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Author Topic: Open AC Ground Problem  (Read 9619 times)

Canute J. Chiverton

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Open AC Ground Problem
« on: August 19, 2013, 11:07:53 am »

You arrive at a venue to do a gig only to find that the Circuit Outlet designated for your use has an Open Ground.  There is no other place nearby where you can plug in or run an Extension Cord.  There is no qualified personnel present to remedy the situation.  What course of action do you take?
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John Roberts {JR}

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Re: Open AC Ground Problem
« Reply #1 on: August 19, 2013, 11:44:52 am »

Use a power strip with GFCI built in... The GFCI works similarly to safety ground by shutting down the power if current leakage is detected.

While ground and GFCI is better... The gear does not need the ground to operate, that is a human safety issue.

JR

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Canute J. Chiverton

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Re: Open AC Ground Problem
« Reply #2 on: September 18, 2013, 12:48:24 pm »

Use a power strip with GFCI built in... The GFCI works similarly to safety ground by shutting down the power if current leakage is detected.

While ground and GFCI is better... The gear does not need the ground to operate, that is a human safety issue.

JR
I did a site Survey yesterday for an upcoming Wedding and found an Open Ground outside where the Ceremony System is going to be and on the stage inside, it tested  as Hot/Neutral Reversed. The venue claimed that they have other means of Power to the Stage.  Probably an 18Ga Yellow Extension Cord. I did not make a beef about it but I am meeting with the Client tomorrow and I will address it with them at that time.  I have to respect the fact that I am not the Venue's Client so they may not want to pay me heed.  I'll let my Client handle it.
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John Roberts {JR}

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Re: Open AC Ground Problem
« Reply #3 on: September 18, 2013, 01:27:35 pm »

You can buy outlet strips with GFCI built in...  If we could depend on outlet grounds, they wouldn't have invented GFCI...

Use the force (technology) Luke...

JR
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Mike Sokol

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Re: Open AC Ground Problem
« Reply #4 on: September 18, 2013, 02:27:25 pm »

You can buy outlet strips with GFCI built in...  If we could depend on outlet grounds, they wouldn't have invented GFCI...

That's correct, but make sure you're all aware that a "Surge Strip" is NOT a "GFCI Outlet". Surge strips work by shunting overvoltage conditions to the safety ground conductor, so if you don't have a proper ground established to begin with, they will do NOTHING to protect you. In fact, without a proper safety ground a Surge Strip can introduce additional shock hazards.

On the other hand, a GFCI Strip doesn't require a safety ground at all to protect you from shock. They work by comparing the outgoing current with the incoming current. Any current difference more than 5 mA will cause them to trip. However, if you lose the neutral conductor for any reason, a standard GFCI will have no AC power to trip themselves. That's why the latest class of portable GFCI breakers have a "set" button that needs to be pressed every time power is restored to the breaker. This fail-safe function is like a dead-man's switch so you don't get electrocuted from what appears to be a dead circuit.

I'm going to post my article about GFCI theory on the PSW online daily. Stay tuned. 

Something like this from Home Depot should do the job, and it costs less than $30.

http://www.homedepot.com/p/Shock-Shield-2-ft-12-3-Ground-Fault-Circuit-Interrupter-Extension-Cord-90214-6HD/100140196#.UjnuuT9MsVc

Mike Sokol
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Mike Sokol
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Brian Jojade

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Re: Open AC Ground Problem
« Reply #5 on: September 19, 2013, 12:08:55 pm »

You can buy outlet strips with GFCI built in...  If we could depend on outlet grounds, they wouldn't have invented GFCI...

Use the force (technology) Luke...

JR

GFCI offers different protection than ground.  If you touch a hot wire and then a properly grounded connection, you'll get a shock.  If you do the same thing with a GFCI circuit, it will see that the path is not going through the neutral line and trip. If you didn't have GFCI, the ground connection in that fault scenario makes it MORE dangerous.
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Brian Jojade

Canute J. Chiverton

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Re: Open AC Ground Problem
« Reply #6 on: September 19, 2013, 12:23:01 pm »

GFCI offers different protection than ground.  If you touch a hot wire and then a properly grounded connection, you'll get a shock.  If you do the same thing with a GFCI circuit, it will see that the path is not going through the neutral line and trip. If you didn't have GFCI, the ground connection in that fault scenario makes it MORE dangerous.
This may be a stupid question but I am not an Electrical Engineer nor do I pretend to be one. I rather rely on one of you experts.  Will a Furman Conditioner (Which is what I have in my Rack http://www.furmansound.com/product.php?div=01&id=PL-PLUSC) do the same job as the GFCI (The Home Depot Link above)? I don't have a problem getting the GFCI I think $30.00 is cheap.
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John Roberts {JR}

