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Dimmer Load?

Discussion in 'Lighting and Electrics' started by zac850, Mar 30, 2004.

  1. zac850

    zac850 Well-Known Member

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    My school is getting 2 dimmers, and I am in the process of making my lighting plot. We're getting one 24 circuct dimmer, 1.2 kw, and a 12 circuct dimmer, 1.2 kw. Power is from 2 100Amp lines. I was wondering how many watts of power I can plug into both lights total. Is it 1.2 kw each circuct, or total, or what? I'm assuming that each circuct can power up to 1.2 kw, but I want to make sure that this is the case.......

    thanks
    Zac
     
  2. zac850

    zac850 Well-Known Member

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    EDIT. i just noticed that there 2.4 kw dimmers.... i'm hoping that it is like this, cause then i can get 4 lights on each..... and that would be nice.....

    thanks
    --zac
     
  3. wolf825

    wolf825 Senior Team Emeritus Premium Member

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    Hiya Zac,
    Yes you are correct--if its a 24 x 1.2kW dimmer pack, then you have 24 circuits and each is rated for 1.2kW or 1200watts. Same for if they are # of dimmers and each are 2.4kW being 2400 watts--that is dimmer per circuit usually.

    Umm....bit of an observation if I may--you said these are being powered by 2 100 amp lines---do you mean these are being powered entirely by 2 100amp feeds from a single phase source (2 100amp lines, a ground and a neutral for the entire thing?), 2 100amp feeds from a 3-phase power source, or are EACH of these packs getting their own "single phase" or "3-phase" 100amp feeds (which is 2 or 3 separate 100amp lines, plus ground and a nuetral)?? You may wish to check on that. I'm concerned your power may not be enough for 36 1.2 or 2.4kw dimmers if its the latter of only a single-phase 100amp feed for ALL of your packs. At FULL LOAD, IOW when ALL your dimmers are loaded with lights to FULL ability of each circuit, and ON at FULL, you exceed the power ability of 100amps per leg on a single feed for both packs... For 36 1.2kW dimmers I would spec at least a 200amp single phase load, or a 100amp 3 phase load (3 legs of 100amps, plus a ground and a nuetral).

    May wish to find this out, and make sure you try your best to balance your loads in your light plot.. Remember for math its about 10 amps per 1000 watts (its really 0.877 "something" amps per 100 watts or 8.77 amps per 1000watts, but 1 amp per 100 watts or 10 amps per 1000 watts is a good rule of thumb to consider ;) ).

    So if you have a 24 x 1.2 and you load it to capacity on each dimmer and bring each dimmer to FULL, you are pulling 28.8kW...or 280 amps...split on 2 lines of 100amps each thats 144 amps per leg. If you have a 3 phase service then its OK as you split that 280 amps by 3 100amp legs. But if you only have a single phase service--or 2 legs of 100samps, you could be pushing it. While you may not use the full pack at full capacity--its a consideration for you when you are calculating what loads go where. If you need more explanation of power calculations, just post back and I'll explain more about single-phase and 3 phase power....

    Hope this helps ya. Happy light-plot drawing ;)

    -wolf
     
  4. zac850

    zac850 Well-Known Member

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    I just went over this today (plus this is what we're doing in Physics...damn I need to pay more attention during that class....)

    It is 2 different 100 amp lines, so a total of 400 amps because for some reason or another which he explained but I still don't completely understand each 100 amp line is really 200 amps.... He said that we will not be able to run everything at full at once, but i was never planing on running everything at full at once, so I don't think this shall be an issue..... i hope......

    anyone with visual things about the 100 amp lines to 200 amps, or really any electronics diagrams of how this kind of stuff works, I would love to see it.... this is what I really don't understand..... and I need a visual diagram or some visual idea to get into my head to understand things....
     
  5. Nephilim

    Nephilim Active Member

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    ALso wolf if you don't mind checking my math :D

    I have 4x 12x1.2kW dimmer packs - 48x1.2kW or 57.6kW

    divide by 120V supply (single-phase supply to each dimmer, at least as far as I can tell that's the case) gives me 480A or 120A per dimmer.

    However, each dimmer only has a 60A breaker in the distro panel. Sooo.... what's my safe load here? We've been sticking to 575W or less per channel, but even then that's pushing it, isn't it? Yet I've never had one of these breakers trip.

    If a breaker takes up more than one 'slot' in the panel, does that make it a two phase or three phase breaker, or just a bigger breaker? Because these packs may be getting 3 phase after all. Or i'm just really confused. I wish I could open that panel up myself. But I can't. It would REALLY help if there was a wiring diagram on the door like there's supposed to be.
     
  6. Nephilim

    Nephilim Active Member

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    After some quick math a 277V supply would yield under 60A per pack. I need to seriously check this out.
     
  7. wolf825

    wolf825 Senior Team Emeritus Premium Member

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    Hiya Zac,
    Ok, I'll try to explain a bit. This sounds to me like what you have is 2 100amp SINGLE PHASE services that are feeding your packs, for a total of 2 single phase systems which will equal out to be 400amps (200 amps per system). A typical 'single phase' service consists of TWO 100-amp lines (a.k.a as LEGS of power or HOTS), a Neutral and a Ground. So you get TWO 100amp lines in a SINGLE PHASE 120/240v 100amp feed (it refers to a single leg of power amperage--not the total amount of amps of combined legs). There are various electrical services out there--all are dangerous. But to understand how it works you have to read up a bit on basic electricity...

