from Andy in Madison, WI:
#242
I've heard that VSD (variable speed drive) air compressors are efficient. Should I add a second VSD compressor to my system when my compressed air needs expand next summer?
No, keep your existing and get another non-VSD base-load.
Great question! The short answer is no. You should keep your existing VSD air compressor online as your trim compressor and get another base-load compressor with simple non-VSD controls to meet your increased demand.
Now for the long answer: The benefit of a variable speed drive (VSD) air compressor is that the controls are able to precisely modulate the compressor's output to match your facility's demand for compressed air. Compressor systems with non-VSD controls such as load/no-load and inlet dampers don't have the ability to vary output with such precision.
Some attempted analogies: Load/no-load controls are like driving your car by starting the engine and putting the gas pedal on the floor, then turning the engine off when you start going too fast. Inlet dampers are kind of like driving your car by putting the gas pedal on the floor and modulating the car's speed by applying the brakes. Both of these techniques are less efficient than controlling the car's speed by continuously modulating the gas pedal. So, why not install two VSD compressors on the same compressed air system? Well, it's a little like putting two gas pedals in your car when one will do the job. If you need more compressed air capacity, get another base-load compressor with standard load/no-load or other simple controls to make up the difference. Or, back to the automotive analogy, if you need more power, you would get a bigger engine or a bigger truck, not another gas pedal.