2 Circuits (outlets) per Dimmer

[CameronLD]

Hello CB!

At my school we have a problem that severely limits our ability to design effectively, which we have always called "double dimmers." I have also heard people on CB refer to it as "repeating circuits." What this means is that every dimmer is in some way connected to 2 outlets on each electrical batten. So where we should be able to to hang and independently control 140 fixtures, we can only have 70. This is especially becoming problematic as I try to design a warm/cool rep plot for the theatre, which currently leaves me with only 3 dimmers left alone in the cats.

I have tried to research and find out what exactly has caused this problem (and of course if it is reversible), but have not been able to find any solid information. I found things about ETC's Dimmer Doubling, but sadly appears to not be what I am looking for. What I am hoping is to find out the source of this problem, and then contact a stage lighting company and see what needs to be done (if wiring has to be redone, etc.) and fix this problem once and for all. Has anyone experienced this problem or have any advice on what might be the cause of it? Thank you for any help you can give!

Here are some specifications of our space:
Dimmer Rack - 2 Sensor SR(48 or 96) Installed Dimmer Rack
Dimmer Modules - ETC Dual 2.4kw Dimmer Sensor Module (D20)
Board - ETC Express 48/96
Dimmers/Circuits - 70 Dimmers, 140 Circuits (or outlets, correct me on the terminology)
Lighting Fixtures - Mostly Strand SL Coolbeams, a few Source Fours, and Fresnels
Visual Representation of problem:

 

[oneeyedpug]

This is typical of how many theatres have been built. How many dimmer do you actually have? to rewire the building is not going to be cheap in most cases were I have seen this solved is in adding more circuits to the raceways.

 

[CameronLD]

I am not exactly sure how many dimmers we have. Since I am a student I am unable to go into the school/theatre until around the start of school (the end of August) and therefore probably won't get to find more specific information until then. Where would you find the number of dimmers one has? Am I right in believing that each dual dimmer module has 2 dimmers? So 2 dimmers per module x 96 (number of modules total (I think)) = 192?

I believe you, but why would theatres be built like this? From my perspective I cannot see how there could be an upside to this system.

 

[rsmentele]

Another option would be buying portable dimmer packs and distribute them where needed.

 

[llburg]

First off, I second the notion that this is completely normal. Sometimes, it's a feature, not a problem/limitation. In most spaces, it's a positive because it allows flexibility where finances don't allow the installation of more dimmers.
Second, I find it very odd that you claim to have (2) SR-48 racks (SR-96 doesn't exist, racks are named based on module spaces) but only 70 dimmers. 70 dimmers wouldn't fill up a single SR-48! Could you give us some more information, such as how many D20 modules you have in stock? We can assume 35, but just to be sure.
To directly answer your question, yeah it's "fixable", but not without a lot of time and (even more) money.
Edit: in your second post, you posit that you own 96 D20's. While certainly possible, (with 2 full SR-48's), if you really do only have 70 dimmers two-fered to 140 receptacles, it's not likely.

 

[CameronLD]

Sorry, I thought I saw something about a SR96 somewhere. What I mean is that we have a full rack of some Sensor model dimmer rack. We also have some sort of dimmer rack that is like 1/4 of the size of the main one, and is off the ground and connected by pipes to the first one. My guess is that we have a SR12 (if that is a thing) and an SR48. So, would that mean, since the modules are dual dimmers, that we have 120 dimmers?

What I was kind of hoping (albeit apparently incorrectly) is that you could just flip the dimmer around, take wires out of some sort of twofers, and then replug them into dimmers individually. Is this likely not to be the solution?

 

[oneeyedpug]

This is not an easy thing to fix, as far as I know. On another note I see 85 Circuits on your plan not 70. It is also possible, and typical for the smaller rack to control the house and work light system.

 

[CameronLD]

Sorry, my apologies, I forget about the circuits in the pockets.

Thats disappointing :/ So is it the wiring that is creating the "double dimmers?" As in, one wire is simply connected to another wire in a series circuit which then flows to the dimmer?

 

[llburg]

No need to apologize, we all learn together. The smaller rack is likely the house/work lights, maybe a few extra stage circuits. Unfortunately, you probably only have as many dimmers as are numbered. It's possible the rack is filled, but schools are usually cheap. In my experience, circuits are normally "two-fered" in the raceway, not the rack. The wires leave the dimmer rack and are routed to the first receptacle, then in parallel, (Not series), to the other receptacles with the same number. It's cheaper at the install (roughly half the copper), but as you've seen less flexible in the event of an upgrade.

