Generator size?

[Zach]

Hello all,
Thanks for the assistanance with everything so far. My rv did not come with a generator and I'm wondering what the most bang for my buck is going to be, considering my tight budget. I envision myself doing maybe 10% boondocking so what would be the smallest and cheapest generator I could get away with? My power requirements will not be too great...tv and dvd player would probably be the extent...maybe the air conditioner?
thanks,
Zach

 

[Gary RV_Wizard]

...maybe the air conditioner?

Your needs were minimal until you added that last item. Running an a/c is a whole different level of consumption than just about everything else.  Your a/c needs just about the total output of a 15A circuit or 1800+ watts.  It doesn't use that continuously, but will demand it briefly at unpredictable moments. A microwave is another such power hog, but you can shut other stuff down for the usually brief time you run the microwave.    For all other routine uses, a generator in the 1000-2000 watt range is sufficient.  A 1000 watt generator is small, usually fairly quiet and can easily handle charging batteries, running tvs & such.  You can also do that by adding an inverter and an extra battery or two.  If you only boondock for a day or two at a time, a pair of good sized batteries would probably provide your power needs OK, both 12V power (necessary) and some 120 VAC via inverter.  Even with a genset, the batteries and inverter are a convenience because you can use them at will and then recharge when convenient. Don't have to run the genset at night, for example, when others may be sleeping or simply enjoying a silent, starry night.

 

[Zach]

Thanks for the reply.
I had a feeling the A/C would be the real killer. I think the 1000 watt might be the way to go and they seem to be in my price range.
thanks
Zach

 

[John From Detroit]

In the kilowatt (1000 watt) class, Genrac makes a nice little unit, so do some other companies,  I had a genrac it was so nice it grew legs and walked off... And if I ever find those legs they are going to walk off again... Of to a court house.

However most AC's require at the very least a 2KW generator to start (I had one that Genrac woudl start, Just one)

So I'd suggest at least 2500 watts or a Honda EU2000

 

[Karl]

Zach,

Bite the bullet now and get at least a 2kW unit right off the bat. A 1kW will NOT run an a/c, and you'll soon become unhappy with having to shut down the coffee maker to use the toaster; for example. Don't even think about running an a/c or microwave off battery/inverter power - it will run your batteries down in a hurry. Maybe a minute or two to heat up water for a cup of instant coffee. Deep-cycle rv batteries are not designed to provide high current draw.

 

[Jeff]

Zach:

Karl is right, go for the 2k or larger unit. I tested a 2k Honda unit this Fall and it has a hard time keeping up with a battery charger set at 10amp input the first half hour or so, a 1k just would not be enough for what you are planning.

 

[29er]

Zack:  Read the data plate on your a/c. I would believe something is going to give and that would be your circuit breakers (hopefully). Honda makes a 240/120 3KW that can be physically easy to handle. Just think that 1,000 watts (consumption) is basically equivalent to 1kw (output). Coffee pot and a/c starting at the same time equals silence..... The 3kw also has a battery charger with all switching being automatic.

In layman's terms look at it this way; supposed you had a screw that was screwed in real tight, the amount of torque it takes to break it loose is FAR MORE than unscrewing it the rest out the way out. Electrical motors also have to overcome their own inertia with a spike in electrical use to get started, then settle down to regular running, just like backing the screw the rest of the way out.. Always plan for the worst and you won't be disappointed (or in the dark).

What is inertia? Think of pushing s car on a level road, the first couple feet take the most effort and after that it's relatively easier. That's overcoming the car's inertia. Don't mean so sound like a know-it-all.

 

[Karl]

29er,

Interesting analogy about inertia -  Newton's First Law: "An object at rest tends to stay at rest and an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force." Unfortunately, I've yet to see a bolt, once broken loose, that will continue to unscrew itself through inertia.  ;D ;D ;D

 

[John From Detroit]

Not only intertia but but in the very first cycle or two something called "Magnetic locking", but most any generator has enough oomph to take that hit (The intertia of the flywheel will absorbe it) and a few other things too. 

As I said, the 1kw I had would start, just, a very small AC I had (Bedroom window on house) it would not start the ones on the Motor Home, they take at the very least 1.5 and I'd really want 2kw to start them.  From time to time they trip 15 amp breakers and that's over 1500 watts  (My other house window job tripped 20 amp breakers from time to time.. It had a very dedicated line all the way back to the breaker box, NOTHING else on that line of this I"m sure (I put it in myself) direct, not even a junction box, between the ends

 

[29er]

Hmmm: Reference the real tight screw "the amount of torque it takes to break it loose if FAR MORE torque than used unscrewing it the rest of the way out" ??

I mistakenly thought Newton was a guy with no inertia laying under a tree. Something happened and now we have apple newtons. Don't hold me to this, but I believe that getting doinked on the head was Newton 85th or 86th law. The more I read here, the more I learn.

 

[John From Detroit]

Getting bonked on the head by the apple was the law of gravity  Not the law of motion.  Same Newton, Different law

Some days it pays to sleep under the apple tree with anyone else but me

 

[Karl]

John,

Not only intertia but but in the very first cycle or two something called "Magnetic locking",

I must admit I've never heard that term before. Locked rotor current draw, yes. Can you explain?

 

[29er]

I believe John was referring to locked current draw combined with locked rotor torque. He was using slang common in Detroit to get the rotor spinning and the measure of current used. You know, to overcome it's inertia.

John, if that was Newtons law of gravity, how come he was hit with kinetic energy. Where'd that come from?

 

[John From Detroit]

The term comes from somewhere else but when you first apply power motors act a bit strange.  This would normally last around 1/120 second by the way. 

I've just spent a week buried in the relation between voltage and current in non-resistive circuits and other friends of Eli the Ice man  and it's been interesting.  Hopefully I'll never need to know this stuff again

 

[Jim Godward]

Yeh, but did you pass the test.  I presume you did if you will never have to know the stuff again.

If so, congratulations!!