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Author Topic: Today's cautionary tale  (Read 5127 times)

Jim Layton

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Re: Today's cautionary tale
« Reply #10 on: February 26, 2018, 03:58:29 pm »

Yes, and that goes double for generator power. Just about every large 3-phase generator I've ever rented can be switched between 208/120 and 480/277 volts and 1-phase vs 3-phase. And one of the local rental houses uses a Japanese brand genny that has no English writing on the controls. Half the time when it's been delivered to my show site it was set for 480/277 and I have to change it. So I never let anyone else test generator power except for me.

Question. Way back I rented a Wacker from a local equipment rental supply company. All I was running was four XTi 4000 amps and my mixer. Outdoor concert with a couple of local bands. Nothing heavy. Recorded music was fine all day. As soon as the band came on I noticed all my amps were showing  red like they were clipping and had low sound output. I was panicked as it was my first outdoor event and generator event. I knew something was wrong on the gen but I had to stay and work with what I had as the band was live. I just had no experience with generators and figured since I explained what it was for the rental place would have it ready to go. I used my own 6/4 cable and distro (those checked out OK). I posted this years ago in the Lab and people seemed to think the voltage was set too low since the XTis were known to go into that mode under those conditions. But could it have been 480/277?  If it was, I suppose the amps would not have worked even for house music?
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TJ (Tom) Cornish

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Re: Today's cautionary tale
« Reply #11 on: February 26, 2018, 04:04:07 pm »

Question. Way back I rented a Wacker from a local equipment rental supply company. All I was running was four XTi 4000 amps and my mixer. Outdoor concert with a couple of local bands. Nothing heavy. Recorded music was fine all day. As soon as the band came on I noticed all my amps were showing  red like they were clipping and had low sound output. I was panicked as it was my first outdoor event and generator event. I knew something was wrong on the gen but I had to stay and work with what I had as the band was live. I just had no experience with generators and figured since I explained what it was for the rental place would have it ready to go. I used my own 6/4 cable and distro (those checked out OK). I posted this years ago in the Lab and people seemed to think the voltage was set too low since the XTis were known to go into that mode under those conditions. But could it have been 480/277?  If it was, I suppose the amps would not have worked even for house music?
480/277 would almost certainly have meant smoke.  Low voltage would be more likely to cause the issues you indicate.
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Jim Layton

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Re: Today's cautionary tale
« Reply #12 on: February 26, 2018, 04:06:07 pm »

480/277 would almost certainly have meant smoke.  Low voltage would be more likely to cause the issues you indicate.

No smoke! Thanks. Lesson learned.
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Don T. Williams

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Re: Today's cautionary tale
« Reply #13 on: February 26, 2018, 05:27:26 pm »

A brand new, never used before, 70KVA generator (name brand but a model I hadn't worked with) was provided by the city for my outdoor event.  We were setting the stage up the day before the event and wanted to unfold and raise the roof on my portable hydraulic stage.  I had checked that we had three legs of 120V and ground and neutral were good.  With the roof in its down position, we unfolded the front and back roof panels so the front and rear stage sections could fold down.  It takes a few minutes to get all of the legs in place and the stage leveled, and during this time we guess the generator decided to go into a "protect itself" mode for some reason with almost no load on it.  The only thing running was that 2HP hydraulic pump which was just idling with no load.  This "protect" mode drops the output voltage of the generator to about 40 volts, which caused the starting coil on my hydraulic pump motor to fail!  The motor turns but with no usable power.  We are in a fairly small town and it's Friday night at 7PM with an 11AM Saturday start time.  The two local motor distributors did return my calls to their emergency numbers, but didn't have the motor I needed.  Hitting every hardware store, auto parts store, lumber yard, and farm & ranch supply at 7AM the next morning yielded enough jacks and support blocks to safely raise to roof about three and one-half feet of its usual additional 8' before the band arrived.  The show only started about 5 minutes late.  The closest new motor I could find was four states away and the 2 day air freight (needed for my next event) was over $350.00.  I purchased and now have a spare motor.  Restarting the generator solved its "emergency", but not mine!
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Laurence Nefzger

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Re: Today's cautionary tale
« Reply #14 on: February 26, 2018, 08:44:43 pm »

Receptacle Testing Article
Thank you for re-posting this concise and well written testing procedure!
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Daniel Levi

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Re: Today's cautionary tale
« Reply #15 on: February 27, 2018, 03:22:02 pm »

As for something that actually looks like it was done by a real profession was a function room in a local theatre, each socket had a coloured plate below it identifying the phase it was on and warning that it had 415V between it and any other socket, something simple but at the same time nice to see, some other sockets in the place are coloured to denote phase also.

But then again there seems to be higher general standards of wiring in the UK to what this forum has exposed to me of the US.
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TJ (Tom) Cornish

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Re: Today's cautionary tale
« Reply #16 on: February 27, 2018, 03:43:58 pm »

As for something that actually looks like it was done by a real profession was a function room in a local theatre, each socket had a coloured plate below it identifying the phase it was on and warning that it had 415V between it and any other socket, something simple but at the same time nice to see, some other sockets in the place are coloured to denote phase also.

But then again there seems to be higher general standards of wiring in the UK to what this forum has exposed to me of the US.
There are voltage-specific color schemes and labeling conventions that should be followed.  Most of the trouble comes from the fact that people screw up - electricians moving things; generator "ops" that don't know how to operate the generator and set it correctly for the load, etc.  The National Electric Code uses the term "qualified personnel" in a number of places.  Those people are not always available when needed.
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Brian Adams

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Re: Today's cautionary tale
« Reply #17 on: February 27, 2018, 11:47:41 pm »

I think every generator that's ever been delivered to me has been set wrong, and the techs or electricians never seem to be able to figure out what I need. I can tell them to their face that I need 208v 3-phase and they'll still set it to 240 single phase or something. Yeah, that's why I gave you 5-wire tails, because I want 240. Or they can't understand why 480 won't work. It's more efficient, so it's got to be better, right? You know what, guy, just pound the ground rod in for me and I'll do the rest. I know how to work a socket wrench just as well as you do.

I never trust a generator unless I verify that it's set correctly and meter it myself. There's too much at stake to trust someone who doesn't get it.

Also, I hate the new computer controlled generators. There's too many "features" that can take down my show. Give me an old school, low-tech, rock-solid genny every time and I'll be happy.
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Brian Adams
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Jeff Lelko

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Re: Today's cautionary tale
« Reply #18 on: March 02, 2018, 06:30:44 pm »

Yep, I ran into a similar situation again just now.  Two 120v circuits/receptacles meter just fine, but a third metered at 213v.  Always check the power before plugging in!
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Mike Sokol

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Re: Today's cautionary tale
« Reply #19 on: March 02, 2018, 06:56:47 pm »

Yep, I ran into a similar situation again just now.  Two 120v circuits/receptacles meter just fine, but a third metered at 213v.  Always check the power before plugging in!

True that!!!
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Mike Sokol
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Re: Today's cautionary tale
« Reply #19 on: March 02, 2018, 06:56:47 pm »


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