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Author Topic: Can Repeated Distro Trips Harm Audio Gear?  (Read 6745 times)

Mike Karseboom

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Can Repeated Distro Trips Harm Audio Gear?
« on: July 01, 2014, 01:34:34 am »

I was a subcontractor on a gig this weekend using  an undersized generator (Whisperwatt 25) and we had repeated losses of power for a variety of reasons.


First due to lack of timely delivery of the 6/4 feeder and spider box, we were running FOH, monitors, and backline off the two 20A convenience GFCI outlets.  Power was delivered through three 100 foot 12/3 SOOW cables.


The first problem seemed to be with the small (1.5 VA) APC UPS unit that was inline before the DR260 system processors and the FOH digital board.  Neither of those devices pulled much current so the UPS was in no way overloaded.  Yet that UPS would squeal with an alarm frequently which was sometimes followed by a shutdown of the UPS.  I am not sure what the alarm meant as it was a continuous squeal and historically the only alarm I have hear from it is the beeping sound it makes when mains power is not present and the battery is engaged.  After a couple of shutdowns that alarm noise became apparent and the battery backup was removed from the circuit.


Then it seemed there was just too much current draw for the GFCI outlets.  The breakers did not trip but the GFCI's did.  After three or four of those episodes the GFCI's seemed to be "fried" as they would no longer reset. 


Fortunately about this time the feeder cable and spider box arrived but unfortunately it was a pretty beat up spider box and only 3 of the GFCI outlets actually worked.  When they tried to runs some lights as well (old parr cans)  there were tripping issues that seemed to involve GFCI trips rather than breaker trips.


Anyway it goes on for a bit but the upshot is that the amps, processors, mixer, and powered monitors were subjected to numerous power resets.  I am wondering if that can be damaging to this equipment?
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Steve M Smith

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Re: Can Repeated Distro Trips Harm Audio Gear?
« Reply #1 on: July 01, 2014, 01:52:00 am »

As far as the individual pieces of equipment are concerned, they are just being turned off and on as normal.  It makes no difference if it is via the equipment's on off switch or by the whole power going off and back on again.

Personally, I would just turn off the amps before putting the power back on.


Steve.
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jasonfinnigan

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Re: Can Repeated Distro Trips Harm Audio Gear?
« Reply #2 on: July 01, 2014, 01:58:23 am »

I would get another generator rental company I think.

Anyway if the GFCIs kept triping it means somewhere there is a voltage leak on the neutral conductor. A GFCI outlet wants to see the same voltage it's that its sending out on the hot leg, coming back on the neutral leg. if its not it will trip as there is a loss which could be from someone getting shocked.
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Mike Sokol

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Re: Can Repeated Distro Trips Harm Audio Gear?
« Reply #3 on: July 01, 2014, 06:29:31 am »

I would get another generator rental company I think.

Anyway if the GFCIs kept triping it means somewhere there is a voltage leak on the neutral conductor. A GFCI outlet wants to see the same voltage it's that its sending out on the hot leg, coming back on the neutral leg. if its not it will trip as there is a loss which could be from someone getting shocked.

Small correction, actually a "current leak" causes GFCIs to trip. Most likely there was a paralleled neutral and grounding conductor (secondary G-N bond). That splits the neutral return current, which now no longer balances with the outgoing line current. GFCIs don't work by sensing ground... they work by sensing a difference between line and neutral currents. Internally they have a current transformer wrapped around the line and neutral with a trigger circuit to trip the spring loaded contact. No ground wire on the GFCI is needed to make them trip.

Below is a graphic I made of the fault current flow that trips a GFCI. Note that the GFCI sensing circuit isn't connected to the EGC/ground at all. It's only looking for an imbalance between line and neutral, sort of like a balanced high voltage mic preamp input.
« Last Edit: July 01, 2014, 09:33:48 am by Mike Sokol »
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Ray Aberle

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Re: Can Repeated Distro Trips Harm Audio Gear?
« Reply #4 on: July 01, 2014, 10:35:49 am »

I would get another generator rental company I think.

This. Right. Here.

If the rental company did the delivery for you, then they should have brought the feeder/box at the same time, set it all up, fired it up, and verified full operation of everything. (That's the nice thing about a governmental inspection; inspector is going to check things like GFCI - and, well, basic circuit operation.)

If you picked it up and did the drop yourself, the person doing the pickup should have grabbed the feeder/box. And when he did not, the rental company should have suggested that it go with it.

If you rented the gennie from one place and the cable/box from another, a reputable gennie rental place would also want to have you bring your cable and box to verify that it works acceptably with the generator. Common sense, I mean, that would have detected at LEAST the 3 non-functional circuits from the get-go.

Hopefully the festival promoter has learned their lesson about getting the right sized generator, and here's an opportunity to bring it to their attention, thus establishing yourself as -- well, maybe a bit more qualified to help them produce their event. You can easily just approach them with, "I can help with any questions you might have next year about power, generators, and grounding, so here's my card, and please feel free to call at any time." Who knows, they may already be considering a new event provider, and will notice you also run sound.

-Ray
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Mike Karseboom

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Re: Can Repeated Distro Trips Harm Audio Gear?
« Reply #5 on: July 01, 2014, 11:54:19 am »

This. Right. Here.

If the rental company did the delivery for you, then they should have brought the feeder/box at the same time, set it all up, fired it up, and verified full operation of everything. (That's the nice thing about a governmental inspection; inspector is going to check things like GFCI - and, well, basic circuit operation.)

