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[kel mcguire]

A venue where I mix regular friday and saturday concerts has a "temporary" deisel generator (for 14 concerts so far) because of a fried transformer that feeds the shops and restaurants in the area around the concert venue. The sound system with lights draws probably around 50 amps plus a beer garden with refrigerated truck . From what I understand, nothing on shore power is interconnected with our little island of stuff. The venue is now asking the sound engineer to power up/down the generator for each show...which wasn't in our job description for the past 6 years...but that's a different story.
 
 Anyhow,
For the most part it has worked reasonably well but sometimes the system has just felt saggy. One time upon turning on the front fill stage lights, which are on the FOH circuit, the entire FOH went dead, then came back on. Scary. Apparently there is an Eco mode on the generator.

The guitar player this past saturday brought his own transformer and voltage tester since he plays vintage tube amps and has encountered issues with power. He mentioned that we were at about 99 volts. So, not having ever tested this new generator setup(too trusting),  another voltage tester was plugged into the circuits and brought up a 100 volts reading. As control, I plugged same tester into a nearby business on shore power and got 117

So, a few questions:
-at what low-side voltage point does digital equipment not function correctly, like digital mixing boards or keyboards? Class D amps?

-Does the voltage output on these generators drift from shutdown to the next concert? over the course of weeks? It is the same generator every week.

-I have unplugged nearly the whole stage after each show before turning the gennie off, then reversed the process by waiting until the generator is warmed up before plugging in all the power amps and FOH. Is this advisable? I'm afraid of voltage ramp up/down from past experiences.

-If I wanted to insure the correct settings, would my process be: to fire up the generator, let it warm up and settle down, meter the edison outlet while massaging the voltage knob? Or would there be reason to believe the voltage on the tails would be different than the supplied edison 15a circuit?

[Scott Holtzman]

A venue where I mix regular friday and saturday concerts has a "temporary" deisel generator (for 14 concerts so far) because of a fried transformer that feeds the shops and restaurants in the area around the concert venue. The sound system with lights draws probably around 50 amps plus a beer garden with refrigerated truck . From what I understand, nothing on shore power in interconnected with our little island of stuff. The venue is now asking the sound engineer to power up/down the generator for each show...which wasn't in our job description for the past 6 years...but that's a different story.
 
 Anyhow,
For the most part it has worked reasonably well but sometimes the system has just felt saggy. One time upon turning on the front fill stage lights, which are on the FOH circuit, the entire FOH went dead, then came back on. Scary. Apparently there is an Eco mode on the generator.

The guitar player this past saturday brought his own transformer and voltage tester since he plays vintage tube amps and has encountered issues with power. He mentioned that we were at about 99 volts. So, not having ever tested anything(too trusting), I plugged a tester into the circuits and brought up 100 volts. As control, I plugged same tester into a nearby business on shore power and got 117

So, a few questions:
-at what low-side voltage point does digital equipment not function correctly, like digital mixing boards or keyboards? Class D amps?

-Does the voltage output on these generators drift from shutdown to the next concert? over the course of weeks? It is the same generator every week.

-I have unplugged nearly the whole stage after each show before turning the gennie off, then reverse the process by waiting till the generator is warmed up before plugging in all the power amps and FOH. Is this advisable? I'm afraid of voltage ramp up/down from past experiences.

-If I wanted to insure the correct settings, would my process be: to fire up the generator, let it warm up and settle down, meter the edison outlet while massaging the voltage knob? Or would there be reason the voltage on the tails would be different that the supplied edison 15a circuit?

Is there not metering in front of the generator? 

[kel mcguire]

Is there not metering in front of the generator?

it read 220 on the voltage meter on the rather course meter

[Nathan Riddle]

ANSI C84.1

"ANSI standards states that the nominal residential service voltage is 120 volts, the minimum utilization voltage is 108 volts, the favorable service voltage is 114-126 volts and the "tolerable" service voltage is 110-127 volts. They indicate a 2.5% drop in voltage from early day to the hottest part of the day is 'normal'. Yet from my highest to lowest I see approximately a 6.4% drop; yet since the lowest voltage is still within their "favorable range" - again they say, "no issue:.

-quoted from: http://forums.qrz.com/index.php?threads/ac-voltage-drop-voltages-still-within-acceptable-range-per-power-company.396325/

http://www.powerqualityworld.com/2011/04/ansi-c84-1-voltage-ratings-60-hertz.html

[Steve Alves]

Whomever setup the generator should have metered at the final connection and made the proper adjustments. I personally would not plug anything into it until they have the output properly set.

[Tim McCulloch]

At the generator itself:  all the hot legs were the same voltage, while under a typical load?  If so, there's a likely problem with the genset's voltage regulator.  If not the same voltage I suspect a neutral issue, most likely a floating neutral that is neither bonded to the genset frame nor the venue grounding electrode.

If the generator is a portable rental item I think the shop should send a replacement and the voltages inside the venue be verified again.  It's possible the issue is in the venue's wiring if the genset checks out.

