ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: 1 2 3 [4] 5 6   Go Down

Author Topic: Should I ground the Stage on Asphalt?  (Read 2196 times)

Ron Hebbard

  • Jr. Member
  • **
  • Offline Offline
  • Posts: 62
Re: Should I ground the Stage on Asphalt?
« Reply #30 on: July 03, 2014, 02:43:23 am »

the cables you refer to are offten CCA (Copper-Clad Aluminum) cables which aren't suitable for this purpose. Also for temporary power sitituations where your grounding rod will likely be distant and near a gennie you really want a go insulator to protect it, those cables aren't rated for the voltage or amperage which may make it melt.

CCA is generally only good for high frequency or low power stuff. DC and AC power just aren't the same. also I believe the cables would be less than 20feet.

Hello again Jason!

Understood; I did write they aren't purpose designed for this application.
Clipped between sections of metal staging I suspect they'd handle a few hundred amps long enough to trip a breaker in a better than nothing situation.  In my neighbourhood they'll survive enough 12 VDC current to crank an icy cold car engine for a couple of minutes.
Quoting you: "CCA is generally only good for high frequency or low power stuff."
High frequency such as 12 VDC and low power such as 150 amps.

Let's not get too serious, or too silly, about this; I did begin with their not being purpose designed for the application.

Toodleoo!
Ron Hebbard
Logged

jasonfinnigan

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 334
Re: Should I ground the Stage on Asphalt?
« Reply #31 on: July 03, 2014, 03:20:36 am »

Hello again Jason!

Understood; I did write they aren't purpose designed for this application.
Clipped between sections of metal staging I suspect they'd handle a few hundred amps long enough to trip a breaker in a better than nothing situation.  In my neighbourhood they'll survive enough 12 VDC current to crank an icy cold car engine for a couple of minutes.
Quoting you: "CCA is generally only good for high frequency or low power stuff."
High frequency such as 12 VDC and low power such as 150 amps.

Let's not get too serious, or too silly, about this; I did begin with their not being purpose designed for the application.

Toodleoo!
Ron Hebbard

Using something like that or even suggesting people us that on a public forum is a liability issue.

Again DC and AC are very different. 12vdc is low power even if high amps.

If you get inspected your show might be called until it is fixed. as even though bonding isn't 100% require (though you could debate it is by the newer NEC codes) if they see something like that in use it will def get their attention.
Logged

Lyle Williams

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 314
Re: Should I ground the Stage on Asphalt?
« Reply #32 on: July 03, 2014, 06:00:23 am »

If there is a wooden deck that makes electrification of the legs unlikely (and conduction of hazardous voltages limited to a section of legs) I wouldn't bother grounding the stage legs.

Double pole GFCI/RCD appears to be a simpler safety solution.
Logged

Mike Sokol

  • Moderator
  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1266
  • Lead instructor for the No~Shock~Zone
    • No~Shock~Zone Electrical Safety
Re: Should I ground the Stage on Asphalt?
« Reply #33 on: July 03, 2014, 07:35:16 am »


Let's not get too serious, or too silly, about this; I did begin with their not being purpose designed for the application.

Toodleoo!
Ron Hebbard

Yes, let's not get too paranoid. The OP did note this is not an approved connector for this application, nor would it pass any inspection. However, I did know one band in the 70's who used car jumper cables to tie their power distro into the bar's service panel. I'm only noting it here to show that just because something DOES work, DOESN'T mean we should do it.

However, as I've noted before, I'm currently in communication with at least one person on the NEC grounding committee that's working on the 2017 code cycle. So if there's grounding/bonding ideas we think should be run by the committee for consideration, I can do that. However, I'm fairly certain that car jumper cables wouldn't make the cut. But I do plan to show them the data for my "bed-o-nails" grounding system for temporary stage and generator grounding.

But let's be careful about posting too much info on non-code ideas on this forum. There's way too much of that crap on the web as it is, and we're trying to be a source of correct info.

Jonathan Johnson

  • Church and H.O.W. Forums
  • Hero Member
  • *
  • Offline Offline
  • Posts: 1264
  • Southwest Washington (state, not DC)
Re: Should I ground the Stage on Asphalt?
« Reply #34 on: July 03, 2014, 10:59:11 am »

Not advocating the use of automotive jumper cables for this purpose, but just want to correct a couple of points that I believe are common misconceptions:

They may only be rated for 12 - 24 VDC but perhaps they'd be up to this sort of challenge.

Voltage ratings of wire and cable are not for the conductor, but for the insulation around it. Current ratings are for the conductors, not the insulation. Since grounding conductors are often provided uninsulated, I would think that the voltage rating of automotive jumper cables should be irrelevant in a grounding application. You just don't see voltage ratings on bare wire.

CCA is generally only good for high frequency or low power stuff. DC and AC power just aren't the same.

And copper-clad aluminum has been used for 120/240/etc.V//60/50Hz wiring in the past, and may still be permissible under NEC in certain applications with listed connectors. Why would someone use CCA? 1) because aluminum is less expensive than copper, and 2) because corroded copper has better electrical properties than corroded aluminum. Uncorroded aluminum is a decent enough conductor; the bad press that aluminum wiring has received in the past is due to its properties when it corrodes and also its softness that contributes to loose connections.

As far as I know**, the NEC hasn't approved any spring-clamp devices for temporary grounding. And if they did, I'd suspect that a welding ground clamp might be a better choice than an automotive jumper cable. I believe any inspector would approve stage grounding using the same fixed "pipe grounding" clamps required for permanent installs. Installing and removing those clamps really doesn't take a lot of time; just a little more than installing and removing a lighting fixture clamp from an overhead truss. And getting a spool of #4 AWG copper wire isn't THAT difficult or expensive in the grand scheme of things.

