A radiator-mounted load bank can be a very practical solution to meet minimum load requirements on emergency generators. The mechanical installation of these load banks can be accomplished in a number of ways, providing the designer with a simple solution for most applications. This article covers the most common installation methods, and tips on how to handle uncommon situations.
As the name implies, radiator-mounted load banks are installed in the path of the radiator exhaust airflow. These load banks use the radiator’s exhaust airflow as the means to cool their resistive load elements. With this “free” cooling air, there is no need for the load bank to have its own fan/motor assembly, which leads to a more compact installation and, of course, lower costs.
For interior generator installations…
When generators are installed inside rooms, the radiator exhaust airflow is ducted to an exterior wall. A radiator-mounted load bank can fit within such installations in various ways. Below are some examples showing the load bank replacing a section of the sheet metal ducting, or inserted within the duct itself. This “plug-mount” method can be very useful in retrofit installations where the ductwork is already in place.
The limiting factor for these installations is the required capacity of the load bank vs. the size of the ducting. While the load bank’s overall height and width dimensions are custom-made to match the ducting, the depth of the load bank assembly is determined based on the number of load elements needed to meet the specified load capacity (a 400kW load bank would be deeper than a 100kW load bank). Barring an application with a very short radiator exhaust duct, size is generally not an issue unless the requirements for the load capacity exceed 1200 kilowatts.
Although not as common, the load bank assembly may also be installed on a wall’s exterior. This can be practical where there is an “exhaust plenum” between the engine room wall and the building’s exterior wall. These concealed plenum spaces are often designed to collect the radiator and engine exhaust air before they are directed upward to atmosphere.
For exterior generator installations…
When generators are installed outside, in their own sound-attenuated enclosures, there is little room to allow installation of a load bank inside the enclosure. For these applications, the load bank may be specified to be installed on the exterior of the enclosure, as shown below.
Whether the load bank assembly is indoor or outdoor, the small load bank control section may be specified to be “unit-mounted” (furnished in a NEMA 3R enclosure), or configured as a “remote unit”, for installation inside the generator enclosure or wherever convenient for the owner. As mentioned earlier, the limiting factor for this arrangement is the size of the required load bank (relative to the size of the generator).
As you can see, there are a number of mechanical arrangements available to allow the installation of a radiator-mounted load bank. As each load bank is customized for a specific project, the following information will be necessary:
- Engine drawings showing the radiator outline dimensions.
- Load bank capacity required (i.e.: kilowatt rating).
- System voltage (480Vac, 208Vac, etc).
- What are the dimensions of the duct or radiator discharge opening, if different from the radiator outline dimensions?
- What is the preferred choice for the control section, unit-mounted or remote?
A couple of final points…
- Consider the temperature rise resulting from the load bank installation. In some cases, exhaust-air hot spots can reach >500°F! Pedestrian access should be restricted if in the path of this exhaust air.
- For typical options and methods for the electrical connection of the load bank to the generator(s), please see this Technical Brief.
I hope this article was useful in illustrating how these radiator-mounted load banks can be a very practical solution for generators that require regular testing, or those that need supplemental loads to run properly. If your next project requires design support for a permanently-installed load bank, feel free to contact me to get your project moving forward!