Tripping breaker

[mjl5007]

Following a complete teardown, cleaning, and rewiring of the sound system at our main church building, we're having problems with a breaker tripping every time we powerup the system. Actually, it usually trips on the first powerup attempt, but then starts fine after resetting the breaker and trying again. I've always been somewhat suspicious of the electrical/power situation in the tech booth, but I'm no EE and would love some input from some more knowledgeable folks on how to approach the problem.

Our equipment rack contains a Furman PF-PRO Series II power sequencer/conditioner, which is rated for 20A and has 3x20A duplex outlets, each in a separate sequence stage. All of the equipment in the rack runs through this unit, which is plugged into a 20A circuit -- this is the circuit that trips. I should mention that although the breaker is rated 20A, the wall receptacle that the sequencer/conditioner is plugged into is only 15A (i.e. it doesn't have the sideways slot on the hot blade socket that usually identifies a 20A receptacle over a 15A). Here's a quick rundown of all the equipment:

• 2 x QSC RMX 2450 power amps: 1 powers L-R house mains in mono parallel input, second powers fills on one channel and subs on the other
• 1 x QSC RMX 1850HD power amp for stage monitors
• Allen&Heath GL3300 mixing console
• dbx DriveRack 260
• 2-channel 31-band EQ for stage monitors (don't remember make/model)
• Peavey Deltafex effects unit
• PreSonus 8-channel compressor/gate
• Aviom AN-16/i 16-channel input module
• DISH satellite receiver
• DigitalMAX DVD recorder
• Sony consumer DVD player
• 13" CRT TV monitor
• custom-built line-level audio DA (basically a homebrew box built by one of our EE-inclined volunteers to split one of our Aux sends to 5 or 6 different destinations)

The powerup sequence has all of the non-amp equipment (including mixing console), plus the 1850HD stage monitor amp, in the first stage; the house mains amp in the second stage; and the fills/subs amp in the third stage.

Until this breaker started tripping, I was under the impression that the outlet the rack was plugged into was on a dedicated circuit, and all the other outlets in the booth were on another circuit(s). But, I noticed that when the breaker trips during startup, the UPS unit that the two computers and another DVD recorder are plugged into, which itself is plugged into one of the other outlets in the booth, loses power and starts beeping. So, at least one other outlet in the booth is on the same circuit as the outlet the rack the plugged into, and I suspect there are others. This means there's also potentially the UPS, two computers and their monitors, a second DVD recorder, a small oscillating fan, a Belkin FireWire hub/repeater, a Sennheiser G2 wireless receiver, a remote IR reciever/transmitter for the projector, a 1x4 composite/S-Video DA, a 1x4 VGA DA, the power supply for the motorized vertical blinds in the Worship Room, and probably a few other things I'm forgetting, also on that same circuit. Again, I'm no expert, but I'm fairly confident that's just WAY too much equipment to run off of a single 20A branch circuit.

On the other hand, as far as I know, we've never had any problems with the breaker tripping during a service; it only happens during initial system powerup.

Any thoughts, advice, questions, prayers, etc are greatly appreciated!

[Johnnycat]

Does it trip after the power sequencer is done with its cycle, or does it trip even before it cycles?

[waynehoskins]

In general, that sounds like more than I'd want to put on a single circuit. In particular, all three power amps. At my church we have twice as many amps in the amp rack (2xMT2400 for subs, 2xCTS600 for mid-highs, and 2xCTS4200 for monitors and fills), and they're split up onto three dedicated circuits: a MT2400 and CTS600 on two of them, and the CTS4200s, IEM transmitters, and DSP on the third. Never get anywhere close to tripping a breaker, even on the rare occasion it's turned up to Eleven. Our booth has two dedicated circuits for all the low-level stuff.

It would help to know where in the sequence the breaker trips.

[mjl5007]

Can't believe I forgot to mention that in my OP.

The breaker trips the instant you press the button to start the power sequencer -- when the mixer, monitor amp, and all other rack equipment come on.

[prochlea]

well - first off, I agree with Wayne, you've got too much on that circuit. I would have it on at least three(that's just a shot from the hip, without running the numbers)

There's gotta be something in that first sequence that has too high of an inrush current. start by taking out the 1850HD and see if that gets you past the trip. Then move it around in your sequence and see how it fares. You also gotta get that other stuff (computers, dvd, etc) on another circuit.

[waynehoskins]

My starting point would be to move the amps to their own dedicated circuit. Ideally I think I'd like to see them on two; if memory serves, the RMX2450 is roughly comparable to a Macro/Micro 24, which is capable of drawing more than 15A. I'd put subs on their own circuit, and mains and monitors on their own. Everything else in the booth could probably go on a single circuit comfortably, but if you're pulling conduit anyhow, I'd throw a second booth circuit in there. My booth circuits are roughly assigned one to audio and the other to lighting and video, more on the basis of physical location and load distribution than anything else (noise combatting, etc.).

