The Physical Plant Manager at our facility thinks that, during "dark" days, we should shut down our 7) 96 racks to save energy by throwing the two main breakers. I've already told him that the rack fans shut off automatically and the CEMs don't use any power when inactive. I am correct, yes?
With all circuits off, and the fan stopped the absolute maximum quiescent power drawn by a ESR48 Sensor+ rack at 230VAC is roughly 70W.
Most of that power is due to the max 100-200mA leakage current through an 'off' triac - so it's a lot less at 120VAC, and it's even less if you've not got loads connected to every dimmer circuit.
In general, power savings from properly powering off compared to 'standby' are generally minimal, and may actually be wiped out by the 'startup' requirements. I remember doing some work at a big plant to find out the energy saving from shutting down their air compressor plant - it turned out that they actually used more energy 'pumping up' the system than they'd burn by leaving it running for a day. (Two days gave a saving though).
The startup energy requirement of a Sensor+ rack is pretty tiny though - the only additional current during boot compared to quiescent is that it runs the fan for a bit.
So yes, you'll save a little bit - but not much.
It may be
worthwhile shutting off when you're dark for a few days, but remember
that the isolators themselves have a limited lifespan!
[edited by: Richard at 11:58 AM (GMT -6) on Thu, Dec 16 2010]
Richard: I am being told that the reason why the one breaker for the dimmer must be shut off whenever there is no one in the theatre. This means it is powered off after every rehearsal (sometimes two and three a day), show, whatever. It is rumoured that the Fire Marshall has decreed this, but in the same convo the mention of power savings is always brought up. I've never cut the power to a dimmer rack for the simple reason that it is designed to have a constant circuit flow after the fans have shut down. To me it seems more economical to avoid throwing the switch 60 minutes before the show and finding out then that a panel or more fail to boot up or otherwise create significant problems. Am I mincing over a small point here? Are there risks involved in power off/power on that should be taken into account by a small 120 seat theatre? And finally, does it really matter if the breaker is off and on frequently - does it affect the life of the 24 channel rack in any significant way. I think that I am concerned mostly because I am new to the Company and don't want to be put into the position where the dimmer system fails abruptly and I am blamed for causing it to fail because I did something to it - and it never failed before. I'm caught in this situation because I do know what I am doing and those in charge of the House know very little. The Lighting Tech who designed and installed the system has left the building, but the breaker to his shrine has not been cut!! What's the very best practise given the need for longevity of the system within affordable means.
Richard: I am being told that the reason why the one breaker for the dimmer must be shut off whenever there is no one in the theatre. This means it is powered off after every rehearsal (sometimes two and three a day), show, whatever. It is rumoured that the Fire Marshall has decreed this, but in the same convo the mention of power savings is always brought up. I've never cut the power to a dimmer rack for the simple reason that it is designed to have a constant circuit flow after the fans have shut down. To me it seems more economical to avoid throwing the switch 60 minutes before the show and finding out then that a panel or more fail to boot up or otherwise create significant problems. Am I mincing over a small point here? Are there risks involved in power off/power on that should be taken into account by a small 120 seat theatre? And finally, does it really matter if the breaker is off and on frequently - does it affect the life of the 24 channel rack in any significant way. I think that I am concerned mostly because I am new to the Company and don't want to be put into the position where the dimmer system fails abruptly and I am blamed for causing it to fail because I did something to it - and it never failed before. I'm caught in this situation because I do know what I am doing and those in charge of the House know very little. The Lighting Tech who designed and installed the system has left the building, but the breaker to his shrine has not been cut!! What's the very best practise given the need for longevity of the system within affordable means.
This has very little effect on the liftime of the dimmer rack. There is a general discussion in electronics circles that implies a slightly longer lifespan for electronics that are never turned off, as most failures happen at power-on, but I don't think there's any conclusive research either way - just anecdotes.
However, opening a circuit breaker every day will reduce the lifetime of the breaker itself - they are generally only built for a few thousand operations.
You may of course have a switch specifically designed for this use, I have seen quite a few theatres that have dimmer rack isolators intended for regular operation.
