Radiators are waaaaay more complicated that most people think!
Since most generators use liquid cooled engines and radiator systems to cool the liquid, let’s look at the basic concept of heat and heat transfer.
All of the heat created by an engine comes from converting the heat value of the fuel. A good rule of thumb is 30—30—30—10. That is 30% of the fuel’s heat may be converted into torque to make electricity. Another 30% is converted into heat and must be removed through the cooling system. 30% more is converted into heat and is discharged through the exhaust system. The remaining 10% of the fuel’s heat is rejected to the atmosphere around the engine through the block.
That means that the amount of heat equal to the electricity you take out of the engine will need to be removed by the radiator. So, an old generator with a dirty radiator that has been working just fine under low load test conditions will most likely overheat and shut down the engine during an emergency when you load it up to near its design capacity.
Just because it works during your monthly test does not mean it will work during a real emergency!
Generators use a “pusher” fan. This type of system takes the air from around the engine and moves it forward blowing out in front of the engine. An unfortunate side effect of this method is that the oil vapors from fuel and engine oil emitted by the engine pass through the radiator. Some of the oil vapors condense on the radiator and make it sticky. Dust and other material collects on the sticky surface and produces the external clog you see in the picture above left.
Inside of the radiator the liquid is a chemical soup. Deposits as seen in the picture on the right above develop and prevent the coolant from flowing through the tubes and being cooled by the air.
When the manufacturers design generator sets, they usually allow very little extra capacity to accommodate dirt and deterioration. Radiators are after all expensive. Radiator maintenance is considered the owner’s problem. NFPA 110 as well as most manufacturers recommend annual radiator flush and cleaning.
Generators and automatic transfer switches as well as their appurtenant devices employ high voltages that can hurt you. Do not attempt to work with this equipment unless you are qualified. Observe all rules and cautions found in the manufacturer’s manuals as well as NFPA 70E, Standard for Electrical Safety in the Workplace.
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