Can someone walk me through setting up power and dimming?

[Lighting Newb]

Hi, everyone. I've mostly worked as hand and ground rigger but I'd like to be a lighting tech so I'd love to learn more. So thank you for any insights.

I know how electricity works and the concept of forward phase-control dimming but I have no practical experience setting power distribution or dimmer racks. I've never had to deal with that in the roadhouses I've worked. Examples of how power branches off and how conventional are connected to dimmers would be great. Basically how to set up a lighting rig.

Correct me if I'm wrong but the way it works out in my head is that power feeds from a generator or company switch (for example one rated 400amps). Those three phases with cam lock connectors plug into a distro that's rated 400 amps 208/120 (or should it be 1600 amps?). That branches off using whatever receptacles are attached, like 200 amps in this distro:
https://m.4wall.com/rentals/8255862/motion-laboratories-120-208v-distro-48-way
to smaller distros and keep going until you get to a distro like a lunchbox that you can plug in L6-20 or edison's at 120v. Or take the saco connections on the distro and run 120 and 208v sacco and break-outs directly to the lights. The loads of all those branches should be 80% of what fed in, so 80% of 1200 amps. Is that right? Do any of the distros draw power even if there's no load?

My real question is how do you dim conventionals? I know dimmer racks are part of the equation. If you use this distro,
https://m.4wall.com/rentals/9758170/indu-electric-120-208v-distro-48-way , how do you connect the distro to the dimmers? Is it with dmx? And if it is, why not just make a home run to the console? Also, I saw someone messing with a dimmer rack like they were a telephone operator. What is that?

Thank you. I don't have much time at work to ask questions and get full answers so I appreciate any help.

 

[SteveB]

How you connect a dimmer rack to the generator and/or company switch is dependent on the size of the rack as well as the power available, but is generally the same as connecting any of the distro's you've mentioned, with Cam-Lok connectors and appropriately sized feeder cable. The dimmer racks typically are equipped with Cam-Lok inputs and sometimes power pass-thru as well.

An ETC Sensor portable 96 dimmer rack would take about all the available power in a 400 amp, 3 phase company switch (which is 1200 amps total, not 1600, as BTW). That's assuming you have it loaded reasonably full. A smaller rack or a 96 not loaded full, would require less power and might then run thru a separate distro. that could then provide power to ML's, LED's, etc.... Google Picture of portable ETC Sensor rack to get a look at what I'm describing as the photo's I've tried to download are too small to image here.

Note that if you were to add up all the dimmers in a Sensor 96 (96) and multiply by the power rating of each dimmer (20 amps) you have an actual connected requirement of 660 amps per phase. The main breaker on the rack is not sized that large (400 amps) however as it's assumed and in practice that you are not loading every dimmer to 2400 watts, thus a smaller main breaker.

DMX is one of the control signal types used to actually control the dimmer output(s) and uses a 5 pin XLR connector on DMX data cable, that in turn connects to the console, or possibly a DMX signal splitter prior to getting to the dimmer rack. Some newer Sensor racks can take a Cat5/RJ45 connection to allow an ETC Net3 console signal to be run direct to the rack. Most dimmer racks (other manufacturers) are simply equipped with a DMX input and pass through connections (you can daisy chain DMX), as well as the dimmer rack having some form of control electronics to tell the dimmers how to listen to the console.

The telephone style internal patch on a Sensor portable rack patches the actual dimmer output to a particular pin connection on the multi-pin connectors on the rack. Note that on the Sensor, you get two types of dimmer power output, 2P&G pin connector and Socapex 6 circuit multi-pin cabling.

 

[Lighting Newb]

Thank you. Someone just explained to me that you can't hook up the distros I was talking about to dimmer racks. So it's best to plug in conventionals to the dimmer rack, follow through to the distros I was talking about for constant power for ML and LEDs. Thank you for clearing that up. I might have turned myself around so tell me off I'm wrong; I understand that for example the draw on B phase for 3 phase is the sum of AB and BC. How can you tell a which sacos go to which legs on a distro so I can balance the phases? And does it differ for dimmer racks which seem to output at 120v?

 

[SteveB]

If you want to dim or otherwise control via the console any conventionals (with incandescant lamps) then you need the dimmer rack, or via DMX controlled on/off relays of some sort.

If your dimmed load is sufficiently under the company switch/generator capacity, you can add a separate distro that will provide 120/208v power to movers and LED's. Note that dimmers in the U.S. are typically outputting 120 volts to fixtures.

The reason for the feed thru CamLok connectors on the distro or dimmer rack is so you can hook up a pass thru set of feeders to the other device. The key is to pay attention to the rating of the device you are passing thru with power. If you have a large Sensor rack and are pulling 280 amps a leg, the distro you pass thru must be rated at that. Or feed the dimmer rack from the company switch first and pass thru the dimmer rack to the ML distro. It all is determined by how much power is needed where.

To determine the loading on the Soca's you need to know how the dimmers are distributed on the rack phase feeders. I cannot offhand recall the portable Sensors, but on the installed rack it's dimmer 1&2 on A phase, 3&4 on B phase, etc... I think the Sensor portables are dims 1-32 on A phase on a 96 rack, but somebody else can verify that (I don't use portables that much anymore). If the Soca patch is 1:1, then obviously the first circuit on the first Soca receptacle will be dimmer 1, etc... Recall that the ETC dimmers are paired in dual modules, so dimmers 1&2 are on a phase together. Not all dimmer systems do it this way, with the 19" rack type dimmers possibly being different, but the manuals typically tells you what comes as standard, or if renting, the shop can tell you. I typically use Lightwright (paperwork software) to find out phase loading as it has a standard template for a Sensor rack, or can be configured to any dimmer phase loading scheme you desire. It then looks at the hookup and if you have punched in all the wattage numbers as well as the rack info, it'll tell you loading.

Since dimmers are almost always 120v, phase loading is easy once you know how many fixtures, at what wattages, on what dimmers. Non dimmed gear running on 208 is different as there a power factor to determine power draw. The device manuals usually tell you the power draw as well, but I'm deferring to others on this question as I never remember it.

 

[derekleffew]

... I think the Sensor portables are dims 1-32 on A phase on a 96 rack, but somebody else can verify that (I don't use portables that much anymore). ...

The color of the receptacle (female) in the patch bay indicates which phase a given given dimmer is on. For touring Sensor 48 and 96-way racks, it's 1-8 ØA, 9-16 ØB, 17-24 ØC, and so on.

Thus the circuits of a multi-cable don't have a phase assignment until they are pin-patched, and if for example, Soca A is patched 1-to-1 into dimmers 1-6, all six circuits A1-A6 will be on the black phase.

It's a little trickier on 208V moving light distro's, as those don't have a patch bay (at least I've never seen one). Two common methods:
1- AB AB
2- BC AB
3- CA BC
4- AB BC
5- BC CA
6- CA CA

While all this is good to know, don't waste too much effort in a feeble attempt to balance your legs.
1. Even if one starts with all conventionals balanced, as soon as the LD writes a cue it all goes out the window.
2. It's only really important when using a generator, and even then the genny will tolerate some imbalance.
3. Type "balance legs" into CB's search box and read some threads I think you'll find enlightening.

 

[SteveB]

Nice pic. Derek, I couldn't find any that would size up to something you could view. Thanks

 

[RickR]

Be aware that other companies and custom racks break all the rules listed above. That's normal for all parts of this crazy industry, right?