Benefits of Load Bank Testing

Mar 28, 2023

Having a standby generator keeps crucial services running in the event of an outage for many companies. Health care professionals, for example, often face situations where power can mean the difference between life and death. A devastating downtime can result in hundreds to millions of dollars in losses for data center operators or financial professionals.

In order to ensure backup power systems actually work when they’re needed most, it’s important to test them under load periodically. That process is called load bank testing. Here’s what you need to know about the generator load bank testing procedure.

What is a load bank and what does it test?

To put it simply, a load bank is a piece of specialized equipment that produces artificial loads on a generator. It does this by bringing the engine to a certain operating temperature and pressure to simulate the process of the equipment being used during an emergency situation. An easy way to think of it is that the purpose of load bank testing essentially acts as a dry run for emergency generator use and allows any flaws or problems to be exposed before a critical situation.

There are many benefits to load bank testing. One of the benefits of having a generator is that you can rest assured that it can provide power in an emergency. Also, it is usually much less costly to repair problems discovered during this process than those discovered during a critical situation. An ounce of prevention is worth more than a pound of cure, and load bank testing ensures that all small issues are handled before a major problem occurs.

How often should a generator be load bank tested?

Load bank testing schedules for generators are often determined by the generator’s classification and its use as a standby. For example, if a generator is used as a backup for services associated with loss of life or serious injury—such as in a hospital setting—the testing guidelines per safety codes are much more frequent, and accurate records must be kept.

Data centers and financial organizations are generally held to stricter requirements, as well. 

These standard guidelines are set by the National Fire Protection Association (NFPA). Critical situations follow NFPA 110, 99 and 70.

In most cases, it is recommended that non-mission critical generators are tested  to at least 80% of their maximum load for 60 minutes once per year. Critical diesel generators could be tested much more frequently, but this wholly depends on individual requirements and industry regulations according to the facility type. 

Things to consider prior to testing

During the testing process, it’s important to follow a checklist of best practices. During the test, this prevents any unexpected outcomes. 

Personnel should wear appropriate safety clothing including eye protection goggles, hearing protection, head protection, steel-toed boots, gloves, and a high visibility vest. Employees should have experience in working with load bank testing and hold a qualification for administering the test. In most cases, it is recommended to handle this process with a certified organization instead of attempting it with your own internal maintenance staff. At Zabatt Power Systems, we have over 70 Certified Generator Technicians to handle all of your load bank testing needs.

The Testing Procedure with Step-by-step Guide

The actual testing procedure itself is not too complicated, but it does take a bit of knowledge to understand how the process works. 

The technician begins by starting and running the generator. In an actual building load transfer, all manual or automatic switches are transferred to the emergency source. During a load bank test, utility power to the facility is not disrupted and no actual power transfer occurs. The generator then receives step loads from the load bank until the desired load level is reached.  After the test has been successfully completed, the technician disconnects the load bank load and transfers all switches back to the normal position, if applicable, before allowing the generator to cool down according to manufacturer guidelines. The load bank process is documented and closely monitored with any failures reported directly to the customer.

In more detail, the process occurs in this manner:

  • Step One: All fluid levels are checked to ensure the fuel tank is full and the oil level is correct. If the generator is water-cooled, it is also important to check the radiator or coolant tank.
  • Step Two: The generator is started and allowed to reach normal operating temperature. The technician watches and listens for any possible issues such as abnormal noises. If any problems are detected, the testing process is stopped until the mechanical failure is diagnosed and fixed.
  • Step Three: The technician then begins connecting the loads. This continues until each leg carries 50%.
  • Step Four: Next, the technician checks the amperage of each leg with an ammeter. In cases where a 110/220 volt single phase generator is being tested, the voltage of each leg is recommended to fall between 105 and 125 volts. The current should be half of the rated watt output divided by the voltage for each leg. If one or more of the legs drops below 105 volts at full load, there is a problem and the test is considered failed.
  • Step Five: The technician continues to monitor the generator while maintaining the same load for the duration of the test and continues to listen for noises and monitors the output. If an issue is discovered, the test is shut down to minimize damage until repairs happen. After repairs, the test is started again from the beginning.
  • Step Six: At the end of the test, the loads are gradually removed and the generator is allowed to run under light load for about an hour.  All loads are removed 5 to 10 minutes before shutting the generator down. Note that some load tests in critical and life safety applications require very specific testing protocols and reports, a process that Zabatt completes hundreds of times per year.  

As a full-service power generation company, Zabatt Power Systems has over 70 Certified Generator Technicians to handle all your load bank testing. Contact us today to ensure your generator is operating at full load capacity!