portable system power requirements

[unc417]

I have a small portable system, a few QSC K series speakers and an A&H analog mixer and a small amount of outboard gear.

I know it's always recommended to run different equipment on separate circuits, but is there really a problem with running everything off of 1? I haven't measured yet because they are new, but I saw on the QSC forums that a QSC engineer said a K12 shouldn't pull any more than 150 watts if I understood correctly. So with a system as small as mine, I know I won't be pulling anywhere near 20 amps. Traveling to various places, it isn't always possible to get multiple dedicated circuits. Sometimes I can't get 1 dedicated circuit.

Is there a real problem with this?
thx

[chazman14]

I ran a system with a traveling group for a year and we had LR main channels, 2 monitor channels, and a 16 ch board with eq and aviom, plus we powered our own guitar amps and 2 key boards running of of a single circuit. There was no problems with our setup. Maybe you could get a power conditioner just for extra comfort.

[tpichler]

Total power is the important part. My personal rule of thumb is I start thinking about moving things to another circuit when I hit 80% capacity and I try not to go live with any circuit above 90% capacity.

It can also depend a little on your equipment. Everything you listed is quite new, which would lower my concern. Older equipment had more trouble with transient power requirements so you really needed to play it safe on the power requirements.

[tdangelo]

Originally Posted by unc417

I know it's always recommended to run different equipment on separate circuits,

Do you mean different departments off different circuits? Like keeping audio seperate from lighting, seperate from video, seperate from computers, etc.?

With the exception of lighting I wouldn't worry that much about keeping audio seperate from other departments. And even with lighting the major concern is that some older or cheaper dimmers can throw noise back on the electrical neutral or ground ... which can make its way into the audio signal.

I've seen more problems occur when the mains into the venue are multi-phase, 220-240v, 440v etc., and the loads on these mains are not balanced well. If the loads are imbalanced you will begin to see differentials between hot->neutral vs hot->ground.

I would not worry at all if your audio gear is on one or more or two or less circuits because in all likelihood both circuits are being fed by the same phase leg or transformer.

Count up how many amps you are pulling. Find out which circuits already have existing draw on them. Don't exceed the maximum draw for any circuit including a 10-20% contingency. Remember that at power-up many items pull more amperage than at idle or use.

[unc417]

I've seen it recommended on forums before to run stage and foh on different circuits. If the system is large enough I can see that, but I don't see why that would be recommended as a general rule. I'll probably be running 2 mains and perhaps 4 or so wedges. Using 150 watts per speaker, that's still less than 1000 watts max. I don't know what a console and outboard gear pulls but I'm sure it isn't much. If my info is correct than one circuit, 2400 watts, is more than enough.

My next event is outdoors at a chic fil a. They are wanting to use power off of their sign. It has flourescents but they will be off since it's during the day. As far as I've been told, there is nothing else on that circuit but they are double checking that for me.

thx

[cmchamp]

I generally run my small portable rig, 2 active subs, 2 active tops, RMX850 for monitors, 4 wireless mics, 2 tube pre-amps, A&H GL2, EFX and an iMac off of 1 15A circuit when in smaller churches. A bit larger churches, I'll run the active speakers on their own 15A, and the rest on another 15A due to current draw because they need to work a bit more to be louder.
My large rig, however, requires 4 20A circuits, minimum.

[waynehoskins]

Since input power is what matters, simply add up the total current draw of all the devices to be powered. 150 watts input on the K12s must be for a particular application. Since they have 1KW (output) plate amps, and an amplifier can't be more than 100% efficient, full tilt would be at best 1KW peak input power as well. I forget what topology they use, but Class AB amps are generally 50% efficient, so 1KW output power would require 2KW input power.

Power supply design could affect AC requirements, depending on how much filtering it incorporates and what sort of duty cycle the program material has.

That said, I've run a pair of K10s, and I think a pair of powered 15" subs as well, on a single 20A circuit. I think that's right, or it might have been only one stack, but I think it was two.

No sense, with larger PAs, trying to get everything on the same circuit, since anything of size will require more than a single 20 or 40 amp circuit. No sense trying to keep it on the same leg either; you'll imbalance the transformer. I'm a fan, even on smaller rigs, of balancing the transformer

[unc417]

I'm still going to do an actual measurement, but I see on the specs from QSC the power consumption is 2 amps at 120 volt. That should give me plenty of room for all I need on one circuit. Thanks