How much power can you connect to an outlet. How to prevent an accident?

[JaneBass1]

Hello,

I have a question about power. I am not too familiar with this.

In the bars I played so far. In one I connected my amp into an extension (owned by the bar), maybe it was not a power surge.

In another i plugged in straight to the wall. Well it was more like an outlet with 4 plugs, and you could see metal cylinders coming from the back of these plugs up to somewhere else.

My question is do you usually bring a power surge to plug in your stuff?

How much can you connect to it?

How do you make sure you are not going to blow up something, create a fire, etc?

Where can I get info about this.

[mrokern]

Surge protectors can be useful (not just power strips, but surge protectors).

As far as how much you can connect? That's what breakers are for.

Overheating occurs / fires start when you're using too small of a gauge power cord for the load you are placing on it. Cord gauge should be matched to the load (e.g. using 16AWG lamp cord on a 20-amp circuit, drawing 20 amps would be a NO-NO!). You'll melt the wire before the breaker trips if things are not matched properly, as in the example.

Now if you used a surge protector (or even power strip) with a breaker, that breaker would have tripped at a lower draw. Even though the overall circuit would have been ok, the breaker on the strip would be set for the rating of the wiring of the strip.

-Mark

[JustOpenYourMind]

You won't blow anything up, all outlets are connected somewhere to a 15 amperes circuit breaker. There can be multiple outlets connected to a single breaker. If anything you plug into a socket draws more than 15A the breaker will trip and it will cut the power on that circuit.

Bassicly you can't blow something up by plugging to many things in an outlet, if you do exceed the 15A limit with your gear (wich I very highly doubt, unless you have 3 heads powering a monster setup plus a monster rack of effects.) the breaker will just trip and you'l have to plug part of your gear in an outlet on another circuit.

The poster above is right about using extensions, you need to use a thick enough guage of wire, 14AWG for 15A and 12AWG for 20A.

[etoncrow]

Typical design criteria according the National Electric Code (NEC) for the types of venues you mentioned would be to have no more than eight duplex outlets per circuit and rate them at a maximum usage of 180 watts/duplex outlet; or, 1.4 KW/circuit. Most designers would use a 15A circuit breaker. Others use 20A. The circuit breaker is designed to shut down in overload to prevent a fire. That obviously does not always occur. Are you calling a surge suppressor a 'power surge' cause they are two different things? A power strip can also be a surge supressor. Always use one that has an integral breaker.

You cannot be sure if you are overloading a circuit. Try to use as many different outlets as you can so you might be spreading your load over two or more circuits. By the way, long extension cords can overheat; especially cheap ones that are not grounded (3-prong) or sized properly to the load and length. Does this help?

edit: Stage lighting is possibly the greatest load you might use. You can blow circuits with high wattage lighting; or a short circuited piece of equipment.

[jtc_hunter]

Quite often, I run my bass amp ,480 watts, a 1000 watt pa amp, and a 500 watt monitor amp off of a single 20 amp circuit. Along with those 3 hogs, my sure wireless, a Fender racktuner, a Sonic maximizer, and a peavey 32 band EQ. The main thing is , dont run any lights on the same circuit as sound equip.

[Ben-Jammin]

Originally Posted by jtc_hunter

Quite often, I run my bass amp ,480 watts, a 1000 watt pa amp, and a 500 watt monitor amp off of a single 20 amp circuit. Along with those 3 hogs, my sure wireless, a Fender racktuner, a Sonic maximizer, and a peavey 32 band EQ. The main thing is , dont run any lights on the same circuit as sound equip.

Basic way to calculate ---

Amps = Watts/Volts

In jtc_hunter's situation he has a total of 1948 watts / 110volts (standard north american voltage) = 17.7A draw.

If he was running on a 15A rated ciruit and the units connected drew full power, the breaker would flip, causing power to be shutoff, thus preventing fire.

[dlstyley]

Sorry to revive an old thread, but this thread comes very close to answer my question, but there is one piece missing.

I get how to convert watts to amps as noted by Ben-Jammin, but what isn't clear to me is the actual wattage an amp draws. I would assume that amps run at less than 100% efficiency, and that the rated wattage is the output wattage. If so, wouldn't the input wattage be higher than the output wattage?

Any rules of thumb here? I ask because we have an upcoming outdoor gig with a single circuit (I'm stilling finding out what that circuit is rated for). I need to know if we can use that, or if we need to order up a generator.