Has any electrical work been done, or switch gear/distribution been subjected to water intrusion?

[Mike Sokol]

it read 220 on the voltage meter on the rather course meter

I ALWAYS meter the voltage of the genny at the tails BEFORE connecting camloks or Cali connectors. Those voltage control knobs can make most of them from low 90's into 140+ volts. Never trust anyone else to set the voltage except you. Also check phase-to-phase to make sure something silly has been done. For a 120-volt/3-phase generator you should read close to 208 volts between any two phases. If you can't get it up to at least 115 volts or less than 125 volts, then don't tie in.

Modern switch-mode power supplies are rated for 90 to 250 volts, but you'll have a lot of gear that does not have smart power supplies. Also note that my Suretest Analyzer has a function where it pings the line with a 15 amp pulse and reads the voltage drop in percentage and actual volts. So if you're on a very long extension cord that's too small for the current draw you can measure 120 volts with no load, but as soon as you hit it with a kick drum or bass guitar note, it can easily draw down to under 100 volts. And most power amps are very unhappy with 100 volts or less.

[kel mcguire]

At the generator itself:  all the hot legs were the same voltage, while under a typical load?  If so, there's a likely problem with the genset's voltage regulator.  If not the same voltage I suspect a neutral issue, most likely a floating neutral that is neither bonded to the genset frame nor the venue grounding electrode.

If the generator is a portable rental item I think the shop should send a replacement and the voltages inside the venue be verified again.  It's possible the issue is in the venue's wiring if the genset checks out.

Has any electrical work been done, or switch gear/distribution been subjected to water intrusion?

the guitar player's voltage test was with no load other than idling power amps. Same with my tests at FOH and on stage.

I wish I could have looked a bit more and taken a few pictures of the control panel but I had a show to mount then went home. One master circuit breaker. A pull out knob that twists and lands into a notch for full power, non eco mode operation.

water intrusion unlikely. Electrical work? Doubtful. I don't know the arrangements made on this particular generator. Seems like an inside deal with shopping center maintenance crew. It's an older generator...if I was to guess 1990's. One master circuit breaker. If I was to guess, I bet no adjustments have been made since it arrived.

still, 14 shows have run on it. My above questions still looming: Once metered and set, do these kinds of generators drift between uses? is 100 volts too low? Can I meter and adjust the knob to a healthier voltage?

EDIT: I see additional information has been added.

The generator has been tied into the panel that supplies the stage & FOH with tails, not twist lock.

[Tim McCulloch]

the guitar player's voltage test was with no load other than idling power amps. Same with my tests at FOH and on stage.

I wish I could have looked a bit more and taken a few pictures of the control panel but I had a show to mount then went home. One master circuit breaker. A pull out knob that twists and lands into a notch for full power, non eco mode operation.

water intrusion unlikely. Electrical work? Doubtful. I don't know the arrangements made on this particular generator. Seems like an inside deal with shopping center maintenance crew. It's an older generator...if I was to guess 1990's. One master circuit breaker. If I was to guess, I bet no adjustments have been made since it arrived.

still, 14 shows have run on it. My above questions still looming: Once metered and set, do these kinds of generators drift between uses? is 100 volts too low? Can I meter and adjust the knob to a healthier voltage?

There is something wrong here, and it's not "drift".  The mechanically locking voltage adjustment knob, if not deliberately moved from its locked position, will not change.  What *can* change is the electronic monitoring of the genset's voltage - the electronic VR can experience component-level failures of its own and is a potential cause here.  If the VR is mechanical (and that's possible) there are other sources of failure...

But no, gensets don't just drift.  There is a specific cause of this failure.

Is this an emergency backup generator for a shopping center or store?  It sounds to me like there is the potential for Code violations here, too, but that's only a suspicion (call it my "Spidey sense").

[Mike Sokol]

Once metered and set, do these kinds of generators drift between uses?

Yes, but in my experiance usually only a few volts over time. However, if it's been out on another rental, then all bets are off.

Is 100 volts too low?

I would say yes, most definitely. If you can't get it up to at least 115 volts I would be really worried.

Can I meter and adjust the knob to a healthier voltage?

Yes, but don't have your distro connected while you do this. It's possible for a tiny tweak of the voltage knob to send it north of 140 volts. That's very bad to do on a live stage.

Also, if this is an old "contractor" generator they're notoriously unregulated both in voltage and frequency. Now, frequency doesn't matter a whole lot unless you have a Hammond B3 on stage, and then it matters a LOT. But good voltage regulation is really important for live gear. And the excuse that "14 shows have run on it" doesn't exonerate you from doing your due diligence and testing it every time you do your own show. For any show I do using a generator I leave myself and extra hour to make sure the ground rod is properly connected, regulator voltages are adjusted properly, and all stage distros are happy. And my stage crew knows not to interrupt me or plug in anything until I give the all clear. It's simply my most important job that day. I'm responsible for the safety of all stage technicians and musicians, as well as the health of the production and stage gear. You really don't want to "plug-n-pray"....

[ProSoundWeb Community]