# Help-- Power in the middle of a parking lot?



## photoatdv (Oct 14, 2009)

I'm running a small sound system for an event at a tailgate. We thought we had a small camp generator, but it fell through. Now I need ideas :-S. The staging co. said one 15A circuit for the power requirements. This is one of those no-budget events (the sound system is donated). Any ideas-- I've heard of using inverters and batteries. And how far would be too far to run extensions in terms of voltage drop?


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## Footer (Oct 14, 2009)

I have ran sound off of inverters.... a 300w amp/mixer combo lasted 20 minutes. That all depends though on how many batteries you have. As far as the extension cord thing... it all depends on the guage of the cable. There is a power formula to calculate the drop off over distance.... but here is a shortcut...

Stealth 316 - Wire Resistance and Voltage Drop Calculator

You will want as beafy as a cable as possible. If you use 12 awg SOW you should be able to get pretty far and still have enough power to get your gear going. I would suggest the generator route though because SOW cable does not take wall to be driven over.


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## DaveySimps (Oct 14, 2009)

I think you really need to get an appropriate sized generator, or have someone with the appropriate equipment and knowledge distribute power from the facility. 

Keep in mind sound is very dynamic, electrically speaking. You will want something more robust than a small camp generator, or batteries / inverters that can handle the surges that are inherent with sound reproduction. 

Voltage drop via extension cords is relative. You should never use any cable less than 12/3. And, thicker guage cable is certainly recommended when going long distances. I recommend against stringing multiple cords together across a parking lot to get your power. Any cabling that is run should be run in some sort of cable ramp or trough to keep it from being damaged.

~Dave


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## KeepOnTruckin (Oct 14, 2009)

Any parking lot light poles nearby? I have been in a number of parking lots that provide an outlet near the bottom, usually to plug in decorations and probably not of enough capacity for your needs, but worth a look


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## len (Oct 14, 2009)

1. Light standard is a good place IF there's an existing outlet. If not, DO NOT MESS WITH LIVE WIRES. That should cover the TOS.

2. If someone is providing the sound system, maybe someone else can provide a small generator. If it's outside, chances are you won't be able to blast it loud anyway, so I doubt the demand is going to be very severe. Chances are a 5000 watt unit will do. The new Hondas are pretty quiet. And you can rent those for about $35 a day.

3. Someone should have a decent 10/3 or even 12/3 100 cord. Surely SOMEBODY in your area owns an electric mower.


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## avkid (Oct 14, 2009)

Be very careful with cheap, small generators.

1. ideally you want something that is voltage stabilized

2. it must always be earthed

3. make sure it runs long enough to cover your event without refueling, as many manufacturers discourage refueling while hot

4. you absolutely must meter your power, hot to neutral, hot to ground and ground to neutral


As always:
If you're unsure, contact someone who knows what they're doing.


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## photoatdv (Oct 14, 2009)

I think I can get AC cords from the staging co. My concern was running them across a parking lot in a tailgate.

If we do get a generator, how big of a no-no would it be to ground it to a light pole (assuming they don't have outlets we use)? Otherwise I'm still running some sort of cable across a tailgate to ground the genny.

Good point about the amount of time it'll run without refueling! I totally forgot about that.

I thought you were only supposed to meter hot-neutral and neutral-ground because hot-ground could throw some voltage onto ground?

If we go the extension cord route we'd probably run it to the side of the parking lot then to an outlet... so most likely it wouldn't get driven over much if at all. Would being driven over once or twice be really bad it we were using 8 or 10 AWG cables? I have a buddy that says he thinks he has some I could use for it. I'm thinking an 10 AWG run of <300 feet around the sides of a parking lot would be okay as long as I meter... is that correct?

What's the lowest voltage I can be getting before the gear will start acting up?

Thanks Guy!

PS-- Not gonna be messing with live wires ... other than metering outlets.


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## avkid (Oct 14, 2009)

photoatdv said:


> I think I can get AC cords from the staging co. My concern was running them across a parking lot in a tailgate.
> 
> (1)If we do get a generator, how big of a no-no would it be to ground it to a light pole (assuming they don't have outlets we use)? Otherwise I'm still running some sort of cable across a tailgate to ground the genny.
> 
> ...


(1) A steel streetlight may very well be grounded, if you can properly attach the correct wire with a split bolt it should be adequate.

(2) If your meter is passing voltage you have a problem.

(3) The length sounds fine, but you do not want anything (especially trucks) running over your cable, many generator rental places also rent cable cable protectors.
Yellow Jacket Cable Protectors - 25 Years of Quality and Innovation

(4) It depends largely on the equipment, anything digital is not going to be happy with much under 110, but some heartier analog things will survive 105 for short bursts


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## cdub260 (Oct 14, 2009)

If there is any chance that your cables will get run over, you must use cable ramps. Your local theatrical rental house should have them available.


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## mrb (Oct 14, 2009)

if you were by chance in So Cal i could help you out.....


