Generators for temporary events

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Ab5gu

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Hi all,

I am seeing temporary events regularly coming into town where they will rent an empty warehouse and put on music/rave/"art" one day event. Most of the warehouses have a minimal electrical load (lighting and a couple receptacles). The promotion companies bring in up to seven portable trailer mounted diesel generators to supply temporary power for sound and stage lighting ( some hung from the building's steel structure). Do the generators need to be bonded together and bonded to the building structure? The generators are never tied into the building wiring in any way. Thank you.
 
For something like this, my take (without citations) is that the generators' grounding terminals all need to tie together, connect to the structure (if metallic), and connect to a common grounding electrode system of some kind. Since they, I assume, aren't operating in parallel, each generator must have it's own SBJ.

On the other hand... if all the loads have a continuous EGC from generator to use, the structure is probably effectively tied to the generator's ground terminal anyway.

Is this being set up by a temp. power rental company? Usually any company renting that much gear has a clue about these things. Not always, though....

(Consider the different purposes of the grounding electrode system, bonding a metal structure, and the equipment grounding conductors.)
 
iwire said:
If it is all cord and plug connected even via cam locs there are no further bonding requirements
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BTW I do agree with iwire, there aren't any code requirements ("need" was probably the wrong word in my reply); assuming the generators are fairly close, I think it's good practice to connect all their frames together somehow*. I'd be interested in any rationale why that's a bad idea.

*to muddy the waters, some sound companies want their power source to be completely isolated from anyone else. IMHO their reasons are usually "unfounded in science or engineering".

Also, some AHJs will want a couple of ground rods or a GES whether or not the code requires it, and it's usually easier to add than argue.. (Requirements for grounding/bonding portable & mobile generators has been discussed here before.)
 
Ab5gu said:
Hi all, I am seeing temporary events regularly coming into town where they will rent an empty warehouse and put on music/rave/"art" one day event. Most of the warehouses have a minimal electrical load (lighting and a couple receptacles). The promotion companies bring in up to seven portable trailer mounted diesel generators to supply temporary power for sound and stage lighting ( some hung from the building's steel structure). Do the generators need to be bonded together and bonded to the building structure? The generators are never tied into the building wiring in any way. Thank you.
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When we do events with portable generators, we always insist that the genny company drive a ground rod and connect to it. Some inspectors look for it, and others don't, but this way, it doesn't matter. We also bond to the building (usually a tent structure) when applicable. Two of my favorite (probably apocryphal) stories: 1) Rock-n'-roll show at a stadium near a waterfront. No matter what the sound guys did, they couldn't get the 60Hz hum out of the system. Genny tech goes out the parking lot to the portable gennys running the show, connects a long length of Cam feeder to the grounding lug on the genny, and ties the other end to a metal shopping cart he found in the parking lot. Once he threw the cart in the river, the hum went away. 2) Film shoot needed a ground "rod" while using a genny in NYC - not the place to be driving ground rods. Someone used a Tweco clip and clamped the ground clamp to an adjacent fire hydrant; can't get a much better ground reference than that ;) SceneryDriver
 
Ab5gu said:
Hi all,

I am seeing temporary events regularly coming into town where they will rent an empty warehouse and put on music/rave/"art" one day event. Most of the warehouses have a minimal electrical load (lighting and a couple receptacles). The promotion companies bring in up to seven portable trailer mounted diesel generators to supply temporary power for sound and stage lighting ( some hung from the building's steel structure). Do the generators need to be bonded together and bonded to the building structure? The generators are never tied into the building wiring in any way. Thank you.
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How do those portable generators synch up?
 
BHoopes said:
Agree with zbang. But my question is: Who is verifying and setting the ground fault and short circuit settings?
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So when the OP asked what is required we are going to just suggest what each of us thinks is the right way to do it.

Again, there is no need, no benefit if everything is cord and plug connected.

Please someone for the love of electricity explain what a ground rod will do?:)
 
iwire said:
Please someone for the love of electricity explain what a ground rod will do?:)
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With the tent and other portable structures we sometimes get involved with, there is a belief that bonding the aluminum structure will (partially) mitigate hazards with lightning. I'm not sure that the effective impedance of a CamLock cable and an 8' ground rod is much less than "too much to matter" at the rise times of a lightning strike, but if it gives people the warm-'n-fuzzys I'll drive the ground rod. It also keeps the Hum Heads (audio department) happy, but at least half of what they do is straight up witchcraft anyway. :) SceneryDriver
 
SceneryDriver said:
With the tent and other portable structures we sometimes get involved with, there is a belief that bonding the aluminum structure will (partially) mitigate hazards with lightning. I'm not sure that the effective impedance of a CamLock cable and an 8' ground rod is much less than "too much to matter" at the rise times of a lightning strike, but if it gives people the warm-'n-fuzzys I'll drive the ground rod. It also keeps the Hum Heads (audio department) happy, but at least half of what they do is straight up witchcraft anyway. :) SceneryDriver
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So in other words it's just tradition.:p
 
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