Brownout repercussions

[marshmolly123]

So last night was our second to last performance of The Crucible, in the round, at my school. We'd had three shows already, all of which had gone off without a hitch. The light plot is pretty simple, with a total of 34 instruments. Most of the show is pretty dim, and usually my levels are at less than half. This definitely made our problem more noticeable.

I walked into the theater and someone immediately ran up to me and told me "Molly! All the lights are on but the board's off and we can't fix it!" I wasn't immediately too worried, because sometimes shutting the board off with channels up causes it to do weird things, and turning it on usually fixes that problem. I walked into the stage area and saw that literally every instrument was at full. I turned on the board, and nothing happened. This was the beginning of a very frenzied hour in which we tried many things: setting the dimmers to zero, switching out the DMX cable, turning the dimmers off and on, trading out the 24/48 for the main board (a 48/96). Finally, our technical director went up to the dimmer room to try to see what he could do. It was interesting, because only one of our dimmer racks was affected. I'm not really clear on what he did, and I'm not sure he is either, but I think he cleared the backup looks and reset the dimmer rack. I returned to the board and saw, to my relief, that everything seemed to be working. We started the show ten minutes late, and everything seemed fine.

Then, 10 minutes later, all of the instruments suddenly flashed back up to full, where they stayed no matter what I did. We were in the middle of the first act, so we couldn't exactly reset the dimmers again. I wrote down some dimmer numbers and we went up to the dimmer room to shut off some of the dimmers, so at least the lights weren't blindingly bright. Meanwhile, the technical director called ETC's technical support to try to figure out the problem. At a lighting change, we physically switched off other dimmers to change to a forest gobo scene.

Finally, at intermission, we were able to figure out what happened. A brownout earlier that day had somehow messed up with the Unison system in the auditorium and locked the dimmers to full. We're not really sure why that happened, as it has never happened in the ten years we've had the space, but fortunately resetting them fixed the problem. The rest of the show went off without a hitch.

We were very impressed with ETC's technical support. The man on the phone figured out the problem and told us what to do in about five minutes.

 

[Lightingguy32]

Ah, the dreaded unison system dimmer lock on. This happened countless times to my old highschool venue which used to run a unison architectural system that went belly up every time we had a blackout, brownout, surge, spike... etc. It wasn't until my junior year after an initial renovation that a bigger problem arised, the brownouts/blackouts actually fried the architectural command modules in both our houselight, and primary FOH rack, luckily we had 2 spares close to town and the loaners stayed with us through the performance. Fast forward almost 2 years later when I am in college, I hear back from the new TD and he tells me that the electricians came back in to check on some connections on the dimmer racks and found out that all three (yes we were unfortunate enough to have 3 separate racks (2 unison and 1 Lighting methods)) racks had loose ground connections and that on the rack that originally housed a unison command module was almost non-existent it was so loose. That being said, after that was fixed nothing has gone wrong since. When this happened, and you initially looked at the dimmer rack, was a small amber indicator flashing and was there a message on the LCD display that said something along the lines of "Bypass Active" or "CPU 01 - 06 FAIL" show up? (FYI the error messages are taken directly from page 27 of the Unison ER and DR series owner's manual).

 

[Lightingguy32]

One more note: the events that occurred to you are very similar to what happened to the DR racks I used to use in my highschool, and this problem will usually persist, if it does it indicates that the Command module is failing and will fail when you least want it to. I strongly recommend you have this command module serviced ASAP.

 

[tyler.martin]

Well, your school possibly has a ETC product *name escapes me* that when it detects voltage shortages, or outages, it trips the Sensor rack into Panic mode which might have been programmed into the system as all at full. Resetting the CEM+ (if thats what you have) might solve the problem, but it will keep happening if there are brownouts. It is a small box that has 3 breakers on it under a class locking lid, take a look and see if there is one.

 

[Lightingguy32]

The Unison DR racks at my school don't have this feature (I know this for a fact since I did go looking for the small box you mention). Thanks for the tip though. Is the product a sub component of the Emergency Lighting Transfer System (ELTS)??

 

[starksk]

marshmolly123, I am glad that we were able to get your Unison system working again. There are a few options for what could have been happening, but it sounds like the processor had partially rebooted in the brownout and captured levels in a background state. We most likely walked your TD through how to release those levels.

The device to which martinty is referring to is called an Emergency Bypass Detection Kit (EBDK). That device senses a normal power feed, and when there is an issue with the normal power feed no longer being present, it will trip a relay that closes/opens contacts that the racks see as an emergency state and go to their programmed emergency look. Resetting a processor that is connected to an EBDK will only exit the emergency state if the EBDK is also out of emergency.

Another option that was used before the EBDK is the Bypass Option Kit. This device is very similar to the EBDK but was integrated into a Legacy Unison Rack and only triggered that rack into Emergency Bypass.

Lightingguy32, an ELTS is different than a device that tells a rack to play its emergency look. An ELTS, when in emergency, actually switches the power from the dimming rack (or other normal source) to an emergency power source.

STEVETERRY wrote a great article, that I highly recommend, about Understanding Control of Emergency Lighting Circuits that appeared in the Summer 2004 and Spring 2010 issues of Protocol.