Control/Dimming - Adding Dimmers - measuring power

[hobbsies]

Hello! I am the ME for a theatre company in chicago that rents out a space for their shows. The space has 72 2.4k ETC dimmers. The company I work for happens to own a 96 dimmer rack of some variety. What I'm trying to figure out is if the space can handle more dimmers, and if so, how many? How do I figure out how much power is flowing into the space? As I understand it, I just need to know if there's enough amperage to support more than 72 dimmers. The director of the space mentioned to me that they have 2 by 200 amps. That seems really low to me, but what would the "2" refer to?

Thanks in advance!

[epimetheus]

This is just an assumption, and you should really verify, but I bet the 2 x 200A probably means (2) 200A, 3 phase, 208Y/120V feeds. A 96x2.4kW dimmer rack typically uses a 400A feed.

[JD]

As we are talking about a "show" as compared to a permanent install, the real question is "What is your load?" The dimmer rating only tells you what the maximum load is that you can load a channel with. I think it is a safe assumption that all 96 dimmers are not going to be maxed out at 2.4k. An unloaded dimmer draws nothing. (well, almost!) I would also question that 200 x 2 statement. Sounds unrealistic.

[ajb]

It's important to know what else is on those feeds as well. If you've got lots of other circuits on those panels you may need to have someone come out with a recording meter to get an accurate picture of your actual utilization. Any commercial/industrial electrical contractor should be able to provide this service. Beyond that, you need to look at how many units at what wattages you're going to be putting on those 96 dimmers.

[derekleffew]

hobbsies, first welcome to the Booth. You could start a thread in the New Member Area to tell us more about the theatre company, venue, and yourself.

The easiest way to answer your question is to follow the feeder cable or conduit back to the panel and see what size and type OPD is feeding the service to the dimmers. As JD said, the size and quantity of the dimmers is almost immaterial--it's the connected load that matters. See Dimmer feeds--How much power is enough?. It's very likely that you already don't have enough capacity for 72 x 2400W loads, but that doesn't prevent you from bringing in a 96x2.4KW rack, and/or even using both simultaneously.

I'd guess, knowing Chicago's propensity for storefront theatres and other "found spaces," that the director of the venue meant two hot legs of 120V each at 200A, which would be one third of what epimetheus thinks.

[Footer]

Agreed with Derek. Chicago is full of theatres that are converted spaces. If this is one of them, odds are you won't find a true 3 phase disconnect. Added to that, if they only put in 72 dimmers to start with (probably with 6-12 packs or 3 24 packs) you might not have enough power to do what you want to do.

Figure out how much power you really have... divide.

As others have said, you can have 600 2.4k dimmers hooked up to a 20amp receptacle in your house.... however you can only use 20 amps of power...

[iLightTheStage]

Hello! I am the ME for a theatre company in chicago that rents out a space for their shows. The space has 72 2.4k ETC dimmers. The company I work for happens to own a 96 dimmer rack of some variety. What I'm trying to figure out is if the space can handle more dimmers, and if so, how many? How do I figure out how much power is flowing into the space? As I understand it, I just need to know if there's enough amperage to support more than 72 dimmers. The director of the space mentioned to me that they have 2 by 200 amps. That seems really low to me, but what would the "2" refer to?

Thanks in advance!

A big question for you is: Why do you want to add another 96 rack? Do you want more control over existing lights, or are you trying to add more lights? Also, do outside groups bring in lights for productions, or is this a rep-plot type of situation?

In terms of determining how much power is there, call a licensed electrician to look at the space. Just because you trace the wires back to a 200amp disconnect does not mean that there is 200amps available, it means that the size of wire required a disconnect rated for 200amps (and even that might be overkill). One venue I work in has three 100amp disconnects in different locations that all end up back at the same 100amp source. So, never assume, know!

[derekleffew]

... Just because you trace the wires back to a 200amp disconnect does not mean that there is 200amps available, it means that the size of wire required a disconnect rated for 200amps ...

