Regarding generator, it must be ensured the generator should run to its maximum capability. This falls to the ability of the engine to deliver enough horsepower to sustain the required kilowatts. The ideal loading percentage of the generator is when running it at 80% load. It can also run to 100% load for a limited time as in emergency situation, but running it continously with 100% load will definitely shorten the life of the generator.
To ensure that the generator is running optimally, it is necessary to load tested it before using to a project. In smaller gen. sets, where loadbank is not available, the owner can use high wattage light bulbs connected in parallel equal to the maximum capacity of the generator.
This individual lamp can have individual switch to turn on and off each lamp. Say for example your generator is 7 kilowatts, by using 10 x 500 watts and 10 x 200 watts light bulbs, the generator can be tested gradually from 0 to 100% load at unity power factor.
The test can start by giving 10% initially for warm up within 5 minutes, then increase to 25% (1.750Kw or 1.8Kw) for 30 minutes; 50% (3.5 Kw) for 30 minutes; 75% (5.25Kw or 5.2Kw) for 30 minutes and 100% (7 Kw) for 1 hour. Test time can be reduced as long it will not be less than 15 minutes for each stage and 30 minutes for 100%.
If for example your generator drops in speed at 5o% load, the frequency will also drop in proportion to the speed, which indicates that the engine can only support that particular load, thus increasing the load will continously drop the speed of the generator until it stops. If this happens, the best thing to do is to take the compression reading of the engine if it is still within standard. (Diesel engine have higher compression reading compared to gasoline engine.) If readings found below standard, then it is about time to replace some rings...instead of using it half functional, in which will only aggravate the problem.