Energy efficient building air compressors

[charles turman]

I work for the federal Government (General Services Administration) my primmary job is replacement of older Mechanical, electrical and life safety equipment in our buildings most of these buildings are over 40 years old. I have been tasked with finding the most energy efficient building control air compressors for the pneumatic HVAC systems. Most of these old compressors are reciprocating air compressors. Has anyone done and evaluation on Rotary Screw or other types of compressors? most of our compressors are 1 1/2 hp - 5 hp

[Rick Collins]

I have some experience with large compressors. We have nothing but rotary screw compressors where I work, but I have some experience with centrifugal & recips. Rotary screws are fairly reliable and in the size you mention, you should be able to find oilless (sp.) type. I assume low pressure, high volume (which is the opposite of my experience). Maintenance on rotary screws are quite a bit less expensive and labor intensive than recips.

The "most energy efficient" types are VFD controlled units, especially if you have variable loads. I am just not that familiar with what is available for the size you mention. There are quite a few compressor manufacturers out there who should have something, such as Ingersol-Rand, Gardner-Denver, Atlas-Copco, Sullair, Kaiser, etc.

I have learned that for fixed speed applications, two-stage rotary screws are not always as efficient as single-stage units. It really depends upon where the "sweet spot" is located. As for building controls it may be a completely different animal than I know.