3000W Chinese Gensets Info.

professor95 wrote:
John,

I elected the down draft fan on the current install mostly because it was my only logical choice. But, on the previous install inside the insulated box the lower center exhaust fan was elected because it was the closest to the normal exit path for both cooling air across the engine and through the alternator.

I did not do any flow testing on updraft fans, but I do know that they work. It just did not seem practical to be bringing heated air back across components I was trying to cool.

It seems to me that if the entire bottom of the genset is open (like the DuroPower) and the fan is placed on the end above the insulated muffler box, the draft will suck a portion of the exhausted engine cooling air that strikes the muffler, suck heat rising around the muffler, and perhaps draft some cool air up and around the alternator ... perhaps enhancing cooling. The exhausted cooling air from the alternator is even farther away from my proposed location of the fan and is directed downward. Hard for me to believe the updraft fan will have much effect on its discharge (I could put a fence on the left side of the alternator exhaust just to ensure it doesn't draft laterally and up towards the fan. The whole shebang is going to be sitting a couple of feet above the ground, so there will be lots of free air circulating.

The biggest mistake I see is NOT considering air flow in the cabinet design. There is (was?) a mistaken theory that hot air came out the back of the alternator. The actual path is into the back of the alternator and out the bottom where the alternator connects to the engine.

Incoming air flow to the engine fan/shroud and rear of the alternator is critical. Absolutely nothing should be there to keep cool air from flowing in or to allow recirculation of heated air from inside the cabinet. Simply putting a big fan on a box will not work!

Looks like if the fan is sucking air out of the top of the area, that will cut down on recirculation of heated air that has risen above the muffler, engine, and alternator.

As for a 12 VDC source, why are you even using yet another battery? I elected to use the on-board camper battery for starting and running the 12 volt fan. Why add weight and maintenance that is un-needed? Additionally, the battery charger output from the generator is unregulated. It “might” recharge a battery in a pinch, but the life span of the battery will be proportionally reduced in relation to the frequency of using the generator battery charger. 10 gauge copper wires are good for running to the starter for a distance of 20 feet. You can go longer but the voltage drop at the 25 amp cranking current begins to become a consideration. Best to parallel twin #10 or even #12 wires after 20 feet unless you want to run larger gauge #8 or #6.

Great idea! You just saved me the cost of a battery! It'll probably be a 20-25' run from the batteries in the front to the genset on the back ... do-able!