NSI dimmer pack question

JahJahwarrior

Active Member
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??

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.

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!

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.

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

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.

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?)

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.

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.

ecglstec said:
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.

Mayhem said:
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

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.

Mayhem said:
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.

Yea, I started thinking about it and realized that if it was turning it on and off that quickly, and I wasn't sure of what it would be.

OK, so from what I'm guessing based on what Mayhem said and what John said, technically its 1000w regardless, but the fuse will see it as less because of how the fuse works, correct?

ecglstec said:
Mayhem,
You're right. I thought he mentioned his pack could be loaded to 2400 watts total (20Amps). In which case it would 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 likely 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.

Yes - you are correct. Sorry - when I read 15A the alarm bells went off in my head as 15A here is 3200W and 10A is therefore 2400W. So I got my US knowledge confused with my AUS auto-pilot safety system (if that makes sense). You are of course correct that you can plug into a lower rated outlet, and as you pointed out, this should only be done PROVIDED that you modify your loadings to suit.

Here the standard outlet is 10A and then we go up to 15A. We do have 20A single phase outlets but once you need more that 10A, most people go to a 3-phase distro.

John - thanks for that info on the circuit protection.

I should not read and respond when very tired and rushed

I’m going to stay out of this debate on power sources for the dimmer pack. The good, the bad and mostly the confusing to figure out so as not to muddy the waters further.

In plugging into outlets however, what the receptacle is and how many other receptacles are on the same circuit as it often become a problem in thinking. Short of a circuit breaker finder and a plotted out room, much less an amp probe to test normal amperages on circuits in case they were tied into the house lighting, it’s very hard to determine how much load is available on any single outlet amongst many.

Often there will be a 15 amp duplex outlet in a house on a 15 amp circuit breaker. More often than having a single outlet tied to a breaker however there will be many more outlets if not even overheard lighting in this room or outlets and lighting in other rooms tied together all on this 15 amp circuit breaker. At other times such as in a kitchen, the outlets might be the same but due to the higher expected current needs, such outlets tapped off a breaker or as a series of them will be tapped off a 20 amp circuit breaker. As a rule a single outlet tied to a 20 amp breaker will be of the 20 amp type, but frequently often also there will be a few outlets tied to this same 20 amp circuit just as on a 15 amp outlet there can be more than one output as per NEC rules.

In this way, the only major rule (beyond rules for calculating load or how many outlets per breaker) of outlet type or number of them on a circuit would be that a 20 amp receptacle cannot be fed by a 15 amp circuit breaker.

All of this does not on the other hand ensure that if you have a few outlets on the same wall they are not on the same circuit breaker just because they are in different locations. It also does not assure that on a duplex outlet, just because there is an open place to plug in, that the second outlet will allow more power to be tapped off the receptacle. It is possible and easy to often split the outlet’s bridges and power it up from two sources so a duplex outlet is more like two single ones, but this is often also fairly rare to see commercially done without specific intent that is often noted on the outlet. In which case more frequently it would be 20 amp in feed - why bother otherwise.

In other words, just because you have an open outlet on a socket, or there are other outlets on a wall, this does not always mean you have more power available to you. Often in more modern wiring such rooms will have two or more outlets that are not a common breaker, but in older times where current draw was overall just a question of convent outlets, they were often powered from the same source as an improvement to one or two outlets per room at best. Older wiring even if on a 20 amp circuit breaker should also be suspect. Frequently someone will install a 20 amp breaker even if the wiring feeding it is only rated for 15 amp on older installations thus the fire hazzard should you overload something short of careful study.

Be very careful about plugging stuff in and where.

