Generator load banks offer a safe and reliable method for the periodic testing of emergency generators. This article discusses a specific load bank design known as a radiator-mounted load bank.
As the name implies, these load banks are installed in front of the engine radiator, and they utilize the cooling air provided by the engine radiator’s fan.
When should you consider this type of load bank? These questions may help guide you to a decision:
- will your facility use a generator with a unit-mounted radiator?
- will the load bank rating be 1200kW or less?
- is a resistive-only load bank suitable for your project (learn more about load bank types)?
- is an outdoor installation impossible due to lack of space, or not practical due to airflow and noise?
- will the engine radiator allow for the additional airflow restriction created by a radiator-mounted load bank?
If you answered yes to these questions, a radiator-mounted load bank may be the best design solution for your project. Here are some benefits:
- Simplicity of design: by using the radiator’s outflow air to cool the resistive load elements, many traditional load bank components are not required (fan, motor, motor starters, motor control and protection logic, etc).
- Reduced size and cost: by eliminating the need for a fan, motor and associated equipment, the load bank size and cost are dramatically reduced.
- Reduced airflow and noise: by using the radiator’s outflow air, the load bank does not require a separate fan to produce cooling air.
- Lower airflow temperature: a radiator-mounted load bank’s exhaust air temperature is lower, relative to a standard freestanding load bank.
- Ease of installation: various installation configurations allow for great flexibility in your design. You may choose direct attachment to the radiator, mounting within an air duct, or wall-mounting indoors or outdoors. This document provides one manufacturer’s view of the different arrangements possible.
What should you look for in these load banks?
- Load elements should be UL Recognized Components.
- Load bank should be equipped with branch fuse protection to maintain system functionality (by isolating a failed load element).
- Elements should be rated for a minimum 1600F operating temperature, thus eliminating the need for system cooldown after operation.
- Automatic over-temperature protection should prevent the system’s failure in the event of a lack of cooling airflow (i.e. due to failed ventilation louvers, etc).
- Control components should be separated and electrically isolated from load elements.
- Automatic load leveling is a great feature and should be included to allow proper loading of the emergency generator in response to dynamic building loads (typical when generators are exercised under insufficient building loads).
But be aware of the following limitations:
- radiator-mounted load bank ratings in excess of 1200kW may not be practical as the number and size of load elements may cause the load bank assembly to exceed the typical radiator’s face area (remember that the load bank elements must be exposed to the cooling airflow).
- applications requiring a resistive and reactive load bank may not be well-suited for radiator-mounted load banks, due to the separate compartments required for the different elements. A pair of freestanding load banks (one resistive, one reactive), connected in parallel, may offer a better solution under these conditions.
- in applications consisting of multiple generators in parallel, it may be best to utilize a single, large load bank. A single load bank is generally connected to the emergency bus via a dedicated circuit breaker and shared by all generators.
Even if not legally required, your client’s facility may still benefit from the convenience of having a permanent load bank on-site. For these instances, a radiator-mounted load bank may prove to be a cost-effective solution worthy of your consideration.
Do you have questions? What is your experience with generator load banks? I look forward to your comments!