Simple Question

[cw4u]

I need help interpreting some blueprints.

I am looking at a panels branch circuits for the panel that feeds among other things, a small, stage dimming system. On the description, it has a bracket around #s 27, 29, and 31. For the amp, it says 60. 3 Pole. 6 Wire.

Now does this mean that they are 3 individual 60 amp circuits that are tied together. Or they equal a total of 60 amps.

If it helps you out any, the panel description says 100 Ampere Main Lugs Only...120/208 Volts, Three Phase, 4 Wire.

Thanks for the help.

[waynehoskins]

Values of voltage and current are always, as best I know, specified per leg. 120/208 is 120 volts any phase to neutral, 208 volts phase to phase.

60A 3ph = 60 amps per phase, three phases.

[tedanderson]

Basically it's a 60 amp 3-phase circuit that feeds your dimming system. The breakers are tied together so that if one trips, they all trip preventing potential damage to the equipment should it still attempt to operate on one or two legs. Also, it ensures that you have disconnected ALL of the power feeding the lighting system if you ever have to turn it off. There is no better way to ensure that you hit the correct breakers.

[cw4u]

Ok. Thanks for the clarification.

Does that mean I can only run, say three 20 Amp dimmers off of it? (For less than 3 hrs) Right now, it currently feed 4 - Chauvet DMX4 dimmers which I think output a total of 15 amps each.

[tedanderson]

Does that mean I can only run, say three 20 Amp dimmers off of it?

Not exactly.. I am not a certified electrician but what I can tell you is that even though the dimmer is rated at 20A, your actual load from the instruments will be much less. The amp rating protects the individual circuits more so than it determines the quantity of equipment that can be connected to it.

So for instance, you could have as many as 8 breakers and dimmers behind a 60A circuit but it's not likely that you have a 160A load.

[FBCaudio]

Originally Posted by tedanderson

Not exactly.. I am not a certified electrician but what I can tell you is that even though the dimmer is rated at 20A, your actual load from the instruments will be much less. The amp rating protects the individual circuits more so than it determines the quantity of equipment that can be connected to it.

So for instance, you could have as many as 8 breakers and dimmers behind a 60A circuit but it's not likely that you have a 160A load.

Mmmmm, Derating Factors......

(gets out code book and calculator)

[Steve Vanciel]

The key question is - what is the Connected Load?

The amount of load demand should not exceed either
a) the capacity of an individual dimmer and
b) the total demand from all dimmers should not exceed the capacity of the feeder circuit breaker.

How you divide it up does not make too much difference with theatrical lighting where the levels keep changing. If you are planning to have everything at full for very long, then it would be a good idea to balance the loads on each phase.
But, with small shoebox dimmers, you do not have too much control over which phase is loaded.

SteveV

[tedanderson]

In our current setup we have 3 8-channel rack-mounted dimmer packs running off of 80A breakers on a 200A 3-phase service panel. If you do the math, you will see that we are technically way over capacity. But we are well within compliance of the code because if 3 or more circuits on the same leg pull 80 amps at the same time, it will trip the main breaker.