Generator advice for LED lighting

[gafftaper]

I own a Yamaha 2000 watt inverter generator for my RV. It's a great little generator and is rated at 51db when operating at 1/4 max power. These little guys have variable speeds depending on the load. So as you increase the load it get's louder. They are not nearly as bad as some of the cheaper models you find out there, but you'll be up around 75-80 db at max power. So be sure to test the generator under a full load to know what it'll really sound like. There are some models that can be linked together to produce more power while keeping the volume down. When I was researching what to buy this summer, I learned that Yamaha and Honda have essentially the same specifications, however I was told by a repair shop that they have a lot more Hondas come in for repair than Yamahas, he said the engines are just a lot better in the Yamahas. So if you are buying I recommend you check out the Yamahas.

 

[mstaylor]

If you are buying throw Onan in the mix.

 

[len]

I had a 5kW generator running last night with 3 small dimmer packs. No issues at all. As for location, get it as far away as possible, and you could try to buy some hay bales to stack between it and the stage. Across the lake, the sound will be worse, since the genny noise will just travel across the water like across a tile floor.

For your needs, I would find out how much amperage the total system will draw, then double that.

Menards now sells twist lock adapters that allow you to use the 30amp circuit on most small generators. They're quite handy and fairly cheap, at about $20.

You should be able to find a rental place that has a 5K or a 7.5kW for under $100. Much cheaper than buying unless you know you'll use it several times in the future. When buying/renting, I try and estimate my cost to rent, including pick up and return times, mileage, etc., versus cost to own and maintain. Each one is a judgment call because you're trying to look into the future.

 

[Sayen]

I really appreciate all of the feedback. We ran the Honda under load using some other equipment, and were pretty happy about the noise level. I'm assuming the group is renting, since there are only 8 concerts.

VA and Watts are seldom the same number and certainly not in your case with everything using power supplies, Watts are only VA with resistive loads like incandescent lamps or heaters.

Can you clarify this a bit? If VA and watts are different numbers, then I'm confused on how to use the VA figure.

 

[JD]

Here is an article that covers it-
What is the difference between Voltage-Amps (VA) and watts and how do I properly size my UPS? - Power Solutions

Basically, switch-mode supplies draw almost all of their current near the peak of the waveform and almost none outside of the peak area. As a result, the current draw is "more" of a square wave then a sine. When both the voltage draw and current draw are sine, then watts is fine. In this case however, the small region of high current draw puts extra stress on whatever is supplying power. The VA rating looks at the "apparent" load that is cause by that distortion. Generally, Watts are about 65% of the VA rating on switch-mode supplies. (ahhh... very generally, as in there is no exact ratio because it changes as the load on the switch-mode supply increases.)

When your power source is limited, like on a small generator, use the VA number.

 

[David Ashton]

Just work it out using the VA numbers, they are always the same or higher than the Wattage, the generator will also have a VA rating but allow a bit more because of the extra strain than switch mode power supplies put on the generator.
[**** JD beat me to it]
"great minds think alike, fools seldom differ"

 

[Sayen]

That's very educational, thanks for the link.

So, if I'm understanding this right, a .4A 30W light is drawing 48VA, and a 3000W generator will only be happy with up to 4950VA (165% of 3000)? So that generator would be happy with 103 some odd fixtures, just using raw numbers and ignoring cable realities?

 

[JD]

If the generator has a VA rating, it should be on the spec plate. If it does not, then I would suggest de-rating the generator and only loading it to 3000VA. There is not really a formula to determine the reverse. It all depends on how the design handles the extra stress. Many modern generators also list the VA rating on the plate. This listing would provide assurance that it has been engineered to handle this.

 

[Sayen]

I couldn't fine one on the manufacturer's page or the unit. This is where using consumer electronics bites you.

 

[JD]

Here's a page I found on the Honda EU3000I which specs it at 3000VA
Honda Introduces All-New EU3000i Handi Generator Featuring Lightweight, Compact and Quiet Portable Power - Honda.com

It's a google find, but it is from the company site.

 

[Sayen]

Thanks. That's embarrassing.

I was looking here.

 

[David Ashton]

That's very educational, thanks for the link.

So, if I'm understanding this right, a .4A 30W light is drawing 48VA, and a 3000W generator will only be happy with up to 4950VA (165% of 3000)? So that generator would be happy with 103 some odd fixtures, just using raw numbers and ignoring cable realities?

no the generator will not supply 4950VA, probably 2700 would be a safer figure, The difference between VA and Watts was usually a result of the current being out of phase with the voltage, so you simply multiplied the VA by the power factor to get Watts, but as explained, switch mode supplies cause problems by wave distortion so you need an extra level of tolerence in your ratings.

 

[dmxinblacks]

there arnt any ducks is this pond? because if not just run one wire and ground it back through the lake, just make sure no one goes swimming.

 

[Chris15]

there arnt any ducks is this pond? because if not just run one wire and ground it back through the lake, just make sure no one goes swimming.

Sure... IF your insurer is cool with that and you can convince the LADJ that it's safe and code compliant... (If you are connecting to the grid then at least here the electricity supplier has absolute discretion to refuse permission to connect to their network and would if they thought it unsafe).

BUT the piece of fibre that connects Sydney to Guam uses the ocean as it's power return, so it is possible, just not something that is suitable for consumer deployment IMO.

The power factor of a switchmode is only 0.65 if they aren't employing active PFC. With active PFC you can get 0.8, 0.9 sorts of PFs.
Apparent power (S) in VA = Real Power (P) in W + j*Reactive Power (Q) in VA = V*I*PF, where PF = the cosine of the phase difference between V and I. Strictly speaking it's |V| and |I| and P = VI*, which is mathematically wrong but it works. (It technically violates the rules of phasor analysis since power is at double the frequency)

I rarely see generators speced in watts. Any real generator will be speced for (k)VA...

 

[David Ashton]

That is perfectly correct with pure sinewaves, but the whole problem with switch mode power supplies is that they distort the waveform and create harmonics which completely screw up these equations, which is why you need an extra safety margin.

 

[Chris15]

That is perfectly correct with pure sinewaves, but the whole problem with switch mode power supplies is that they distort the waveform and create harmonics which completely screw up these equations, which is why you need an extra safety margin.

Ditto with non sine wave dimmers.
And when you have audio in the equation, you always need to provide headroom anyway...