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Author Topic: Safety updates for poor mans distro  (Read 5386 times)

Scott Holtzman

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Safety updates for poor mans distro
« on: June 28, 2016, 02:31:58 AM »

I closely follow the safety discussions and it is clearly time for me to update my simple poor mans distro's to include integrated GFCI protection.  In my search for products I found the below item that looks to sense a ground fault and will trip the standard shunt style breaker.  Opinions?

http://www.nssltd.com/pdfs/Layout%20for%20sensing%20module%20cutsheet.pdf

The second item is I want to build a very small 50amp distro in a pelican style case with an exterior inlet connector.
Does this panel mount breaker raise any alarms?  It has a nice form factor and only needs a simple hole drilled in the panel.
Quote
Specifications:
Amps: 20
Maximum Resistance in ohms: .006
Trip time @ 200% of Rating: 6 to 30 seconds
Input Power: 125 VAC / 250 VAC / 50 VDC.
Dielectric Strength: 1500 VAC / 1 minute.
Interrupt Capacity: 125 VAC x 1000 A, 250 VAC x 2000 A.
Insulation Resistance: > 100 M
Calibration:
25 C-100% of rated current-continuously carried.
25 C-between 101% to 145%-may trip or not.
25 C-150% of rated current- trip within 1 hour.
25 C-200% of rated current-trip within 1 minute.
Contact Endurance: 125 VAC x 150% of rated current - 500 cycles
Endurance: 1,000 times at least
Calibration: Breaker will continuously carry 100% of rated load. It may trip between 101% and 144% of rated load, but must trip at 145% at 25º C.
Dielectric Strength: Over 1,500 volts RMS.
Max. Operating Voltages: 50VDC, 250VAC
Interrupt Capacity: 2,000 Amps, at 50 VDC(1-30 amp Models) 1,000 Amps, at 250VAC (1-30 amp Models)
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Scott AKA "Skyking" Holtzman

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John Roberts {JR}

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Re: Safety updates for poor mans distro
« Reply #1 on: June 28, 2016, 12:47:17 PM »

It took a little googling to figure out what an ELCI is/does. It appears to come from the boating/marine field to deal with dodgy shore power and questionable boat wiring.

As far as I can tell the ELCI senses for current in the safety ground and trips for 30mA after 100mSec. So more current and slower action, to avoid nuisance trips. Not unlike how some swimming pool lights trip 5mA GFCI so use(d) a higher current version GFCI. 

Sensing for ground current seems redundant in addition to a GFCI for a basic one power drop system, BUT in sound reinforcement where a performer can get between two different power drops (FOH and backline), it is possible for a singer to get shocked by an energized mic without tripping a backline GFCI that only cares about backline line and neutral current.

I would have to look closer but i am not sure an ELCI will protect in this "hot mic" scenario. My understanding is that the ELCI breaker opens the line but keeps neutral and ground connected. 

My fancy uber-GFCI (that I abandoned as too exotic-expensive) used a 3 pole relay to disconnect line, neutral, "and" ground in case of a primary GFCI trip. In addition to the GFCI loop current sensing, I added a current sense in the ground leg, that would also disconnect all 3 relay poles in case of detecting ground current independent of the GFCI loop.

I do not know that UL would ever embrace opening up the safety ground, but in my judgement that is the only way to protect humans in the multiple power drop environment (or against RPBG). Note: my stinger cap ground approach would also protect from this hot mic or RPBG scenario (but is not UL approved?).

I like the idea of quad boxes loaded with GFCI outlets that can be spread around back-line. However a GFCI plugged into a RPBG outlet will energize the safety ground no matter the status of the GFCI loop. For that matter I do not know how an ELCI will behave in a RPBG scenario. 30mA of current in the ground will trip it's breaker but not open the hot ground.

Sorry for now it looks like NCVT remain your friend. GFCI drops will still protect against dodgy guitar amps.   

JR
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David Buckley

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Re: Safety updates for poor mans distro
« Reply #2 on: June 28, 2016, 06:22:10 PM »

Scott, I don't get why you cant use a standard GFCI, or a GFCI/breaker combo.

John - ground-to-ground shocks.  Yes, these are terrible things, and nothing off the shelf protects against them.
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Scott Holtzman

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Re: Safety updates for poor mans distro
« Reply #3 on: June 28, 2016, 07:43:53 PM »

Scott, I don't get why you cant use a standard GFCI, or a GFCI/breaker combo.

