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#1 Christopher Wedding

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Posted 05 October 2007 - 10:54 PM

How long can I run from a 300 amp genie. I've got a scene
on the 5th floor of a building and I have to run up the stair
well. I was pretty sure it wasn't a problem, and I plan on
consulting my set lighting technician's handbook. But any
one got a quick answer?

Thanks,
Chris
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#2 Michael Nash

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Posted 05 October 2007 - 11:02 PM

It depends on the cabling but you should be fine. Just check the voltage at the D-box for line loss before plugging in any electronic equipment (SOP anyway).
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#3 Christopher Wedding

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Posted 05 October 2007 - 11:47 PM

It depends on the cabling but you should be fine. Just check the voltage at the D-box for line loss before plugging in any electronic equipment (SOP anyway).


Michael,

Thanks for the quick response. By the way, what is SOP?

Chris
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#4 robert duke

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Posted 06 October 2007 - 01:03 AM

You might find a shorter route up the exterior. I have done 12 story runs up the exterior of a building through windows and fire escapes.
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#5 Michael Nash

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Posted 06 October 2007 - 09:54 AM

Michael,

Thanks for the quick response. By the way, what is SOP?

Chris


"Standard Operating Procedure."
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#6 timHealy

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Posted 06 October 2007 - 07:17 PM

hey Chris,

Simply checking your voltage may not be good enough. It depends on the distance of your set from your power source, the cable you have run, and also your load. You may get 120 volts but when lights starts turning on voltage can drop quickly.

Generally speaking, a voltage drop starts to occur after a few hundred feet. But again if you run banded # 2 cable instead of 4 ought you are going to have problems as your load gets higher. In that example a couple of kinos and small tungsten will be fine on the #2 banded, but if you wnat to use a few more powerful HMI's, you start to see the line loss. It happens this way: You turn on one HMI and your fine. Maybe you turn on a second one and everything seems fine. Then you try and turn on a third and the first two go out. The amperage draw on the third tries so hard to strike the voltage drops the below what it needs to keep the others on.

Another thing that is done often is that one can double pump cable runs and sometimes when using a lot of dimmers or square wave ballasts, the neutral is double or even triple pumped due to harmonics. But normal double pumping increases one abilities to operate lights at farther distances reducing the effects of line loss.

I would say if your generator is at the base of your five story building you will be fine. You just have to calculate the right cable amperage for your job.

Best

Tim
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#7 Chris Walters

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Posted 06 October 2007 - 07:56 PM

Hey Tim, I might be wrong on this but I thought that line voltage only had to do with distance and not the load your pulling. That's the amps being drawn. The only reason you need to worry about having the right size of cable is because of the amps it can handle and the distance you need to travel. Because of the line loss you need to turn it up at the genny depending on what your reading is at the Dbox given that you have no loads ahead of that d-box. Again I might be wrong but that was my understanding of it. Please correct me if I am wrong.

Chris Walters

hey Chris,

Simply checking your voltage may not be good enough. It depends on the distance of your set from your power source, the cable you have run, and also your load. You may get 120 volts but when lights starts turning on voltage can drop quickly.

Generally speaking, a voltage drop starts to occur after a few hundred feet. But again if you run banded # 2 cable instead of 4 ought you are going to have problems as your load gets higher. In that example a couple of kinos and small tungsten will be fine on the #2 banded, but if you wnat to use a few more powerful HMI's, you start to see the line loss. It happens this way: You turn on one HMI and your fine. Maybe you turn on a second one and everything seems fine. Then you try and turn on a third and the first two go out. The amperage draw on the third tries so hard to strike the voltage drops the below what it needs to keep the others on.

Another thing that is done often is that one can double pump cable runs and sometimes when using a lot of dimmers or square wave ballasts, the neutral is double or even triple pumped due to harmonics. But normal double pumping increases one abilities to operate lights at farther distances reducing the effects of line loss.

I would say if your generator is at the base of your five story building you will be fine. You just have to calculate the right cable amperage for your job.

Best

Tim


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#8 timHealy

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Posted 07 October 2007 - 08:06 AM

hey Chris,

It all affects your voltage. I believe the Harry Box book has charts about cable and distances where line loss can be expected and even a formula to figure it out how much loss you have per hundred feet. But when cable is run more then a few hundred feet and you start putting loads on the cable, the loss or I guess more acurately the resistance of the cable becomes greater. especially when you start getting to 75 percent capacity of said cable.

An example would be if you had a 1200 amp generator and a three phase run of 2 ought over 500 feet or even longer. The voltage may read 125 hot to nuetral at the genney and maybe 123 at the end of your run. Based on the generator and cable you should have 600 amps available. But one 18 or even two may came on normally but striking the third may knock out the other two. If one read the voltage with two lights on you may see 115 on the run with one HMI phase plugged in but perhaps 110 with the leg that has two 18k phases plugged in. Cranking up the voltage can certainly help but personally I would rather see the cable double pumped. One may have equipment plugged in at or close to the generator or the sound and video departments may have things plugged in on the set. If someone starts turning off lights the voltage will pop up as the loads decrease. So maybe you'll find 130 volts or more on the set with no lights on.

Best

Tim
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#9 Chris Walters

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Posted 12 October 2007 - 04:13 PM

You are correct sir I actually looked it up in the Box book the other day before reading this post. Thank you for straightening that up for me.

Chris
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#10 timHealy

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Posted 14 October 2007 - 09:07 PM

Your welcome Chris. We are all here to help each other.

Best

Tim

Edited by timHealy, 14 October 2007 - 09:11 PM.

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Media Blackout - Custom Cables and AKS

Willys Widgets

CineLab

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FJS International, LLC

Opal

The Slider

Technodolly

Broadcast Solutions Inc

Abel Cine

rebotnix Technologies

Metropolis Post

Tai Audio

Wooden Camera

Visual Products

Rig Wheels Passport

Gamma Ray Digital Inc

CineTape

Glidecam

Ritter Battery