Question for those who work on these situations professionally... I run sound and lights for band and commonly work in clubs where the only quality power available is an older style 30A to 50A "range" or "dryer" style outlet with 2 hots and a neutral. I have used some "distros" built by others where they split each hot through a 20A breaker to an Edison quad box. The grounds are then simply "tied off" inside the distro box, without any real ground connection. Interestingly, the typical outlet tester shows this combo as valid but I wonder about the safety! Would it be better to bond the Edison outlet grounds to the Neutral line, as I think was done with appliances until the code changed to the newer 4-prong outlets? Or, should I make my own ground connection to available cold water pipe, etc.. ?? None of this optimal, but looking for the safest most logical thing to do for temporary hookups... thanks!

Hmm, I don't have a reply for this post, but I find it interesting enough to bump up.

Ian A.

Ian the post is four years old, I doubt that the poster is still out there.

That said the answer is simple, they can not legally power a 120/240 volt portable distribution panel from a 3 wire receptacle.

They need a 4 wire receptacle with two hots, neutral and ground.

Bob

GFCI would make it safe.

A functional GFCI may make it safe.

I point that out as GFCIs have a very high faliure rate. (OR they had, I am not sure how they are doing now)

However it will not make it code compliant.

For what it's worth protecting a Feeder with a GFCI is not a great design.

The cumulative leakage current of all the branch circuits will likely lead to nuisance tripping of the feeder.

And having a feeder nuisance tripping is much more than a nuisance.

If the tester is just one of the types with three neons connected across each permutation of the wires, this wouldn't be entirely unexpected. Neons draw only a tiny current, so it's likely the ones tied to the "floating" ground could have a sufficiently low-impedance path to glow via either capacitive coupling or leakage through the various equipment connected to the distro board.

I hate to think poor AeroSKI5150 had been checking in everyday to see if his post had been addressed.

I could see him telling the band "no, we will have to do acoustic sets with out lights again this week, I'm still waiting for some advice, it should be any day now.

Roger

Bob, I wanted to see out of curiosity what the answer/solution would be.

I have a similar question- when backfeeding a portable generator into a 3-prong range/dryer outlet, should the generator chassis be grounded to the neutral or just left to float?

(ducks)

And this is a problem in Britain where an RCD (GFI) can protect an entire distribution panel or an entire installation, even though the trip current is 30mA rather than 4 to 6mA.

I heard a story recently about a bright young college student who was trying to get some sleep in his dorm room, but was unable to because of loud music and partying. In frustration, he grabbed a piece of wire, shorted neutral-to-ground on a plug, and pushed it into the socket, instantly tripping the ground fault sensor on the switchboard and turning the building black. Since it was N-G, no amount of playing with breakers could fix it. The kid unplugged it the next morning, and was never caught.

What an *******!

I have personally tripped the GFP protection of mains (800 amp, 2000 amp) by accidentally causing branch circuit ground faults. It is definitely possible.

That said, I am curious why there was a GFP main tripped by what I have to assume was a 120 volt circuit.

GFP is not required below 250 volts to ground and a 480Y/277 volt GFP device is blind to a ground fault on a SDS.

It is possible to trip a feeder breaker without GFP with a branch circuit short but it is not guaranteed.

I bet he was a EE..... and you don't piss off EE majors for we know how to make and BREAK stuff.

The really smart ones can break stuff without being caught or electrocuted.....

And the really, really smart ones have an even larger stereo to fight back with.... At least, that's our plan for revenge.... and the neighbors are in support of us! The guys playing rap music all the time on Saturday have ticked us off.

Can anything good come from that?

Maybe the 208Y/120V Service was GFPE???

I have heard of an installation where there was GFPE on the Service Disconnect of a 208Y/120V 3Ø 4W. system - and it was for Campus Housing (Dorms).

The question was asked to me, if the service required GFPE per the NEC (an Engineering firm had produced the Electrical Plan Set, which was being bid from).

Not having any OSHPD / similar experience, my response was to verify with the CEC (California Electrical Code), along with the AHJ(s), to verify if the service disconnect or Panelboard Feeders required GFPE.

Never heard from that person, which leads me to believe _SOMEONE_ must have required it (or the EE firm is padding the installation for a higher commission).

Other than this possibility, the story sounds like "Bandini Information" to me!

*** "Bandini Information" may be thought of as:

1. Information having a Male Bovine Fecal Factor, higher than 0.995 - near unity fecal factor,
2. Information that is typically found in 2-3 cubic foot bags, in the Lawn and Garden section of Home Centers,
3. Information, which when spread across Lawns, will result in the Grass growing much greener,
4. Information, that made up the "Bandini Mountain", of which the person was Skiing down in the Bandini Fertilizer Commercial - circa 1970's,
5. Information having a very offensive odor to it.

Opinions???

Scott

If it's required and you don't have it, it's illegal. If it's not required, but you have it anyhow, that's OK.

IMHO, there are very few situations where ground fault/zero-sequence protection is a bad thing. (Especially considering the wacky hijinks college kids pull.) It's no different than electricians installing $2 receptacles instead of $.39 cent receptacles- the $.39 outlets are all that's legally required, right?