Using a generator

[Martin E]

Some way ahead yet but we've just been booked for an outside gig where we will have to use a generator as no power is available.

Unfortunately I have a vivid memory of watching a band last year using one of these things where the power or voltage? would dip and the PA would cut out momentarily which ruined their set.

Anyone got any practical advice on what we should be looking to borrow or hire please to avoid this problem.

Thanks

[machinehead]

Add up all the maximum power requirements (watts or kilowatts). That will give you your kW figure for the generator you need. EDIT Be careful to use the kW consumption figure, found on the nameplate, not the amp rating as in say, a 50 watt Fender amp doesn't actually consume 50 watts, it will be a higher figure consumed.

However, sudden increases in demand cause the engine to slow down and it takes time to recover to its normal running rpm. This drop in engine speed causes the supply frequency (hertz) to drop. The voltage will also drop under sudden load increases. This is called speed and voltage droop. (cue jokes about drinkers droop).

More expensive generators deal with these issues better than cheaper ones but I assume you will hire a Honda or similar when a diesel one might be better.

So you need to get a generator that has a kW rating of at least twice your max kW requirement to avoid frequency and voltage droops. Doessn't really matter if its several times your kW requirement although if it's underloaded, it will be inefficient and tend to need more servicing.

I hope this helps.

Frank.

Edited January 29, 2011 by machinehead

[chris_b]

Don't worry about the set... worry about your gear and your health!

I don't believe a drop in power will cause damage but spikes would. Also find out about earth issues. I think you are OK without and earth if everything you can touch is powered from that one generator.

Get the organisers to guarantee the quality of power supply and don't do the gig if they won't.

[gary mac]

[quote name='chris_b' post='1107160' date='Jan 29 2011, 01:14 PM']Don't worry about the set... worry about your gear and your health!

I don't believe a drop in power will cause damage but spikes would. Also find out about earth issues. I think you are OK without and earth if everything you can touch is powered from that one generator.

Get the organisers to guarantee the quality of power supply and don't do the gig if they won't.[/quote]


Absolutely spot on.

[clauster]

Anyone know if several generators can be earthed together?

[bumnote]

I used to do Portsmouth harbour cruises many years ago with a guy that played a Hammond. Their boats electricity supply was erratic, and linked to something that had a big current draw. Everytime whatever it was clicked in, the Hammond used to wail up and down like Keith Emerson, and then stabilise a semitone lower. and a couple of miniutes later, it would happen again, and the organ would revert to normal pitch.
Made singing interesting, although we bought an electric piano in the end

[Hamster]

[quote name='clauster' post='1107245' date='Jan 29 2011, 02:38 PM']Anyone know if several generators can be earthed together?[/quote]

I can't see it would do any harm to have them earthed together - as long as they are earthed. It would be better if each one was earthed (just a metal stake into the ground) so if one of the earths failed, there would be several others?

[xgsjx]

Like is said above, make sure it has a decent KVA (or even MVA). Depending on what all is being powered, you might wanna make sure it's at least 60-100 KVA .
I'd suggest using a surge protector also.

[Alien]

[quote name='clauster' post='1107245' date='Jan 29 2011, 02:38 PM']Anyone know if several generators can be earthed together?[/quote]

I wouldn't recommend using multiple generators unless their outputs are fully synchronised (and if they're small enough to be moved without a truck they probably won't be.)

The reason for this is that the AC signals may well be out of phase, and if your amp is plugged into one phase and your mic into another then you could end getting zapped in a big way.

A

[clauster]

Cheers guys

[xgsjx]

[quote name='Alien' post='1107281' date='Jan 29 2011, 03:32 PM']I wouldn't recommend using multiple generators unless their outputs are fully synchronised (and if they're small enough to be moved without a truck they probably won't be.)

The reason for this is that the AC signals may well be out of phase, and if your amp is plugged into one phase and your mic into another then you could end getting zapped in a big way.

A[/quote]
A better option here if several generators are needed is to just use each individually & not overload it (like running the lighting rig & some other stuff off one generator & the PA & backline off another etc).
They don't need to be linked to supply more power & earthing them is a spike in the ground.

[icastle]

[quote name='clauster' post='1107245' date='Jan 29 2011, 02:38 PM']Anyone know if several generators can be earthed together?[/quote]

No you can't.

