Aprilaire 1750A - Mechanical Installation; Duct Collars & Backflow Damper; General Ductwork Recommendations

FIGURE 3 – Install Damper in Collar
90-1503
FIGURE 4 – Install Collar with Damper on Outlet
90-1503
FIGURE 5 – Minimum Ductwork Bend Distance
90-1503
DUCT COLLARS & BACKFLOW DAMPER
The backflow damper installs on the outlet side of the dehumidifier, using features molded
into the duct collar.
1. Remove the duct collars and backflow damper from the inner pack.
2. Place the backflow damper in the collar with the damper pivot shaft resting in the slot in
the collar (see Figure 3).
3. Position the collar and damper with damper pivot shaft up and install on the outlet panel
using four #8 x 1” field supplied sheet metal screws (see Figure 4). The collar should sit
flush on the outlet panel and secure the backflow damper.
4. Verify that the damper swings freely by lifting up on the damper and allowing it to
swing closed.
5. Make sure there are no bends in the ductwork coming off the outlet for a minimum of 4”.
This will ensure that the ductwork will not interfere with backflow damper function
(see Figure 5).
MECHANICAL INSTALLATION
INLET
OUTLET
4" MIN.
BACKFLOW
DAMPER
CAUTION
Only install
damper on outlet.
Dehumidifier will
not function if
damper is installed
on inlet.
GENERAL DUCTWORK RECOMMENDATIONS
•WhenductedtotheHVACsupply,theoutletfromthedehumidifier
must be located at least 6” downstream of the cooling coil to
prevent outlet air from pulling moisture from the coil.
•Tominimizesoundfromairmovementandvibration,install5feet
minimum of flex duct on the inlet and outlet of the dehumidifier.
•Usetheleastamountofductworkpossible.ULapproved,insulated
duct is recommended for all connections.
•Useinsulatedductforventilation.
TABLE 2 – Maximum Duct Lengths
1750A 1770A
CFM 250 500
External Static Pressure 0.6”w.c. 0.9”w.c.
Amount of Ducting 8” dia., 70 ft. 10” dia., 350 ft.
Notes:
1. Duct length totals include both inlet and outlet sides.
2. Elbows, turns, and the static pressure of the HVAC equipment
will affect the airflow through the dehumidifier.
3. Maximum duct length recommendation assumes 0.2” w.c.
pressure increase due to filter loading. Maintenance of filter is
important to maintain airflow.
4. Ductwork to be installed in accordance with SMACNA Standards.
5. Duct size recommendations based on maximum velocity of 900
FPM inside of duct.
5