IT'S A MIRACLE! 13.5AC on EU2000i Generator!

pnichols wrote:
I couple of dumb questions and a dumb point just came into my mind. :R

1. Why does an A/C unit require more power to run with high outside temperatures ... I can understand it running with longer compressor ON cycles ... but why more watts when it is running?

2. Why does a generator care about high ambient temperatures? It's either staying cool enough to not destroy itself or it will eventually stop for good.

3. The point being: Why in warm weather would a 13.5 K A/C/Honda 2000i combination that works together (using the Easy Start kit) not work in really hot weather assuming the generator could keep it's cylinders cool enough?

The power available from any naturally aspirated generator has to do with what is referred to as "the standard lapse rate."

All naturally aspirated engines are power rated at a given air pressure and temperature. Typically the standard is 59 degrees F @ sea level and 29.92 inch Hg air pressure. Many manufacturers cheat on this to make their product look better. The standard lapse rate rule states that as you go up in elevation the air pressure decreases and the air temperature decreases. The rule of thumb is +-2.5 degrees F decrease per 1000 feet increase in altitude. (This is why it is typically colder in the mountains at higher elevations.) The air pressure also decreases about 1 inch Hg per 1000 feet increase in elevation up to about 15000 feet msl.

Translated into English that means that for every 1000 feet you are above sea level you lose about 3% available power due to elevation. For every 10 degrees F above standard temperature (59F at sea level) you also lose an additional 2.5% power at that elevation.

So, if you have a 10 hp generator running at 3000 feet mean sea level and 90 degrees F you can expect only:

3 x 1000 = 3% x 3 = 9% loss in power due to the elevation increase

59 - 3 -3 -3 = 50 90 - 50 = 40 / 4 4 x 2.5 = 10% power loss due to increased temperature (it should be 50 degrees F at 3000 feet
under standard conditions)

19% total power loss at the engine. So, you now have a 8.1 hp engine powering the same generator section.

If this generator is maxed out and rated at say 5500 watts at sea level under standard conditions you now have a
5500 x .81 = 4455 watt genny at the given elevation in the example.


THIS IS WHY MORE EXPENSIVE GENERATORS (i.e. Onan) HAVE LARGER THAN NECESSARY ENGINES THAN NEEDED TO GENERATE RATED POWER AT SEA LEVEL.
But they are mechanically governed to 3600 rpm and rated power.

They (Onan) are also able to generate rated power longer as you go up in elevation. You get what you pay for.

Chum lee