3000W Chinese Gensets Info.

This is the post that gave my my original inspiration for the project. I don't have 12v at the generator so I am using a few different ideas I found at other places mixed in wiht some of my own ideas. This is the post that started it for me and for that I thank you.

professor95 wrote:

BFRXLT wrote:
I did see this posted. This would not work for my situation. I need more complete sound abatement.

How about something like this?

Professor95 wrote:
Sound Abatement Enclosure Details and Photos
Copyright Professor Randy T. Agee, E.ED., October 15, 2007


This is not the first enclosure I have built. But, it is the most thought out and successful enclosure to date. Before building this enclosure I spent several months doing research on noise abatement and transfer of thermal energy. Not that I really needed to, it was more of an exercise in confirming the ideas I had previously developed.

My goals were simple:

1. Cool the engine. Keep the cabinet temperature under
170 degrees F in the most severe operating situation.

2. Cool the AVR and alternator. Ideally, keep these
components under 140 degrees F.

3. Achieve a noise level equal to (or better than) the
Honda 3000 Inverter model. This would be 59dB
at 21 feet away under no to moderate loads and
62-63 dB under full load at the same distance.

4. Keep the size and weight as close as possible to the original genset.

5. Allow easy access for service or repair, especially spark plug and oil changes.

6. Keep it safe. Gasoline in a closed compartment disturbed me greatly.
I could not come up with a method of achieving this that would let me sleep
comfortably at night.

7. The cabinet needed to be weather resistant.

8. Cost was also a factor. I set a limit of $200 for the entire unit.
Anything over that was out of the question.

9. And, lastly, re-purpose as many materials and components as possible.
This reduces trash in our environment (or at least delays it) and lowers
construction/materials cost.

I had done some experiments earlier with fuel pumps and remotely mounted gas tanks. The carburetor on the GX200 engine was not designed for a pressurized fuel system. The close as I could get to something that worked was a 2.5 psi electric pump designed to work on 12 VDC, but run on 6VDC. At 12 VDC gas would seep out around the float needle valve. While a system of relays and voltage reducers could make the pump safer and shut it down automatically when the engine stopped, I was still uncomfortable with the design.

Gravity feed was an option. But the tank would mount over the top of the enclosure, making access problematic. I just did not like the idea of using gasoline with an enclosure. I began to research LPG options and discovered the conversion was extremely simple, and surprisingly inexpensive. In fact, I could convert to LPG for a comparable cost of a remote electric fuel pump. LPG became a no-brainer.

Effectively getting rid of excess heat was a major consideration. Much of the heat from the genset comes from the muffler. It is a giant heat capturing device and radiator. Again, it was a no-brainer that the muffler needed to be relocated outside of the enclosure.
The next issue was the volume and path of cooling air. On the Chinese gensets there are two major cooling paths. One is into the grill around the recoil starter and across the cylinder head fins. The other was the movement of air into the alternator grill (on the end) and out the bottom of the alternator near the engine. Simply sucking or blowing air into a box would only serve to recycle lot of hot air. Brute force systems using several large fans might work, but efficiency would be really low. My research had shown that what was needed was a small enclosure that would allow evacuation of air rapidly, a directed airflow into the engine cooling side and an additional cooling intake for the alternator and AVR.

My design included a 6” diameter, 12 VDC, 300 CFM exhaust fan, a shroud over the engine intake around the recoil starter to direct air flow, and complete isolation of the air intake on the end of the alternator from hot air in the cabinet.
Just for good measure, I added a small 50 CFM fan to the end of the alternator to force cooler outside air across the AVR and alternator coils. This airflow design has proven to work extremely well keeping cabinet temperatures well within the desired maximums.

