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Why is Generator Loadbank Testing Done? 

Your generator set is a valuable resource that provides a dependable emergency power to your business when power from the utility grid is suddenly lost, or power is not available in your environment. In the event of a power failure you want to have peace of mind that your backup power supply will spring into action seamlessly on a moment’s notice. But what happens when the power goes out and your generator fails function as expected? The result can often be costly and sometimes catastrophic depending upon your application.

This is precisely the reason generator loadbank testing is an essential piece of a comprehensive preventative generator maintenance plan, which you should ideally have conducted on your genset(s) each year. Loadbank testing helps to ensure that your generator will be fully dependable and operational, as well as completely capable of the highest possible load it may be required to handle at any critical point in time. Load testing your emergency standby generator system should be part of a standard planned maintenance program for all systems.

Reasons to Test Your Generator

  • To make sure the generator will perform as designed, when it is needed most. This is the only true way to check the performance of the generator. A load test will allow verification that the generator system will produce and maintain full load without overheating and shutting down. It also allows testing of all components of the system, to ensure all work together as designed and intended and can help identify any potential weaknesses in controlled conditions. This allows proactive maintenance, as weaknesses are identified during controlled conditions, not during a utility outage when a weakness can cause the system to fail. The load can come from building load, but that may cause business interruptions when transferring from utility to generator. It also does not allow the load to be applied in steps, where performance can be monitored and recorded. Generally, utilizing a portable loadbank is the preferred method of load testing a generator system.
  • Most generator systems are programmed to exercise on a regular basis. Typically this exercise period is under no (or very little) load. Monitoring the exercise period to ensure the generator starts and runs as programmed is also important, but does not ensure the generator will operate as designed.
  • Most generator systems are installed and then put into automatic mode. As the generator ages, the possibility of weaknesses in the system will rise. Among other potential enemies, weather, pests and age can negatively affect the efficiency of a generator system. A good planned maintenance program that includes load testing is the best way to spot and minimize potential weaknesses in a generator system.
  • In addition, because many of the installed generator systems that utilize a diesel engine present another challenge. That challenge is referred to as wet-stacking. If not addressed, wet-stacking will degrade the performance of the system and not allow the system to operate as designed. Many systems are designed with some redundancy on load or for future expansion. This means many systems are not loaded appropriately to eliminate wet-stacking. At a minimum, I recommend all diesel system be load tested with a portable load bank for a minimum of two hours, annually. If a diesel system hasn’t been load tested in over a year, longer testing may be required. This annual testing will reduce the impact wet-stacking will have on a generator system.

A good planned maintenance program that includes regular load testing should be a standard component of a generator system. The regular testing of the system will provide the highest comfort level that when the system is required, it will operate as designed.

What is Generator Loadbank Testing? 

Generator Loadbank Testing is an Important Aspect of Preventative Maintenance. A generator loadbank test involves an examination and assessment of a genset. It verifies that all primary components of the generator set are in proper working condition. The equipment used to conduct a load bank test produces artificial loads on the generator by bringing the engine to an appropriate operating temperature and pressure level. This is especially important for standby and emergency generator sets that do not run very often and/or may not be exposed to carrying heavy loads on a frequent basis. The general rule is – if your generator is not exposed to higher than 30% of its rated kW load then you should be considering a load test.

Loadbank testing involves firing up a standby or prime power generator and running it under an artificial load at its maximum capacity for a specified period of time. During loadbank testing, data can be recorded that offers a more thorough look into the health of the gen set on the whole. The test verifies that the generator is capable of handling incrementally higher kW loads, that it is still capable of accommodating its maximum specified load, and that it can work for an extended period of time. So, at its simplest, load bank testing is a way of verifying that your standby or prime power generator is still capable of kicking on and operating at its maximum kW output.

A loadbank test ensures that your generator will run property when it’s needed so that you can fully depend on it during an emergency situation. The key to a proper load bank test is that it tests your generator at its full kilowatt (kW) output rating. Because many generators do not regularly operate at their full kW rating, it’s especially important that you verify your generator can actually produce the highest possible horsepower that may be required – while at the same time maintaining adequate temperature and pressure levels that will allow it to run as long as necessary.

The recommended procedure to follow for the loadbank test would be to:

  • Start and run the generator until the water temperature stabilizes.
  • Transfer all manual or automatic transfer switches to the emergency source.
  • Step load the generator with the load bank until the desired load is reached.
  • Remove the load bank load first, after the test.
  • Transfer all transfer switches back to the normal position.
  • Allow the generator to cool down according to manufacturers’ guidelines.

It will be discussed in detail in the following section.

Carelabs can help in designing the proper planned maintenance program for your standby generator system, and our team of factory trained technicians will make sure your planned maintenance will be carried out skilfully and any issues found will be brought to your attention immediately, ensuring you are prepared for the next interruption in utility power.


Loadbanks are electrical devices that are temporarily wired into a generators AC voltage output. Load is applied to the generator through switches that are calibrated to produce specific Kilowatt (Kw) output.  This allows the operator to apply specific load steps during the testing process to match the generators rated capacity.

A loadbank test ensures that your generator will run property when it’s needed so that you can depend on its proper operation during an actual emergency situation. The key to a proper load bank test is that your generator operates and maintains its full kilowatt (kW) output rating.  Most generators do not operate at their full kW rating during their routine exercising.

It is especially important that you verify your generator can actually produce the highest possible horsepower that may be called upon to produce. Only through this type of testing can you verify your unit’s proper operation of recommended temperature and pressure levels throughout the full range of operational status.

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