The 'earth' provided by a generator is actually the Neutral.
As there's no way that two generators are going to run in synch without a suitable interlink control (big and expensive) your earth would end up all over the place!

[chris_b]

I am not an expert here but I was told that multiple sources of power are the reason we need an earth. A single generator is the safest system and a third wire (the earth) is not needed. Because of this a surge protector won't work either, because it needs the third wire!

Also does anyone know if a power conditioner would protect your gear from power spikes?

[chris_b]

I would also ask if the equipment provided has current PAT test certificates and if the promoter has Public Liability Insurance.

This might backfire because he may ask if you have PAT and PLI as well!

[icastle]

[quote name='chris_b' post='1107365' date='Jan 29 2011, 05:05 PM']I would also ask if the equipment provided has current PAT test certificates and if the promoter has Public Liability Insurance.

This might backfire because he may ask if you have PAT and PLI as well![/quote]

+1
And make sure your gear is insured as well.
Most modern generators are pretty stable but if you're renting one it might not be as 'clean' as it could be...

[Martin E]

Thank you all for your replies. very interesting and informative and some things I hadn't thought about.

We're playing several sets during the day at a large village fair/fete type event so lighting won't be required. Just the amps and PA to power fortunately.

Cheers

Martin

[paul_5]

We played through generators a couple of years ago - they kept tripping out. Eventually we asked a steward to sit with their finger on the 'reset' button. Nobody died.

[icastle]

[quote name='Martin E' post='1107418' date='Jan 29 2011, 05:49 PM']Thank you all for your replies. very interesting and informative and some things I hadn't thought about.

We're playing several sets during the day at a large village fair/fete type event so lighting won't be required. Just the amps and PA to power fortunately.[/quote]

Oh - and from first hand experience, watch out for anyone trying to plug stuff from the beer tent into the generator as well...

[crez5150]

FYI - This is the generator we hire on a regular basis for powering outdoor functions. We run the whole Stage from this including FOH and Full band, backline and lighting with no issues
[url="http://www.gofer.co.uk/20kva-road-tow/"]20kVA Genny[/url]

[machinehead]

[quote name='icastle' post='1107331' date='Jan 29 2011, 04:23 PM']No you can't.

The 'earth' provided by a generator is actually the Neutral.
As there's no way that two generators are going to run in synch without a suitable interlink control (big and expensive) your earth would end up all over the place![/quote]

We need to be careful here. Safety first and all that. Electricity can kill.

icastle, The earth and neutral conductors might well be connected together but the earth isn't the same as a neutral.

I agree that if you are going to use two or more generators, then don't try to connect them together. Use one for say, the PA, the other for guitar amps etc.

There would be no harm in bonding the metal parts of a two or more generators together.

chris_b, Where you said "I am not an expert here but I was told that multiple sources of power are the reason we need an earth. A single generator is the safest system and a third wire (the earth) is not needed. Because of this a surge protector won't work either, because it needs the third wire!"

Be careful of listening to amateurs when your life and health is at stake. Nothing you've been told is correct. The earth is there to ensure your safety by automatically disconnecting the supply if a fault occurs. The earth wire should be regarded as the most important wire. I won't go into more detail.

To the OP - thinking about it, you would be best to get an electrical engineer or even a good electrician to sort this for you. Don't take risks with internet advice because you don't know if the poster is a professional or a DIYer. I've been in this business for 38 years and I've designed and commissioned loads of systems but I still think you need someone experienced to actually be there. Much safer than mucking through it based on internet advice.

Frank.

[icastle]

[quote name='machinehead' post='1107624' date='Jan 29 2011, 09:11 PM']The earth and neutral conductors might well be connected together but the earth isn't the same as a neutral.[/quote]

No, I didn't state that particularly well - I was trying to avoid going down an unnecessarily confusing path talking about potential.

[TimR]

We had problems with volt drop on a very long extension lead when we played a gig. When we were asked to play again the next year we borrowed a genny. I think it was only a 2.2kV. we took it with us to every outdoor gig after that just incase.

Rather than hiring lots of smaller gennys you're better getting one the right size. They're very quiet but everytime you add one you increase the sound. Put it as far away from the stage as possible, they sound loud if you listen for them but once your drummer starts they're inadiable, but that's nothing compared to the complaining your singer will do when they're breathing lungfuls of exhaust.