Don't you have that a bit backwards? The wire size determines the OPD? Agreed that the disconnect may not be the final determining factor; more investigation is often necessary.

[STEVETERRY]

Don't you have that a bit backwards? The wire size determines the OPD? Agreed that the disconnect may not be the final determining factor; more investigation is often necessary.

That is correct--you can have a wire size with an ampacity larger than the rating of the OPD, for purposes of voltage drop compensation, for example. But, you can never have a wire size with an ampacity smaller than the rating of the OPD, except in special cases under the "tap rule" which does not apply here.

ST

[tjrobb]

In response to dereklefew, if you are running 120/240 (single phase), I know Sensor racks, and likely most other racks, require 3 phases for 96 dimmers. There may be a way for the factory to adapt them, but if they are already bought they are likely not going to work on one phase power.

On the other hand, if the amperage is available (from the service onward), are the added harmonics going to cause problems with your transformer? In theory anywhere running large amounts of non-sinewave dimmers already has transformers that can deal with harmonics, but its best to avoid overloading / damaging the transformer. This is something that would best be asked to a licensed electrician.

[iLightTheStage]

Don't you have that a bit backwards? The wire size determines the OPD? Agreed that the disconnect may not be the final determining factor; more investigation is often necessary.

I'll agree and also slightly disagree with this one. I was thinking of simply a disconnect, and not a breaker, since he could trace back to a disconnect, and the breaker for it be farther up the line, sometimes hidden in an electrical room somewhere else. Therefore the disconnect wouldn't be an OPD because it is just a big ol' switch. But otherwise, yes, a breaker should always be sized to the wire...although in many spaces we've all seen many "should be, but not" situations.

Mainly my point was: he should call a licensed electrician to find out for sure. But I do appreciate the correction/elaboration.

[gordonmcleod]

It would also be prudent to determine what the main feeders to the building are and what other house loads are on it
If the 200amps is the mains to the building then you would have issues
if it is a dedicated company switch for stage then that is what you have and there may be more available on the house service
A proper load study needs to be done

[hobbsies]

hobbsies, first welcome to the Booth. You could start a thread in the New Member Area to tell us more about the theatre company, venue, and yourself.

The easiest way to answer your question is to follow the feeder cable or conduit back to the panel and see what size and type OPD is feeding the service to the dimmers. As JD said, the size and quantity of the dimmers is almost immaterial--it's the connected load that matters. See Dimmer feeds--How much power is enough?. It's very likely that you already don't have enough capacity for 72 x 2400W loads, but that doesn't prevent you from bringing in a 96x2.4KW rack, and/or even using both simultaneously.

I'd guess, knowing Chicago's propensity for storefront theatres and other "found spaces," that the director of the venue meant two hot legs of 120V each at 200A, which would be one third of what epimetheus thinks.

I think this is accurate. There are two large circuit breakers that feed directly into the dimmer rack.

The space is a very old theater, although it's very storefront-like. It's the Chopin Theater and it's been around since 1918. The guy who runs it now bought it in the 80's and fixed it up.

I don't think we'll be adding this 96 dimmer rack, but he did have some analog dimmer packs I'm going to try to use. We definitely don't max out dimmers, especially since all the circuits are edison and have a max load of 1800w (some 1200w ty cheap extension cords).

I'm curious, do a lot of people here have official electrician training? I go to college here as well, but there doesn't seem to be a lot of electrician courses, it's more about design.

[derekleffew]

...The space is a very old theater, although it's very storefront-like. It's the Chopin Theater and it's been around since 1918. The guy who runs it now bought it in the 80's and fixed it up. ...

Interesting history here. Theater (Nickelodeon)>bank>disco (for only one night!)>vacant>theatre.

[mstaylor]

I don't think any college is going to teach electrical courses as part of your theatre training. You should get a good background in wiring cables of all types, 110v, mic cables and DMX. You should learn how to determine how lights to a dimmer, how to program boards and the same type of thing on the sound side. Being an electrician is a whole different course of study.