Disaster !! I need some SERIOUS advice !!

[ChillinBoy]

We rented a bunch of equipment in order to do an event at my school. It was outside. We had,

LIST
Pioneer DJM 800 – 32W or Numark M6 – 12W
(2) Technics SL-1200 – 13.5W
Belkin USB Hub – NEGLIGIBLE
Macbook Pro – 30W
Numark NS6 – 12V , 2A → 24 W
Samsung Laptop – 19V , 3.6 A → 64 W

I know the capacity of power outlets are 120V, 15/20A. This gives outlets a capacity of 1800W/2400W.

Then we also had an AP4040 amplifier (1130W, 1800W at max peak), 2 Yorkville E215s and 2 Yorkville LS801Ps (792W, 900W at max peak).

On top of that, we were using 3 plugs (2 From ONE outside portable, and 1 from ANOTHER outside portable [2 portables in total]).

The Setup + LS801P was on ONE plug of a portable (with the help of Power Bars).
The AMP was on ANOTHER plug of the SAME Portable.

The other LS801P was plugged in the other portable.

However, the sound kept cutting off like crazy! I'm trying to make sense of this and why it would cut off... I'm assuming that all the plugs in one portable are in a SEPARATE circuit from the other portable.

One known mistake was the fact that we put the LS801P AND the AP4040 on one circuit. That will certainly surpass the capacity if the circuit has a 15A capacity, and that is exactly what happened. Therefore, we unplugged the LS801P, which would cause the circuit to draw about 1330W at the very most, and I doubt that the AP4040 was drawing a max peak of power (1800W). So in retrospect, the sound SHOULDN'T be cutting off anymore.

But it still did... and it was really embarrassing.

I was also open to the possibility that BOTH portables were on one circuit. So we tried our best by removing all our items from the "LIST" except the Numark NS6, and the Samsung Laptop.

Thank you guys!

[DJMC]

This is one reason why I have 300' of 12 ga. power cord, and use a Tripp-Lite LC-1600 Line Conditioner whenever I'm doing outdoor events, or running off a generator.

I'm surprised that a school's electrical system could not deliver enough wattage through a single circuit. In Northern CA, they deliver 30 amps. My biggest system (without lights) only draws 12-15 amps.

However, this is the most likely scenario that I've encountered in my two-plus decades as a mobile DJ:

Someone had a compressor going on that circuit? (Usually an old refrigerator, a jacuzzi, an A/C unit, or HVAC system will cause interference with music playback systems on same circuit)

OR- Did they have a 50-cup "Coffee Urn" percolator running on same circuit.
Many schools use those old fashioned coffee makers, usually in the cafeterias, which draw about 5000 watts of power thru their heating coils.

An old fashioned percolator urn will cause the kind of power interruption that you described!

[Evil Steve]

Chillin
Where were you?
Are you going to do this again?
Was this just a one-time thing? If so, consider it a valuable lesson.
When you get into situations like the one you describe, it's a box of chocolates.
If you have the opportunity to scope out the job beforehand, power supply is one of the things you should make sure to scope out.
Most people don't have a clue what they're talking about when it comes to power supply, especially event organizers at schools. Many event organizers are so stupid about technical stuff that they don't realize that there's a wire between a switch and a light. They're always sure that you'll magically have whatever you need, and if you don't, the solution will be a simple thing. It usually is a simple thing for them. They just wave a magic wand, and the little people make it happen.

Sounds like you had quite a system set up.
Did it cause you problems right from the beginning, or did the problems come on as you dialed the volume up?

[ChillinBoy]

@DJMC
Now that I think about it.. there COULD have been some devices plugged into portable that could draw some power as well (school appliances) ... but I doubt it was a compressor or a percolator. May I please ask what the purpose of the power conditioner is?

@Evil Steve
You're absolutely correct. They have no idea what type of effort goes into this. We only had two people and we had to load up the van with all this stuff, set it up, go through a bunch of shit from friends and teachers and then load the equipment up to return it. But I'm a bit grateful this happened, only because it was nothing but a learning experience. I was in my high school at the moment, and I doubt they will let me do it again. It was me and a friend: I had the DVS setup, and my friend had the NS6 setup.

Problems came when I turned the volume up... but sometimes I would keep the volume a bit down and it would STILL cut off. I don't know if this made the situation better or worse, but it got to a point where dialed down the volume of one speaker on the amp to ZERO, just so it doesn't have to feed as much power.

[ampnation]

I'm not an electrical engineer or even close as some here seem to be, but from what you've written so far there are two things, probably related you should investigate...

