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Author Topic: Should I ground the Stage on Asphalt?  (Read 1263 times)

Mike Karseboom

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Should I ground the Stage on Asphalt?
« on: July 01, 2014, 01:06:41 am »

I have an annual event where a metal stage is on asphalt and the local utility company ties into some overhead power lines and provides a panel mounted distro for stage and FOH power.   The distro has about 8 duplex edison outlets  for 120V service with 20A breakers for each duplex.


After all the reading on this fabulous forum about grounding and bonding, I am now wondering whether the metal stage should  be bonded to the ground at the distro panel?  I know this is not currently being done.



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jasonfinnigan

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Re: Should I ground the Stage on Asphalt?
« Reply #1 on: July 01, 2014, 01:27:54 am »

I have an annual event where a metal stage is on asphalt and the local utility company ties into some overhead power lines and provides a panel mounted distro for stage and FOH power.   The distro has about 8 duplex edison outlets  for 120V service with 20A breakers for each duplex.


After all the reading on this fabulous forum about grounding and bonding, I am now wondering whether the metal stage should  be bonded to the ground at the distro panel?  I know this is not currently being done.

If the stage is metal yes, it should be. anything that can be conductive should be. Wood stages of course can't be.
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Mark Cadwallader

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Re: Should I ground the Stage on Asphalt?
« Reply #2 on: July 01, 2014, 01:31:30 am »

And as a follow-up question, what guage wire is appropriate for that purpose? 

Which leads to the next question:  Do I also need to bond the lighting truss/ground support to earth (the distro panel), if the truss is not integrated into the stage structure?

Do all of the segments of a modular stage (e.g., Wegner Versastage) need to be bonded together?

I apologize for any thread-jacking with my questions. Mark C.
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jasonfinnigan

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Re: Should I ground the Stage on Asphalt?
« Reply #3 on: July 01, 2014, 01:55:25 am »

And as a follow-up question, what guage wire is appropriate for that purpose? 

Which leads to the next question:  Do I also need to bond the lighting truss/ground support to earth (the distro panel), if the truss is not integrated into the stage structure?

Do all of the segments of a modular stage (e.g., Wegner Versastage) need to be bonded together?

I apologize for any thread-jacking with my questions. Mark C.

For wire size it depends on your over all power draw. I would use either 10, 8, 6, 4 depending on what you are using for your feeder and it's amperage, it's normal for the ground to be smaller than the conductors.
The Wegner Versastage will bond to each other already as they interlock.
Yes, lighting trusses should also be grounded as well.



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Mike Sokol

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Re: Should I ground the Stage on Asphalt?
« Reply #4 on: July 01, 2014, 06:21:19 am »

For wire size it depends on your over all power draw. I would use either 10, 8, 6, 4 depending on what you are using for your feeder and it's amperage, it's normal for the ground to be smaller than the conductors.
The Wegner Versastage will bond to each other already as they interlock.
Yes, lighting trusses should also be grounded as well.

Yes to bonding the stage to the incoming ground (EGC - Equipment Grounding Conductor)

Yes to bonding the lighting truss to the EGC as well.

The size of the ground/bond wire required is a function of both max circuit breaker capacity and lightning protection. So you should match whatever size ground wire is coming in from the POCO if possible, but probably not smaller than 8 gauge for lightning protection. Also, avoid sharp turns with this bonding wire if possible (no right angle bends) since that will promote lightning side flashes. That's in the amateur radio manual, and those guys worry about lightning a lot. 

Yeah, we don't like to think about lightning, but by definition these shows are outside in the summer and typically the highest structure in a flat field. Even if you evacuate the band and stage crew when lightning rolls in (you do, don't you), your equipment will stand a much better chance of surviving a nearby lightning strike if the stage and lighting trusses are properly bonded to earth.
« Last Edit: July 01, 2014, 07:27:11 am by Mike Sokol »
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Stephen Swaffer

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Re: Should I ground the Stage on Asphalt?
« Reply #5 on: July 01, 2014, 08:41:11 am »

Typically a POCO will bring in 3 wires and an overhead drop (I am assuming since it is temporary) will usually be no smaller than #4 AL.  Someone should be installing/connecting to a grounding electrode (ground rod/s) at the service disconnect?

