Running power around an arena

[Les]

This is technically about confetti, but my question is concerning electrics.

We are going to be using confetti blowers at a 10,000 seat arena soon. There will be 8 of them, equally spaced, along the upper ring (they will be aimed through the windows in the picture below). During my initial site visit, I found that the circumference of the arena is approximately 600' (based on about a [-]70'[/-] 70-yard diameter). The upper ring is continuous.

The confetti blowers use a squirrel cage blower to operate (essentially a modified carpet fan). The specs are 1/4hp, 3A. Now, I would like to go the simplest route possible. They will be controlled from one location, which will most likely be next to one of the fans. My initial thought is to branch out and have a left and right line, so each extension would cover 4 fans (about 400'). Based on my calculations, each fan will be about 75' apart. There is not a lot of run time for these effects.

There will also be a separate channel for air-actuated cannons which will shoot streamers. It will use the same set up, and this is why I do not want to use DMX relay packs and the like. I don't want to have to deal with signal issues -- especially having something fire the cannons prematurely.

First thoughts are to buy several 12g 75' extensions and "tap off" at each connection (4 per side). What do you guys think?

Here is a picture and a very simplified drawing of the space (each arrow represents a blower & cannon).

 

[JD]

The only thing that comes to mind is that all 8 motors will be starting at the same time. Might want to do a real-world test to see if the inrush is a problem. The other thought is to double check the actual cable distance, including any routing in and around doorways etc. Other than that, I agree in having the switch thrown manually as compared to DMX, especially on the streamer cannons.

 

[BillESC]

I don't see a problem with the proposed solution.

 

[Amiers]

Well JD you beat me to it with the 8 motors starting up at the same time :/ I think it will work just fine and make sure the windows are open hehe.

 

[Footer]

With the splitting method you do have more points of failure. You also need to figure out what the inrush is. Having 6 connections between your power source and your last fan could be an issue in terms of voltage drop. I would probably do 4 home runs and only run two fans per tap. Half as many points of failure, plenty of headroom, etc. 12 amps running draw does not leave much room for inrush or voltage drop over that length. If your in an old arena breakers could pop at 18 amps instead of 20.

Finally, I would work on your load out plan. I would highly advise you to get the hell out of the building before the night gang arrives to clean the building.

 

[derekleffew]

Looking at the thread title, I thought it was going to be simple, as running power around an arena is something I do quite a bit of, on occasion.

Eight 75' 12/3 extension cords and six cube taps should work fine. I'm guessing you're concerned about potential voltage drop due to the long runs and its effect on the fan motors?

I want to draw it out and do the calculations, but need more info about the exact cable in question to be accurate (The online calculators always ask too many hard questions!).
The first cord, from the Source to Fan#1 would be 75' long and carry 12A.
The run to Fan#2 would carry 12A on 75' then 9A on 75'.
The run to Fan#3 would carry 12A on 75', 9A on 75', then 6A on 75'.
The run to Fan#4 would carry 12A on 75', 9A on 75', 6A on 75', then 3A on 75'.

Source-----12A-----Fan#1-----9A-----Fan#2-----6A-----Fan#3-----3A-----Fan#4.
Using this calculator (better calculators ask more questions),
and starting with 120V at the source:
Voltage at Fan#1: 117.14
Voltage at Fan#2: 115.0
Voltage at Fan#3: 113.57
Voltage at Fan#4: 112.86

All hypothetical, and I would expect to lose some minimal percentage of voltage at the connections as well.
A similar scenario to color scroller head-feet calculations.
My hypothesis is that it won't be a problem, although each fan will be running at a slightly different speed because each will be getting a different voltage. Unless they are frequency controlled fans; are they?

... I found that the circumference of the arena is approximately 600' (based on about a 70' diameter) ....

Check your maths; something's amiss. C=∏d.

Looking at it another way, the circular arena's stated area is 21,290 ft^2, which gives us a diameter of 165' and a circumference of 518'.
.

 

[len]

3 amps each? Are those windows to luxury suites or something? If so, I'll bet there is wall outlets in each suite and they are on mostly separate circuits. If so, I'd put each on a relay and do wireless dmx with the receiver sitting in the window. While I'm mostly in favor of running cables as opposed to wireless, this seems like a big pain to run power around the venue. Unless, you can run power outside the windows, but that would look uglier.

 

[Les]

Thank you all for your help so far! derekleffew, I really appreciate all of your calculations. As much as I would like to say that we plan on using 12/3 SOOW, it will probably be 12/3 black extension cord. Also, they may end up being 100' in length in order to give us some slack here and there. Failing that, maybe we can rent some cables locally. The ring/catwalk we are running these cords around and shooting from is essentially a circular hallway with a concrete floor. No luxury boxes or anything like that -- it's pretty open except for an electrical room every 100' or so (some of which I can cable through, and some that I will need to go around). I am concerned about the voltage drop and inrush current, so I may be taking len's advice and doing more home runs. This is a very old arena - Dallas Convention Center Arena which I believe dates back to the 50's. [1957.]

The clean up crews are going to hate us. This is a 15-day event with "A,B &C" performances. Confetti will be blown on all "B" days (5 total). Streamer cannons (which are super easy to clean up after) will be fired on "C" days. "A" days are pyro only. First performance is on 7/22 and it will end on 8/7.

Thanks for your advice on the windows, Amiers .

