Point-Of-Use versus Central Systems for 400Hz Power/PC Air

While absolutely every project is different, there are basic principles to these two approaches that, once understood, may prove beneficial in planning your next project.

Whether POU or Central Systems, it is wise to consider an investment in systems where efficiencies in delivery of power and PC Air reduces APU usage.  The following graphs depict an average installation situation which can be used to compare the differences between central and POU 400Hz systems.

The graphs above show that POU systems have a lower initial cost until about 10 service points, but the maintenance costs are higher than that for central systems. It is also clear that the operational savings are similar up until 10 service points, and then central system 400Hz begins to become the larger cost savings system. The reason for this is that true central equipment is too large and cumbersome for the less than 10 service points, which means that maintenance and operations costs will be excessive for the capabilities and services received. There are still reasons to use central 400Hz systems on small projects. One example would be a 400 Hz system design that includes long cable runs where voltage drop is a problem. Another example would be where a designer needs to consider planning for future capabilities.

The graphs above are all based on 400Hz units. The same argument is congruent with the PC Air central systems versus POU systems, except that the numbers would be approximately doubled what is represented on these 400Hz graphs. This also means that the operational savings between the two systems would double as well.

In considering which technology would be chosen for your next project, I would strongly recommend beginning by calling a manufacturer or consultant who clearly understands both technologies and is not biased to one or the other based on manufacturing limitations or preference. There are several engineering firms who are excellent in producing cost analysis for these systems and who can also take into account other specific factors which will drive a decision between these two technologies. Because of improved competition over the last few years and other advancements in the central system technologies, I invite you to consider this article as a starting point as you consider either solution. The only wrong solution is to run the aircraft’s APU which costs a lot more than investing in electric power and air.

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