how big of a gen needed

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how big of a gen needed

Postby tatonka » Wed May 22, 2013 6:04 pm

just want to run a microwave and a toaster and charge batts with , what size do I need? Will have a camper with propane stove and fridge , dont want to use stove that much , so thought of adding a microwave.
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Re: how big of a gen needed

Postby trilobyte » Wed May 22, 2013 6:12 pm

Look at the devices you want to power, add up the power requirements. As a rule, you probably want no less than double that…if not triple. Generators are usually sold based on their peak performance, with average loads being less (for example my camp has a Honda 2000 watt generator, the 2kilowatts is peak, it's actually rated at 1600 watts), and generators won't be at peak performance on the playa (altitude and other factors).

You may not think you have much in the way of power requirements, but you've got a lot of appliances on that list.
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Re: how big of a gen needed

Postby tatonka » Wed May 22, 2013 6:19 pm

so if ya didnt run them all at once , then a smaller one could be used . Could nuke your main meal , then toast your bread , then charge batt to camper ( lights ) and batt for swamp cooler. If I did them seperatly
it would be less and could get by with a smaller quieter one.
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Re: how big of a gen needed

Postby FIGJAM » Wed May 22, 2013 6:54 pm

A good microwave uses 1100 watts.
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Re: how big of a gen needed

Postby motskyroonmatick » Wed May 22, 2013 7:07 pm

If there is going to be an air conditioner used on the camper that will probably be your biggest draw and your generator will need to be sized for that. I consider a eu2000i or same in companion model (so it is easy to link to other honda generators) to be about the minimum practical generator. Go much smaller and you hit serious limitations and if necessary you can double your power by adding a second generator.
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Re: how big of a gen needed

Postby GreyCoyote » Wed May 22, 2013 7:09 pm

Ideally you want a genset that will put-out about twice what your load will be. This gives you some elbow room to handle startup surges and future growth. Ideally you would tailor the genset to your particular loads, but usually it doesn't work-out that way in practice. Most people will buy what they can afford and then re-engineer the loads to match available power.

I can tell you from experience that a Honda EU2000i will run a small microwave on the playa without issue. It will also run any toaster you can throw at it. But it won't do both at once. There is some reserve power available when you are toasting, but the microwave will take most of what the EU2000 puts out at the density altitudes found on the playa. As far as charging batteries, this will not tax it at all. It is a rare battery bank indeed that can safely handle more than a couple of hundred watts of charging power.

FWIW, generators vary radically in how quickly they derate. I like the Honda's because they don't suffer from the extreme derating that some the cheap gensets do. Basically you get what you pay for. I have seen a new 5KW B&S throw-away struggle to start a 12000 btu AC on the playa, whereas a 3K Honda did it nicely. The Honda put out nearly the nameplate sea level watts even though it was facing the same 7500 foot density altitude conditions as the Briggs. In the end it's all about conservative design and how much surplus torque the engine can produce compared to the generator end (or inverter) rating.

If you want to get nerdy, a good density altitude calculator is here: http://wahiduddin.net/calc/calc_hp_dp.htm It can be used to derate quality engines, but it will not accurately predict the effects on a throwaway-type engine.
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Re: how big of a gen needed

Postby tatonka » Wed May 22, 2013 7:28 pm

thks for reply all :)
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Re: how big of a gen needed

Postby ygmir » Wed May 22, 2013 8:09 pm

all great info! do you have a generator yet?
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Re: how big of a gen needed

Postby trilobyte » Wed May 22, 2013 8:30 pm

Yes, if you're not running all at once, you could sneak by with less. If you plug in more than it can handle it'll choke and die. If you routinely run it with a high draw, you risk undue wear and shortening the lifespan. I've never run refrigerators or freezers by generator, so I don't have much practical info to share, other than they typically need to always have access to power, and when they kick on they have a higher draw.
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Re: how big of a gen needed

Postby tatonka » Wed May 22, 2013 8:36 pm

thks again , dont have one purchased yet.
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Re: how big of a gen needed

Postby ygmir » Wed May 22, 2013 8:52 pm

there's a couple of good generator threads here somewhere, if I can find. or, try a search? good advice and such related to noise, cost, durability, function at altitude and such.
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Re: how big of a gen needed

Postby Captain Goddammit » Thu May 23, 2013 9:49 pm

There are pages of generator discussions on here. I can condense it down for ya' - get a Honda EU2000.
They're kind of expensive, and worth every cent. The cheap sets are SOOO tempting at the stores or online... where they sit there quietly... until you fire them up!
Other sets will put out lots more power, for less money; but in real life they are no bargain because they put out ZERO watts when you and/or your neighbors can't stand to listen to it. Loudness specs are easy to get the wrong idea about, too. The decibel scale isn't linear. They say a 3dB increase is perceived as twice as loud. When one set says 59 dB and a cheaper one says 62 dB, it's not a small difference!
The other shitty-generator issue is they run at 3600 RPM, all the time. They have to because they use mechanical means to create 60 Hz AC power. Irritating! Those little EU2000 Hondas run at idle and throttle up as needed - they create the 60 Hz 120VAC electronically.
You'll be out about a grand for one, new, but they show up on Craigslist for around $700-ish.
They cost... but you'll end up buying one after you hate the Coleman or Champion or Generac you pay less for, so you're ahead of the game if you don't waste your money on a shitty set.
You can directly connect two or more of the Hondas to combine their output. You don't need the stupid "companion" model either. All you have to do is make a short extension cord with a male plug at both ends, and plug one set into the other.
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Re: how big of a gen needed

Postby gyre » Sun Jun 16, 2013 11:08 am

I have a mid quality chinese generator from northern tool, now discontinued.
Just because they look alike, does not mean they're the same.
Tolerable noise level, no EU.
Much quieter than the identical looking low end ones.
Big and heavy by comparison with EU, cost a fraction.
3500 watt model, will run a small fridge and full size microwave simultaneously.
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Re: how big of a gen needed

Postby GreyCoyote » Sun Jun 16, 2013 1:58 pm

Something that I have not yet seen covered, but is a big factor in generator selection, is the ability to get the full rated output. Most gensets in the 3kw and up class have a split output, ie they have two 120v windings placed in series and center-tapped. Neutral floats and all of your 120 volt loads are powered from a connection between the floating neutral and one of the windings. This means you can draw half of the rated load from each winding. Or you can connect a 240 volt load to each hot end and get the full rated output.

Here is the issue: most loads at burning man will be 120 volts, not 240 volts. If you have a 3000 watt genset, and try to pull more than 1500 watts from either 120 volt leg, the genset is overloaded. Taking this to an extreme, if you have a nightlight on one leg, and an 1800 watt microwave on the other leg, your 3000 watt genny is overloaded and will likely flip the breaker or burn-up a winding.

The way to fix this is to get a genny with a "full power" switch. This switch puts the two 120 volt windings in *parallel* and gives you the full rated genset output at 120 volts. With the switch in "full power" mode, any 240 volt outlet will be disconnected. But now you can run an 1800 watt microwave at 120 volts and still have 1200 watts to spare. The head will also run cooler, as both windings now share the loads equally.

One other bit that might be useful: if your existing genset is not equipped with a paralleling ("full power") switch, and if it is a 4-lead head (meaning both windings are brought out of the stator separately), you can easily install such a switch if you are handy with a meter and soldering iron.
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