Damper Type Selection
There are two basic types of dampers available in mass today. Although, there are other damper types such a “balloon” type and pneumatic controlled dampers (used more commonly on DDC systems not included), for this context we will discuss these two main types of dampers:
- Spring Open or Close (Spring Damper)
Power Open & Power Close (Power Damper)
Power Open /Power Close dampers use three wires to either power open or power close. They zone panel is responsible for supplying a 24VAC signal to either the PO (Power Open) or PC (Power Closed) terminal of these dampers. This type of damper was traditionally reserved for “higher-end” or commercial applications because of the cost. In recent years, however, motor prices have decreased and power dampers have become much more affordable (often no more expensive than the spring equivalent especially when labor and reliability are factored in.) Primary advantages of Power Dampers include lower power consumption, quiet operation and more reliable parts. Given the choice, Power Dampers, are almost always preferable. The only exception to this is when code requires Spring Dampers.
The way Spring Dampers work is they have a motor that, when energized by the zoning panel, it closes the damper. When the damper is ready to open, the motor stops powering the damper closed and a spring opens the damper blade back up. Spring Dampers have been used in an “economy” application for many years. The two primary advantages of a Spring Damper are: 1. If the system loses power they “fail” open… but if the system loses power, the equipment isn’t going to be running either and therefore will not matter in MOST cases. 2. They only require two wires for operation. One of the negative arguments against Spring Dampers has historically been reliability. This mostly a result of one of its benefits… the cost. The inherent lifecycle of any spring actuated mechanism (even if it is in the millions) is less reliable than a system that doesn’t include this potential failure point. In addition to this, the motor that is used has to be a very specific model that allows for running backwards without damage yet still has to be powerful enough to overcome the spring trying to pull the blade in the opposite direction. This leads to probably the BIGGEST downfall of using a Spring Damper - the power consumption. Most Spring Dampers on the market use 3 to 4 times the power of the equivalent Power Damper (10-12 VA vs. 2-3VA). This could be the difference in using a standard sized transformer and having to go to a very large (and expensive) over-sized transformer. In summary: spring dampers are NOT recommended unless absolutely necessary for some reason.