[Brad Weber]

Originally Posted by mjl5007

I should mention that although the breaker is rated 20A, the wall receptacle that the sequencer/conditioner is plugged into is only 15A (i.e. it doesn't have the sideways slot on the hot blade socket that usually identifies a 20A receptacle over a 15A).

That sounds like it is perfectly fine, it is okay to have multiple 15A receptacles, and a single duplex is two receptacles, on a 20A circuit. The receptacles themselves are likely capable of handling the full current and the idea is that each individual load on any individual receptacle would then be limited by the connector type to devices drawing less than 15A with the overall load from multiple receptacles limited to 20A.

Of course this does beg the question of how the Furman PS-PRO II is plugged into a 15A receptacle. The PS-PRO II manual states:

The PS-PRO II also uses a 20 amp line cord, identified by the perpendicular blades on the plug. In 20 amp products, use of a plug of this type is required for UL safety certification. It is compatible with 20 amp outlets (such as those on the rear panel of the PS-PRO II).

That suggests that either some adapter was used or the power cord modified to even allow the PS-PRO II to be plugged into a 15A receptacle.

It is standard practice to try to keep loads at or below 80% of the rated value, so the normal load for a 20A circuit should be 16A or less. The 1/8 power pink noise current draw rating for your three amps totals 18.7A, which by itself suggest providing more than one circuit just for the amps, especially as their inrush current may be much greater. Add everything else you noted and you are almost certainly significantly overloading one 20A circuit. You ideally also want to keep things like the oscillating fan on separate circuits and since NEC prohibits it you may want to avoid things like plugstrips plugged into other plugstrips. I'd probably be looking at three if not four circuits for everything you have listed.

[mjl5007]

We initially tried putting the RMX1850 (monitors) on the third delay with the second 2450 (fills/subs), and the breaker tripped every time when the third delay activated. The current configuration, I believe, was the only way we could get the system to startup successfully -- most of the time.

I also verified that the other three outlets underneath the sound desk are on the same circuit that the rack is plugged into -- bad news. Curiously enough, the breaker for the circuit is labeled "SR console" (SR I assume stands for "Sound Room), but there's another breaker labeled "SR Rack", and I have no idea where the outlets for that circuit are, or what might be plugged into them (if they even exist). Likely just a case of old, incorrect labeling, but who knows.

Oh, and Brad is absolutely right about the PS-PRO II line plug; from the looks of things, the original plug was cut off and replaced with a regular 15A connector (the kind you'd buy at Lowe's/HD for repairing a power cord). My guess is that it was done by the company we had come in and install the Furman units a year or two ago, who I've never really been fond of in the first place. Unfortunately I wasn't present while they were installing, otherwise I'd have thrown the guy out for that stunt.

From what I've been told, there was some work done on the wiring several years ago (before I came) to deal with issues of noise on the AC lines, supposedly caused by the lighting circuits. We have two separate load centers, both of which are full, and apparently all the lighting stuff is on one load center and all the sound-related or -connected stuff has to be on the second load center otherwise we get noisy audio, particularly in the sends from the mixer to the recording equipment (computer, DVD recorder, etc). Bottom line, it likely will not be as simple as just adding another circuit or two, unfortunately. I think we're going to contact an electrician today to have them come in and see what they can do as far as getting us at least three different circuits, preferably four, without introducing any noise issues.

If we can figure out a way to do that -- and that's a big 'if' -- is there some way to have the existing Furman sequencer control the powerup of another circuit? The PS-PRO II manual says that we can connect multiple PS-PRO II's in parallel with low voltage wiring but power them from different circuits and they'll sequence simultaneously... but that's another $400+ for another sequencer. Is there some other piece of equipment we can power from another circuit (or two), but have it controlled by the PS-PRO II's sequencing?

[RickR]

Each device is supposed to have a lable with it's electrical requirements. (in US)
Some are in amps some are in watts.

Read them all and add it up!

[D.R.HADDOCK]

Most electrical equipment also has a start up current !
With little things its not much.
But with bigger stuff like power amps,
its a different story altogether.
When a power amp is first switched on,
the first thing to happen is the huge filter caps in
the power supply have to charge up.
Big amps means big supplies and huge caps,
so for a short time there will be large current draw
until the caps charge up fully, then it will settle down.

So if you have many amps, then there could be a short
but large current draw,
too much for your power circuits.

To get around this I would reccomend a dedicated power
circuit for each amp, with current to spare.
allow 2 x the normal running current for each amp.

I had simulair problems !

Each of your three amps should have its own power circuit.

[tedanderson]

We had a very similar set up in one of our previous buildings (QSC amps and all) and to solve this problem...temporarily.. we moved one of the amps to another sequence box so that they both wouldn't power up together.

[Brad Weber]

You can get into very specific factors. I recall a college stadium project where the amps would trip the breakers when you turned the system on, but it would work fine if you could get it up and running. Everything was solved by simply replacing the circuit breakers in the panel with ones that had the same current rating but handled a greater inrush current.