[Steve]

Watts devided by volts will give you amps.


these will be nominal values as 110, 115, 120 and 125v. are all considered correct voltages at the outlet and will obviously provide different numbers.

Will the voltage sag under load? Probably
Enough to really matter in the real world? Probably not.
Is the building wired properly? Maybe, maybe not.

NEC requires all circuits in a commercial occupancy to be not less than 20A.
NEC requires all electrical conductors in a commercial occupancy to be not less than #12 AWG
NEC requires that all circuits serving continuous loads (Defined as a load that remains on for 3 hours or more) be loaded to not more that 80% of it's maximum capacity.

NEC requires a circuit capacity of 180VA. (Watts) per general use outlet in COMMERCIAL occupancies.

If you have 15A circuits and 14AWG conductors, you are in a "dwelling" (House), those calcs. are based on square footage not per outlet.

As far as how much you amp draws...the load is too inconsistant with too many unknowns (efficiency being one as you noted) to get a handle on realistically.

My PLX 2402 manual shows a worst case maximum electrical load of...42A @ 2 ohms, 120V both channels driven.
In the real world, I'll bet I'm dragging up because it's too effing loud before that thing draws 6 amps.

Unless you know EXACTLY, and I mean EXACTLY what you are doing, don't run a band off a generator. Most real electricians don't even know how to properly ground and stabilize the output of a generator well enough to make it clean enough for a band. Especially if there is anything digital onstage.

[davecanady]

dlstyley,
The wattage consumption is printed on the back of many electrical appliance. My GK bass amp is rated at 240 watts output but at max power could uses 410 watts. Our lead guitar player's 60 watt Hot Rod Deville draws 180 watts max. If we ran all our gear at max the walls would come down. I'm never above 4 and I compete with two tube amps with 410 and 412 cabs.

Our sound proofed garage band room was designed by our lead singer. He teaches electrical engineering at a local college. On one single 15 amp breaker we run: PA, 2 guitar tube amps, a bass amp, 3 different pedal boards, 2 wireless guitar systems, 1 wireless mic, and three 12" fans.... plus the lights for the room. No issues. At gigs we add 4 stage lights and 2 more fans to the mix....often from a single receptacle or 4 or 6 gang box....never multiple circuit breakers.

Some of the bars we play are old and ratty. Buy a ground tester at the hardware store. For $8 you can test to see if the 3 prong receptacle you are using actually has 3 wires attached. Sloshed drinks, metal mic stands, metal mic screens, and non-grounded power are a bad combination. Use 12 gage 3 prong extension cords, use power strips. Working with a racked bass amp, I have a Furman power condioner as well. It's a good investment. In summary, don't worry about the wattage/amps, worry about the ground!

[dlstyley]

Thanks Dave,

I appreciate the peace of mind from the info you provided. I asked because we played this same outdoor venue a while back, but the show was much larger (4 bands) and they had a professional sound guy. He felt the need to use a generator, but he also had a bunch of stage lights, a very large PA, monitors, mixing board, etc, etc..

I think we'll be fine with our small setup (vocal PA, 3 guitar amps and bass amp).

Thanks!

[davecanady]

Worst case...bring a 100' extension cord along. You can plug into an outlet that's not on the same breaker and split your lights from your sound.

What I have learned playing in bars and old clubhouses....
Don't share power with a popcorn machine.
Don't use an outlet that works off a wall switch.
Never plug into an outlet that's behind a locked door.

You can guess why I know all of this!

[Bob Lee (QSC)]

Originally Posted by dlstyley

Sorry to revive an old thread, but this thread comes very close to answer my question, but there is one piece missing.

I get how to convert watts to amps as noted by Ben-Jammin, but what isn't clear to me is the actual wattage an amp draws. I would assume that amps run at less than 100% efficiency, and that the rated wattage is the output wattage. If so, wouldn't the input wattage be higher than the output wattage?

Any rules of thumb here? I ask because we have an upcoming outdoor gig with a single circuit (I'm stilling finding out what that circuit is rated for). I need to know if we can use that, or if we need to order up a generator.

Yes, the input mains power (in watts) is higher than the output audio power (also in watts). There can be short-term peaks where the amp's output power briefly exceeds the mains power in because the amp is drawing more from the internal reservoir.

Another important thing to consider is that at any given time the amp's output power is almost always much less than its maximum.

Contact the manufacturer to find out what the amp's current draw will typically be for a given load impedance. Current draw measured with pink noise at 1/8 of full power into a certain load impedance will usually tell you what the typical worst-case current draw will be.