Interpretation #7458
Published March 18, 2015
Original Request
- Code Version
- 2007
- Code
- BUILDING
- Code Description
- Building
- Chapter
- 13
- Section
- 503.2.9.1
- Topic
- Discharge dampers
Question
This question is in regard to the 2010 Florida Energy Efficiency Volume, Section 503.2.9.1. The selection for the referenced code doesn't list this particular code. Does the note at the end of the section which states "Discharge dampers are prohibited on constant volume fans and variable volume fans with motors 10 horsepower and larger" prohibit the use of larger multi-zone air handling units that many times have motors exceeding 10hp?
Answer Published 03/18/2015 at 8:46 AM
Maybe, please see the attached commentary.
Commentary
Traditionally, there were three time-honored ways to
control VAV systems: discharge dampers, inlet vanes and
variable frequency drives (VFD's).
The reliability and low cost of VFD's has virtually made
discharge dampers and inlet vanes obsolete. The use of a
discharge damper to balance a non-VAV air handler or a VAV
air handler is a very inefficient way to accomplish the
task. It is the intent of this paragraph to prohibit such
an installation.
Any multizone unit that exists and continues to be in use
may remain. If a new mutizone unit, as described (if they
are even available any more) is installed, the use of
discharge dampers would be prohibited, unless a device
(such as a VFD) is also introduced so as to provide an
efficient balancing mechanism.