If you are renting a stage, do you really think the stage provider is going to appreciate you scratching through the paint to get a good ground? Better talk the issue over with them first.


**I haven't studied a recent copy of the NEC.
Logged
Stop confusing the issue with facts and logic!

Mike Sokol

  • Moderator
  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1266
  • Lead instructor for the No~Shock~Zone
    • No~Shock~Zone Electrical Safety
Re: Should I ground the Stage on Asphalt?
« Reply #35 on: July 03, 2014, 11:54:18 am »


**I haven't studied a recent copy of the NEC.

That's a separate issue since many of us don't feel like dropping money on a book we infrequently use. But I have a contact at the main NFPA office (the agency in charge of NEC content and publication) who has hinted there were online resources available which included parts of (or maybe even all of) the latest NFPA 70E document. If that's the case I'll ask if I can post those links here in the interest of educating sound professionals who aren't exactly electricians, but who perform many electrical tasks including stage and generator distro and grounding, etc...

I'll shoot him an email this afternoon and see if he responds. Could be next week before he gets back to me since we're soon into the July 4th Independence Day holiday. For our non-USA readers, that's a really big federal holiday with lots of fireworks and family BBQs. Yum!  ;D

Tim McCulloch

  • SR Forums
  • Hero Member
  • *
  • Offline Offline
  • Posts: 13212
  • Wichita, Kansas USA
Re: Should I ground the Stage on Asphalt?
« Reply #36 on: July 03, 2014, 12:06:19 pm »

That's a separate issue since many of us don't feel like dropping money on a book we infrequently use. But I have a contact at the main NFPA office (the agency in charge of NEC content and publication) who has hinted there were online resources available which included parts of (or maybe even all of) the latest NFPA 70E document. If that's the case I'll ask if I can post those links here in the interest of educating sound professionals who aren't exactly electricians, but who perform many electrical tasks including stage and generator distro and grounding, etc...

I'll shoot him an email this afternoon and see if he responds. Could be next week before he gets back to me since we're soon into the July 4th Independence Day holiday. For our non-USA readers, that's a really big federal holiday with lots of fireworks and family BBQs. Yum!  ;D

There is a link on the NFPA website for "Free Codes."  You can't print or download, and I've not found a way to browse within chapters - you have to flip pages sequentially (though that could be due to the javascript blocker I use with Firefox).  You have to register with an email address (NFPA will send you a nice letter suggesting you make an eventual purchase) to use the free service.

http://www.nfpa.org/codes-and-standards/free-access
Logged
Chewing through your wimpy dreams
They eat without a sound,
Digesting England by the pound.

jasonfinnigan

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 334
Re: Should I ground the Stage on Asphalt?
« Reply #37 on: July 03, 2014, 12:34:34 pm »

But let's be careful about posting too much info on non-code ideas on this forum. There's way too much of that crap on the web as it is, and we're trying to be a source of correct info.
Exactly
Logged

Jonathan Johnson

  • Church and H.O.W. Forums
  • Hero Member
  • *
  • Offline Offline
  • Posts: 1264
  • Southwest Washington (state, not DC)
Re: Should I ground the Stage on Asphalt?
« Reply #38 on: July 03, 2014, 01:27:11 pm »

As far as I know**, the NEC hasn't approved any spring-clamp devices for temporary grounding.

I should've googled this before. A search for "temporary grounding clamp" reveals a bunch of options (try an image search for the same). They seem to be mostly marketed toward utilities for use when they're working on the lines. However, the few that I found prices for (I didn't research extensively) show that they are hideously expensive, between $100-200 each and up to $600 for a prefab jumper with a clamp on each end. If you're going to bond several stage sections together with them, that gets awfully expensive in a hurry.

A spring clamp might be fine for a jumper cable (where it is used very temporarily and in full view of the user) or a welding clamp (where if it comes off it's obvious because things don't work), but for a safety ground I doubt it would be approved since it could easily be dislodged accidentally. For a safety ground, I would expect a screw clamp of some sort would be required to prevent inadvertent disconnection.

An ideal clamp for our application (bonding metal stages to ground) would have a single-sided clamping mechanism (to allow it to clamp onto the edge of a large plate) and be capable of clamping flat or curved surfaces from 1/4" to 3" in thickness. It would accept either bare wire into a lug, or a cam-lock connector. Clamping would be by means of handscrews, requiring no extra tools.
Logged
Stop confusing the issue with facts and logic!

Rob Spence

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1137
  • Boston Metro North/West
    • Lynx Audio Services
Re: Should I ground the Stage on Asphalt?
« Reply #39 on: July 03, 2014, 02:09:39 pm »

Maybe we need a vise grip like thing with a lug on it to connect a cable? It could clamp pretty securely to flat and round objects.


Sent from my iPad using Tapatalk HD
Logged
rob at lynxaudioservices dot com

Dealer for: AKG, Allen & Heath, Ashley, Astatic, Audix, Blue Microphones, CAD, Chauvet, Community, Countryman, Crown, DBX, Electro-Voice, FBT, Furman, Heil, Horizon, Intellistage, JBL, Lab Gruppen, Mid Atlantic, On Stage Stands, Pelican, Peterson Tuners, Presonus, ProCo, QSC, Radial, RCF, Sennheiser, Shure, SKB, Soundcraft, TC Electronics, Telex, Whirlwind and others
Pages: 1 2 3 [4] 5 6   Go Up
 

Page created in 0.082 seconds with 22 queries.