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## fredthe (Oct 14, 2009)

avkid said:


> (1) A steel streetlight may very well be grounded, if you can properly attach the correct wire with a split bolt it should be adequate.


I believe you meant to say that a _Qualified Electrician_ can possibly tie into a streetlight ground. Don't go opening them up yourself.

-Fred


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## avkid (Oct 14, 2009)

fredthe said:


> I believe you meant to say that a _Qualified Electrician_ can possibly tie into a streetlight ground. Don't go opening them up yourself.
> 
> -Fred



I was talking about using the frame of the post, not opening it up.

But still, only qualified personnel should perform the work.


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## photoatdv (Oct 14, 2009)

I was talking about the housing of the street lamp. I have no intention of taking anything apart.

I'm not in CA. :-(

How specific do I need to be in telling the staging co. what I need? Would it be acceptable to say I need a laptop (1/8") input and a mic or do I need to say I need I mic, xlr cable, mixer, 1/8" to xlr adapter, ect.?


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## fredthe (Oct 14, 2009)

avkid said:


> I was talking about using the frame of the post, not opening it up.


Ah, in my haste I read your post as "attach *to *the correct wire."

-Fred


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## mrb (Oct 15, 2009)

def. dont want to be opening parking lot lights. many (most) are 277/480 which will quickly kill you.


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## avkid (Oct 15, 2009)

mrb said:


> def. dont want to be opening parking lot lights. many (most) are 277/480 which will quickly kill you.


The voltage isn't what kills you though.


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## photoatdv (Oct 15, 2009)

Voltage hurts though...

how specific do I need to be as far as equipment requests?


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## howlingwolf487 (Oct 15, 2009)

Make an itemized list of what you need...list the length, type and amount of each piece of gear needed. That way, it helps you plan out what you'll need AND there will be no disputes as to what the company is expected to provide. Sure, they can wave it in your face if you forgot to put something on there, but that's their right if you were negligent.

As to the AC power issue: If the gear provider told you that a single 15-amp circuit is what the rig requires for your intended use(s), then you may be able to have a long power run to the location. 

If that doesn't/cant' work, Honda makes some great, QUIET little generators. It would be an investment for you (or whomever buys it) and you can also use it again and again and again and...well, you get my point. This is DEFINITELY the preferred way to go about powering a rig when no wall power is nearby. Grounding is essential, however, especially because this is a public event.

Oh, and voltage is more like the _potential_ amount of hurt/pain that can be inflicted. It's the current (amperes) that kills you (stop the heart...cause arrhythmia, etc.). A typcial home electrical line is 15-amp, 120VAC. Industrial/Commercial lines start at 20-amp, 120VAC and only go up from there...way, WAY up. By the way, it only takes about 1 amp to kill you.


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## avkid (Oct 15, 2009)

photoatdv said:


> how specific do I need to be as far as equipment requests?


An itemized list is probably best.

Microsoft Excel should work nicely for this.


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## howlingwolf487 (Oct 15, 2009)

avkid said:


> An itemized list is probably best.
> 
> Microsoft Excel should work nicely for this.



I like how you think


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## photoatdv (Oct 15, 2009)

My problem is for example I need a 1/8" input to the board... well if the board has RCA jacks, I've got those adapters, but if it has XLR, I need them to provide it (actually I could do XLR to 1/8", but it would involve about 3 adaptors/cables). I don't know what type of cables need to run between their speakers... could be xlr, could be 1/4", ect. So should I just put 20' speaker cable? Ect... can you tell I've never put together a gear list in this detail before (unless it's stuff I'm familiar with).

I'm guessing I should also tell then that I'm kinda new to the whole putting together a system and ask if they'll check it?


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## avkid (Oct 15, 2009)

If you don't know what you're getting I don't think you can make a very good list.
I would suggest you contact them and see what is available before you do anything.


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## howlingwolf487 (Oct 15, 2009)

photoatdv said:


> can you tell I've never put together a gear list in this detail before (unless it's stuff I'm familiar with).


Yes...


> I'm guessing I should also tell then that I'm kinda new to the whole putting together a system and ask if they'll check it?


If you can't go through every cable and component of the system on a piece of paper, you are better off having the company decide what is adequate.


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## len (Oct 15, 2009)

photoatdv said:


> My problem is for example I need a 1/8" input to the board... well if the board has RCA jacks, I've got those adapters, but if it has XLR, I need them to provide it (actually I could do XLR to 1/8", but it would involve about 3 adaptors/cables). I don't know what type of cables need to run between their speakers... could be xlr, could be 1/4", ect. So should I just put 20' speaker cable? Ect... can you tell I've never put together a gear list in this detail before (unless it's stuff I'm familiar with).
> 
> I'm guessing I should also tell then that I'm kinda new to the whole putting together a system and ask if they'll check it?



If you're getting this rental stuff from a qualified rental company they should have the adapters/cables. Just tell them "I have a X output" and they'll be able to get you cables to connect. If you're unsure about cabling, bring your output in and connect it all at their shop.