First - power compression. As you turned up the volume, the problems started. I believe when your drivers start experiencing significant power compression from being driven too hard they create a more strenuous load with has a feedback loop effect in the sense that it affects the delivery of power which in turn exacerbates the power compression which in turn affects the delivery of power more, etc. Once volume is reduced, everything is still "heated up" so the reduction would have to be down to below what would have been a good level before power compression set in... Those of you in the know, please tell me if I'm wrong here.

Second - As DJMC mentioned about the size of his power cables, too small a power pipleline at any junction can lead to your equipment not receiving enough power. So, 16 guage power cables could be a problem, or a power strip that isn't up to snuff. Or an extension cord with non-visible damage where the conducting cables are partially severed inside the jacket. A multimeter can help diagnose this.

Also, was it hot outside? that can exacerbate the power compression problems and cause your amps to work harder than they should.

My bet is though, you had a little of these problems combined with power supply problems at the point where you plugged in meaning they weren't delivering to you what you thought you were getting. Older facilities especially can have some very dodgy electrical systems.

Also, what do you mean by "a portable?" A generator?

[windspeed36]

Imma take a stab in the dark and assume that when you say 'portable' you mean portable external classroom? You mentioned you though each 'portable' ran off a seperate circuit. The last time I came accross a similar venue - the block of portables were all running off a single 3phase 32amp 415v feed from somewhere else in the school -this was then split to lighting and poweroutlets throughout the rooms. How many portables were there?

Somehow I don't think you exhausted the buildings power supply, rather you just didn't have the right cables to supply the power you needed

[SockoPro]

I can tell you what was happening.

You where not using heavy enough gauge cords for the distance of cable run. As you used more amperage the voltage would sag to the point that the amps where shutting down due to under voltage. Electricity flow is governed by ohms laws.

For example. Assuming the voltage in the classroom was 120 volts (likely lower depending on a variety of factors) , you use a 100 foot orange 16 gauge extension cord. While everything was fine during setup once you started to push the system you create constant and transient amperage load. When powering reactive loads (such as an audio system where amperage requirements vary based on how hard the equipment is pushed) the transient load can peak for a few milliseconds way above their constant ratings. As you draw more power your voltage began to sag. If you where hitting 20 amps transient you where dropping the voltage to about 100 volts. Most sensitive equipment will shut down at that under voltage.

[djscrizzle]

When I can't get the power I require from a building, I highly recommend hiring in a generator (and possibly a power distro for a larger rig) to give me the power I require, where I require it. Beats the ever-living snot out of sweating over long AC power cable runs.

[djscrizzle]

This is one reason why I have 300' of 12 ga. power cord, and use a Tripp-Lite LC-1600 Line Conditioner whenever I'm doing outdoor events, or running off a generator.

I'm surprised that a school's electrical system could not deliver enough wattage through a single circuit. In Northern CA, they deliver 30 amps. My biggest system (without lights) only draws 12-15 amps.

However, this is the most likely scenario that I've encountered in my two-plus decades as a mobile DJ:

Someone had a compressor going on that circuit? (Usually an old refrigerator, a jacuzzi, an A/C unit, or HVAC system will cause interference with music playback systems on same circuit)

OR- Did they have a 50-cup "Coffee Urn" percolator running on same circuit.
Many schools use those old fashioned coffee makers, usually in the cafeterias, which draw about 5000 watts of power thru their heating coils.

An old fashioned percolator urn will cause the kind of power interruption that you described!

Those coffee urns you describe would just happen to perfectly answer a question of why one of the hotels and a couple schools where I live at would have NEMA14-50 receptacles placed around the room, near the doors and one more in the back.

Those same outlets are 120/208 (they're single phase like a typical range outlet) 1phase at 50 amps 3pole/4wire, which is a perfect way for me to plug in my spiderbox power distro safely...

I, too carry a LOT of AC Power cabling, I have a couple hundo ft each of #14/3 STW, and 12/3 SOOW. Also a fair amount of #10/4 SOOW to power up a amp rack's distro. My spiderbox has a 6' cable for it, and uses Calif. standard (CS-6364) twistlocks to allow me to rent more feeder cable as needed on the cheap.

[SockoPro]

A 14-50r is single phase 120v to neutral outlet composed of 2 - 120 volt legs (x & y) W - Neutral, G - Ground. Leg to leg is 240v.

A 120-208v wye system is 3 phase (x,y,z) N & G. In that system all legs to neutral are 120 volts, Leg to leg is 208v.