25 Kw Generators and Distros

[skienblack]

I'm working with an event company on a large triathlon and we are investigating using a centralized generator and distros for our post race area, but I don't have experience with this. We will need between 10K and 15K watts in one of our locations, but we need power on both ends, which is about 900'. Is it feasible to put the generator at one end where most of the power is needed and then run a feeder to the other end into a distro? Or is this distance just to great? Thanks.

 

[shiben]

Is it feasible to put the generator at one end where most of the power is needed and then run a feeder to the other end into a distro? Or is this distance just to great? Thanks.

Not an expert about feasibility, but its definitely possible. Just a matter of the size of the feeder cables and the power of the genny. One potential issue is that I can not think of tons of people who actually want to run 900 feet of feeder, and the cost to rent this would probably be fairly high. Whats the power needs at the other end? A smaller genny might be cheaper.

 

[MNicolai]

Is there any reason you can't run two smaller, localized generators and run far less feeder?

 

[DaveySimps]

I would second the idea of 2 smaller gennies located closer to where they are needed if that is feasible for your needs. By the time you include the extra feeder for the one gennie, and the labor costs to run and strike all the feeder, it may not be as expensive as you think. Plus you avoid issues such as a big voltage drop down the longer run of feeder.

~Dave

 

[skienblack]

Is there any reason you can't run two smaller, localized generators and run far less feeder?

I think that would be a safer and much better idea. The units we are looking at are 59 db at 23 ft. I'm more of a lighting guy, that's very tolerable for an outdoor environment, right?

 

[Edrick]

dB Comparison

Sound Levels of Music
Normal piano practice 60 -70dB
Fortissimo Singer, 3' 70dB
Chamber music, small auditorium 75 - 85dB

 

[LuxMax]

You are much better off with two powerplants. 900 feet of feeder is very labor intensive and you'll need larger guage to handle the voltage drop. It'll be cheaper with two units.
Most trailer gennies are pretty quiet, you should be ok with those sound levels.

 

[museav]

Looking at dB numbers is of limited use as those numbers tell you little about the frequency content and you have no general ambient noise level information to compare to. For example, if the 59dB contains a strong tonal (specific frequency) component then that would likely be perceived as being much louder than it it was a broader spectrum sound. And a 1,000Hz tone of 59dB would likely be perceived as significantly louder than a 59dB 100Hz tone. But the biggest issue might be knowing what is acceptable in the specific application, e.g. things like the ambient noise levels, what the generator noise might interfere with and how far the listeners are from the noise source.

 

[skienblack]

So we decided to go with 2 large generators. Now I'm just trying to determine how long I can run the cable from each unit. If I'll only be pulling around 4000 watts from each feed is it ok to run it 250' with a 6 gauge cable? I don't believe the voltage drop would be to significant.

 

[bishopthomas]

I don't have the formulas memorized and don't feel like hunting them down to do the math, but #6 cable seems a little small. #2 is pretty standard for this type of setup, 2/0 even better. Many local codes require the hots to run down separate insulated cables. I worked for a guy who ran his entire PA (medium sized line array rig) off a 100' multiconductor #6 wire. We were very happy to coil the 5 100' runs of #2 wire when he finally broke down and bought the "right" stuff.

 

[mrb]

I don't have the formulas memorized and don't feel like hunting them down to do the math, but #6 cable seems a little small. #2 is pretty standard for this type of setup, 2/0 even better. Many local codes require the hots to run down separate insulated cables. I worked for a guy who ran his entire PA (medium sized line array rig) off a 100' multiconductor #6 wire. We were very happy to coil the 5 100' runs of #2 wire when he finally broke down and bought the "right" stuff.

"right stuff" ? 6/4 Cable with 50 amp CS connectors is very common in temporary power. If you want to get really technical with the code, the guy probably isnt a 'qualified individual' and isnt allowed to connect single pole connectors -but 6/4 with 50 amp twistlocks would be ok.

What is this local codes requiring hots to run down seperate insulated cables?

As far as running a 4kw load on 6/4 going 250ft, youll be fine. With 20 amps on each phase, your voltage drop is a little over 2% which is more than acceptable.

 

[kendal69]

You'll drop 4.063 volts over that run so if you start out at 120 on the Gennie you will still have 115 at the end.
What I do is crank up the generator output and them meter at the end till I get 120 IF I NEED IT.

http://www.nebulan.net/solar/voltagedrop.asp

When you say LARGE generator what size are you thinking? A 25 KW will give you 55.6 Amps PER LEG on three legs.