 

[oneeyedpug]

This is also called a Combination Circuit, are you in high school? if so you are doing very well and have no need to apologize.

 

[Les]

Sorry, there isn't really any easy way around this. It's just the way your space is wired, and the only hope of changing it is having ETC come out and pull more wire. It doesn't sound like you have enough dimmers to independently supply power to every circuit in the raceway - so no, you can't just switch some wires around.

Designing around these issues will help you grow.


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[gafftapegreenia]

There really is no "fix" for this. I think it's a hold over from the days of full stage border lights. The likely solution for more dimmers is distributed dimming.

Since you are a student, think of this as a great opportunity to overcome a design challenge. Making spaces work as they are with what they have will get you a lot farther in life than trying to "fix" every space you work in.

Sure it's nice to have individual control of each light in your down light system, but how often do most designers really take advantage of that anyway?


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[AudJ]

My guess is a full rack of 96 dimmers,(48 modules) and the remaining dimmers feeding house lights. There could be some constant modules, to feed Edison outlets and other constant power needs. The numbers on your circuits seem to support this theory. There may be some spares in there also, but utilizing them will involve a bit of expensive work.

Your room is wired very similar to mine, and I have lots of free dimmers.

Why not take advantage and plot your warms and cools in pairs on the same dimmer? For example, if you have a warm and cool on circuit 31, you can point them in opposite directions at a Downstage Right general area (upstage of the first electric). You might start with a grid of say 9 or 12 areas, and alter based on your needs. If you find a variety of circuits that pair to fill your stage, you have general area control, as well as a lot of extra dimmers freed up.

 

[CameronLD]

Yes, I am a rising Junior at my high school.

AudJ, is that something that is commonly done? I will attach my current plan for a warm/cool rep plot below, but I thought that you would usually want to control each system independently?

 

[oneeyedpug]

What you have drafted looks exactly like the layout I would do. In my opinion putting dimmer and closest dimmer on the plot confuses things, do you channel your lights different than the dimmer they are in? also why do you have a 26 deg as the closest area and a 36 deg as a more upstage area?

 

[CameronLD]

We ususally just use a 1-1 patch, but that may change next year. And I am using 26 degs for the front two rows as those areas are smaller than the last row. In addittion, my supply of 26 degs FAR outweighs the supply of 36s that we have. In fact we are going to have to buy a few 36s just to make this plot work. I put closest dimmer to denote position/to try and avoid confusion with the other circuit (b/c of the double dimmers).

 

[oneeyedpug]

Typically the plot would have foot markers so you know were to hang the lights, for me (and this is just me) having closest dimmer is more confusing. I have attached an old plot I fould to help ilistrate my point, this may or may not help.

 

[BillConnerFASTC]

A project budget determines how many dimmed circuits. The choice to parallel two outlets is from each dimmed circuit is mostly independent of the number of dimmers. On dimmed circuits, we often do two parallel receptacles, but I'm more likely to do them adjacent (1-1-2-2-3-3 rather than 1-2-3-1-2-3) because I think it's easier to keep track and they are basically a built in twofer (at lower cost, less maintenance, and no storage required compared to twofers).

Today, however, with the move to LED and other lighting that just requires power, I'm not sure you can put in too many receptacle per (non-dimmed) circuit.

 

[derekleffew]

... So is it the wiring that is creating the "double dimmers?" As in, one wire is simply connected to another wire in a series circuit which then flows to the dimmer?

Almost. One pair of wires (hot & neutral) for each circuit runs from each dimmer in the the dimmer rack to the raceway in the lighting position. Then the two (sometimes more) receptacle s of the duplicating circuit are two-fered (wiring, parallel) inside the junction box at the end of the connector strip. The system designer/electrical engineer did this to help you, to eliminate you having to use actual two-fer s. But, as noted by everyone, the duplicating circuits are seldom in a scheme that works for every lighting design. Most would much rather have only one outlet per circuit and a pile of two-fers and cable jumpers. Adding more dimmed circuits means having to add wires in the conduit from the dimmer rack to the lighting position, unless one uses the ETC Dimmer Doubler system which opens a whole new set of complications.

Most simply ignore the repeating outlets and adopt, "If I use this circuit x here, I can't use that circuit x there." Makes the original intent futile and a waste, but it is what it is. Good lighting designers learn how to work within and around limitations.

 

[AudJ]

I can't speak for what is common, just one way I have learned to deal with the issue in my space. There are lots of different ways to go at this. Your initial concept is a better way to go, but when resources are limited, we have to become more resourceful with our planning.