There are many methods to reduce the transfer of sound. The cheapest and perhaps most effective, especially for low frequency reduction, is a small cabinet with very thick open cell material to capture sound pressure. To meet this requirement, I selected a full 2” thick foam insulating board made by Dow Corning. It is available at most home stores in 4x8 foot sheets for less than $25.00 (one brand is pink, another brand is green). The foam board is easily cut with a common saw and really smooth edges can be accomplished on a table saw using a fine tooth blade and slow feed. Openings are cut with a fine tooth saber saw set on a low speed. Once sized, the foam board can be painted with a latex paint “as-is” or laminated. I chose to laminate mine with Filon, a 1/8” thick fiberglass board similar to the material used on the outside of many campers. It is available at home stores for less than $30 for a 4x8 foot sheet. It can be trimmed with a router using a laminate bit. Just be sure to use a latex contact adhesive. Other adhesives may dissolve the foam board.

I had previously made a new frame for the genset from surplus angle iron re-purposed from discarded bed rails. This made it easy to attach the foam panels since the surface was flat and square. If one lacks welding equipment, I am of the opinion a similar frame could be made of hardwood 2”x2” lumber.

The foam panels were attached with Velcro. I used the industrial variety. It doesn’t take much to securely hold the foam board in place and it is not affected by the heat in the box. Open gaps between foam board and angle iron faces caused by the pieces of Velcro were filled with 1/8” thick rubber gasket material used to seal camper caps to the bed of pickup trucks.

The stock front genset panel was retained. A piece of ¾” thick, Formica laminated outdoor grade plywood was cut to fit the contour of the stock panel and then covered with Filon. I used plywood here since I needed a rigid panel to mount accessories. Cutting this piece on the bandsaw was scary – it was the same saw I severed my left little finger on last May 14th. This was the first time I had used it since the accident. I did need to use spacers under the OEM genset panel to get the right offset for a flush fit to the plywood.

Both cooling fans were 12 VDC. The genset was electric start, so a relay was needed to energize the 12 volts to the fans. I had a surplus 120 VAC single pole, single throw relay in my junk box. I connected the coil of this relay to the output of the generator. When the generator started, it would pull in the relay and supply 12 VDC to the fans. If there had been no battery, I could have just direct connected the fans to the 12 VDC out of the genset.

I needed good venture vacuum to prime the engine so it would start or an electric solenoid that could push the primer on the demand regulator. US Carb does sell an electric primer solenoid as part of their RSK kit, but that was more money to spend. To get the vacuum, I had to retain the choke. So that a remote start system could be implemented, the choke needed to be electric. I borrowed a 12 VDC solenoid from an old surplus computer disk drive. The solenoid was configured to pull in the choke on start. Other solenoids such as those used on automotive door locks should work equally as well.


I found two surplus automotive gauges in my junk box. One was an automotive water temperature gauge, the other a DC voltmeter. I placed the probe for the water temperature gauge against the cylinder head fins on the engine. I now have a head temperature gauge.

As an added safety feature, I exchanged the 120 volt, 20 amp outlet for a GFCI outlet. I changed the wiring behind the control panel so that the cooling fans were before the GFCI outlet. This was done to be sure a GFCI trip would not stop cooling. I added a new circuit breaker for the inside outlet used to fed the 120 volt relay for the cooling fans.

Changing oil could be a problem with an enclosure. I ran a tube from thbe engine's oil drain plug to outside of the front panel to make this service a whole lot easier.


I had previously purchased a "hatch" from West Marine for use on my boat, and then decided not to use it. While not necessary since the top of the enclosure is removable, I felt like I should use the hatch somewhere and decided what better place than the top of the box for quick and easy access.

Were all of my objectives met? You bet they were! 58dB at 21 feet with low to moderate load. 62dB with the air conditioner compressor locked in on the camper.
This system is as quite as, if not quieter than the Honda Inverter. It beats any installed motor home genset hands down. Temperatures inside the box all fell within my established limits, even on a hot 90 degree October afternoon..

My total cost was also well under the $200 limit I had established.

This is one quite and cool puppy!

(Additional Photo Links)


21 foot view

view with top off

150 VAC full scale meter to replace 300 VAC full scale meter

only front panel on - sides off

bringing starter rope to front panel

added HR meter to keep track of service due intervals

generator end

engine panel showing 6" to 8" ductwork transition used as fan shroud

real-time air temp reading inside cabinet