NSI dimmer pack question

[JahJahwarrior]

Hey, I've noticed on some dimmer packs a gruop I worked with rented once, NSI ones, something wierd. They have four channels, and say 1200 watts per channel. But, then they also say 2400watts total. 1200+1200=2400. So, it sounds as if you could only run two channels full up, with 1200 watts per channel. Am I right, wrong?? is that stupid?? WHY wuold would only build a dimmer to light up two channels at a time??

[Mayhem]

Well you can have a total load of up to 1200W on any of the 4 channels, but you cannot exceed 2400W in total.

You could put 2x 300W on each channel or 1x 500W/600W on each channel, or

You could put 1x 1000W on one channel and then 1x 500W/600W on two of the other channels, or

You could put 1x 1000W on two channels,

and so on and so forth.

Basically, as long as you stay within the max load per channel and max load overall, you will be ok.

Some of the smaller 4 pac dimmers that I have are a total load of 2400W (we are 240V here) per channel and overall. So, I can link all my lights onto one channel or I can balance them out over all 4. Can get a little confusing but calculating your loads (and being able to convert that into amps) is a good habit to get into, especially if you are using distro boards. That is a subject for another post however.

Hope thais is helpful.

[JahJahwarrior]

to me, that is stupid. EVERY dimmer ought to be built to run it's 1200 watts per channel on every channel at the same time. That just doens't make sense to me....oh well though I'm not NSI, I'm jsut stuck using htem....

(actualy, our main dimmers are 8x1200, and you can have 9600 watts total, I did the math (ok, it only took a second...) and I have have all channelsl oaded to 1200 watts and run them full up at the same time. Now, seeing as I only use 500 or 1000 watt lamps, really I'll only have 1000 watts per channel. But whatever. )

ok, thanks for answering my question!

[Mayhem]

It all comes down to supply and demand. You can only suck as much power as the feed into the dimmer can handle.

So, if you want to load up more lights, you need to get a dimmer that either has a higher single phase feed, or go to a multiple phase feed. The small 4 pac dimmer I referred to in my initial post can go up to 3200W, if I plug it into a 15A feed, rather than the standard 2400W / 10A feed (Remember that I am in Australia and our power is 240V).

The dimmer you are talking about is designed so that it can be used from a standard receptacle (if I understand enough about your power in the US)

Somebody please correct me if I am incorrect on this.

[ecglstec]

If your pack has a normal 15/20 amp plug on it, like the ones you see in your house, then look below. If not ignore this.

If you plug in to an outlet with two straight slits and one hole in the bottom ( 15 amp outlet) then you can only load your pack to 1800 watts total before you blow the circuit breaker at the venue.

Here is why:

Watts = Volts * Amps

Watts = x
Volts = 120 (Common US voltage)
Amps = 15 (Your plug is a 15 amp plug)

x = 120 * 15
x = 1800 Watts

So the maximum you could load your pack TOTAL would be 1800 watts.

Say you have an outlet with two slits and a hole, but one slit also has a horizontal slit . Then you have a 20 amp outlet. SO:

Watts = Volts * Amps

Watts = x
Volts = 120 (Common US voltage)
>>> Amps = 20 (Your plug is a 20 amp plug)

x = 120 * 20
x = 2400 Watts

Your pack can be loaded to 2400 watts total.

So the reason your pack can't have a load greater than 2400 watts ( 20 Amps) is that the supply for the pack can not got beyond 2400 watts.

In order to load your pack to full you would need 4800 watts.

Watts * Channels = TOTAL
1200 * 4 = 4800

That requires a supply circuit (Outlet) of 40 AMPS. Thats double what the normal outlet provides.

Watts / Voltage = Amps
4800/ 120 = 40


So really your pack is limited by the lack of energy avaliable from the wall. Some people like to open the packs and divide the dimmers into two banks and power them from seperate circuits. Its not a good practice and can be dangerous.

Quick note:
The above calcualtions do not take into effect a saftey factor or the resistance of the wire between the breaker and the pack.

DO NOT attempt to change the plug in an attempt to get more power. It's dangerous and he pack is likely fused and will not allow it.

[zac850]

there are some pack's that come like that, for the exact reason. The pack's are made with 2 plugs, and half of the circuits are controlled by one plug, and the other circuits are controlled by the other plug.

also, how often are all your lights at full?
that will cut down a few watts from the plug (acutely, thinking about that, i'm not sure if thats true. If you have a 100 watt light on a dimmer at 1% is it pulling 1 watt or 100 watts?)

[ecglstec]

Split packs like we're talking about are OK, but modifying packs to accept two circuits is not a good idea. I don't like the fact that you could possibly have 240volts in a pack designed for 120 volt operation.

As for your question about wattage when dimmed:

I'm not sure how the wattage is exactly ( I might just put a meter on a dimmer to figure it out), but if you have a 1200 watt load on a 1000 watt dimmer and leave the channel at 70% it normally will stay on.

I DO NOT recommend ever overloading a dimmer past its stated capacity. If someone brings everything to full all at once you risk putting a huge shock load on the building electrical system.

[Mayhem]

Originally Posted by ecglstec

If you plug in to an outlet with two straight slits and one hole in the bottom ( 15 amp outlet) then you can only load your pack to 1800 watts total before you blow the circuit breaker at the venue.

Here is why:

Watts = Volts * Amps

Watts = x
Volts = 120 (Common US voltage)
Amps = 15 (Your plug is a 15 amp plug)

x = 120 * 15
x = 1800 Watts

Yes - but only if the internal wiring in your dimmer is rated for 15A!

If not, (depending upon the internal protection) you could seriously damage your dimmer.

If in doubt - ALWAYS follow the instructions on the dimmer.

Zac - 1000W is 1000W regardless of the percentage of dimming. Triac and SCR dimmers work by turning the lamp on and off at a high rate. Our eyes then see this “high speed flashing” as changes in the intensity of the light.

[DMXtools]

Originally Posted by Mayhem

Zac - 1000W is 1000W regardless of the percentage of dimming. Triac and SCR dimmers work by turning the lamp on and off at a high rate. Our eyes then see this “high speed flashing” as changes in the intensity of the light.

Not exactly true. Most fuses and breakers look at average power over time - and the time per half-cycle of the AC line is pretty short (.0083 second at 60 Hz). If the dimmer is at 10%, that means that every half-cycle, the power will be ON for .00083 second and OFF for .00747 seconds. The instantaneous power during the brief period when it's on may indeed be 1000 watts, but the average for the half-cycle will be 100 watts. Those pulses at 1000 watts WILL contribute a little more to the stress on the circuit than would a 100 watt lamp at 100%, but nowhere near as much as if the 1000 watt lamp was on 100% of the time.

John

[ecglstec]

Mayhem,
You're right. I thought he mentioned his pack could be loaded to 2400 watts total (20Amps). In which case it woud be limited to 1800 watts on a 15 amp circuit. However, most outlets in commercial buildings are 20 amps will give out 2400 watts. His pack is most likly fused at 20 amps.

ALWAYS check the dimmer for the rating. Never assume that the dimmer can handle 2400 watts on a 20 amp circuit.