Conventional Fixtures Electrical Needs

RenegadeProducer

RenegadeProducer

Member
Ok this is going to sound kinda amateurish, but oh well. I'm a small scale designer here in S. Florida, and like my previous experiences in other parts of the country I generally find myself in very small 99 seat (or under) venues. I do have to chance at times to work in larger houses, but usually they are established houses and I really just need to know the dimmer capacity and the fixture inventory. I rarely think about the raw power aspect of things. Until now.

I am assisting a small theater in relocating to new and better(?) digs. I was charged with booking the electrical upgrade for the space - its a church chapel. my problem lies with electrical contractors and the art of load calculation. I know that as a general rule lighting designers will use every available amp that they can get their hands on...even if it means unpluging the coffe pot and microwave :) How do you get that thru the heads of the typical contractor. We just installed a 200A (4wire) upgrade into this building so I could at least get the current packs (chauvet TFX-D12) online and ready to go. I thought that seemed a little light (12 * 10A) on 2 packs

what do you guys think? I was hoping to get him to pull a full 3phase service and try and get 300-400A to be able upgrade later..is this too much to ask, Am I not figuring this right? Or am I being totally unrealistic? His reply (he's legit btw) : "You will NEVER EVER more that that 200A EVER". I just scratched my head and went off to look at the specs for a typical ETC 48/96 rack.....PLEASE help/enlighten. I also hope to be able to start work on my own space in the next year or so, and I would like some advice on what I should be looking for in the power department as I compare spaces .

THANK YOU!, Sorry for the long post..I'm just lost, confused and in need of a drink now :)

-Nate
South Florida
 
In this case I suspect when you say 4 wire you are talking about HHNG, which would give you two 200 amp legs for a total of 48kw of power. Your current setup is 1/2 of that. Even if you de-rate the incoming feed as having a 100% duty cycle that is still over 38 kw continuous use. Unless you add more equipment, fully load each dimmer, and like to turn everything on and leave it on all the time, I suspect he is right.

There are specific profiles in theater written into the code that allows for the fact that in the real world dimmers are not often fully loaded and that dimmer capacity can therefore exceed the distribution supplied to it. I am sure your electrician can fill you in on the specifics.
 
Nate,
I'd add up the wattage of every stage lighting fixture the venue owns, then add a factor for potential new purchases and/or rental equipment. Assuming a 3Ø service, divide your total watts by 120, then by 3. This will give you amps per leg.

See also Dimmer feeds--How much power is enough?. In general the fewer the number of dimmers, the more likely they are to be loaded tp a higher percentage of capacity, but I would minimally want the ability to load every dimmer to 50% capacity.
 
Echoing John D's comments, there was a whole thread about this back in July - http://www.controlbooth.com/forums/lighting/20694-electricity-question-dimmer-feeds.html

One of the things Steve Terry was pointing out was that *typically* loads have been coming down with the use of 575w lamps as well as LED's etc... The load survey that ETC did in '05 and whose link was posted in the thread, supports that. ST's opinion is that the requirement to provide a Sensor 48 full of 96x2.4kw dimmers @ 800 amps per phase is inappropriate due to the lesser loads typically being applied.

My premise was that for large systems with 4 or more Sensor type racks full of 2.4kw dimmers as example, there's always a lot of spare circuits spread around a space that get only occasional use, BUT that with smaller facilities with 1 rack, or less, that the dimmers tend to get loaded closer to capacity. Much depends on the "architecture" of the space - I.E. how many fixtures can physically fit in the space, on the available positions ?. That often times, tends to drive the load calculations, combined with the wattages of the current and planned inventory.

The de-rating John referes to is the requirement to treat the 200 amp breaker as a 160, in the event you turn everything on and leave it on for more then 3 consecutive hours, which believe it or not can sometimes happen, even in a theater.

Thus you, as the LD need to plan for that plus whatever extra's you think the typical budget might allow for, and chances are you'll come up with a figure much like what John is suggesting.

SB
 
Correct, its HHNG. based on what you saying - I think I figured this out prior to this whole mess and forgot it :( The 200A is per leg - DUH!. My electrician doesn't really work with theater's at all - this was kind of a favor. If I wanted to upgrade this system later and get up in the 48 x 2.4k range what do you feel I need to be looking for with regard to my incoming service. I know I need a separate panel for the rack- that's obvious. But if we assume that the service isn't ever going to be maxed out, how do we figure what we need? I know that at this level (small-tiny) I tend to use every bit of juice I can possibly squeeze out.
 
I was posting while yall were so I just now saw your replies - thank you!

