Zoning System Design Manual
For retrofit applications, first you have to ensure that the duct system is adequate for room/zone loads, and that
the existing HVAC system is properly sized to deliver heat/cool. After that, planning the zone system is very similar
to new construction.
Rigid Duct, Rectangular Sheet Metal Duct, Knockdown (KD) Duct
Using a retrofit round damper (RRD) significantly reduces
labor—it installs in a fraction of the time—and overall system
installation cost. A retrofit damper slides into rigid round pipe
for quick installation.
Honeywell offers dampers for rigid round duct in 5-, 6-, 7-, and
8-in. diameters. Multiple RRD dampers may be wired in parallel.
Fig. 8. Installing retrofit round damper.
For retrofit applications in flex duct, use round ARD dampers. The round ARD is a galvanized steel single blade
damper with a low-leakage gasket, and comes in a range of sizes from 5–20 in. You can use multiple ARDs on any
duct—just wire them in parallel.
The existing thermostat can often be used for one zone, but as it might be difficult to run wires to the other zones,
Honeywell wireless thermostats can be used.