Circuit breaker tripping

bdesmond's theory is correct but isn't the power draw in this case about 9.5A (he is only loading the dimmer with 1150W).

Although, having said that, the tolerance of the breaker may not notice the difference. Most breakers will allow some current draw to sit above the threshold of the breaker for quite some time before tripping and given that you can get a few hours before tripping, that seems to be the case here.

Ampacity – Have you checked that there is nothing else running on the same circuit as that will certainly contribute to your problem. Is it possible that the breaker could be faulty? Have you tried running the dimmer off another circuit? This information would be very helpful.

Given that you are close to the limit in what you are running, I would certainly follow bdesmond’s advice and limit your intensity. I very rarely push my fixtures past 80% as the visible difference is negligible (in my opinion).
also, if I remember correctly, I believe that the circuit breakers trip and a lower voltage over time, so that 1.2 kw dimmers after a time may start tripping at 1.1 kw.

also, I do not know if this was just for my school, but we got 3 smartpacks from ETC, new, and 2 of them were eather delivered with, or within a month, had 1 dimmer per pack failed full on. Also, one of them had an incorrectly inserted chip and the keypad was installed up-side-down.

I don't know if this was just on our smartpacks, or if the smartpack line has had problems like this.
Nucence tripping? Possible that it trips on it's own with a lower load, but normally that is when something makes it do so such as phase harmonics, larger lighting loads, voltage drops, shorts, someone kicking the dimmer pack etc. As Mayhem said, there could be any number of reasons a dimmer can trip or nucence trip. Try re-patching as he observed especially into a different phase of power, in a different breaker of a different dimmer pack and observe. Could be some dimmer trip ratio has warn some. I have some 100amp four pole main breakers that take a lot of effort just to turn on not that they can be trusted for a show with a similar problem. The thing about such a breaker that is warn is in turning it on and off. Said breakers that trip too easily will most likely not like to go on and off. They will instead go from off to tripped mode instead of on.

128% by the way is the normal temporary pre-tripped loading possible on a circuit breaker I read somewhere once. Just about enugh time to melt down a 100amp main breaker when seriously un-balanced - my own education in balancing your load. This balancing your load and just an idea, how is the loading of the dimmer arranged? Is your load balanced and where is this breaker placed on that power distribution? Might if daisy chained and feeding a heavy load be possible that the extra resistance/current even passing thru the breaker's in terminal if that type, could be sufficient to overheat the breaker especially if first to the point it trips at a lesser loading.

Than again it could also be electronics and lots of other things. Follow the process of elimination first. Narrow it down first to if it's the circuit fed or the dimmer feeding. Given the dimmer feeding, is it the elctronics, wiring to it or the circuit breaker itself? If possible swap out dimmer cards, and even circuit breakers (supervision required) to narrow down the actual cause. Once you track it to the breaker, it's not un-common that a circuit breaker especially if used as a switch which it is not, will wear out.
zac850 said:
...had 1 dimmer per pack failed full on.
am i right in saying that they fail full on when the dimmer part itself over-heats. case they have to obsorb enery [turn it into heat] when they stop it going to the light. and so when it is on full the dimmer has no work to do at all.
No - modern dimmers use high speed control circuitry and switches which effectively turn the lamp on and off.

When you actually dim a lamp it is turning it on and off. However, it does it that quickly that your eyes do not register the on and off but see it as being a lower intensity.

It does this by sampling the sin wave and firing the trigger at set points but I do not understand it enough to explain it - sorry - but I am sure that others on this site can go into this detail if you so desire.

The dimmer on a household light works using a variable resistor and this is why they heat up and burn out over time. This is also why they are of no use in this industry.
Just to kind of elaborate on what Mayhem. (Which is very true)

Because the light is dimmed by turning it on and off, not resisting the current flow, a light will draw the same amount of power weather it is at 100% or 50%, so just dimming them will not be a good way of keeping the breaker from tripping.

^ I do not understand this logically. Yes, I understand how its not being dimmed, its just turning on and off really fast, but there from 100% to 50%, its off 50% of the time, so wouldn't there be less draw over the total time because of all the time that the light is off? Over any given milisecound then the draw would still be 100%, but over time the draw should be 50% because of the half-time when the light is off... Or is it more complex then that?
^ I do not understand this logically. Yes, I understand how its not being dimmed, its just turning on and off really fast, but there from 100% to 50%, its off 50% of the time, so wouldn't there be less draw over the total time because of all the time that the light is off? Over any given milisecound then the draw would still be 100%, but over time the draw should be 50% because of the half-time when the light is off... Or is it more complex then that?
Most dimmer pack or racks use inexpensive thermal circuit breakers rather than the much-more expensive (and accurate) magnetic type. The tolerance of a thermal breaker can be +/- 10% of rated current. A lot depends on the ambient temperature - the breaker actually trips at a certain temperature. Its calibrated such that the increase over room room temperature caused by a certain amount of current will cause it to reach the trip temperature. If you start from a higher room temperature, it needs less of an increase (less current) to trip, so look at how well-ventilated your rack is and whether there's any dust built-up on the fans or inside.