I remember reading the ETC article a while back, and I will agree with you Steve that at the level I am working at we tend to max out what we using. I know that the packs we just reinstalled are 1Ø so that's what they installed for. I assume that If I am able to squeeze some more blood out of the proverbial turnip I maybe able to upgrade and that will mean going thru this all over again and upgrading to a 3Ø service..ARGH!
 
So you currently have 2x 12x10A packs, fed by a 200A split-phase service? Do you have more than 48x 500W/575W fixtures? I see no reason you couldn't add an equal number of the same capacity dimmers, with no change in service. Again, go by the load, real and potential, and not the dimmer packs' faceplate rating(s).
 
SteveB said:
One of the things Steve Terry was pointing out was that *typically* loads have been coming down with the use of 575w lamps as well as LED's etc... The load survey that ETC did in '05 and whose link was posted in the thread, supports that. ST's opinion is that the requirement to provide a Sensor 48 full of 96x2.4kw dimmers @ 800 amps per phase is inappropriate due to the lesser loads typically being applied.
Click to expand...

So are you trying to say that its not necesary to have an 800amp 3phase disconnect for a Sensor+48 rack because Not every dimmer will be maxed out and ontop of that you wont use every dimmer. Did I understand you correct?

So Im curious, does it cost more to install an 800amp disconnect vs a 400 or 600? I mean, If I have an 800 amp disconnect but only use 480 amps of power. Would it cost me any different than Using a 600 amp disconnect and maxing out power with 480 amps?? (20% deratting. Check my math?) And If there is no cost difference, would it not be smarter to just get the 800 amp disconnect JUST IN CASE. Im sure you wont max out to 640amps, but what if I want 500 amps of power. Then wouldnt I need a 800 amp disconnect?
 
It is much cheaper to install a 400 amp service then it is an 800 or 600 amp service, this is because an 800 or 600 amp service requires larger or more conduit, more copper and more work to pull through the conduit. The likelyhood of someone needing the full capacity of a Sensor+ 48 rack is very small. In fact most Sensor+ 48 racks are installed with 400 amp services, even in professional installations. NNHS's 3 brand new Sensor+ racks have 2 400 amp feeds and a 225 amp feed. Trinity Repertory Company's 4 racks each have a 400 amp feed, The Zeriterion has 400 amp feeds for each of their 3 racks. In fact most of the Sensor+ 48 racks I have seen have had 400 amp feeds.

I do believe the biggest factor as to why 400 amp feeds are so popular is you can pull an entire 400 amp 3-phase feed with double neutrals through a single 6 inch conduit. However when you get up to the 600 and 800 amp feeds it requires 2 4" conduits and ether thicker cable or two sets of thinner cable, both of which cost more money due to time in labor and materials.
 
It sounds to me like you have two issues. One is to figure out what a reasonable amount of power is. The second is to convince your Contractor / consultant that you have not been smoking the funny weed.

The key thing to remember ( that I have not seen addressed in this thread ) is that it is not the number of dimmers you install that drives the amount of power you need, it is the number and wattage of the fixtures you will be putting in the space. This is not the number of fixtures you have, it is the number of fixtures you will ever want.

In my experience the best way to figure this out is to do a full on design for the space with no practical limits on the number of instruments you have. What is a reasonable max number of fixtures / wattages you will want in the space to fully light it. Use that number to determine how much power you need.

For example, 60 S4's at 575 watts plus 20 ParNels at 575 watts plus 20 fresnels at 500 watts would get you to 56,000 watts. Dividing by 120 volts, this gives you a need for 466 amps. Assuming three phase power, 200 amps would be plenty. For a small space with no cyc, this might be fine. The point is that you need to do the design because you are the guy who understands the space and what kinds of work will be done there.

Once you do this analysis, you can show your electrical guy why you believe you need more power, assuming you do. (The HVAC guy really needs this number as well as you may be undersized on AC).

As to pulling in more power later - probably a much more expensive and difficult alternative. Generally it is better to get the power in once, instead of several times.

Good luck with the project - sounds like fun
 
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derekleffew said:
(His profile page lists some of his accomplishments. Did also you know that, in the summer of 1986, he invented DMX?;))
Click to expand...

And all this time I thought his greatest accomplishments included wearing sandals into the office everyday. :p

To clarify the topic on dimmers, the trend is that people want control over more fixtures individually. 2.4kW is a sensible amount of power for a dimmer as you can three-fer three 750w lights on a circuit or four-fer four 575w lights on a circuit.

The reality is that people are stubborn about change. Many theatres (typically those who have circuits to spare) only two-fer occasionally, and almost never three-fer. If four-ferring was a regular-enough thing, it'd not sound as weird to say.

