Some nooby dimmer questions.
- Thread starterMillburyAuditorium
- Start date
STEVETERRY
Well-Known Member
Erich--
A dimmer rack is generally considered a dead-front switchboard. I think NEC Table 110.26(A)(1) Condition 1 for 151-600V applies, which would mean 36" clearance rather than the 42" you mentioned.
Condition 2 would require 42" space, but modern dimmer rack design makes it highly unlikely that there will be exposed live parts during inspection or servicing--the rack will be de-energized. This is especially true in light of the arc-flash requirements of NFPA70E.
Was there a reason I missed that you specified 42"?
Cheers
ST
Last edited:
teqniqal
Well-Known Member
My apoligies for not being more clear. When I said "houselights" I meant it inclusive of any supplementary aisle lighting. "Houselights" are a system of fixtures, not just the ones in the ceiling. It can also include wall sconces, cove lights, emergency lights, exit lights, etc.
The reason I quote the 1/2 foot-candle level is because 0.2 (1/5) fc is the minimum requirement, and most light meters that people use in theatres do not have NIST traceble calibration, and may not be that accurate to begin with, so to err on the high side tends to ensure that you have not erred on the low side. Then there is the effect of lumen depriciation, burned-out lamps, dirt, and other human factors that have to do with old people not being able to see well in low lighting conditions.
As noted elsewhere, just because people do it doesn't mean it is legal. I think that if you run the idea of doing something illegal past your school's legal department, you will usually get a resounding "NO", so why bother? (doing the illegal thing that is, not asking the legal department). With regard to section 7.8.1.3 (4), I think we run enough risks working in dark theatres that it's hardly "worth it" to put the audience in peril for such an effect. At least I wouldn't want to have to sit in courtroom and explain it to a jury. I've got better things to do with my time.
-Erich Friend
Teqniqal Systems, LLC
MillburyAuditorium
Active Member
All of our exits have the lit EXIT signs on them.
teqniqal
Well-Known Member
No, you didn't miss anything as far as the NEC applies. The reason I use the 42" rule is that frequently there are other panelboards that meet that requirement in and about theatres, so I use the broader definition as a blanket dimension. Why confuse people with "this is 36, that is 42" ? An extra 6" of clearance is typically a good thing anyway, as people will always try to crowd things right-up to the limit.
Also remember: the 36"/42" rules are a minimum requirement, not an absolute distance. Another reason for the 42" specification is that the 36" rule is frequently misinterpreted as being measured from the wall, not from the face of the dimmer rack / panelboard, so this assures a bit more clearance (even though they will come-up short in the long-run).
And lastly, I like a little more room to work around electricity - so what is the harm in laying claim to a little more real estate?
-Erich Friend
Teqniqal Systems
ptero
Active Member
Regarding how many dimmers are in a 96 rack:
I once ran across a newly installed ETC 96 rack in a high school. They were having trouble making some fixtures work when hung and plugged into a numbered outlet. Turned out they wired the place for 96 dimmers, there were 96 numbered outlets throughout the theatre, but they loaded the rack with 24 dual modules for a total of 48 working dimmers.
So, any of the 96 outlets could be used, BUT modules had to be shuffled around in the rack to 'power' the desired outlets. The Dimmer One position in the rack = Outlet #1 in the theatre. But without a module - no workie.
With a module in place to drive #1, #2 was also drivable, due to the 2 dimmers/module deal. That is - drivable separately, assuming the softpatch on the console was patched to control them separately with separate Channels.
When hanging a plot, they had to pay attention to using outlets in pairs. Then go to the rack and move modules accordingly. Or, not use all 48 dimmers. Oy. They sort of ended up with the modules in every other slot as a basic setup. Then they'd shuffle them as necessary for specific needs.
Boy, I hope that makes sense.
I imagine someone was thinking of future expansion by way of just having to purchase modules to fill it up in the future. But the basic paperwork and manual on site made no mention of this.
ANYWAY, look for all those breakers. Make sure the rack is indeed full 48 Modules/96 Dimmers and not a bunch of filler airflow blanks. Because there is a numbered outlet out there doesn't mean it's gonna work.
I once ran across a newly installed ETC 96 rack in a high school. They were having trouble making some fixtures work when hung and plugged into a numbered outlet. Turned out they wired the place for 96 dimmers, there were 96 numbered outlets throughout the theatre, but they loaded the rack with 24 dual modules for a total of 48 working dimmers.
So, any of the 96 outlets could be used, BUT modules had to be shuffled around in the rack to 'power' the desired outlets. The Dimmer One position in the rack = Outlet #1 in the theatre. But without a module - no workie.
With a module in place to drive #1, #2 was also drivable, due to the 2 dimmers/module deal. That is - drivable separately, assuming the softpatch on the console was patched to control them separately with separate Channels.
When hanging a plot, they had to pay attention to using outlets in pairs. Then go to the rack and move modules accordingly. Or, not use all 48 dimmers. Oy. They sort of ended up with the modules in every other slot as a basic setup. Then they'd shuffle them as necessary for specific needs.
Boy, I hope that makes sense.
I imagine someone was thinking of future expansion by way of just having to purchase modules to fill it up in the future. But the basic paperwork and manual on site made no mention of this.
ANYWAY, look for all those breakers. Make sure the rack is indeed full 48 Modules/96 Dimmers and not a bunch of filler airflow blanks. Because there is a numbered outlet out there doesn't mean it's gonna work.
My drama teacher has told me that we are getting some new digital dimmers - what's the difference between the new (tiny little box) of digital ones and the old big huge ones?
Thanks
K
The difference is mainly in control. Newer dimmers take a digital control signal, where older dimmers used and analog control. The other major thing you will notice is that newer dimmers are smaller. The technology has advanced such that we can fit all the electronics into a smaller form factor.
renegadeblack
Active Member
Ace. Apparently we won't use the huge toilet-handle style switches too?
Thanks
Nope, you'll be using something different and that will be much easier to use. Something like the ETC Element, or if your school is cheaping out and doesn't like you, the Innovator. If you find yourself with an Innovator, save your sanity and quit now... I wish I had...
Tex
Active Member
Now, now. There's no need to scare the poor guy.
I have an Innovator, and while it's not what I would have chosen, it's been quite servicable so far. I'm even using it with intelligent lights and I haven't punched a wall or pulled out any hair (not even my own.) The only problems I've had have been (L)user created.
You'll be OK, even if you do get an Innovator.
