Hi all, first post here and I hope you can help me out with a little
fluorescent dimming problem I have.
I need to find a way to dim single 5
foot T8 tubes, either F40T8 (40w) or F58T8 (58w), with an
ETC Sensor. The problem is that the only dimming ballasts I have found are for F32T8 (32w) tubes or lower.
So my question is: Will using a 32w dimming
ballast on a 40w or 58w tube create any problems other than lower brightness?
I'll begin with several questions:
When you say a single 5' tube, 5' would be 60" neither 40" nor 58".
Is this a normal, indoor, tube as opposed to something fancy intended for exterior use where it may need to start in sub zero temperatures?
Is this something you're cobbling together for a show, basically a short run application or is this something being installed for a long term application?
There used to be dimming ballasts with a dimming lead which, when energized, saturated the core effectively removing it and reducing the
ballast to a coil of
wire acting as a simple series resistance. Nowadays, I believe most ballasts are electronic.
Without knowing your answers to my above queries, here's my instant thought:
If this is for a very short period of time, let's say two or three performances and maybe 15 minutes per performance, here's what I'd try. I'd take your
fluorescent tube, along with whatever
ballast it's normally happy operating on at normal
line voltage, connect a purely resistive "
dummy load", maybe a 500
Watt fresnel, in parallel with it,
wire it to the output of your normal
stage dimmer and observe the results. Check for any / all adverse effects such as abnormal noise, vibration and / or overheating. If it works, it works. If not, it's cost you little more than your time to try. If it works, it may work just as well with a lower wattage
dummy load. I had a show where dimmers in a 48 slot
Strand CD80 rack were successfully dimming neon, flicker-flame, candle lamps with only a single 120S6 6
Watt lamp as the
dummy load per
dimmer. Of course you'll need to locate your dummy loads somewhere out of sight AND be sure to check them as part of your nightly lamp checks. Two dummy loads are ALWAYS better than one as you know, if you only use one, it'll burn out leaving you loadless at the worst possible time. Edsel Murphy and his laws fully apply to the use of dummy loads when they're being used to do the otherwise impossible for budget theatrical purposes.
Toodleoo!
Ron Hebbard.