As has been said before, add up all the ratings on your amps, but be aware that these are likely to be peak ratings. You'll only notice problems when pushing your gear to the limits and then proably only on the loud notes. Things that suffer when the voilts drop are the digital equipment, the amps tended to be OK soundwise but the reverb unit, feedback destroyer, keyboard and guitarists effects were all over the shop, lighting up like christmas trees and dropping out.

We didn't earth it but I couldn't get any real info from anyone about doing this for temporary short term (3hours max) considering all the equipment we were using was in good condition. The genny had a metal frame in contact with the ground.

If you are playing outside on grass (even in a marquee) it may be wise to insist on a wooden floor or at least a waterproof tarpaulin to stand on, even if it just stops any damp getting into your amp from the grass it's a wise electrical safety precaution.

Turn your amps and everything OFF BEFORE you start or stop the genny. Your amps and your ears will thank you.

Edited January 29, 2011 by TimR

[deepbass5]

An interesting and Important Topic. But be careful to get sound electrical advice the Musicians union will help. But find a friendly local electrician

I am lucky to be a qualified electrician and often wonder how any band survives without a spark in the band.

Firstly playing off a generator always worries me. It’s the unknown.

If it’s down to you, get one that will do twice what you need, it will be more stable, just like your bass amp you need some headroom. Small sets tend to fluctuate with load that means Voltage and current going up and down. Volts x Amps = power so if the voltage is down you will draw more power than normal. (Your gear may not be tolerant to that) Do not have anything else running off it then you know where you are. Modern Alternator sets are fairly stable. But note they are often designed for the construction industry; I got caught at a large steam rally where we were the evening band in the big Marque. They had provided a couple of sets one for the Bar and tent lights and one for the band. Looked new about 6KVA but I always test sockets for polarity and earth even in hotels etc. and it showed an earth fault. I rejected the first set so the organiser swapped it with the Bar Geny. That showed the same fault. It wasn't until after the Gig I realised that because the sets had a 240v socket and 110v socket, the 110v is centre tapped to earth so you can only get 55 volts shock to earth (construction site rules). The 240 socket came from the same source different tapping so was also centre tapped to earth. Probably would have been OK. But I had already used up all my spare set up and sound check time and was now in panic mode. One of the fairground people we were playing to offered his set from the Dodgems drove it round the back probably 50-60 KVA set perfect No faults.
We were cooking on gas that night.
I carry as part of my kit a blue 240v round geny socket to double RCD outlet socket. Sits under the van seat just in case. If you do nothing else use an RCD socket, so whether damp grass or no earth stake, if something leaks to earth it will protect you.
Never attempt to link Alternators together, that’s for engineers with the right monitoring kit. Keep them well apart. I wouldn't even trust having two running different bits of kit in the same stage area.

Buy a Martindale socket tester and use it on every gig. Write into your contract that it is the venues responsibility to provide a safe source of electricity as defined by the electrical supply regulations. And that you reserve the right not to play if you find an unsafe supply. You would not believe the times I have ended up sorting venue wiring problems when I should be sorting my sound.

The Hammond organ storey above made me smile, it happened to an old band of mine. They have tone generators inside that is voltage and frequency dependant, the Stranglers comes to mind. A fairground was off the generator that night and every time a ride started up the Hammond changed key.

Be safe not sorry..

Just to add, A single 13A plug will deliver 3000W (3KW) So think back to what you need indoors. If you use PAR cans you can soon get to 3kw on lights alone. Our band used to draw more than 3KW and I was always looking for two wall sockets to avoid a problem, with LED lighting we are now back under that figure which is handy. Work out what you bands current usage is, write it down so you know next time you have to share power with the Caterers or DJ.

Edited January 31, 2011 by deepbass5

[Martin E]

More wise words. Thank you all again for taking the time to answer my original query in such detail. Much appreciated and I'm sure of interest and use to others on here as well.

Martin

[teej]

Some food for thought here. I'll read back over it all again, but for now, I'll say I use a generator once a week on average all year round and have done for something like 12 years. I also know plenty of other acts who do this regularly. I guess one major difference is that we're using them in the street with less kit than most bands. Ours is a small Honda, the kind you can pick up with one hand and walk down the road with, powering a Yamaha Stagepas500 (with vocal and double bass into it), and a '70s Roland Cube for the guitar. In fact we don't add any more kit for gigs, but, being street performers we're starting out from a stripped down approach anyway.