The cost of installing 1.2kW dimmers, at the modules at least, is negligible. In this sense, people don't want to not be able to hook three of four fixtures up to a dimmer simply because they didn't toss a few extra dollars at the dimmer modules.

Imagine, though, if theatres were all equipped with 1.2kW dimmers and all of the wiring was downsized respectively. You could probably save a lot on wiring, conduits, distribution, and cables. Imagine not having to chop your leg off to pay for a 50' 12/3 SOOW cable because instead you could safely use 16/3.

But -- I digress. Theatres aren't straying from 20A circuits anytime soon. As an industry, we'd have to reinvent the wheel with crafting up UL-listed 10A connectors, teaching ourselves that we really don't need all of that extra power (most of us, anyways) because instead what we seek is more control. Personally, I can't remember the last time I two-ferred lights together except for the occasions when they're in a room without dimmers and I need to get them combined on the same wall outlet. Others can't think of a show where they didn't two-fer some lights together.

As this subject relates to the thread, though, there are NEC policies in place to acknowledge that few theatres max out their dimmer racks. The ones that do are the ones that just plain wish they had more dimmers in the first place so that they could individually control more lights. Before hopping on the boat though to determine your power feed by multiplying how many dimmers you want by their rated capacity, instead figure out how many lights you realistically want to turn on. From there, give yourself some headroom because things change. Different products are released, renovations happen, different users enter a space and may want to use it in a way you had never imagined possible. Do your best to future-proof changes that you make so that a few years down the road someone doesn't want to undo them or has to add to them in what is usually a very expensive after-the-fact.

Unless you really plan on four-ferring your lights though, don't think having (3)SR48 racks filled to the brim with D20's means you need 1920A/3ph or the electrical inspector is going to shut you down. We have that dimmer rig and we have just 800A/3ph, and I'd say we actually use maybe 350A/3ph -- if we hang every light and turn every circuit on including the lobby and house lighting.
 
Funny thing looking back in time- In the 1980s, I saw many traveling shows adopt DPC (Dimmer Per Circuit) using 1.2 k racks and the prime reason given was to lighten cable load. Many traveled with 16/37 SDN cable with the old military style 37 pin Veams. As time went on, the "1k" Soca started showing up. (14/14 or 16/14) Now we are back up to 12/18 Soca. In fact, #12 is the accepted (if not required) norm in most applications. Looks like we have come full circle and in the process lost the DPC advantage. Still has some as you can soft-patch as compared to drag cable, but the advantage to touring shows has dropped.
 
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3-Phase 4-Wire is HHHN, with the ground not counted (just like they aren't counted in portable or NM cable). Then again, a second neutral would not be counted either.
As a note, we have two 48/96 ETC racks off one 600A main breaker. Can plug every light we own into the system (actually, we ran out of plugs before instruments) and not trip any breaker. Maybe this gives you a place to start.
FYI, 80% rating typically does NOT apply to magnetic-only and electronic trip breakers; these types are often found in switchboards and the dimmers themselves.
Now cable derating, that is another, evil, beast...
 
tjrobb said:
3-Phase 4-Wire is HHHN, with the ground not counted (just like they aren't counted in portable or NM cable). Then again, a second neutral would not be counted either.
As a note, we have two 48/96 ETC racks off one 600A main breaker. Can plug every light we own into the system (actually, we ran out of plugs before instruments) and not trip any breaker. Maybe this gives you a place to start.
FYI, 80% rating typically does NOT apply to magnetic-only and electronic trip breakers; these types are often found in switchboards and the dimmers themselves.
Now cable derating, that is another, evil, beast...
Click to expand...

Funny you should mention cable derating. I have just finished an article for ESTA Protocol called "Understanding Hidden Electrical Diversity in Entertainment Lighting Systems". I thiink it may be interesting to many CB'ers.

ST
 
tjrobb said:
3-Phase 4-Wire is HHHN, with the ground not counted (just like they aren't counted in portable or NM cable). Then again, a second neutral would not be counted either.
As a note, we have two 48/96 ETC racks off one 600A main breaker. Can plug every light we own into the system (actually, we ran out of plugs before instruments) and not trip any breaker. Maybe this gives you a place to start.
FYI, 80% rating typically does NOT apply to magnetic-only and electronic trip breakers; these types are often found in switchboards and the dimmers themselves.
Now cable derating, that is another, evil, beast...
Click to expand...

I believe the original post was referring to a single phase 4 wire arrangement (or two legs of three phase) which would be HHNG. The poster was wanting them to upgrade to 3 phase. Also, de-rating would depend on the source breaker on the feed which typically would not be magnetic. Equipment cost tends to jump quite a bit when that third leg is added, which probably is why he is meeting resistance.
 
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