Running light loads on generator

[katwalatapan]

Hello,

I had a query regarding running light loads on generator. If load on generator is over 25% of rated generator output, would it be recommended to run light load on generator without encountering major loss in efficiency or durability? Is it possible to adjust the output of the generator so that it could be configured to run light loads?

Thank you.

Regards,

Tapan.

 

[TheBlacksmith]

Insufficient data. The generator shouldn't care (or know). The prime mover, particularly a diesel, will not take kindly to light loads. A diesel could suffer from include oil dilution, slobber and/or carbon buildup with continued light loading and there are no adjustments for that.

 

[waross]

No problem electrically. There will be good electrical efficiency if not the best.
However a diesel engine does not like to run lightly loaded. The fuel economy is poor and at light loads the piston rings do not seal properly. The possible poor piston ring seal may lead to oil pumping, also called "Wet Stacking" or "Slobbering". Light loading may also lead to cylinder glazing which may also lead to oil pumping.
The next step in the progression is when the load, and the exhaust temperature and gas velocity increase. This may result in dirty oil being blown out of the exhaust and in extreme instances, flaming, dirty oil being blown out of the exhaust system.
That said, life is hard for an engine driving a generator. There are installations where a generator must be sized to start a large hard starting motor and when the motor is running the generator load drops down to a low percentage of the set rating. I have encountered that situation. The solution is to seat in the rings by loading the set with a load bank for several days. When the set is in service it is watched for any sign of oil pumping or oil consumption. If oil pumping is caught early it may be corrected by bringing the load bank back for a few days.
Another possible result of oil pumping is complete loss of lubricating oil.
Run at light load if you must but be aware of possible issues.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[katwalatapan]

Sorry for the insufficient data. The generator is concern is a gas fired one (propane fired to be accurate). The rated output of the 35KW generator is approx. 120A per phase. Now the load that it has to support is total of about 55A. So my question was whether it would be recommended to run a light load on this generator. If so then would it encounter any long term issue?

Thank you.

 

[catserveng]

Biggest problem I see with SI prime movers (natural gas or propane) is plug fouling at light loads. Seems auto derived prime movers have less problems than do industrial engines of similar sizes. But in general, you'll likely see ignition system problems early on, then wet stacking or slobber the longer you run at lighter loads.

Mike L.