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## mrb (Oct 15, 2009)

avkid said:


> The voltage isn't what kills you though.




NOT going to get into this argument, but yes its the current flowing through you that kills you. 100ma to 200ma is the range which causes death. Higher voltages cause more current to flow through your body.


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## Soundman0001 (Oct 16, 2009)

Here's my advice, use a small generator like other posters have said, you can get a Honda eu2000i for around $30 dollars a weekend where I live, and it will give you a 14 amp outlet if I remember correctaly. Having a quiet gennerator is key if you don't want long power runs, I found this out the hard way when I helped with a local church and their parade float, they were going to cover bringing a genny, and they brought one of thes small camp generators! Man thoes things are loud! An acoustic guitarest competing with a rattaling noisy smelly generator? That was a fun mix... Anyways, I have fallen in love with the whisperquiet honda generators, they can go for a couple hours on a single tank of gas. Also, for music playback, I have ran a mackie active rig, 2 tops and sub, 2 times off the hona generator that I mentioned with absolutly no problems, and a JBL VRX rig with no issues at full volume. Also, of you just ask the local sound co. for what you need (1/8" hookup) they should be able to get you set up no problem! Most importantly however, is have fun! Personially I love setup and wrapping cables just as much as I love mixing a whole band, it's just so dang addicting and fun! I know that with the right gear it will go off without a hitch!

Sidenote, If you do get a Honda genny, make sure you open the air valve on the fuel cap! I made that silly mistake once, it ran for ten min. But suddenly it died! Thankfully we were just setting up! Also, make sure you engage the Eco-throttle, then it will be whisper quiet!


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## Anvilx (Oct 16, 2009)

GRL's suggestion for Power. They used this for their Lazer tag project.

Humorous: yes

Good Idea: *NO*


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## mrb (Oct 16, 2009)

Anvilx said:


> GRL's suggestion for Power. They used this for their Lazer tag project.



wow, is that nice and illegal. tampering with a public utility is a great idea


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## fredthe (Oct 16, 2009)

Anvilx said:


> GRL's suggestion for Power. They used this for their Lazer tag project.


This reminds me of a recent trip to NYC, where I was amazed by the number of trees (the living, growing kind) that had power outlets at the bases.


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## NickJones (Oct 17, 2009)

We have a Battery Powered PA system that works really well, the company that makes ours is Australian but I'm sure there is a similar equivalent in the US.
Nick


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## Chris15 (Oct 17, 2009)

To comment on a few things noted...

If you are writing a gear list and the one company is supplying all the gear, it can be assumed that the company is capable of working out what connectors need to be on the ends to suit THEIR gear and so saying a 20m speaker cable and a 10m mic cable ought to be adequate. For your iPod input say something like 1x cable to adapt 3.5mm stereo TRS to mixer inputs - that makes the mixer input end their problem to work out...
Basically specify what matters and assume (stupidly or otherwise) that the company is capable of working the rest out when connecting their stuff together.

Note that all of the numbers being tossed around for effects of current are for a healthy adult. People with existing heart conditions and other ailments are more vulnerable and will have lower thresholds. This is why RCDs in hospitals are 10mA devices not the 30mA devices used more generally.

I disagree that an inverter and battery supply is an unwise choice. As always it depends on the load amongst other things, but because of the battery you have the ability to take peaks better than with a generator in many ways.
In contrast a generator (particularly if the audio load is the only load) is liable to have it's supply characteristics vary with the load, affecting voltage sure but also potentially affecting the frequency stability of the supply, especially in small generators and even more so in cheap generators. (This has to do with back emfs and other such fun)

If you are to use a generator, do ensure you have the thing fuelled before you start, it's embarrassing otherwise. Chances are if you get the generator to start it will behave, but I've lost count of the number of times I've had issues with generators...

Agreed that if you are causing a current of any significant magnitude to flow by metering Active - Earth then your meter needs to be divided into small pieces and disposed of thoughtfully. Note also that you need to be used a meter appropriately rated for the fault voltage potential - in this case I believe you would need a Cat IV rated meter.

The current draw for your rig will depend a lot on the character of the music being reproduced - simply bass needs more juice. With an analog voltmeter and not much residual load, you would be able to watch the voltage drop in time with the kick drum beats if they are amplified...

If you go for the long cable route, then you would be very well advised to ensure the feed is RCD protected. Running over cables causes non visible damage to the internal structure of the cable which affects things like the insulation resistance - this can become BAD. Has it happened before? Sure Is it good? No. Now I won't explicitly say it but power cable is probably going to survive temporary point loading better than audio multicore or dread the thought fibre (which for most fibre will die there and then and be non field reterminable - some of the milspec stuff will survive but may sustain internal damage that causes attenuation of the signal.)

And in the food for thought department for competent professionals, the Australian Standard for Temporary Power (Shows & Carnivals, AS3002:2008) throws this curler:

AS3002:2008 Clause 3.2 said:


> ... Earthing of the generator frame, or equipotential bonding system, by use of an electrode or stake is not required and not recommended.


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