The distro box is important if you can get a box that can take of power output you will be better off. Some companies us those JOB BOXES which are only 50 AMP per box even though they have 12 outlets so be aware. When you reach 50 AMPS the box trips.

A full five wire distro box with a 60 amp three hot wires will give you 60 AMPS PER LINE. So one box will do the work of 3 job boxes.

 

[bishopthomas]

"right stuff" ? 6/4 Cable with 50 amp CS connectors is very common in temporary power. If you want to get really technical with the code, the guy probably isnt a 'qualified individual' and isnt allowed to connect single pole connectors -but 6/4 with 50 amp twistlocks would be ok.

What is this local codes requiring hots to run down seperate insulated cables?

As far as running a 4kw load on 6/4 going 250ft, youll be fine. With 20 amps on each phase, your voltage drop is a little over 2% which is more than acceptable.

Yes, I use 6/4 cable with California connectors quite often. I'm talking about 200 amp service with Camlok disconnects. I thought that it was code to run separate lines, but maybe I'm wrong. Maybe it has more to do with the cable guage (wouldn't really want to stuff 2/0 cable into a multi) than anything.

 

[len]

900' of feeder to pull? No thanks. If that's 900 linear feet you could be looking at more like 1000' after turns, obstacles, etc. Get 2 smaller ones. It's not worth the headaches.

 

[epimetheus]

Yes, I use 6/4 cable with California connectors quite often. I'm talking about 200 amp service with Camlok disconnects. I thought that it was code to run separate lines, but maybe I'm wrong. Maybe it has more to do with the cable guage (wouldn't really want to stuff 2/0 cable into a multi) than anything.

Single conductor cables must be 2 AWG or larger per NEC 525.20(B). You can use high ampacity, multiconductor cable, 4/0 for example, but you must use the appropriate multicondcutor fittings. You can't use single conductor fittings on a multiconductor cable, i.e. no cams on a multiconductor cable.

 

[bishopthomas]

Thanks for the clarification.

 

[jjkool]

If you have two gensets - why do you need to run so far?

Assuming you are running 120v at a distance of 250' and draw of 33 amps, you are looking at a voltage drop of 12.90 volts. If you arent running anythign close to the gen you can always increase the output voltage by dialing it up. If you are running three phase, you are looking at a drop of 11.17 volts.

To run 33.3 amps over a 250' run, you would need 2awg wire which produces an appx drop of 3.6v.

The sound level is very quite and will be fine for close proximity to a stage. We normally use Caterpiller 25 kW gens around the same noise and they are amazing!

 

[skienblack]

You'll drop 4.063 volts over that run so if you start out at 120 on the Gennie you will still have 115 at the end.
What I do is crank up the generator output and them meter at the end till I get 120 IF I NEED IT.

Voltage Drop Calculator

When you say LARGE generator what size are you thinking? A 25 KW will give you 55.6 Amps PER LEG on three legs.

The distro box is important if you can get a box that can take of power output you will be better off. Some companies us those JOB BOXES which are only 50 AMP per box even though they have 12 outlets so be aware. When you reach 50 AMPS the box trips.

A full five wire distro box with a 60 amp three hot wires will give you 60 AMPS PER LINE. So one box will do the work of 3 job boxes.

If you have two gensets - why do you need to run so far?

Assuming you are running 120v at a distance of 250' and draw of 33 amps, you are looking at a voltage drop of 12.90 volts. If you arent running anythign close to the gen you can always increase the output voltage by dialing it up. If you are running three phase, you are looking at a drop of 11.17 volts.

To run 33.3 amps over a 250' run, you would need 2awg wire which produces an appx drop of 3.6v.

The sound level is very quite and will be fine for close proximity to a stage. We normally use Caterpiller 25 kW gens around the same noise and they are amazing!

I have calculated similar results to the 3.6 V drop. How do you get 12.9 V?

 

[skienblack]

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?

 

[kendal69]

No the 50 AMP spider box will only give you 50 AMPs. The connectors are rated at 50 amps, the box only delivers a total of 50 amps, ans the breaker the box is connected to is only 50 amps. Even if you daisy chain two boxes together then those TWO boxes combines only get 50 amps.

I made some custom LUNCH BOX's made that are 60 amp THREE PHASE so I get 60 amps a leg. It's the same work to pull 60 amp three phase as it is 50 amp single phase but I get three times as much power to the lunchbox.