To ground rods, NEC reqires no that #6-and #6 would need to be used for either a 100 A or 200 A temp service.

EGC is determined by NEC 250.122 depending on breaker feeding equipment  as Mike said.  This should cover most any distro you run across.

15 amp breaker-#14
20 amp breaker-#12
30 amp to 60 amp-#10
70 amp to 100 amp-#8
over 100 amp to 200 amp-#6

Thought about lightning a lot around here yesterday!


 

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Mike Karseboom

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Re: Should I ground the Stage on Asphalt?
« Reply #6 on: July 01, 2014, 10:38:24 am »

If the stage is metal yes, it should be. anything that can be conductive should be. Wood stages of course can't be.


Is there some particular section of the NEC or OSHA  regulations that I can refer to when requesting that the power company ground the stage when they set up the distro panel? 


It is surprising how often you get push back when asking for fairly simple things that could be very important safety wise but might involve a little more work on the installer's part.  I would like to have some code to support my request. 


Or maybe they figure grounding anything that needs grounding to the distro is my job and they want to make a clear cut boundary between their "system" and the rest of the world, perhaps for liability reasons.
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Tim McCulloch

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Re: Should I ground the Stage on Asphalt?
« Reply #7 on: July 01, 2014, 11:04:58 am »


Or maybe they figure grounding anything that needs grounding to the distro is my job and they want to make a clear cut boundary between their "system" and the rest of the world, perhaps for liability reasons.

This. Grounding someone else's stage isn't the power company's job.
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Mike Sokol

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Re: Should I ground the Stage on Asphalt?
« Reply #8 on: July 01, 2014, 01:13:46 pm »

This. Grounding someone else's stage isn't the power company's job.

Correct. And it's not the generator rental company's job to "ground" your stage either. They're just supposed to drive a ground rod for the generator and make sure the genny's Ground and Neutral bus connections are bonded to it. (Or at least they're supposed to)

And remember that you're not "grounding" the stage... you're bonding it to the incoming EGC (Equipment Grounding Conductor) from your power distro, or directly bonding it to the GEC (Grounding Electrode Conductor) which is your genny's ground rod. See below for basic definitions. 

GEC - Grounding Electrode Conductor. The phrase "grounding electrode" is the ground rod (or other thing that is stuck into the dirt). So the GEC is the wire that goes from the service point to the dirt.
   
EGC - Equipment Grounding Conductor. This has to do with equipment. This is the green wire you attach to the external metal parts of equipment, and the one that provides a path for fault current to flow back to the source. I have heard it called the "safety ground."

frank kayser

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Re: Should I ground the Stage on Asphalt?
« Reply #9 on: July 01, 2014, 02:06:29 pm »

Correct. And it's not the generator rental company's job to "ground" your stage either. They're just supposed to drive a ground rod for the generator and make sure the genny's Ground and Neutral bus connections are bonded to it. (Or at least they're supposed to)

And remember that you're not "grounding" the stage... you're bonding it to the incoming EGC (Equipment Grounding Conductor) from your power distro, or directly bonding it to the GEC (Grounding Electrode Conductor) which is your genny's ground rod. See below for basic definitions. 

GEC - Grounding Electrode Conductor. The phrase "grounding electrode" is the ground rod (or other thing that is stuck into the dirt). So the GEC is the wire that goes from the service point to the dirt.
   
EGC - Equipment Grounding Conductor. This has to do with equipment. This is the green wire you attach to the external metal parts of equipment, and the one that provides a path for fault current to flow back to the source. I have heard it called the "safety ground."


Thank you. Thank YOU. THANK YOU! And all folks part of this thread for these important instructions and clarifications!


So... Would this be adequate?


Metal quad box with mounting "tabs" attached to aluminumm stage, two edison outlets, both bonded to the box and the EGC of 10/3 SEOOW feeder from 20a GFCI outlet?


That wouldn't satisfy GEC connection.   Can I use say stranded 8ga screwed to the stage, and clamped to the ground rod?
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