Oh and you guys should have seen all the Super Troupers in this place! Seems like they had some newer ones near the windows (they were square), but they had nearly a dozen parked near a wall in the upper ring. They appear to be unmodified carbon arc units. Doesn't appear that they use them anymore as each unit seemed to be missing some parts.

 

[JD]

Oh and you guys should have seen all the Super Troupers in this place! Seems like they had some newer ones near the windows (they were square), but they had nearly a dozen parked near a wall in the upper ring. They appear to be unmodified carbon arc units. Doesn't appear that they use them anymore as each unit seemed to be missing some parts.

 

[Les]

Yeah... I might be seeing if they have a surplus website or any auctions I can go to

Here's a quick picture I took of them. Didn't mean for it to be such a closeup. They're huge!



Derekleffew, thanks for the catch regarding the math. When I typed the post, I forgot to convert to feet. I used my viewfinder to check the distance from one window to the window across the arena from me, which came out to be between 68-69 yards. I rounded up quite a bit (kind of a habit when we're measuring clearances for pyrotechnic effects. If this were for a pyro effect, my numbers would be quite a bit more precise. Luckily, we usually only have to worry about straight lines ).

 

[Chris15]

One could use a series of relays to achieve the best of both worlds...
Use a mains feed from the control point to power the relay coils, switching power to each unit picked up locally.
Or you could use low voltage for the coils and reduce the cable needs (and code compliance requirements...)

 

[museav]

I'd be concerned about the routing and paths available as I believe you are usually not supposed to run extension cords through holes in walls or ceilings, above ceilings or in walls or through doorways or window openings. I'm not sure how you will get through or around the Electrical Rooms without violating at least one of those.

I also wonder about the code compliance of a daisy-chaining extension cords using multi-taps as that is effectively a power distribution device plugged into another power distribution device or at least an extension cord off a power distribution device.

 

[Les]

Thanks for your reply, museav.

The arena LX rooms are set up as follows:



Looks like I can still use the entire hallway area and be unrestricted by walls and not have to pass through doorways. I will need to pass in front of them, but I will use cable paths (none of these door openings actually have doors attached). That, or I may take the outside perimeter.

Unfortunately, I don't know of any other way to do this without connecting a bunch of cords together. DMX is obviously not a viable means of control for confetti cannons that need about 0.1 seconds of power to pop the solenoid. Chris15's relay idea would work for us, but we don't have the time to order the parts necessary (we just received the contract on Monday). A more "packaged" approach to Chris' idea would be the on/off switch panels that DJ's use with remote relay packs and analog cable, but I'm thinking the system is a little clumsy for the lengths of cable we'd be running, and the number of packs that we would be daisy-chaining together.

 

[SanTai]

A few thoughts about alternate solutions.

I would trust dmx for the blowers, even a very long burst of bad dmx(in the timescale of electronics) would, if at all, barley get the fans moving. You probably know this but not perhaps everybody else here, many commercial confetti blowers use a universal engine and the manufacturer sugests using a dmx dimmer for control. It is simple, cheap, easy and clean.

What kind of streamer cannons are you using? Are you sure your normal pyro controller(pd,f1,galaxis?) do not deliver enough power to trigger them? Worth trying. One module at each position and you are good to go. Could work with both the one-shot kind and solenoid kind. Check the specs and try it out. By the way, having a few relay modules that you can connect to the output of any pyrocontroller for simple mains control is really useful tool to have laying around at the warehouse.

Another thought, why not take the chance to try out some new rookies. If you are only turning on a blower on cue, usually not extremely time critical, there are not much to screw up. If it is not extremely important with timing on the streamers you could fire them manually as well.

 

[Les]

...

 

[Les]

Just a quick update.

We looked in to the Holatron firing system relay. Unfortunately, they only have two of the 24v input (which is the output voltage of our firing system) models in stock. We went ahead and ordered them since we can use them to fire our Co2 jets, but I'm back to square one on the blower/cannon setup.

I hate the idea of extension cords, but it looks like I may have to go that route.

I could build something, but I'm not sure I have the time since I'm also coordinating the construction of the confetti blowers as well as other logistics for this event. The relay I'd need would need to close when a 24 volt input voltage is initially applied and reopen when the same voltage is applied again (the firing system sends these voltages out in a burst when they're firing cues). But again, I doubt I have time to source all the components and build/test the system in such a short time frame.

 

[SanTai]

I would sugest that you check the datasheets of your solenoid valves for the streamer lunchers(you said they were made in house). Usually there are no difference between 230VAC(or 110VAC in your US case) solenoids from a 24VDC(not always true the other way around), but the specs do change. On some you can even change only the part connected to the cord to change outlet.

I would try to see if you can trigger them with FireOne, it might not be strictly legal to have a mains female outlet with 2 bare wires(and GND) on the other end, but it is an easy test. This would however not solve the fan issue, but that can easily be solved with dmx.

Building your own non-latching relays is simple, but if you do build one with latching I would suggest adding an arm cue. Getting a sequence like, Q1)arm Q2)open Q3)close Q4)disarm, where Q1 and Q4 are the same pin and Q2 and Q3 are the same pin(4 cues on 2 pins). If the close cue would fail the disarm cue will at least shut it off.

I hope this post was kind of coherent, I have only slept a 3h on a sofa for the last 48h. Crazy day.

 

[Les]

Totally coherent. Thanks for the advice!