Efficiency Information for Compressed Air Systems
The following list provides details about what to look for in different types of systems for energy efficiency and Efficiency Vermont standard rebate eligibility.
Variable Frequency Drive Screw Compressors
A variable frequency drive (VFD) modulates compressor output by increasing or decreasing the rotating speed of the motor in response to a signal from the pressure sensor. VFD controls are the most efficient way to control screw compressors with variable loads below 90%.
- 10-40 horsepower (HP) compressors only are eligible for Efficiency Vermont standard rebates. (Please contact Efficiency Vermont for information on custom rebates available for larger compressors.)
- Compressors typically loaded at 90% or higher do not benefit from VFD controls.
Air Receiver Tanks for Load/No-load Screw Compressors
An air receiver tank is a pressurized vessel that stores compressed air and acts as a buffer between the compressed air system’s demand side (end users) and supply side (compressors).
- Compressors must be equipped with load/no-load controls for the system to qualify for Efficiency Vermont standard rebates.
- Rebates are based on compressor horsepower and corresponding minimum air receiver tank size (in gallons) as noted on the rebate form.
- Air receiver tanks must meet or exceed the minimum tank size for the system to qualify for Efficiency Vermont standard rebates.
- Both new and retrofit air receiver tanks are eligible for Efficiency Vermont standard rebates.
- Modulating control compressors can often be made to work as Load/No-load, and adding sufficient storage improves efficiency and is eligible for rebates.
Cycling Refrigerated Thermal Mass Dryers
A dryer removes moisture, in the form of condensate, from the compressed air, maintaining the quality of the compressed air and helping to prevent end-use issues. Refrigerated dryers cool compressed air so that the moisture condenses and precipitates out. Cycling refrigerated dryers are the most efficient option—more efficient than standard refrigerated dryers—turning on and off in response to demand rather than operating continuously.
- Dryers with up to 300 CFM capacity only are eligible for Efficiency Vermont standard rebates.
No-Loss Drains
No-loss drains allow condensate to be expelled from compressed air systems, with no associated loss of compressed air. They are usually installed at the compressor, air dryer, filter, storage tank, and at any point in the piping where moisture might collect. No-loss drains open a valve only when signaled by the condensate level control, making the no-loss drain a more efficient option. The alternative, timed drains, use a timer which is usually set to drain the worst case condensation condition and therefore often release valuable compressed air along with condensate.
- Timed drains are not eligible for Efficiency Vermont rebates.
Air-Entraining Air Nozzles
Both handheld and fixed air nozzles use compressed air to clean or dry things. In comparison, an air-entraining air nozzle uses less compressed air to do the same work by grabbing or entraining surrounding atmospheric air, making it a more efficient option.
- Nozzles exceeding 14 CFM at 100 psi do not qualify for Efficiency Vermont standard rebates, but may be eligible for custom rebates.
- Nozzles must be listed on Efficiency Vermont’s Compressed Air Eligible Products List to qualify for rebates.