25 Kw Generators and Distros

[MNicolai]

One additional question. If I am using a spider box fed with 50 amp 240V. Does this provide me with 100 Amp of 120V power since its two 120V feeds of opposite phase?

Sort of. If you are pulling four conductors, Leg A, Leg B, Ground, and Neutral, with Leg A and Leg B 180 degrees apart and at 120v each, then you'd get a 50A chunk of 120v on Leg A and another 50A chunk of 120v on Leg B. This is not to be confused with a 100A feed, because if either pole of the 50A/2-pole breaker sees over 50A, it'll trip.

Should all of those "if" conditionals be met and your distribution box be [appropriately configured], then you'd see the following results:

Leg A - Leg B - Result
40A - 40A - No Trip
60A - 0A - Trip
0A - 60A - Trip
50A - 50A - Eventual Trip

So theoretically, you can have access to 100A @ 120v, but not in a single chunk and practically you'd only be able to use ~80A continuously and ~100A as an instantaneous max to prevent tripping the breaker.

 

[LuxMax]

Just to clarify, legs in a 3 phase AC system are 120 degress apart, not 180.

 

[MNicolai]

It depends what you're delivering to the spider box and how the spider box is configured. I was speaking in regard to a 120v/240v single-phase 50A configuration. If you're delivering a 120v/240v 3-phase feed, then yes, it would be 120 degrees instead of 180. Also, you'd have another chunk of 50A to use.

 

[mrb]

It depends what you're delivering to the spider box and how the spider box is configured. I was speaking in regard to a 120v/240v single-phase 50A configuration. If you're delivering a 120v/240v 3-phase feed, then yes, it would be 120 degrees instead of 180. Also, you'd have another chunk of 50A to use.

not entirely. If you are taking two hots and a neutral from a 3 phase 4 wire wye source, you will have 120/208. Also the neutral is considered a current carrying conductor in this configuration.

 

[kendal69]

These are the specs from a typical Spider Box.

* GFCI's provide open neutral and reverse phasing protection
* "Power On" indicator lights on GFCI's
* 240V High Voltage Shut-Off with indicator light
* 1 - 50 AMP 125/250 Volt feed through receptacle
* 1 - 30 Amp 250 Volt non-GFCI receptacle
* 6 - 20 Amp 125 Volt GFCI individually protected receptacles

 

[KevinNRP]

I would like to know what is the longest length you can use 6/4 feeder cable. Doing an event this weekend and the distro would be about 250 ft away. I was also wondering if I should just tell the client that we need another one.

 

[avkid]

Are we still talking about 25kw.
If so, you better be using at least #2.

 

[FMEng]

It all depends upon how current is drawn and how much voltage loss is tolerable.

Voltage Drop Calculator

 

[ejsandstrom]

If you are renting the generators, rent the cable. Any decent generator rental place has 4/0 cam-loc cable in bins waiting to go out the door. They will also have the distro to go with it. DO NOT DO NOT call your local rent-all that can rent you a lawn mower, a hammer drill and fill your propane tank to rent a generator. You will only invite problems. I would even shy away from places like united rental. Call your local Cat or Cummins distributer and rent from them. If the generator fails, they have techs that will come to you and fix it. If you get it from Joes House of rental stuff, he will either tell you to bring it back or (total long shot) send out the guy that sharpens the chain saw blades to look at it.

You wouldnt rent a $30,000 light from a guy that picked it up at a garage sale, treat your rental power the same way.

 

[len]

I would think 2 generators are more feasible. 900 feet of cable would probably create a lot more trip hazards.

As for noise, most of the newer trailer generators are really quiet, about as loud as an average car. And at an outdoor event, I doubt they would be noisier than the people around them would be.