23 Nov, 2016

Posted by ryanfmm

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Load Bank Testing

We recommend load bank testing every 12 months, which will help minimize potential long-term Issues. This test artificially boosts the load placed on the generator, usually to about the height of the generator’s output capacity. This helps to erase any effects of wet stacking or other buildup, and to verify that a generator is capable of performing at its peak output rate.

What is the difference between weekly exercising and a load bank test?

Exercising your standby generators weekly is basically an unloaded test. For natural gas or liquid propane units, exercising confirms that your generator can run but does not check your unit’s performance which can be critical for ensuring you are ready for a real power outage event. For diesel engine driven generator sets, unloaded tests or weekly exercising can cause ‘wet stacking’. Wet stacking is when unburned fuel accumulates in the engine exhaust. This is caused by under-loading a generator. When exercising a generator or running it for short duration outages while under loaded, the engine may not reach its optimum operating temperature. When this is allowed to continue for long periods of time the unburned fuel accumulates, and can become harmful to the engine’s efficiency and life span.

How is a load bank test performed?

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. 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.

In more detail, the process occurs in this manner:

Step 1: 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 2: The generator is started and allowed to reach normal operating temperature. Our 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 3: Our technician then begins connecting the loads by starting with any large 200 volt loads and adding smaller 110-volt loads. This continues until each leg carries 50% on any one leg.
Step 4: Next, our 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 a failure.
Step 5: Our technician continues to monitor the generator while maintaining the same load for the duration of the test and continues to listen for noises and monitor 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 6: 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 down the generator down.

What are the benefits of load bank testing?

Load bank testing allows the engine to reach this full operating temperature and ‘burns out’ this accumulation of unburnt fuel. The result is a unit that runs cleaner and more efficiently. It also offers peace of mind that your standby generator is operating as it was designed too. Any generator set, whether the prime mover is diesel or gaseous fuel driven, can benefit from having its load bank tested.