Another thing to look at is the voltage rating of the lamps and the actual voltage being applied to them at full brightness. What controls the amount of current through a lamp filament is its resistance, which doesn't change. The 575 watt lamp will actually use 575 watts only if operated at its rated voltage. Assume it's rated at 110 volts. If operated at 120 volts it will actually use 684 watts! It makes for considerably more light, but shorter lamp life... and more current through the breaker (5.7 amps per lamp or 11.4 amps for two lamps... through a 10 amp breaker). You might want to choose a slightly lower-wattage lamp, or one rated for a higher voltage (in spite of the amber shift).

And as Ship mentioned, breakers wear out. Each time it trips (or is turned off as if it was a switch) makes it just a little easier to trip the next time. If the rack has a couple years on it, it might be time to look for replacement breakers.

I'm sorry; I should have been more specific.

Yes Zac, you are correct in saying that there would be less power draw over time. However, (Just as an example) if you had a bulb that drew 40 amps at full power, and dimmed it to 50%, it will only use half as much power over time, but because it is turning completely on and off it still needs to draw 40 amps to turn on.
So, as another example, lets say that you had two bulbs, one that used 40 amps, and one that used 20 amps. If you run the 40 bulb at half power, and the 20 bulb at full power, over time they will use the same amount of electricity. However the 20 bulb is on all the time drawing 20 amps, and the 40 bulb is on half of the time drawing 40 amps.

I hope that that helps, and I apologize to anyone who I just confused more :)

o im remembering, now, someone drew me a picture of how it works once.
i think it was that if it is at 50%, say, the the second and 4th quarters of the sine wave are cut off back to zero.
so its like:
-for the first quarter of the wave it climbs from zero to 1 in its normal shape
- then cuts instantly down to zero and stays there till half way
- then for the third quarter it goes down normally to -1 (the opposite of the first bit)
- then it cuts up to zero and stays there for the last quarter.

so if it was at 75% it would go up and then start going back down for the first three eighths, then go to zero for one 8th and so on

and it would always be at the same frequency (50hz over here)

i think thats qhat he said
Ron a very expeienced in tech buddie of mine (you think I or any of us know stuff...) asked me to post this response... at least until he joins himself.

Hi Bri';

There's a fellow on that new lighting form you introduced me to who has several ETC SmartPack dimmers with failures virtually right out of the box. Maybe you'd be good enough to pass the following along to him.


ETC Marketing News
SmartPack ® power-cube problems 294MN
November 13, 2003
ETC recently discovered that a batch of power cubes used in our SmartPack portable packs are defective. The power-cube vendor identified a manufacturing flaw with these cubes after reviewing units that had recently failed in the field. This defect has been found in the 12-channel versions of ETC's SmartPacks that began shipping in May 2003. Specifically, any packs using the Q211 power cubes with the 0305 or 0306 date codes may be affected.
The following ETC SmartPack models may be affected:
Model # ETC Part Number Description
SL1210A 7020A1001A 12 Ð 10A dimmers, 120V, Edison
SL1210B 7020A1001B 12 Ð 10A dimmers, 120V, Pin
SL1210P 7020A1001P 12 Ð 10A dimmers, 120V, PowerCon
SL1210V 7020A1001V 12 Ð 10A dimmers, 120V, VSC
SL1210W 7021A1000 12 Ð 10A dimmers, 120V, Wall Mount
All European 12-channel models
Please keep in mind that only Q211 cubes marked as 0305 or 0306 have been identified as flawed at this time. There may be SmartPacks in the field that contain power cubes with a combination of date codes. The 6-Channel SmartPacks do not have this issue.
A customer reporting typical power-cube problems such as "the output of a dimmer is stuck on"
or "I have a dead dimmer" may have a flawed power cube.
As a precaution, we are asking both dealers and end users to check their unit's serial
numbers. The serial number is found on the back panel of the SmartPack, in the upper right-hand corner, above the power input. Units shipped May 1, 2003, and later will have the following serial numbers:
100-510070-xxx and above (510071, 510072, 510073, etc.)
If you have one of the above packs, please verify the power-cube date
codes in your units. The date codes are found on the side of the cube,
under the ETC Part # and registration mark. (See photo.)
If any of the suspect cubes are found, please contact ETC Technical
Services for information and procedures for replacement (800/688-
4116). ETC standard warranty applies and the issue will be addressed
pursuant to that warranty.
We apologize for the inconvenience and appreciate your assistance in helping us proactively address this issue.
294MN 11/03

Ron Hebbard

While I get but just as much often do not read Martin technical briefs, it seems somone gets advised about the ECT product line. Thanks Ron! Hope this helps.
Thank you, this just helped me a lot. The dimmers my school just got had 1 dimmer per pack failed on. This release will help with talking to the company that sold the packs to us to get 2 new packs or to get the 2 packs fixed.

Where on the ETC site can you find all of these notices. I just looked and I couldn't find this info. on the smartpacks.

Anyway, thanks a ton

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