    Here is a link to a site that explains a LOT about general electricity in laymans terms for the most part. It may help you understand--scroll down to find the various info on single phase, sub panels and types of services etc...

    http://ourworld.compuserve.com/homepages/boyce_smith/referenc.htm

    If you have specific questions about power you still do not understand--feel free to post and I will gladly try to answer.

    -wolf
     
  8. wolf825

    wolf825 Senior Team Emeritus Premium Member

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    Hiya Nephillim,
    If a breaker in a panel ties up more than one slot in a panel--it could be a two pole or three pole breaker (pole=phase). It all depends on the breaker--some wide slot breakers are single pole, some are two pole, some are three pole--depends on the breaker and the panel. So its impossible for me to say what it is. You NEVER want to open up a breaker panel that is live.

    For your math--you have 48 1.2kW dimmers. At full power on max loads that is 57.6kW and well over 400 amps of draw...but again how often do you pull full max loads on all your dimmers at once? Probably never.

    divide by 120V supply (single-phase supply to each dimmer, at least as far as I can tell that's the case) gives me 480A or 120A per dimmer.

    Actually each 1.2kW dimmer pulls "roughly" 12 amps at max load. In reality is it less since 100watts ia 0.837 amps typically...but as I said 1amp = 100watts is a good rule of thumb when calculating estimates. In a 12x1.2 rack at full load on each dimmer, you can have a maximum amperage draw under 144amps...divide that by the number of phases feeding your dimmers--2 or 3, and you can figure out the "safe" amperage service you need to operate at FULL. So on a 3 phase service to cover 144 amps--each of those 3 legs needs to be able to supply 48 amps. (144 amps divided by 3 legs of power = 48). So a 60amp 3 phase service per dimmer 12-pack works fine and is safe. If this was a single phase 60amp service--you exceed the 60 amps because (follow along with the math here) if you have 144amps (roughly) and divide that by TWO legs of power in a single phase service, you have 72amps each leg needs to provide for max load. Quick way to find out whether you have single or 3 phase dimmers is to look for the number of large power cables feeding the packs--if you have 4 cables that would be single phase (2 legs, a ground and a neutral)..if you have 5 cables that would be 3phase (3 legs, a ground and a neutral). Solook in theback of your pack and see what the number of cables are feeding the power to your packs. If you have one BIG multi-cable..only way to find out is to open up the dimmer pack and look really to be sure. (DO NOT DO THIS.)

    You should keep in mind that whatever you draw in amperage matters to what you have attached. A 1.2kW dimmer does NOT automatically pull 1.2kW when you go to full....it pulls what you have on it. If you only have 575w fixture on a 1.2kW dimmer you are only going to pull 575w when that dimmer is at full. If you had a 575fixture and a 150watt Inkie on the same dimmer--you are then pulling 575w + 150watts for a total of 725watts at around 7 amps. If you have NO fixture on that dimmer--you pull NOTHING even if you send that channel to FULL.

    That help ya?

    -wolf [/b]
     
  9. Nephilim

    Nephilim Active Member

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    I know the rating is a max, not a constant figure :p

    I think I may just shut off the dimmers at the breaker and loosen the input wiring's jacket and take a peek. Thanks a bunch!
     
  10. wolf825

    wolf825 Senior Team Emeritus Premium Member

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    Be VERY careful if you choose to do this. I do not suggest anyone messing around with power. But if you have any questions you need some clarification on, feel free to ask. :)

    hope these answers helps ya figure things out... :)

    -wolf
     
  11. Inaki2

    Inaki2 Active Member

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    Can anyone clarify this for me?

    divide by 120V supply (single-phase supply to each dimmer, at least as far as I can tell that's the case) gives me 480A or 120A per dimmer.

    I'm confused by the 2 different amperage figures. :? 120V systems are driving me crazy. Over hre you either get single pase (220V on one hot, plus a neutral and a ground) or 3 phase (220V per phase, plus neutral and ground) Between phases we get 380V, which is only used in heavy machinery.
    So is that figure between 120V and 240V? I find it very amusing that your "single phase" sstems are actually "double phase" systems. :D
     
  12. wolf825

    wolf825 Senior Team Emeritus Premium Member

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    Hey Inaki,
    Well if you are comin here---get used to it!!! ;) :lol: :lol: His amperage figures were off--I posted what it should be. But as for voltage--your stuck with it at 120 here in the states. The power over here in the states is 120v/60hz. A typical feed line for a house is 120/240v/60hz single phase (which is two legs of power, a ground and neutral here). Outside the US everything is 220v/50hz (yea us yanks are baked..first we don't do metric or celcius, and now voltage--intolerable to the rest of the world I'm sure)...so basically think of it as your 220v hot minus 100volts ;)

    You will learn about power somewhat when you are here...and I'll gladly fill you in on the rest, pal if you have any questions. :) Lots of other FUN POWER and AC definitions to learn too..WYE, Delta phase, Split phase and the list goes on...


    -wolf
     
  13. Nephilim

    Nephilim Active Member

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    Better than exposing potentially bare wires, I opened the wallbox that the dimmers are fed from. 4 wires - single phase with 2 hots coming in. The dimmer specs ask for a 60A supply if it's a single phase supply, so we're good to go. I think I finally get the way this thing works. Now I just need to know what the total amperage into the panel is and how the dimmers are phased.
     

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