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Re: Open AC Ground Problem
« Reply #7 on: September 19, 2013, 12:39:51 pm »

This may be a stupid question but I am not an Electrical Engineer nor do I pretend to be one. I rather rely on one of you experts.  Will a Furman Conditioner (Which is what I have in my Rack http://www.furmansound.com/product.php?div=01&id=PL-PLUSC) do the same job as the GFCI (The Home Depot Link above)? I don't have a problem getting the GFCI I think $30.00 is cheap.
No, if it did it would list that as a feature and require a reset button for the GFCI.  It looks like a simple voltage spike clamp.

JR

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Jay Barracato

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Re: Open AC Ground Problem
« Reply #8 on: September 19, 2013, 12:51:34 pm »

This may be a stupid question but I am not an Electrical Engineer nor do I pretend to be one. I rather rely on one of you experts.  Will a Furman Conditioner (Which is what I have in my Rack http://www.furmansound.com/product.php?div=01&id=PL-PLUSC) do the same job as the GFCI (The Home Depot Link above)? I don't have a problem getting the GFCI I think $30.00 is cheap.

I have a couple of simple plug in GFCI's that are the same brand as the cable Mike linked to. You simply plug them in to the edison outlet and then plug your power cables into them. They are the simplest way I have found to add GFCI to an existing circuit.

http://www.lowes.com/pd_145275-33536-30339011_0__?productId=1135923&Ntt=gfci
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Jay Barracato

Mike Sokol

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Re: Open AC Ground Problem
« Reply #9 on: September 19, 2013, 01:44:09 pm »

No, if it did it would list that as a feature and require a reset button for the GFCI.  It looks like a simple voltage spike clamp.

JR

Correct.... The Furman is a spike/noise clamp unit, definitely NOT a GFCI, and it will do nothing to prevent electric shock if powered from an ungrounded outlet.
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Mike Sokol
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Canute J. Chiverton

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Re: Open AC Ground Problem
« Reply #10 on: September 19, 2013, 02:24:35 pm »

Correct.... The Furman is a spike/noise clamp unit, definitely NOT a GFCI, and it will do nothing to prevent electric shock if powered from an ungrounded outlet.

No, if it did it would list that as a feature and require a reset button for the GFCI.  It looks like a simple voltage spike clamp.

JR
  I do thank you chaps for the information. My life is more important to me than the Gig even if it is over $1K.  If things don't get fixed before I perform I am willing to walk away.  My Agent may not be too happy about it but I will. I do not want to be blamed for any mishaps.  I sure do appreciate the knowledge.
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Mike Sokol

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Re: Open AC Ground Problem
« Reply #11 on: September 20, 2013, 04:34:54 pm »

GFCI offers different protection than ground.  If you touch a hot wire and then a properly grounded connection, you'll get a shock.  If you do the same thing with a GFCI circuit, it will see that the path is not going through the neutral line and trip. If you didn't have GFCI, the ground connection in that fault scenario makes it MORE dangerous.

As promised, here's my article on how GFCI's work. It's a clever device - that can save your life (hey, that's pretty good rap, I think). http://www.prosoundweb.com/article//no_shock_zone_understanding_and_preventing_electrical_damage_and_worse/
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Mike Sokol
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Stan Sakamoto

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Re: Open AC Ground Problem
« Reply #12 on: October 08, 2013, 02:38:39 am »

You arrive at a venue to do a gig only to find that the Circuit Outlet designated for your use has an Open Ground.  There is no other place nearby where you can plug in or run an Extension Cord.  There is no qualified personnel present to remedy the situation.  What course of action do you take?

I had the same problem working as an audio engineer overseas in Europe and Japan. To be prepared for open ground problems I made plugs with the hot and neutral prongs missing with only the ground pin intact. Then connected the plugs to a long 10 gauge wire in each end, only with a ground prong. I would then connect the first end in the power strip that's connected to the outlet with the open ground and the other end to a circuit that has a good ground on the same circuit. Because there's no prongs for the hot and neutral the only thing that's connected to the circuit is the ground. By doing this it's a emergency fix for an outlet with the open ground. It is very important to make sure to use a circuit on the same phase to avoid ground loops. I would also take it a step further and wire up some plugs with the hot and neutral reversed in case I had a problem with reverse polarity.
I also had a grounding cable reel with a grounding rod at every job site.

Hope this helps you, good luck!
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