-Ray


This Whisperwatt 25 was purchased by the consortium of small time promoters that lease the outdoor venue and put on 3-4 shows a year.  It is out in the sticks and in a way it is pretty cool that they have purchased this high quality unit.  The generator is in good condition. 


The problem was the stage and lighting provider who also said he would bring the distro and feed cable for audio.  While he did construct a very good 30'wide  x 20' deep x 5' high  covered stage, everything was done late so instead of setting up sound gear at 5:00PM we started setting up at 1:00AM. By 3:30AM when we were ready to plug into the spiderbox we realized the feeder cable was going directly into his multi channel light dimmer box. 


It is a long and sad story spanning over two days of festival  where various partial and inadequate solutions were implemented.  Lots of temporary halts of performances and one act that just did not really get their set.  By the evening of the second night we finally had a stable situation with two separate feeder cables and a spider box just for audio.  Even then that spider box was iffy as only 3 of the GFCI outlets worked.  Also due to the small size of the generator and the fact that stage lighting was from parr cans, the  lights had to be run with just 1/4 of them in service and with no gels.  I was a sub to the main audio guy so it was really not my place to demand anything.  But the lame service provided by the stage contractor sure caused me to loose a lot of sleep and experience a lot of stress during the show. 


In the end it was mostly the promoters, performers and the folks involved with production that were feeling the pain.  The crowd was pretty laid back and seemed to enjoy the weekend without a second thought to the power drop outs.


Why is it always about the POWER??  It is the first thing I ask about when someone offers me a gig and I give detailed minimum requirements  for good results.  Regardless of the assurances  that everything is taken care of, it always ends up being about the POWER!
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--Mike
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Ray Aberle

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Re: Can Repeated Distro Trips Harm Audio Gear?
« Reply #6 on: July 01, 2014, 12:12:07 pm »

This Whisperwatt 25 was purchased by the consortium of small time promoters that lease the outdoor venue and put on 3-4 shows a year.  It is out in the sticks and in a way it is pretty cool that they have purchased this high quality unit.  The generator is in good condition. 

The problem was the stage and lighting provider who also said he would bring the distro and feed cable for audio.  While he did construct a very good 30'wide  x 20' deep x 5' high  covered stage, everything was done late so instead of setting up sound gear at 5:00PM we started setting up at 1:00AM. By 3:30AM when we were ready to plug into the spiderbox we realized the feeder cable was going directly into his multi channel light dimmer box. 

It is a long and sad story spanning over two days of festival  where various partial and inadequate solutions were implemented.  Lots of temporary halts of performances and one act that just did not really get their set.  By the evening of the second night we finally had a stable situation with two separate feeder cables and a spider box just for audio.  Even then that spider box was iffy as only 3 of the GFCI outlets worked.  Also due to the small size of the generator and the fact that stage lighting was from parr cans, the  lights had to be run with just 1/4 of them in service and with no gels.  I was a sub to the main audio guy so it was really not my place to demand anything.  But the lame service provided by the stage contractor sure caused me to loose a lot of sleep and experience a lot of stress during the show. 

In the end it was mostly the promoters, performers and the folks involved with production that were feeling the pain.  The crowd was pretty laid back and seemed to enjoy the weekend without a second thought to the power drop outs.

Why is it always about the POWER??  It is the first thing I ask about when someone offers me a gig and I give detailed minimum requirements  for good results.  Regardless of the assurances  that everything is taken care of, it always ends up being about the POWER!

I hope that you were paid well for your hellish hours! I mean I worked my guys like crazy this past weekend, but when they're getting $800-$900 for a couple three days of work, they remain upbeat. :)

I think the lesson here is for the audio guy who hired you to purchase his own 6/4 (or even 4/4; opinions vary, but the NEC (I seem to recall) specs that 6/4 is good for only up to 45a/conductor?) and a spider box. That would be an investment of-- well, a full 100' roll at Homo Depot is like $450. Connectors can be readily found online for under $60 total. A used spider box for $500 or less-- so maybe a grand and he can be assured that feeder and distro will be solid in the future?

Sounds like a cheap insurance policy to me! :)

-Ray
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jasonfinnigan

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Re: Can Repeated Distro Trips Harm Audio Gear?
« Reply #7 on: July 01, 2014, 01:59:45 pm »


This Whisperwatt 25 was purchased by the consortium of small time promoters that lease the outdoor venue and put on 3-4 shows a year.  It is out in the sticks and in a way it is pretty cool that they have purchased this high quality unit.  The generator is in good condition. 

IMO Owning a generator is not the best way. Renting usually comes out ahead even if you are doing an event every week needing it hauling, and maintenance are very expensive for generators, on the other hand renting is cheap around $100-$150 for a 30Kw + Generator. 3-4 times a year really probally means the generator isn't being run enough, they need to be run once a month in my opinion to keep the coils good. they also need a lot of up keep & maintenance.
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g'bye, Dick Rees

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Re: Can Repeated Distro Trips Harm Audio Gear?
« Reply #8 on: July 01, 2014, 02:11:34 pm »

3-4 times a year really probally means the generator isn't being run enough, they need to be run once a month in my opinion to keep the coils good. they also need a lot of up keep & maintenance.

I call BS.
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jasonfinnigan

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Re: Can Repeated Distro Trips Harm Audio Gear?
« Reply #9 on: July 01, 2014, 02:20:29 pm »

I call BS.
You might call it BS but generators can lose their magnetivity and will not properly generate power.
« Last Edit: July 01, 2014, 03:00:38 pm by JasonFinnigan »
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Re: Can Repeated Distro Trips Harm Audio Gear?
« Reply #9 on: July 01, 2014, 02:20:29 pm »


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