3000W Chinese Gensets Info.

bill h wrote:


That's pretty good. It will be 10 db quieter than my Champion.

Bill,

I know from previous postings that you have been disappointed with the dbA readings of your 3,000 watt class open frame Chinese generator. I believe we will all agree that the 67dbA specification given across the board by the Chinese manufacturers for these products are measured under ideal, fixed field conditions and can vary under actual use depending on location and load. This video is one I made of such a generator tested under ideal conditions in an open environment at 7 meters with a sound meter elevation of 4 feet. 67 to 68 dbA with a 1,500 watt load was attainable.

But, I have also found that the noise level figures given for the supposedly quieter inverter class generators are not realistic when they are under load and the engines are running at a high speed. Short story - add 4 to 6 dbA to the sales figures for any portable generator for real-time usage when camping.

Sound abatement for the Chinese 3,000 watt class open frame generators has been an ongoing experimental project of mine since 2005. I have designed numerous enclosures that reduce outside sound levels while continuing to allow proper cooling for the engine and alternator. Some have been successful - others have not.

One of my projects involved placement of a Chinese 3,000 watt class open frame generators in the front "cave" of my fiver. This required a thermostatically controlled down-draft exhaust fan, the addition of a RV outside refrigerator grill to the cave door to bring in cooling air, relocation of the muffler to the outside, a cooling booster fan for the AVR at the intake to the alternator as well as conversion to LPG with gasoline as a back up - gasoline usage is from a sealed tank vented to the outside and a vacuum actuated fuel petcock. An array of temperature sensors and carbon monoxide detectors will shut down the unit if anything goes awry. The inside of the cave is covered with sound absorbing acoustical grade flame proof foam.

Now - I have a video to share. But, before I give the URL I must emphasize that the generator WILL sound LOUD in the video. This is due to the extreme sensitivity of the camera microphone. What one must pay attention to is the comparison of the loudness of my voice as I talk and the readings on a sound level meter - my voice is louder than the generator. Just listening to the generator in the video will leave the impression that it is a thrashing machine. At the standard 7 meters this thing is way under the annoying sound level radar and several dbA quieter than a same size inverter generator sitting outside.

As we have learned, the majority of loudness on these generators does NOT come from the exhaust. In fact, the physical point of the greatest amount of measurable noise is in the engine crankcase and carried out into the alternator casing. Effective sound abatement for the Chinese 3,000 watt class open frame generator needs to be focused on mechanical noise, not another muffler or exhaust. If one compares the "noise" of an inverter generator to a 3,000 watt class open frame Chinese generator they will immediately notice the absence of the "clanging" or mechanical noise in the 300 Hz and up range. Compression or bass level 300 Hz down to 50 Hz noise is still apparent in an inverter generator and is the most difficult to abate. Of course, a loaded inverter generator running at 4,000 RPM produces a similar high frequency clanking noise but it is abated by panels on the generator with acoustic foam. An unloaded inverter generator can be extremely quiet due to a much lower engine RPM.

Many of my projects and experiments are somewhere in this thread's archives, as are those of several other successful experimenter/builders.

Anyway - listen to my voice and look at the meter in the video below. Please do not evaluate the loudness from the overly sensitive built in camera microphone. Click here for the video.