At one point I was paid to design a new theater and office space. Here I spent hours upon hours maximumizing the layout much less distributing and balancing the power requirements for the building. Say two office complexes, one theater, and one rehearsal hall per floor. The plans were approved of by the architect and general contractor than handed off to the Polish electricians who barely spoke English and tended to test for power with a touch of the wire, as opposed to a short to shut off the circuit breaker. They had this constant problem of tying all outlets on an entire floor into about three circuit breakers, and all lighting into one or two more when not wiring hot for 120v and neutral for a opposing phase of 120v. These being a bad example of electricians, simple and quick is still the goal within safety limits. Don’t expect that unless you specified and tested a circuit to be fed individually and specifically for a purpose that there are not other taps on it in other locations in the room or elsewhere in the complex.

Available outlets are one thing, available circuits without other taps on them are often another.

yeah, the 4x1200 watt packs are standard edison plug, 120 volt. The 8x1200 dimmer packs packs are fed by two seperate circuits, 240 volt. Not sure of amperage. But I know that they are on two seperate circuits. (on the circuit panel on stage, one breaker turns on flourescent worklights, circuit 1. Circuit 7 turns on the first dimmer pack, 11 turns on the second. )

Ditto

I've run into similar problems. I have always believed that a lighting designer must know more than anyone about the facility. It's their responsibility to know how the building is circuited and serviced.

One of the most unfortunate experiences I've witnessed was when a inexperienced director purchased two three-phase dimming packs only to realize his facility only had spil-phase service. Unfortunately, these particular packs could only operate on three-phase service without voiding the warranty.

So, the moral of the story: Know all there is to know about your facility BEFORE you begin your rig. (I learned this the hard way in high shcool.)

Not sure of your connectors in the US but the number of active (hot) wires represents the number of phases. The three wires your refer to is a single phase one.

double phase would be active 1, active 2, neutral, earth.

three phase therefore is active 1, active 2, active 3, neutral, earth.

Each phases uses a common neutral and earth and multiple phases can be distributed into single phases (as in a distro).

I have never used split phase equipment, but my understanding is that the equipment can accept 2 single phase feeds. i.e., one half off of one phase and the other half off another phase.

As I said, this part is unfamiliar to me, so I am hoping can set us both straight.

In any production the Master Electrician or Production Electrican is responsible for knowing that information. While sometimes the job is included with Lighting Designer. It's not technically the LDs job to know about the electrical service of the building.

Not sure of your connectors in the US but the number of active (hot) wires represents the number of phases. The three wires your refer to is a single phase one.

double phase would be active 1, active 2, neutral, earth.

three phase therefore is active 1, active 2, active 3, neutral, earth.

Each phases uses a common neutral and earth and multiple phases can be distributed into single phases (as in a distro).

There are many different type systems avaialbe. Let me try to explain.

In almost every US household you have single split phase service. This is one phase from the power company split at the transformer to provide 120/240v service.

Double phase is hardly ever used any more because it is not as efficeint as three phase. Don't confuse split phase with double phase.

Three phase can come in many flavors. Each one has three HOT wires. Each phase is 120 degrees of out line with eachother at the generator. They can be all 120 volts to ground and 240 volts phase to phase. You can have a delta system where you have 120/208/120 to ground and 240 from phase to phase. There are higher voltage phases, but no need to get in to that. Anyways, in three phase your neutral load is the result of an unbalanced system. So the neutral carries any current that can not be balenced from phase to phase. Not every system has a neutral capable of holding unbalanced loads. Every system should have some sort of equipment ground. If you have 30 amps on each phase the current going throuh the neutral would be 0.

Sometimes you can't distribute three phase in the theatre, because one leg may have a higher voltage, like 208. This is called the high leg.

It is against the NEC to have three phase running on a standard 15amp outlet, not to mention crazy. Three phase will have at least 4 conductors and likely 5.

This gets very complicated and I don't feel like typing the rest. To see if you have three phase look at where the power comes into the building. If you don't see three insulated wires plus a uninsulated wire you probably have split phase.

BE AWARE: Electricity can kill. Don't make any tie ins without understandind how your load effects the building electrical system. If in doubt get and electrican.

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