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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => AC Power and Grounding => Topic started by: Ray Aberle on July 07, 2014, 11:33:14 pm

Title: Amp Rack Feeder Cabling/Interconnects
Post by: Ray Aberle on July 07, 2014, 11:33:14 pm
So all of my main amp racks use MotionLabs Rack Packs, with L21-30 input/outputs. I get the ones with 4-20A circuits, but that means two of those breakers are on the same leg of L21-30.

In a situation where I am running only 1 or 2 30A/3 circuits, would I be best served by adapting my L21-30 jumps to shift legs (i.e. wire the cable so X on one end is Y on the other, Y goes to Z, and Z goes to X) to ensure that the leg getting 2 circuits on each pack changes every time I jump from one rack to the next.... or should I just not bother and keep watching Saved by the Bell re-runs tonight?!?

Alternatively, I could pull the racks apart and alter them so they're keeping the extra load on different legs, which means I don't have to always rely on my custom cables, especially for a cross rental, but I am also feeling like it might not be worth that effort.

Finally, I could leave the amps with the lowest potential draw (i.e. the IT4000s handling the HF and MF of VT4888s) and always gang those up on one leg, and call it a day.

Just wanted to see what others have done to alleviate this problem, if it is even a problem at all!

Thanks,

Ray
Title: Re: Amp Rack Feeder Cabling/Interconnects
Post by: Cailen Waddell on July 08, 2014, 12:06:00 am
Our amp rack distros are single phase. L14-30.  Even number racks have tops on a and subs on b. odd number racks have tops on b and subs on a. It works for us.  We usually do not daisy more than 2 racks.


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Title: Re: Amp Rack Feeder Cabling/Interconnects
Post by: David Sturzenbecher on July 08, 2014, 06:42:10 am

So all of my main amp racks use MotionLabs Rack Packs, with L21-30 input/outputs. I get the ones with 4-20A circuits, but that means two of those breakers are on the same leg of L21-30.

In a situation where I am running only 1 or 2 30A/3 circuits, would I be best served by adapting my L21-30 jumps to shift legs (i.e. wire the cable so X on one end is Y on the other, Y goes to Z, and Z goes to X) to ensure that the leg getting 2 circuits on each pack changes every time I jump from one rack to the next.... or should I just not bother and keep watching Saved by the Bell re-runs tonight?!?

Alternatively, I could pull the racks apart and alter them so they're keeping the extra load on different legs, which means I don't have to always rely on my custom cables, especially for a cross rental, but I am also feeling like it might not be worth that effort.

Finally, I could leave the amps with the lowest potential draw (i.e. the IT4000s handling the HF and MF of VT4888s) and always gang those up on one leg, and call it a day.

Just wanted to see what others have done to alleviate this problem, if it is even a problem at all!

Thanks,

Ray

I would simple distribute the load so one racks has HF on A, one has MF on A, and another has LF on A... Or similar. Custom cables are for the birds and could be potentially dangerous or maybe even illegal?


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