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benchman

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i was just wondering... for future reference... how much room(amps/wattage) is usually left on a dimmer channel/pack to insure no false trips of their breakers during heavy use? also... and this will show my green underside but... i'm arguing with an electrician who isn't used to wiring for lighting... he's wondering why he can't power a dimmer with a dimmer. i'm not sure of the answer myself but i'm pretty shure it's not a good idea...lol somebody give me the tech on this so i can tell him once and for all.... the venue has a bunch of old studio dimmers that he want's to power some dmx satalight dimmers with. i would rather he just supply me with the 20 amp outlets I'm asking for.

thanks

dave
 
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i was just wondering... for future reference... how much room(amps/wattage) is usually left on a dimmer channel/pack to insure no false trips of their breakers during heavy use? also... and this will show my green underside but... i'm arguing with an electrician who isn't used to wiring for lighting... he's wondering why he can't power a dimmer with a dimmer. i'm not sure of the answer myself but i'm pretty shure it's not a good idea...lol somebody give me the tech on this so i can tell him once and for all.... the venue has a bunch of old studio dimmers that he want's to power some dmx satalight dimmers with. i would rather he just supply me with the 20 amp outlets I'm asking for.

thanks

dave

Well that just sounds ridiculous. The reason you dont do it is its a waste of a dimmer, you have only one channel when you could have 2! As for the power question, I believe that a 20A dimmer (2400W) needs to have a breaker on it rated for 100% load constantly. In practice, actually hitting exactly 2400W is not incredibly common, mainly because most lighting fixtures dont add up properly. I usually try and design for 2 S4750 or 2 1k Fresnels on one dimmer if it will be on constantly, and 3 S4750s if they are for an effect that will last less than 10 minutes at a time (just to play it safe, I know it comes in under). In theory at least, as long as you do not overload the smallest point in the system (for example, a 20A dimmer pack being supplied 15A (I think thats illegal tho) can only be loaded to 15A, not 20A) you should be ok, as long as it is not at full for a very long time (although this may be a function of using old CD80 racks from eons ago)
 
The rule is that the constant load on a circuit may not exceed 80% of the rating of the overcurrent protection device, unless that device is listed for constant operation at 100% load. Most dimmers use OPDs that fall into this latter category.

The reason why you can power a dimmer with another dimmer is the non-perfect AC waveform coming out of a SCR or IGBT dimmer; which will cause havoc on the electronics.

With an SCR dimmer, it's the choke in series with the output. When the downstream dimmer is running around 50% with a large enough load, the firing and cutout timings can get screwy, which means a distorted dimming curve. That said, if the load on the downstream dimmer is light enough, this could be a perfectly serviceable way to increase your control. But in almost any case, a couple of extension cords are a better option. An IGBT dimmer will not have the same problem if it's adequately smoothed due to a different mode of operation (PWM as opposed to phase-chopping).
 
The rule is that the constant load on a circuit may not exceed 80% of the rating of the overcurrent protection device, unless that device is listed for constant operation at 100% load. Most dimmers use OPDs that fall into this latter category.



With an SCR dimmer, it's the choke in series with the output. When the downstream dimmer is running around 50% with a large enough load, the firing and cutout timings can get screwy, which means a distorted dimming curve. That said, if the load on the downstream dimmer is light enough, this could be a perfectly serviceable way to increase your control. But in almost any case, a couple of extension cords are a better option. An IGBT dimmer will not have the same problem if it's adequately smoothed due to a different mode of operation (PWM as opposed to phase-chopping).
If it is a temp thing then get him to install a disconnect beside the dimmers and use the old dimmer power to feed the new dimmers. Again you are losing dimmers but it will work better than one running the other.
 
Wow, we've really seen an increase in crazy dimmer questions lately.

Dimmers are designed to dim lights, and in my opinion, this is all they should be used for. (Yes, some gobo rotators and effects - like the GAM FilmFX can be run off a dimmer).

My concern to the "electrician" wouldn't be 'can it be done' but 'should it be done'. If either of those dimmers catches fire, would the insurance cover the damages? Because obviously, these dimmers weren't rated to run (or be run off of) other dimmers.

Your electrician sounds pretty lazy and out of his league to me, just my opinion of course.
 

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