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dimmer interference?

Discussion in 'Safety' started by benintights, Mar 15, 2004.

  1. benintights

    benintights Member

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    A few weeks ago a concert took place at my church. We had our conventional lights above, but wired some 38 pars and coemar moving heads across the stage.

    Something very unsual happened when I powered up the entire system. Instantly I noticed signal degradation. When sending out signals, lights sometimes took between 2-9 seconds to power up, and it apperaed completely random which ones would respond first. Our dimmers recieve their power from circuit breakers in the back of the room. I killed several of the dimmers (some powering conventional lights), and instantly the signal was back to its strong self. I tried to remove the signal from going through these "trouble dimmers," but the signal going through them wasn't the issue--the signal only got better after power was completely terminated. Interference? I'm not sure. I eneded up having to kill the breakers for the concert, and then turned them back on when speakers came onto the stage.

    Any ideas about what caused the problem?
    benintights
     
  2. wolf825

    wolf825 Senior Team Emeritus Premium Member

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    Off the top of my head, the problem sounds like an over-draw of amperage / voltage drop on a leg(s) of power feeding your dimmers. Can you see if your dimmers that were problems are all on the same phase(s) of power? Example of what I refer to in moving lights--if you try to strike ALL your fixtures at the same time from the same power-source, you can loose suffecient power to do that because the draw is pulling heavy and voltage can drop to where the lights cannot get enough power to charge the striker, on such a at-once draw of power. Trying to draw too much power at once may be the culprit...At least that is what I would think off the top of my head. When I wake up a bit more I may have a better idea ;)
    yawn...sleeeepy mondays....

    -wolf
     
  3. benintights

    benintights Member

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    I think each circuit was isolated, but I'll double-check.

    benintights
     
  4. wolf825

    wolf825 Senior Team Emeritus Premium Member

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    Hiya,
    They may be isolated circuits (each their own breaker) but what FEEDS them in main power is what I am asking about. In a breaker panel, as in most dimmer racks, you have 2-3 legs of power that come in to feed each breaker or dimmer (depending on if its 3 or single phase). These are different phases of mains power, and to balance you should not load all your needs onto just ONE phase but these should be spread out evenly. Most dimmers and panels do the breakers or dimmers each on a different phase in order, so if you had 3 phase power feeding: its phase one, two and three for power of dimmers 1, 2 and 3. So in a rack--all the stuff on phase 1 will be dimmers 1, 4, 7 etc and phase 2 would be 2, 5, 8, and so on, depending on how they are set up Each rack and panel s different but the principle is the same usually). They do this to balance the loads and spread out the phases (especially if they have a double breaker that is feeding two poles of 120 etc, but even a lighting guy sometimes has to balance what gets plugged into what in how they load their circuits. Now--do NOT go into your dimmer or panel to find this out--its dangerous. But if you happen to notice that every dimmer that gave you problems was say every second or third one, with the ones between that one being ok--then that info may tell you if it is one or two phases being squirrely. Additionally--if this is a sub panel feeding--other things like AC or Heaters or building needs could also be tied into the same power feeds--and give you problems so it may NOT be just all your lights.. Its something to consider tho....

    Here's a 'bad' example to explain what I am talking about, but say on dimmers 1, 4, 7, 10 and 14 you loaded ALL your 2k fresnels on that, and on dimmers 2,5,8,11,15 you only loaded each with a 150w MR16 lamp. The loads between each phase are not balanced--and if the mains power feeding phase 1 (with all your 2k fresnesl) is not large enough to handle the 10kW and near 100amps that it will draw (say its only a 100amp feed per phase)--when you try to do it all at once you will occasionally get slow ramp-ups, delays and dips and power issues as each tries to draw its load but the amount of power it needs to do that just isn't there--(or you will just pop your mains 100amp panel fuse if you do it enough ;) ). So what I am saying is that you may not have had a balanced load for your lights over the weekend..and that MAY have been the cause of your problem. If you added real power hogs--like some moving lights, large wattage lights, or foggers can be--its easy to unbalance a load. The result would give you IMO similar problems to what you experienced. Try bringing up each light separately and see if you get the same problem. As you get closer and closer to all the lights and your max load ability on your mains feed--you should start to see problems.

    That is of course IF this is actually what is going on..again its a possibility and just something for you to check and possibly rule out..or see if it is actually so. If it is actually so--it means you are limited in the amount of lights/power you can use, or your dimmers need a higher amperage power feed to accommodate your inventory.

    -wolf
     
  5. benintights

    benintights Member

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    Great thing to look into, thanks. Very thorough.
    benintights
     
  6. lights11964

    lights11964 Member

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    HEy also what u should do is take an air compressor before each show and blow out the dust from each and every dimmer. Or at least that is what we do that keeps our lights from flickering randomly.
    -daniel
     
  7. digitaltec

    digitaltec Active Member

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    I would take a DMM and see what your output into the connectors at full power is. You probably are using single phase service and I have ran into problems with running even 20 1k Par 64's that I noticed a drop in voltage to a point that I was triping the breaker or seeing a delay due to a surge in the lines. If you said that it was a problem when you brought the lights up to full then I might have some sugestions for you. But like I said before, I would try metering the output voltage. If you see a huge drop then you might have bad dimmers, or a small service for that type of dimmers. What is your total amp draw? (Im throwing out power issues that I can think of.) Honestly to me it seems like someone did not do their math right. But there are so many possibilites. You just have to think of ever possible problem and trouble shoot. It could even be a problem witht eh DMX or Polerity, or RFI, EMI. The list goes on... :)


    lights11964, If you have to blow your dimmer rack out before ever use, I think you might want to get that looked at. There is a whole bunch of stuff that could be causing that and im sure you are on the verge of starting a fire! I would call an electrician right away to get that looked at. You dont want to mess with electricity, it always wins.
     

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