John - ground-to-ground shocks.  Yes, these are terrible things, and nothing off the shelf protects against them.

I have no been able to find a GFCI in a panel mount that will fit a cutout like in a Motion Labs panel. 

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Scott AKA "Skyking" Holtzman

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Stephen Swaffer

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Re: Safety updates for poor mans distro
« Reply #4 on: June 28, 2016, 09:43:04 PM »

It looks like Motion Labs uses Square D breakers-might be worth seeing if there is a gfci breaker that would be a direct replacement.  They do take more room so might not work.  The breaker specs look fine-low interupting capacity, but that should be fine in this application.
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Stephen Kirby

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Re: Safety updates for poor mans distro
« Reply #5 on: June 29, 2016, 12:19:09 AM »

Scott,  does your PMD have PowerCon or Edison outlets?  If it's Edison, simply replace the outlets with commercial outdoor GFCIs.  What this does do, and has been pointed out in several threads, is if you have a backline stringer, all the outlets will go off with any GFCI trip.  Thus shutting down most of the band.  It's better to have separate GFCIs in the quad boxes so that the old 2 wire Fender amp plugged in backwards doesn't shut off the bass and keys when the guitarist grounds themselves against something.

My PMD and regular 50A distro are PowerCon.  So are the connections to amp racks.  My first order of business (I'm out of the country right now) will be to put GFCIs in the backline stringer so the musicians are protected.  Then I'll work my way though the Edison feeds to powered monitors and powered tops.  Although since those are completely under my control, it's less of a concern.  The monitors are probably more important than the tops since they're on stage and people may touch them.
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Scott Holtzman

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Re: Safety updates for poor mans distro
« Reply #6 on: June 29, 2016, 01:33:05 AM »

Scott,  does your PMD have PowerCon or Edison outlets?  If it's Edison, simply replace the outlets with commercial outdoor GFCIs.  What this does do, and has been pointed out in several threads, is if you have a backline stringer, all the outlets will go off with any GFCI trip.  Thus shutting down most of the band.  It's better to have separate GFCIs in the quad boxes so that the old 2 wire Fender amp plugged in backwards doesn't shut off the bass and keys when the guitarist grounds themselves against something.

My PMD and regular 50A distro are PowerCon.  So are the connections to amp racks.  My first order of business (I'm out of the country right now) will be to put GFCIs in the backline stringer so the musicians are protected.  Then I'll work my way though the Edison feeds to powered monitors and powered tops.  Although since those are completely under my control, it's less of a concern.  The monitors are probably more important than the tops since they're on stage and people may touch them.

Yes,  both have Edison's.  The one in the pelican case is straight edison.  The one in the bottom of the sub rack I am adding powercons to go to the stage stringers.  I now see the issue that the breaker leaves the neutral and ground connected.  I liked the idea of having the breakers in a central location and not having the GHCF's on the stringers will avoid silly arguments with the talent.

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Scott AKA "Skyking" Holtzman

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Stephen Kirby

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Re: Safety updates for poor mans distro
« Reply #7 on: June 29, 2016, 03:50:43 AM »

While I intend to poke a NCVT at any vintage amps I see, the way I look at GFCIs on the stringer is that if some funky amp trips it, everyone else is still running fine.  The only "argument" with the talent concerns the one bad amp.

From previous threads I've worked out that even if someone has a shorted stinger cap in a two wire amp, if they get the power polarity right, it won't trip a GFCI.  So by verifying with an NCVT or letting the guy touch a mic and trip it and then flipping their ground switch and resetting the GFCI the rest of the show can go on.  If something totally shorts in the amp tripping the GFCI when the power polarity is correct, the amp isn't going to work anyway.
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Jonathan Johnson

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Re: Safety updates for poor mans distro
« Reply #8 on: June 29, 2016, 10:34:53 PM »

I have no been able to find a GFCI in a panel mount that will fit a cutout like in a Motion Labs panel.
Would something like this work?

http://www.homedepot.com/p/206001151

Basically, the same form factor as a typical GFCI receptacle, without the receptacle.
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Rob Spence

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Re: Safety updates for poor mans distro
« Reply #9 on: June 29, 2016, 11:45:09 PM »

Would something like this work?

http://www.homedepot.com/p/206001151

Basically, the same form factor as a typical GFCI receptacle, without the receptacle.

Called a dead front GFCI .


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Re: Safety updates for poor mans distro
« Reply #9 on: June 29, 2016, 11:45:09 PM »


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