Load bank tests help facility managers determine if their load bank generators will meet their nameplate rating. This is ideal for managers that want to avoid the problem of having a defective generator on the premises during a power outage. It is imperative to point out that the absence of regular load bank testing may lead to having generator failure during a real emergency. This is the primary reason why load bank testing plays a vital role in the generator maintenance program.

Wet stacking takes place when unburned fuel builds up in the exhaust system. This typically occurs when the generator operates at less than a full load. This makes it tough for the generator to produce enough heat to burn off the excess fuel. The unburned accumulation of fuel will cause severe damage to the engine valves, exhaust system, and fuel injectors. The engine will not run at its optimum level if the proper mixture of fuel and air is not maintained.

When it comes to wet stacking, carbon buildup takes place when the generator’s engine does not produce enough heat to eliminate the buildup. The piston rings within the engine will malfunction if the carbon buildup is not monitored. Research shows that the superheated fuel/air mixture travels past the rings and damages the sides of the pistons.

Load Bank Basics

A load bank connects a durable controllable electrical load to the generator. The load bank can be permanent or portable. It is also suitable for an AC or DC charge. Many load bank generators come with an internal fan that keeps the resistive elements cool and transports the high-temperature air away from the unit. The load bank unit must be positioned away from the combustible material to make certain that it does not overheat.

There are two main types of load bank testing methods (resistive and reactive). Resistive is the most popular field testing method because it includes the entire kW rating of the generator and the primary engine systems. Reactive testing normally takes place at the onset factory to test kVA ratings.

Load Bank Testing Schedule

Generators should go from a cold start to a full load within a matter of moments. The generator must be exercised at 30% load for at least thirty minutes each month. This monthly test will keep the internal engine parts lubricated, minimize oxidation of electrical contacts, uses fuel before it deteriorates, and helps the engine start properly.

An annual load bank test should only take place when the generator’s kW capacity is at 100%. Experts state that the test should last for at least one hour. The load should be increased gradually during the testing period.

Testing Tips

Load bank testing can detect problems in a controlled situation with ease. Let’s take a quick look at a few tips that can help you discover problems with your generator.

-Be ready for unexpected results or system failure during a load bank test.

-Keep a backup generator on the premises if you are running a healthcare facility or a business that cannot afford a power outage.

-Test the generator during non-peak hours if you are running a facility that can afford a power outage for a short period.

-Make certain that the generator is disconnected from the facility.

-Check for visible leaks, loose connections, and abnormal performance.

-A good generator will produce black exhaust during the testing period. This is a sign that the engine is doing a great job of eliminating the carbon buildup and the fuel in the exhaust system. However, the engine may need repairs if the smoke does not clear before the testing period is completed.

High cooling system temperature and low oil pressure can take place during the testing period. A faulty thermostat or blockages are the culprits for high temperature. Low oil pressure can occur when the oil pump needs to be repaired.


It is vital for you to keep a dependable load bank generators on the premises. Load bank testing should always be a part of the regular generator maintenance schedule. This ensures that the generator will run at its optimum level. Testing also helps the operator find out if the onset can run at its full kW level. Following the tips above can help you maintain your generator with ease.