Preface: I've known you for almost 40 years, and we've installed a lot of systems together.
BUT, with all due respect, you're wrong.
Take a look at the attached
ETC Load Survey. It's far less
power per rack than you suggest.
It's not just the cost of the
power service, it's the associated cost of the
HVAC capacity.
Cheers
ST
As a preface. When ST tell me I'm wrong, it certainly makes me re-think my comments, so as reply
Steve,
I'm assuming you take exception to my recommendation to supply a 96x2.4kw
dimmer rack with a 600 amp service, correct ?. And that your disagreement is based on the load survey of 2005 that clearly indicates that the typical loading is nowhere near 20 amps per
dimmer, in a typical theatrical space. One thing that is not
clear in the survey is that with TV and Film facilities being roughly 8 percent of the survey (but not necessarily 8 percent of all the systems in existence, just what responded) what are their loading requirements ?. And do other facilities ever have the need to load dimmers at or near there capacity of 20 amps ?. The survey Food for Thought summary even indicates the troublesome question of “How many 2.4kw dimmers” would be appropriate and that's an un-answered question.
So perhaps a follow up survey would answer whether the managers of the lighting systems would feel comfortable with a
system made up exclusively of 1.2kw dimmers. I don't even begin to know how to establish that for my own space,, although I would probably be just fine with it, and with a number of
deck located 2400
watt dimmers available.
But where does that leave the end user ?. The survey was done in 2005 and answered what everybody suspected about how the Source 4 575
watt lamp, as well as other follow on similar lamps, has greatly reduced the need for fairly large
feeder systems. The Food for Thought comments correctly asks if 1200
watt dimmers should become the norm, and the answer is Yes.
But 5 years later, and unless I'm not seeing something on assorted company websites, no manufacturer of installed rack dimming systems makes a 1200
watt dimmer in a modular design, which is the most useful configuration, unless you consider assorted systems that are 12/24 dimmers mounted in a 19” rack type design, but whose individual dimmers are not modular, per say. I'm assuming that the reason is that the existing 2400
watt systems are so cost effective to manufacturer, that the companies are awaiting a
drop in component costs before they move to the next generation of
sine-wave at 1200 watts, in a modular design that is as effective as the
current industry standard Sensor, as well as similar
Strand systems.
So if I think like a consultant (which I am not), or an end-user that has to think about this often and I ask myself, can I simply just install a 96x2400 rack and pretend it's a 1200
watt dimmer (cause that's what's available) and then provide a feed that is roughly half what was recommended 10 years ago ?. Hardly. I would not do that and I think it's bad practice to recommend that. Yes, the loading is reduced and in truth, the industry is changing very quickly with a requirement for dedicated
power for
LED's as well as 208/240 volt
power for ML's, but until the
dimmer size itself is reduced, I would hesitate to assume that the loading is not ever going to increase to use up some of that 20 amp
dimmer capacity.
Recall as well that you wrote an article many years ago about the concerns in under-feeding a
dimmer rack, as it can reduce the usefulness of the capacity of the dimmers and that a desirable method to avoid such “zone limitations” is to buss racks together on a large feed
breaker, that allows the capacity of the rack to be used as needed in a zone of the facility, or for the feed capacity to be shared for the smaller loading that is now common. When only one rack is present, bussing is not an issue, but under-feeding may well be. Just for curiosity, do you now think that your recommendations of many years ago are not as relevant today ?.
EDIT: Some things I forgot:
1) Is it legal/code compliant (in NYC as example) to provide for wiring appropriate to 1200
watt dimmers - I.E. #14
THHN type ?. Or is the
NEC and other codes requiring a minimum of 20 amp
rating, as that certainly impacts any cost savings in moving to 1200
watt dimmers.
2) If #1 were allowed, what I'd love to see, and that I have a
current need in a new building, would be 192 or so, 1.2kw modular dimmers, don't have to be
sine-wave, in thw space of a Sensor 48. Like the old
LMI quad 1.2's.
And have we really known each other 30 some odd years ?. How can that be when I'm still 30 ? (grin).
Thanks,
