The above Ad will no longer appear after you Sign Up for Free!

NSI Dimmer Pack Question

Discussion in 'Lighting and Electrics' started by Herr_Sprecker, Jul 18, 2008.

  1. Herr_Sprecker

    Herr_Sprecker Member

    Likes Received:
    Norman, OK
    I was wondering if anyone has had experience with NSI Dimmer equipment. I do not recall the exact model of NSI that we have, they are 8-channel rack mount packs, 1200w per channel. Dimmer modules are still available for these units, and it is a good thing because these modules seem to have the lifespan of a dayfly.

    Each channel has a safety breaker, but the module is kind enough to save the safety breaker by blowing out before the safety breaker can save it in the event of a short. And it never takes much. We've also got a couple channels that are always stuck at 100% regardless of what the control board tells them they are supposed to be at.

    I was wondering if this is normal behavior for NSI equipment, or if we are overlooking a serious issue as we repair these units. Any info would be helpful.
  2. JD

    JD Well-Known Member

    Likes Received:
    North Wales PA
    For some reason, a number of manufacturers seem to have taken to using 15 amp triacs, such as the BTA16-600 on 1200 watt dimmers, with the results you speak of. Strange, as the BTA24-600 is only $1.78 for a 25 amp triac, which is only two cents more! Check your warranty status, and if all are out, have your local qualified servicer take a look at the pack. If they are using the 15 amp triacs, I would steer clear of buying anymore of that unit. As a rule of thumb, Triacs on any dimmer should have a 200 to 400% safety factor above the rated load. (Half that amount if they are SCRs, as the "pair" gives you the total current.)
  3. waynehoskins

    waynehoskins Active Member

    Likes Received:
    Arlington, TX
    The ones that are stuck on have bad triacs too and should be replaced. A triac (or SCR or SSR) achieves dimming by turning on and off really fast, and it's the ratio of on time to off time that determines intensity. When such a device fails, it simply no longer switches, so it sticks in either the always-on condition ("latched on") or the always-off condition "latched off".

    Because of the PWM dimming technique, and the nonlinear resistance of a lamp filament, it's very easy to overload a dimmer if you think (as we all did before we learned) that you can put double the rated load on a dimmer if you only turn it up to half. It actually draws effectively full current, because of the peak-response nature of power cubes and the nonlinear resistance of filaments (their resistance increases as they heat up, so a cold filament is nearly a dead short while a hot filament isn't, so the relatively cold filament at, say, 10 percent intensity, draws the same current as a hot full-intensity filament would.

    All that to say it's very possible to overload dimmers without thinking you're overloading them.
  4. TimOlson

    TimOlson Member

    Likes Received:
    Las Vegas
    some of those racks also have a switch that latches the dimmer on at full. does yours?

    peace, Tim O

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice