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Grounding a metal stage


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Did an event recently where stage grounding has become a question to me. For this event, the promoter utilized a very large military flatbed trailer as a stage. Power was provided via GFI hard wired circuits located in an outdoor area, meter check confirmed all was wired right. At one point during sound check (and only one time) a performer said she was getting a little "bite" from one of the mics. This didn't happen to her again and it didn't happen to anyone else even with the same mic. Got me to wondering what may have been the cause, should the trailer have been grounded ? how about their use of large carpet sections on the stage ?

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Tomm, here in Montana (especially during the winter) our relative humidity gets so low that small static shocks are quite common. (You learn to ground yourself before giving your sweetie a kiss or petting the cat.). Synthetic carpeting, low humidity, and a little shuffling about might cause enough static to be noticeable.... Pure speculation on my part, but a possible explanation. Mark C.

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Interesting point Mark. Here in Susanville, we are in a high altitude desert region. Humidity is a rarity here. As I believe she was the first person to sound check that mic, wondering if she wasn't the one who helped release any built up static ? Going over to PSW to read that thread.

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The trailer is something you don't want grounded. The more rubber between you and the actual ground the better. Its like wearing rubber sneakers vs using bare feet on a wet cement floor. If the trailer has rubber wheels there's less chance of being zapped.

 

If you do have cool dry air and you're having static issues that's a different story. Last winter I had a band over and the lead singer kept getting a shock from the mic. I did a check and made sure all was good. She wasn't holding a guitar so there wasn't any issue between the mic and instrument grounds which often occurs with a ground loop.

 

I couldn't use a wind screen because I was recording. The simple fix was for me to take a spray bottle fill it with water and add a little laundry fabric softener in there. I then sprayed the rug down a little and the problem was gone. Fabric softener has static eliminators in it and since its your shoes that develop most of the static potential, it dissipated the static from the singer.

 

The way you know is if you comb your hair and it stands up, you know you have the potential to have static buildups. I treated my entire studio rug by the way. Static can just as easily blow electronic components and since my studio is loaded with gear, it makes sense to avoid those problems before they occur. .

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Trailer stages should ALWAYS be grounded to the power service and it may also be necessary to utilize a supplemental electrode ground (driven ground rod) for equipotential voltage gradient reasons. There are code sections that deal with such situations. It's not just to protect somebody on the stage in the event of an electrical fault but also to protect somebody who might be standing on the ground touching the stage that would otherwise be electrified if not bonded to ground. WRGKMC, How about not presenting bad and dangerous advice as fact?

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The trailer is something you don't want grounded. The more rubber between you and the actual ground the better. Its like wearing rubber sneakers vs using bare feet on a wet cement floor. If the trailer has rubber wheels there's less chance of being zapped.

 

 

This is completely wrong. It's not possible to safely isolate a large object like a stage. There will always be the problem of having the trailer/stage energized and having some other conductive object on it that is firmly grounded to the GES. What then??? You want the trailer/stage to trip OCPD's in the event of a fault, not sit there energized and waiting to kill someone.

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I didn't realize how dangerous this could be. many a time my band has setup on a construction trailer, usually for a township job where the township electrician runs the AC from the nearest light pole to the trailer via an extension cord . never saw any grounding of any kind and wondered how safe it was. I always check the source for correct wiring with my handy recepticle tester and always checked out good. Not too long ago we got caught in a fast mving rainstorm down while performing on one of these trailers.

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I didn't realize how dangerous this could be. many a time my band has setup on a construction trailer, usually for a township job where the township electrician runs the AC from the nearest light pole to the trailer via an extension cord . never saw any grounding of any kind and wondered how safe it was. I always check the source for correct wiring with my handy recepticle tester and always checked out good. Not too long ago we got caught in a fast mving rainstorm down while performing on one of these trailers.

 

It's one of those things that is just fine 99.9% of the time. You just don't want to be the 0.01% guy, or have to get to know his lawyer.

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