornish

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Re: Event hall fun
« Reply #5 on: November 20, 2017, 02:28:52 pm »

It could be that that plate was there from the original install and was originally wired three phase then someone converted the receptacle to a 14-50R moving one phase to the neutral.  It wouldn't be the first time an electrician was tripped up by someone elses failure to follow code-especially confusing at the panel end, if they left the 3 pole breaker in place and just abandoned one pole.  Of course, it should still have been tested before they left the property.
That's possible. 

I've complained before that I have yet to encounter a legal distro panel provided by a venue.  My original fear is that someone made up a "special" distro panel that uses the H-H-H-G configuration - 3 hot legs and a bonded neutral and ground, and intentionally changed this receptacle to be "correct" for their "special" distro.  As the other receptacles seemed to be wired right, which causes me to lean to an electrician goofing up rather than this being intentionally miswired.

I will have more events in this room in the future, so I'm going to stay on the venue to make sure it gets fixed.
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Mike Sokol

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Re: Event hall fun
« Reply #6 on: November 21, 2017, 09:12:45 am »

That's possible. 

I've complained before that I have yet to encounter a legal distro panel provided by a venue.  My original fear is that someone made up a "special" distro panel that uses the H-H-H-G configuration - 3 hot legs and a bonded neutral and ground, and intentionally changed this receptacle to be "correct" for their "special" distro.  As the other receptacles seemed to be wired right, which causes me to lean to an electrician goofing up rather than this being intentionally miswired.

I will have more events in this room in the future, so I'm going to stay on the venue to make sure it gets fixed.

I've seen a number of facilities that have a "maintenance man" who does all this type of rewiring, and they have no electrical training or knowledge of code. They're the most dangerous of all since they really don't understand the implications of wiring up a neutral on a hot leg, etc...

This is also the best reason for metering every receptacle before plugging in. It could have been wired correctly for decades and you may have used it dozens of times, but after the "maintenance man" works on wiring, anything is possible.
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Mike Sokol
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Matt Greiner

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Re: Event hall fun
« Reply #7 on: November 22, 2017, 12:27:23 am »

That's possible. 

I've complained before that I have yet to encounter a legal distro panel provided by a venue.  My original fear is that someone made up a "special" distro panel that uses the H-H-H-G configuration - 3 hot legs and a bonded neutral and ground, and intentionally changed this receptacle to be "correct" for their "special" distro.  As the other receptacles seemed to be wired right, which causes me to lean to an electrician goofing up rather than this being intentionally miswired.

I will have more events in this room in the future, so I'm going to stay on the venue to make sure it gets fixed.

I actually made this mistake a few months ago, also having been at the venue before (not the same one as you, but one in Iowa).   However, I plugged my distro in, plugged my Mac 250 Entours in and poof, gone.  The fixtures I used in the past were auto ranging, so there was no issue.  This time, I'm out 8 fixtures.  Same thing, a 14-50 was wired in 3 phase.  After talking with other production companies in my area, it has been this way for years.  The hotel also has several home made distros, that are wired incorrectly so that it makes this wiring issue seem to go away.  That is until someone like me comes in and plugs in my correctly wired distro.  Not going to name names, but it is a very large hotel chain.

On a side note, I realize that my Entours could handle the 208, but I would have had to open them up and move the switch.  Which I wouldn't have had a problem doing, had I know of the issue.  Always meter!!!  Duh!
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Ray Aberle

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Re: Event hall fun
« Reply #8 on: November 22, 2017, 09:52:47 pm »

That's a hard way to learn that lesson, but thankfully it was only gear this time, and not someone!

-Ray
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Matt Greiner

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Re: Event hall fun
« Reply #9 on: November 22, 2017, 10:02:07 pm »

Agree completely.
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ProSoundWeb Community

Re: Event hall fun
« Reply #9 on: November 22, 2017, 10:02:07 pm »


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