Powering a band, PA + lights from a generator

hassleham

Hi All,

My function band has had a gig enquiry and we would need to be powered from a generator. This would be the first gig where we've supplied and run our own sound system, along with the rest of our equipment, from a generator, and I am unsure how to go about making sure the generator is of a sufficient size. 
I have 0 experience in generators so I have no clue if all our equipment will explode if the wrong generator is used! Is there a minimum size of generator that I can tell the client that we need? Otherwise, how do I work out what is required?

Vague details of gear:
Digital mixer,
2x Mackie SRM450 tops,
2x JBL subs,
2x active floor monitors,
guitar amp,
keys amp,
bass amp,
5 LED par lights.

If accurate wattage values are needed then I would need to do some research and get back to you..

Any help and advice would be appreciated!
Cheers

Danny1969

You can generally get a 6KVA for around £130 a day where I live. You don't need that but lesser ones aren't that much cheaper so I normally go with the bigger ones and the peace of mind. Pick a silenced one, the un silent ones are well noisy 

Christophe

Best to calculate your total maximum power requirements in kilowatts then drop it into here for a rough calc http://www.enlightenedlighting.co.uk/resources/generator-power-calculator-kva-watts-amps from this you can see if a certain size, say 20kva is enough. You do need to factor in some headroom as you don't really want to run more than 60-70% of capacity. alternatively speak to a local hire company who can advise. Useful link here too http://www.sgs-engineering.com/help-advice/power-soundsystem-using-generator/

ESBlonde

Always go bigger, the pulsing current of music and flashy light puts a strain on just adequate power supplies, even though your lights are low power LEDs the subs will suck current big time.

hassleham

Thanks guys. 
The generator provider wants to know exactly how much power we need so i'm going to have to add it all up.

hassleham

Just an update for anyone searching for threads on this subject later..

I was struggling to find the power requirement for every piece of equipment in the band. I found an article, http://www.soundonsound.com/sound-advice/power-electrical-safety-stage, which advises to multiply the output power by 1.4 to get an approximate value for mains power requirement.

The total I found for the band's equipment was 8.7kW, which works out at around 11kVA according to the calculator at the link posted by @Christophe. ;
I multiplied that by 1.5 to add 50% headroom to the total, which finally brings me to 16.5kVA. 
This is the value I plan on giving as the bare minimum to clients requesting to power us via generators.

I will let you know if/when anything goes wrong!
Thanks for the advice.

Danny1969

You sure your bands total is 8.7KW mate .... that's quite a lot ..... what the fuck are you using

hassleham

@Danny1969 ;

Pair of 1000W subs, pair or 1000W tops, 500W monitor and a 200W monitor, 900W bass cab, 200W keys amp, 30W guitar amp and 5 60W lights.

Multiply that by 1.4 as the article says and it's pushing 8kW. Do you think that's too high?

Thanks

Danny1969

Well basically you would struggle to run 8.4K off a mains ring without blowing the 30 amp fuse  ... so you would be in jeopardy everytime you plugged it in .... 

SRM450 tops aren't 1KW each,  those things thermal before they ever get near their rated RMS power and they are quite efficient  ... you wouldn't need 1KW for both .... maybe your thinking peak power not RMS ? 

spark240

Surely thats speaker wattage ..not current draw !

This is your current per Mackie 450.

http://mackie.com/sites/default/files/PRODUCT RESOURCES/SPECS/Spec_Sheets/SRM350v3_450v3_SS.pdf

And I bet in rehearsals you run it all off a couple of 13A sockets....what does that tell you?

ICBM

The Mackies are 500W RMS/1000W peak. If they're not clipping they won't be averaging any more than 250W at most, and they're probably fairly efficient so I would guess the power draw at 300W each, maximum. The subs could be double that, and the monitors probably around 400W max, but you're still only at 2200W for the whole PA. 

The bass amp likewise - it's very unlikely to be drawing more than 500W, probably less - and the keyboard amp 150W. The odd one is the guitar amp, which could be putting out well *over* 30 if it's cranked because it will be driven into distortion, but the maximum draw of something like an AC30 is around 125W, so that's still less than 800W for the backline. 3KW total so far… the mixing desk could be around 100W and the lights 300W, and you're only at 3.4KW. You'd probably be OK with the whole lot run off a single 13A socket (3120W).

A 5KW generator should be more than enough really.

hassleham

Thanks for the further replies!

To be honest I just added up the maximum power of every part to be on the safe side. I did ask the client to pass my number on to the generator supplier so hopefully they will be in touch..

hassleham

@ICBM ;
The amp is a mesa lonestar special, if that makes any difference?

@Danny1969 ;
Yes, I was adding up the peak power. 

Jalapeno

hassleham said:

@Danny1969 ;;

Pair of 1000W subs, pair or 1000W tops, 500W monitor and a 200W monitor, 900W bass cab, 200W keys amp, 30W guitar amp and 5 60W lights.

Multiply that by 1.4 as the article says and it's pushing 8kW. Do you think that's too high?

Thanks

Might be totally wrong, but amp output is not the input power requirement (eg. 30W guitar amp, 900W bass amp etc).  Should tell you on the back panel of the amp what the input power requirement is.

hassleham

@Jalapeno ;
I posted above about this:

"I was struggling to find the power requirement for every piece of equipment in the band. I found an article, http://www.soundonsound.com/sound-advice/power-electrical-safety-stage, which advises to multiply the output power by 1.4 to get an approximate value for mains power requirement."

I realise that it's not a 100% accurate way of doing it but it was an easier solution than finding exact specs for every piece of equipment.

Jalapeno

My Boogie Mini Rec - 25W max output (into 8ohms) for a 630mA peak current draw, roughly 150W

Our old lights on the otherhand are voracious - 4x500W bulbs per unit = (circa) 2Kw / 8amps each

Danny1969

What you have to consider is the  average current draw when playing in your normal manner then have plenty in reserve ..... but you don't need to go crazy. You won't ever be using anything to it's maximum current draw, any speaker will be howling in feedback and thus turned down well before that happens. A Mackie SRM450 will thermally shut down well before that happens. 

My own company 2020Studios  typically use 6KVA  to 10KVA generators for a lot of outdoor work and that's running a 4.2K of  HK PA , band  backline and 4 to 6 stage monitors with a couple of rows of LED PARS ... I haven't had any problems when mixing all kinds of  bands outdoors with this setup.  You can generally expect in normal use to get about 76% of the KW you need from the generators KVA rating. 

Here's one of our typical outdoor PA's running from an 8KVA jennie



As you can see it was enough for Freddie and Brian  




Corporate gigs can be so sad ..... quite amusing though

mudslide73

Great looking setup @Danny1969 ;

hassleham

@Danny1969 ;

Super helpful, thank you!

BigMonka

@Danny1969 would you recommend using a UPS in line if running digital equipment off a genny?

By the way that inflatable stage looks like a great setup

Danny1969

BigMonka said:

@Danny1969 would you recommend using a UPS in line if running digital equipment off a genny?

By the way that inflatable stage looks like a great setup

We use a UPS for our digital desks simply because any power drop out will cause the desk to reboot into the last saved scene .... and unless you keep saving it as you go everything like the monitor sends as well as the main mix will be out of whack. That's not just when using generators but all the time indoors as well. 

Any digital equipment with a shut down procedure should always be on a UPS ... anything that you turn off by cutting the power with a switch with no shut down procedure should be fine,  although repeated on \ off \ on \ off power can cause problems

No idea about AxeFX or Kemper .... do they have a shut down procedure ?