3000W Chinese Gensets Info.

Salvo wrote:


I'm really not sure the 100F ambient was the cause of your voltage drop at 2600W. My guess you're exceeding the 3500 VA limit.

Is the 2% reduction per 10 F increase over 85 F a typo? That would mean at 105 F, the power is reduced to 0.96 * 3500 = 3360 VA. That's not much of a reduction.

If correct, your gen at 100V should still be able to handle 3360 VA. Another reason to believe it's a VA and not temp issue.

From your data I see it's important to power the fan from the battery, and not from any gen power (12V or 120V) source. Do you have a manual switch to turn fan on and off?

I'm not sure what causes the gen to reduce power at altitude. Is it a lack of oxygen? What about temperature, is there electronics involved to fold back power?

Sal

When I conducted the test at 2600VA (V*A=W), the enclosure temperature and engine temperature apparently reached a critical level that caused the engine to stumble and lose RPM. One person suggested that the fuel in the carburator started to boil.

These units are advertised at 3500W. Advertisers tend to stretch or distort reality a bit. Generator-guy, who provided some in depth testing about a year ago, said that his unit produced 3300W at 50 degrees F at about sea level. If I reduced his output by 3.5% per 1000 ft. elevation and 2% per 10 degree F temperature rise, I should have a max of about 2850W. That's close to my measurement of 2900W using my inexpensive measurement equipment. Both Professor Randy and I have voiced our opinions in the past that these generators should be limited to 2800W continuous output to insure a reasonably long service life. I would even further reduce that recommendation at higher ambient temps to protect the genhead wiring. I personally try to stay closer to 2000W continuous output at high ambients. There is also a temperature sensor that shuts down the engine if the enclosure temp reaches 160 degrees.

You mentioned running at 100V. I get uncomfortable if my voltage drops below 110V. My generator produces a pretty steady 120V until it gets close to its max output.

Altitude is by far the larger factor in output loss. This is due to the reduction of available oxygen used in combustion. The temperature also reduces the density of the air and to a lesser extent than altitude, also reduces the available oxygen. By the way, Onan is my source of the info regarding power reduction for altitude and temperature.

Both of my 120V fans together use about 100W of generator output. I don't mind losing that much output for good cooling. The fans run continuously while the generator is operating and use a timer to shut off automatically after the cool-down period. When my generator is shut down, the fans continue to run for 15 minutes using my inverter and 12V battery for power. Fifteen minutes of fan time cools the enclosure down to around 10-15 degrees above the ambient temp.