Resistive vs. Reactive Load Banks

Depending on your generators and how you use them, you may need resistive, reactive or both types of load banks. These devices put different kinds of loads on the generators. Resistive models are the most common, while reactive include inductive and capacitive power loads.

1. Resistive Load Bank Uses

Resistive load banks draw power from a generator in the same way lights or appliances would. These testing devices work well with generators used for general power purposes that involve transforming electricity into heat or light. Light bulbs, lamps and space heaters are examples of tools that convert electrical energy into heat.

These types of load banks draw a specified real power load, in kW, on the generator to ensure the operation of the power supply's cooling system, exhaust and engine operation. They do not test the generator for full apparent power in kVA, which is what a reactive load bank tests.

2. Reactive Load Bank Uses

Reactive load banks can simulate inductive loads, often used commercially in construction or in backup power supplies. Inductive loads create a lagging power factor, whereas capacitive loads generate a leading power factor. Of these two types, inductive appears more commonly in objects that turn power into motor operation through magnetism.

For facilities that rely on emergency generators to run equipment for business-critical operations or life support, such as data centers and hospitals, reactive load bank testing is the most effective.

load bank uses

How Do Resistive Banks Work?

Resistor load banks convert all of the applied electrical energy into heat. Larger kW load banks typically have an integrated blower for cooling. Some load bank designs, such as Duct Mounted, do not have their own cooling system but rather rely on cooling airflow from other sources such as an engine radiator.

Self-contained resistive load banks are commonly found up to 3,000 kW. For full kW load testing, make sure to choose a load bank with a capacity equal to or greater than the power source at the rated output voltage.

How Do Reactive Load Banks Work?

Reactive load banks test the full apparent load in kVA of the power source. Though not as commonly used as resistive load banks, reactive models are part of the testing requirements set out by NFPA 110 for nonunity power factor equipment field or factory acceptance testing.

Unlike resistive loads that generate a power factor of 1.0 and a load of 100%, reactive has a 0.8 power factor with a 75% load. This difference in power factors and loads leads to voltage drops from the generator of 25% more than from the resistive loads. In this way, reactive load banks test for systems that have a sensitivity to voltage dips. 

Advantages of Resistive Load Testing

Resistive load testing is very common as it is the most cost-effective way to test a power source. For generators, this method checks the ability of the generator to respond at a full load. With the generator producing full power, you can assess the capability of the mechanism's fuel and cooling systems to operate under the effort.

Resistive load banks also prevent diesel generators from losing efficiency through wet stacking, which happens when unburned fuel clogs up the exhaust system. By putting a higher load on the generator than it typically experiences, a load bank encourages the engine to burn more fuel, reducing the chances of wet stacking.

If the condition has already set in, using a resistive load test at full power can reduce the effects by burning excessive moisture in the engine.

Another benefit of using resistive load banks is they allow the generator to exercise its exhaust system to reach high enough temperatures to properly treat the fumes flowing through it and operate at its peak.

Additionally, resistive load banks can be used to supplement the actual load on a generator to optimize its performance. Often you will find generators operating at 50% loads or lower, which can lead to wet stacking. Resistive load banks with Auto Load Leveling Controls can automatically add and subtract kW to help maintain a minimum load.

Reactive load testing offers some additional benefits that resistive testing cannot and can warrant the extra expense for certain applications.

Advantages of Reactive Load Testing

Reactive load testing more closely replicates the type of load a generator will experience during typical use in kVA and kVAR. It helps evaluates not only transient loads, but also load sharing and alternator capacity.

When doing testing with a reactive load on systems in parallel, you can look for hot spots using an infrared examination of the electrical system. You can also use the load conditions to assess the electrical connections, cables, bus work and other components.

Depending on your equipment, you may need both reactive and resistive load testing. If this is the case, we have models that can fulfill both needs. Should you need a unit with the capabilities of both resistive and reactive testing in a single model, we have a solution for you. These load banks have high capacities up to 1,875 kVA and load up to 1,500 kW. Resistive-reactive models do the job of two load banks in one powerful unit.

Find the Load Banks You Need

At LBD, we manufacture both resistive and reactive models. We offer permanent, stationary designs, as well as portable solutions for on-the-go testing. Whatever testing challenges you face, let us know, and we will help you find a load bank to meet your needs from our industry-leading selection.

If you are ready to get one of our prepared models or need a custom option, request a quote from our team.

load banks for generator testing

Contact Load Banks Direct

125 W 34th St.
Covington, KY 41015

Toll Free Phone: 1-855-LBD-CALL
(855-523-2255)

International: 859-554-1534
Fax: 859-554-2530

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