Circuit breaker tripping

[Ampacity]

Has anyone experienced tripping of the 10 amp. circuit breaker on a 1200 watt dimmer channel with two 575watt HPL lamp after an hour or two at full brightness? The dimmer being used is an ETC Smartpack. Thanks in advance. Ampacity

[bdesmond]

Well, Amps = Watts/Volts, so, Amps = 1200W/120V = 10 Amps. That's right on the mark. I can certainly see the breaker blowing here. You might consider turning the intensity level down five or ten percent to allow some room in the power draw.

[Mayhem]

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).

[zac850]

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.

[ship]

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.

[halojen]

Originally Posted by zac850

...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.
?

[Mayhem]

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.

[nickpl]

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.

-Nick

[zac850]

^ 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?

[zac850]

^ 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?