The coolant level in the radiator or expansion tank must be kept at the appropriate level for the engine to be adequately cooled. The cooling system may contain hot coolant and steam under pressure. To prevent injury, wear rubber gloves, an apron, and a face shield or goggles when removing the radiator cap or working with the coolant. Always wait at least one hour before removing a cap after the engine shuts down.
Remove the cap from the expansion tank or radiator if a gauge is absent to visually check the coolant level. Using a ladder (never climb on a machine), position yourself safely to remove the radiator or expansion tank cap. This process should be done slowly and carefully to release any pressure that has built up in the system gradually. Ensure that your head is positioned well away from the cap.
If the radiator has a level gauge, the indicator needle should show a full condition. Most gauge faces feature white, black, or red graduated markings, indicating the coolant level. Verify that the indicator is functioning correctly by turning the knob lever to the “low coolant” position. The low coolant alarm should sound if the gauge is “wired” to an annunciator. Upon releasing the knob, it should return to its full position and silence the alarm.
Checking the Coolant Level
Check the coolant level to ensure it is not below the top of the core. (The level of coolant on expansion tanks will be dictated by the manufacturer’s guidelines and installation manuals.)
- If necessary, add coolant using a funnel until the proper level is reached. Only use the mixtures and brands of coolants that the EPS manufacturer recommends. In the case of ethylene glycol, a 50/50 solution with water should be used.
- Replace the cap and ladder. Record the amount of coolant added to the weekly inspection checklist and compare it with previous reports for any signs of trend development.
Whether the radiators are mounted on the skid with the EPS or in a remote location, they can only work if air can move freely through the core’s “fins” to disperse heat generated by the engine and transferred to the coolant passing through the block and heads.
- Using a flashlight, inspect the core of the radiator for any foreign substance that might impair the flow of air and remove it carefully.
Not only is the flow of air necessary to cool the radiator, but a constant flow of air is necessary to cool the alternator and provide combustion air for the engine. Make sure that all pneumatic louvers operate as designed.
Note: This will necessitate starting the EPS and observing the movement of the louvers during the monthly test or after all of the following steps have been completed during the weekly inspection checklist and the unit has been restored back to service.
The belts on the front of the EPS are also to be checked, both with the EPS running and in the off position. Fan belts drive the fan, which forces air through the radiator if the radiator is located on the EPS. Fan belts can also operate other equipment, such as the water pump and battery charging alternator.
- With the EPS off, the belts should be checked to ensure tightness. In most cases, there should be no more than 1/2 inch deflection from the center line.
Note: When replacing multiple belts with the same part number, a matched set should be purchased to ensure all belts are of the exact same circumference.
- The belts should also be inspected for dry rot and any fraying.
- Check the cooling system for leaks. Any leak should be considered critical. Remember, if it is a leak, you will observe dripping. Wetness caused by seepage is not necessarily a leak, but it should be reported to your supervisor.
- The water pump forces coolants through the engine and through a series of hoses to and from the various components to be cooled. The water pump must be examined for evidence of leaking at the weep hole at the bottom. If evidence of leaking is apparent, report this condition immediately.
- The top and bottom radiator hoses must be examined for seepage and leaks. Remember that the coolant may be hot and under pressure. Squeezing the hoses is not recommended, as a brittle hose could split. Hose clamps can deteriorate and break, so they also need to be checked.
- All other hoses, such as the inlet and outlet block heater hose(s), need to be checked also. Care should be taken since these are typically hotter than the other hoses unless the engine has been run
- Check any water filters for signs of leaking.
The last item to be checked on the cooling system is the block heater and/or the heat pump if installed. The purpose of the block heater or heat pump is to maintain the diesel engine at the manufacturer’s recommended levels in the standby position and ensure that it will start and accept the electrical loads without damage to the EPS within the time specified by the AHJ.
NFPA 110, 5.3.1 The EPS shall be heated as necessary to maintain the water jacket and battery temperature determined by the EPS manufacturer for cold start and load acceptance for the type of EPSS.
The block heater can be installed in various locations outside the engine or, in some prime movers, in the block itself. The thermostat, element, housing, hoses, clamps, wiring, and circuit breaker are block heater components that need to be checked.
The thermostat and element can be checked by feeling the engine block. An extremely hot block (above 90 degrees F or the manufacturer’s recommendation) can result from the thermostat being stuck in the closed position. A cold block can result from a thermostat being stuck in the open position or an element being open. The circuit breaker must also be checked to make sure it is in the closed position.
Conclusion
Proper maintenance of a generator’s cooling system is critical to ensuring the reliable operation of an Emergency Power Supply System (EPSS). Regular inspections of coolant levels, radiator airflow, belts, hoses, and heating components can prevent overheating and system failures during an emergency. Careful attention to leaks, proper coolant mixtures, and the integrity of critical components such as the water pump, block heater, and pneumatic louvers will help maintain system efficiency and compliance with NFPA 110 requirements.
By implementing a structured inspection routine and addressing potential issues before they escalate, facility managers can enhance the longevity and performance of their EPSS. Diligence in documentation, reporting abnormalities, and following manufacturer recommendations will further support the cooling system's reliability, ensuring the generator is ready to provide uninterrupted power when needed.
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