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Author Topic: Grouding issues and large pools of water  (Read 11001 times)

William Nexsen

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Re: Mic level isolation transformer
« Reply #30 on: November 02, 2005, 04:10:45 pm »

Agreed, Bink, except this situation needs to be idiot-proof.  As the memory of this event fades, someone will, in time, move or replace the mike/xformer/pin-1-lifted-cable and discover that it was really all unnecessary and replace it with an off-the-shelf mike cable and skip the isolation xformer.  Everything will be fine until somewhere a fault develops, and another preacher gets killed.
I'm sending a copy of the article to all my clients who dunk along with a recomendation they use only a wireless in the font and the reasoning behind this.
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glasgowsoundman

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Re: Mic level isolation transformer
« Reply #31 on: November 02, 2005, 04:41:31 pm »

Michael 'Bink' Knowles wrote on Wed, 02 November 2005 20:52

Mike McCloskey wrote on Wed, 02 November 2005 12:42

I will bet that many churches will review their configuration  for baptisary mic's in light of this unfortunate accident. Many will assume that since they aren't using phantom power that all is OK (obviously a misnomer).

But it appears that the only fully safe solution would be the wireless mic on a boom. A second would be a hanging condensor choir mic, well out of reach.

Am I missing something?


At least one more safe solution to the problem would be a wired dynamic mic connected to the mixer through an isolation transformer with pin 1 not connected and its housing not grounded.

-Bink



Feels weird to quote myself, but another solution would be to alter the format of the baptisms.

http://srforums.prosoundweb.com/index.php/m/84698/6165/?SQ=a 2abc79b3e6910a4881776a121f63e09#msg_84698

Regards,

Duncan
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Duncan Hutchison
Technical Team Deputy Leader
Sound & Recording Engineer
Destiny Church Glasgow
1120 Pollokshaws Road
Glasgow
G41 3QP
Scotland
UK
www.destiny-church.com

Preston Edwards

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Re: Grouding issues and large pools of water
« Reply #32 on: November 02, 2005, 05:03:15 pm »

I've been a lurking member here for a few months but just haven't posted much.  Embarassed

I am a college student at Baylor University and was present at this church on Sunday when it happened. While a terrible tragedy no doubt, I have had numerous calls and e-mails from churches that I have done A/V work for wanting to know what they can do to make sure this doesn't happen at their place of worship. This is a good thing, as people are becoming more aware as to the dangers of improperly grounded systems and wired components next to water.

As many have said in this thread, use a lapel wireless mic if you're ever in this situation. If one's not available, make sure the mic you're using is positioned so that it cannot come into contact with the water or the person in the water. The mic in this case was much too close and was too easily manipulated to be anywhere near safe.

As many have also said, in my experience as Director of Media at a large church in San Antonio, churches typically cut corners and have to deal with volunteers, etc., and so this type of thing, while unfortunate, has the potential to happen more often than it does. In this case it was a pastor, but it could have been anyone that triggered conditions exposing the fault.

As most of us have heard: Lose a neutral, lose some equipment; lose a ground, lose a life.

My heart goes out to the family and to the church as they struggle with how to proceed in the future.
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Preston Edwards
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Trinity Baptist Church of San Antonio

John Roberts {JR}

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Re: Grouding issues and large pools of water
« Reply #33 on: November 02, 2005, 05:09:49 pm »

Mike McCloskey wrote on Wed, 02 November 2005 14:42

I will bet that many churches will review their configuration  for baptisary mic's in light of this unfortunate accident. Many will assume that since they aren't using phantom power that all is OK (obviously a misnomer).

But it appears that the only fully safe solution would be the wireless mic on a boom. A second would be a hanging condensor choir mic, well out of reach.

Am I missing something?


Agreed, as previously stated a wireless mic seems eminently appropriate for this situation and this has happened before.

Water needs to be respected as a low impedance path for hazardous currents, which for the record we are still speculating about the source of.

JR
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William Nexsen

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Re: Grouding issues and large pools of water
« Reply #34 on: November 02, 2005, 05:53:07 pm »

In the quest for an idiot-proof solution, one thought might be to install a mike jack in a location convenient to the bapistry incorporating Bink's suggestion of transformer isolation that's permanently installed out of sight behind the mike jack.  It isn't completely bulletproof, but would probably work until the church redesigned their baptistry...
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John Roberts {JR}

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Re: Grouding issues and large pools of water
« Reply #35 on: November 02, 2005, 06:31:27 pm »

william wrote on Wed, 02 November 2005 16:53

In the quest for an idiot-proof solution, one thought might be to install a mike jack in a location convenient to the bapistry incorporating Bink's suggestion of transformer isolation that's permanently installed out of sight behind the mike jack.  It isn't completely bulletproof, but would probably work until the church redesigned their baptistry...


I recall reading a book years ago called something like the "science of failure" (?) I don't recall the exact title but it was basically a study of why systems or plans failed and it comes down to "factors" that aren't properly evaluated and considered. The problem with making a system "idiot proof" is that the idiots evolve and find ways to get around your idiot proofing.

I still think wireless mics, as cheap as they are these days, are pretty hard to become a shock hazard unless you hold one over your head while standing on a hill top during a thunderstorm. It's not about mitigating the mistakes you can imagine but protecting against the ones you haven't.

JR
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DTownSMR

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Re: Grouding issues and large pools of water
« Reply #36 on: November 03, 2005, 01:44:50 pm »

I'll show my ignorance here. Would placing the mixing desk (or whatever is connected to the jacks on the chancel/stage) on a GFI circuit prevent such a tragedy?
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in His service,
Scott

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Re: Grouding issues and large pools of water
« Reply #37 on: November 03, 2005, 02:05:18 pm »

NO.  The GFCI would kill power to the mixer. It would NOT help if the power was coming from the other side, such as a fault in the baprisry water heater...
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Mark Smith

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Re: Grouding issues and large pools of water
« Reply #38 on: November 03, 2005, 02:34:55 pm »

Mike is correct, but are you sure it would kill the power to the mixer?  I thought the gfci looked at the difference in the phase and neutral current, not the ground current itself (if the fault came from another source it may not see it).  I could be wrong on this.
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Re: Grouding issues and large pools of water
« Reply #39 on: November 03, 2005, 03:17:45 pm »

I meant if the fault were on the mixer's side (power to the SR equipment.)making the mic 'hot' and the pool the ground. Not if the pool was acting as the 'hot' and the mic was the ground.

Not an electrician, don't play one on TV, so open to correction!
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ProSoundWeb Community

Re: Grouding issues and large pools of water
« Reply #39 on: November 03, 2005, 03:17:45 pm »


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