Ventilation fans with continously variable speed operation are becoming more important and more available all over the world. In the last 15 or so years the EC Motor or ECM has emerged as the defacto standard for nearly all HVAC systems, refrigeration pumps and water pumps. This is especially true for new industrial and commercial buildings that use computer based systems such as building control systems (BCS) or building automation and control systems ( BAC) or building management systems (BMS).
These new computer based systems all have one thing in common - they communicate with all fans, pumps and other motors by a two way communication protocol that includes an output to command the motor speed using a DC voltage from 0 to 10 VDC (0 is off, 10 is highest speed) and speed or RPM feedback as an output back to the computer. In this way new construction can be automated for the optimum power and performance needed for every motor based system.
There are very few sources for truly variable speed fans. In fact, there are just 9 companies presently listed on http://www.VariableSpeedFanGuy.com. You will find that the HVAC motors are not listed there because so far HVAC motors are typically a fixed number of speeds, usually 4. Only fans with the ability to control an infinite number of speeds between low and high speed are listed.
Here are 3 of the companies highlighted on the web site:
Invisco Variable Speed Fan Company's inventor, Kurt Shafer, used the advent of DC voltage control capability to create the first automatic speed control for whole house fans. SmartSpeed(TM) automatically runs the fan at high speed when the room temperature is over 85 degrees F and as the temperature falls below 85 the speed is reduced until the fan is off at 70 degrees. The control has a manual speed option for those times in the winter when you burn your toast.
Greenheck Fan Corporation has the largest selection of variable speed fans for commercial and industrial use in the world. Their Vari-Green(tm) motors are designed for energy-efficiency, controllability and low maintenance.
Xpower in California just introduced their first infinitely adjustable speed fan in a stackable design meant for water mitigation and general ventilation, the X-41ATR with 3600 CFM capacity.
There are several more sources that will be added to the web site.
For more information go to http://www.invisco.com or call Kurt Shafer at the number on that web site or email him at smpr@invisco.com