fairground power

[yanert]

I need to provide power at a event at a fair ground. I need to hook up some small 240 volt equipment and some 120 volt loads. These loads are in a main distribution panel with over current protection in the form of breakers. The fair ground provides 240 volt, single phase power with a 30 amp, 3 wire, 240 volt plug. This config is all over the site. It appears to be two hot conductors and a ground.
Do I treat this plug as a new electrical service, run my hot conductors into the main distrubution panel, and bound my nuetral and my ground together and then drive a ground rod? I only have one path back to ground, its using the ground of the the three wire cord. What would happen if I lost my ground? I cound have potential at my main distrubution panel. Or I cound back feed on my 120 volt loads and create 240. It appears to me I have to bond and then drive a ground rod. Is this right? Thanks for any suggestions!

 

[tom baker]

Re: fairground power

Start off with reading Art 525 and 527 in the NEC.

If its cord connected then it falls under Art 527.

You must not tie the ground and neutral together odownstream of the service, and if you don't understand why please contact a qualified electricain to help you. Its not something that can be explained here

 

[yanert]

Re: fairground power

ouch! bad day or what Tom.

 

[charlie b]

Re: fairground power

No, not a bad day. Tom is trying to express a deep concern for your safety and that of the people attending the fair. Based on the way you chose to word your question, I have the same concern. What your question suggests resembles (to me, at least) the suggestion that we dispose of a collection of old rusty nails by tossing them into the sand at a public beach. It?s not a question of whether anyone will get hurt; someone will! The only questions are (1) Who, (2) When, and (3) How badly.

To directly answer your question: The power source offered by the owner is absolutely inadequate for its intended use. You need a 240/120V source, supplied with a cable that has two hots, one neutral, and one ground. If the owner cannot provide this source, then you will need to install a transformer with a 240 volt primary and a 240/120 volt secondary. Then, because you are deriving a separate power system from the original system, the neutral and ground need to be bonded at your panel, and that point needs to be run to a ground rod.

 

[iwire]

Re: fairground power

I bet the fairground folks say "no one else needed any transformers, we do this all the time"

Probably no OCPD beyond the 30 amp outlet most times either.

3 wire 30 amp cordcap feeding two 4" squares with 120 volt duplex outlets in them.

 

[ryan_618]

Re: fairground power

My city building official had me inspect some power for an event similiar to this last month. I got there at about 3:30 and left at 8:30

 

[audiocableguy]

Re: fairground power

Working in South Florida it is easy to find the "Fairground Symptom". Miami is notorious for such situations in the older hotels indoors and out. If I am faced with such a situation my only legal option is a transformer 3 wire in, 4 wire out. Bond ground and Xo derived neutral inside a subpanel to ground rod. Feed newly created feeds from subpanel. Is this correct?

 

[tom baker]

Re: fairground power

AudioCableguy: sure you've created a SDS, no different than a building. Have you every used a Square D mini power zone? its a primary disconnect, transformer and secondary panel in one box. I'm sure there are others that are similar.