Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums > AC Power and Grounding

Open AC Ground Problem

(1/3) > >>

Canute J. Chiverton:
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?

John Roberts {JR}:
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

Canute J. Chiverton:

--- Quote from: John Roberts {JR} 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

--- End quote ---
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.

John Roberts {JR}:
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

Mike Sokol:

--- Quote from: John Roberts {JR} 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...

--- End quote ---

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

Navigation

[0] Message Index

[#] Next page