Sensor Installation retrofit

"The second rack is to provide additional circuits to the stage and another space, rather than increase available power"

Some thoughts on what you might be trying to do here:

1) I would explore with the folks at ETC, the practicality of partitioning a rack for dual spaces.  Might be easier to have 2 - 24 module racks, one for ea space, depending on numbers of dimmers needed per space.  It's no a big deal to have one 48 module with dual DMX or Net2/3 inputs driving a partitioned rack, it's just easier down the road to keep track of dimmer numbers with dimmers assigned to different spaces.  Do any of the existing and/or new dimmers get control from an architectural Unison type system ?.  Just things to consider.

2) Instead of bothering with bussing, might be cheaper to simply add add'l feeds and breaker to the new rack, leaving alone the existing, excepting whatever changes need to be made for the 90 degree turn.  Bussing makes you think about having to increase the feeders and main breaker.  Perhaps some add'l info about the plan for feed powe,r would be helpful, are you bringing in a add'l service ?, adding a breaker to existing for new rack ?.

Steve B.

The intent is to get a second rack and partition it into the 2 spaces, partly to add additional circuits in the main theatre and partly to provide new circuits for the new space. Taking away circuits from the existing dimmer rack to give to the new space would exacerbate the shortage of stage circuits in the main theatre. We've been thinking about how to accomplish things for a number of years now. A second Sensor 48 is the best option for us at this time. 2 Sensor 24s means an additional CEM. We considered a Smart system for the rehearsal hall but there's a lot to be said for having similar gear servicing both spaces.

Point 2 is what I am wrestling with. The building is serviced with 600A 3phase and the existing rack has dedicated 200A feed. . It's a fairly straightforward run from the disconnect to the dimmer closet, maybe 30 or 40 feet with a couple of right angle bends. I can't decide if it is worth it and was hoping to get some ideas from here before going out to our electrical contractor for estimates.

Today it is possible but unlikely to trip the feed to the existing dimmer rack if we were to load up every circuit to its maximum but we would have to use every instrument in our inventory running at maximum to do it. We have never done it in any real world situation. For any typical show it would mean hanging a triple wash and having every special in the show running at the same time. Even with the 2 spaces, the rehearsal hall would be limited to 36 dimmed and 4 relay circuits. It is unlikely (but not impossible) that we would be hosting concurrent performances. In the future we would be replacing some of the higher power instruments with LED, LIPI or some other more efficient technology and ultimately reduce the load, maybe switching out D20s for R20s as time goes on since a lot of the newer fixtures come with integrated dimming.

So does that warrant a separate feed and breaker?

The very first thing that raises my eyebrows, is the 200 amps currently feeding an existing 96x2.4kw rack and the plan to add an additional 96 dimmers/relays to that feed.  That's very little capacity in terms of demand load, (but offers a lot of control), in that you have excess circuits that you probably can never load up.  Doing some math, if you were to put a 575 watt load on every one of the main space 152 - 20 amp circuits, you'd end up with a demand load of 242 amps per phase, in the main space alone.  That concerns me.

One thought for the whole upgrade might be to go the route of shoebox dimmers, such as SmartModules.  I'd have an electrician install a lot of electrical outlets, all running back to a circuit breaker panel(s).  I'd then buy as many Smart Modules as you can afford (and power up), adding them into the space(s) as needed.  You'd have the power already located and that very same power could be used down the road for LED's, scrollers, ML's etc...with no need to buy relay of constant modules.  You could also add as budget allows. Distributed also give you dimmers designed for individual loads, as opposed to many more 2400w dimmers whose headroom you can't use.

As well, somewhere in the future you'd need to deal with data distribution to the LED's, scrollers, ML's etc... and if you put in DMX or Net3 now, that data is in place for the distributed dimming as well as accessories down the road. 

Going distributed also simplifies the dimmer numbering scheme, which is problematic in the rehearsal hall, where it starts at 153 or so.  Somebody long after you is going to have to deal with no circuit 1 and that kind of stuff drives people nuts.  With distributed you simply leave the addressing as whatever, plug the units, note the address numbers, patch and be done.  Everyone gets used to the flexibility, readily enough.

Steve B.

My mistake, it's a 400a feed to the existing rack. I'm not sure what I was thinking when I typed 200a.

We considered the SmartModule line as an option about a year ago as we first started looking at fitting up the rehearsal hall. It turns out that given our existing infrastructure, which includes several empty conduit runs to the stage and rehearsal hall, it is actually more expensive to implement distributed dimming. 

We would have to get the SM6-10X-C (GTL) to stay compatible with the main stage and be able to use any of our 750W instruments. We would also have to beef up our inventory of NEMA 5L-20 extension cords. Since the main stage is all Socapex and NEMA 5L-20, it's actually easier to use existing fan-outs and greatly reduce the need for extension cords.

My mistake, it's a 400a feed to the existing rack. I'm not sure what I was thinking when I typed 200a.

We considered the SmartModule line as an option about a year ago as we first started looking at fitting up the rehearsal hall. It turns out that given our existing infrastructure, which includes several empty conduit runs to the stage and rehearsal hall, it is actually more expensive to implement distributed dimming. 

We would have to get the SM6-10X-C (GTL) to stay compatible with the main stage and be able to use any of our 750W instruments. We would also have to beef up our inventory of NEMA 5L-20 extension cords. Since the main stage is all Socapex and NEMA 5L-20, it's actually easier to use existing fan-outs and greatly reduce the need for extension cords.

Yup, you're thought process makes sense.

Thus I understand the thinking behind bussing the racks, as 400 might well be enough to satisfy the demand load.

Using 750w fixtures totally changes the idea of shoe box dimmers, as you end up needing 1200w dimmers, but there are plenty of those available.

Still, hard to say which is cheaper, adding the Sensor 48, bussing the racks, then paying to install 96 circuits around the 2 spaces, or buying 1200w distributed dimmers and laying in power from circuit breaker panels.

Remember too, to consider the data distribution needs down the road and is it better to get it layed in now, while you have work being done ?, or later.

We faced a similar question when designing a new black box in a new building.  The original concept was distributed.  Then it developed that the shoebox dimmers weren't that cheap, in the numbers required and the consultant ended up spec'ing Sensor (or equal). 

SB

Were already good for data. We have CAT6, DMX, and coax to most areas of the facility, secure wireless, and dry runs of conduit in various diameters to pull through whatever else might be needed. With that, and network nodes we ought to be able to be reasonably future-proofed.  Given that most of us volunteers have day jobs in the telecom industry we're pretty adept at IP networking.

We actually have few low-end shoebox dimmers that we use for controlling practicals or the odd PAR36 tucked in to a tight space. Educating some of our volunteers in how to use them has proven to be a challenge. Some of them just won't grasp the concept of patching nor the difference between an address and a channel.