Load Bank Testing Services

Load bank testing is integral part of any facility that relies on generators.   Testing the generator In some business sectors, it’s actually required to meet NFPA code and must be performed on annually.  Whether you opt for load bank testing as part of our preventive maintenance program or as a standalone service, our experienced technicians can perform load bank testing at your facility whenever you need it. WPP has load banks ranging in size from 100 kW – 2000 kW.

Contact our Service Department today for a FREE estimate!  713-434-2300 or service@wpowerproducts.com

Full Service Preventive Maintenance Programs

Our PM inspections include an 80-point inspection checklist. 

We also offer FREE diesel fuel sampling.

WPP service truck with load bank on trailer
CAT generator undergoing load bank test

What are the benefits of Load Bank Testing?

Whether your generator is diesel or natural gas, here’s what a consistent load bank testing schedule can do for you:

  • It ensures your backup generator will meet your power needs during an outage. 
  • It helps you avoid “wet stacking,” which hinders a generator’s output capacity. 
  • It allows you to run the generator at optimal load, an especially important consideration for generators that are frequently run at low loads.
  • It extends the life of your engine.
  • It verifies your genset was properly installed and that everything is working as intended by testing all parts of the system in a controlled environment. 
  • It helps you avoid unnecessary downtime and repairs by giving you actionable advice based on real-time test data.
  • It keeps your business in compliance with local, state, and/or federal requirements and even insurance company stipulations, in some cases.

What is Wet-Stacking and How Does Load Bank Testing Help?

Annual generator load testing allows the engine to reach its full operating temperature, so it burns out accumulated fuel and prevents wet stacking. This ensures the engine runs cleaner and more efficiently.

When a diesel generator is operated for an extended period at little or no load, unburned fuel can collect inside the engine exhaust and produce black smoke and pooling oil. This is known as “wet-stacking,” and it hinders your generator’s ability to provide power. It’s also a fire hazard.

By exercising the generator at or near its maximum rated output, a load bank test can reach its recommended operating temperature and actually burn off that accumulated fuel. This allows it to perform optimally with respect to both efficiency and environmental concerns.

How Often Should I Load Test My Generator?

When considering how often to have your generator load-bank tested, it’s important to note the difference between exercising a generator and load bank testing it. 

According to the National Fire Protection Association (NFPA)…

Diesel generator sets in service shall be exercised at least once monthly, for a minimum of 30 minutes, using one of the following methods:

(1) Loading that maintains the minimum exhaust gas temperatures as recommended by the manufacturer

(2) Under operating temperature conditions and at not less than 30 percent of the EPS standby nameplate kW rating.

– NFPA 110, Section 8.4.2

Some generator owners rely on either weekly no-load testing to exercise their units, or they let the occasional power outage suffice for their generator’s exercise time at full load, or both. 

Neither is a recommended practice, however, as running a generator with too light of a load for more than 15 minutes can lead to wet-stacking, and utility outages are too unpredictable to base a responsible generator maintenance program on them.  

Compared with generator exercising, a load bank test is a more comprehensive inspection of the generator that verifies it can handle not just starting and running for a brief period, but carrying a full load for many consecutive hours, if necessary. 

In most cases, non-mission-critical generators should be tested at 80% of their maximum load for one hour at least once per year. Both the NFPA and the National Electric Code (NEC) have stricter standards for load bank testing emergency generators where failure of equipment could lead to loss of human life. 

How Does the Process Work?

We will perform a resistive load bank test, a reactive load bank test, or a resistive/reactive load bank test

A resistive load bank works well with power draws that involve transforming electricity into heat or light. 

A reactive load bank mimics a motor or inductive load, making it a good fit for commercial applications. 

A resistive/reactive load bank combines both types in one unit for the most thorough generator testing.  

Before a load bank test, we identify the best time and place for the procedure–ideally during hours when a power outage would not be catastrophic (simply as a precaution), and somewhere with open air space to ensure sufficient cooling and exhaust of hot air from the portable load bank. We will either disconnect the generator from your facility or use a dedicated bus so that disconnecting and reconnecting are not necessary.

How long the test takes depends on the application and the generator itself. Most tests can be completed in 3 to 8 hours, although they can take up to 24 hours with larger units. 

The steps proceed as follows:

Step 1

The technician checks the levels of oil and fuel. If the generator is water-cooled, he also checks the radiator or coolant tank. He also verifies that the circuit breaker is open and the safety ground connected.

Step 2

The technician starts the generator and allows it to reach normal operating temperature. The technician monitors the generator for unusual noises and other issues. If any problems are detected, the testing process is stopped until the mechanical failure is diagnosed and fixed.

Step 3

The technician then begins connecting the loads by starting with any large 220 volt loads and adding smaller 110 volt loads until the desired load is reached (80% in a reactive test, 100% in a resistive test). 

  • This continues until each “leg” (or conductor) carries at most 50% of the generator’s maximum continuous rated load, with its voltage between 105 and 125 volts (for single-phase generators).  If one or more of the legs drops below 105 volts at full load, there is a problem and the generator fails the test.
  • The technician checks the current of each leg with an ammeter. The current should be half of the rated watt output divided by the voltage for each leg.

Step 4

The technician continues monitoring 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 5

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. While disconnecting the load bank, the technician isolates the breaker as an added precaution, and returns all transfer switches to the “automatic” position.

Step 6

After the test, the technician creates a digital test report from the data generated during the test and emails it to you for your records. In addition to the unit’s pass/fail grade, the report will include information on several factors as recorded at different intervals as the test progressed, such as:

  • Load level 
  • AC voltage
  • Hertz
  • Amperage
  • Voltage
  • Coolant temperature
  • Ambient temperature
  • Oil pressure

The technician will also include any comments, concerns, and recommendations for maintenance or repair work, if any.

Load Bank Tests From WPP

Caterpillar G3516B Natural Gas Generator Set Load Test

Kohler 1000kW 16V2000 Tier 2 Generator Set Load Test

Caterpillar 3512 MUI Power Module – 1250 kW Load Test

Choose Worldwide Power Products for Your Load Bank Testing Needs

Backup generation is more important than ever as a safeguard for your business, and proper testing and maintenance are vital to ensuring your backup power is ready to go when called upon. Load bank testing is a cost-effective investment every generator owner needs to make to prevent major headaches and repair costs down the road. 

At Worldwide Power Products, we are seasoned experts in servicing power generation equipment.

Our certified technicians take the hassle and the risk out of load bank testing by conducting your test in a secure area away from personnel and other activities. They are always equipped with extensive safety clothing and gear including goggles, hearing protection, head protection, steel-toed boots, gloves, and a high visibility vest.

Need to rent a load bank? Explore our load bank rentals.