CHooSInG a loCaTIon
DISPeRSIon TUbe
When choosing a location for the dispersion tube three things must be considered: Location in duct, elevation with respect to the humidifier, and
distance from humidifier to dispersion tube.
Duct location
The preferred location for the dispersion tube is in a supply duct because higher temperature air will more readily absorb the moisture. Whether
installed in a supply or return, the dispersion tube must be in a straight section of duct to avoid turbulent air and must be far enough upstream
of any obstruction or bends in the duct to allow the steam to be fully absorbed to prevent condensation. The exact distance from obstructions in
the duct depends on air temperature, RH set point, and airflow velocity in the duct. Table 2 provides absorption distance for typical conditions.
The higher the RH setting, the longer the absorption distance. Warmer air shortens the absorption distance. If absorption distance is a concern,
install dispersion tube in supply duct and configure humidifier and control to operate only during HVAC system heat call. Call Aprilaire Tech
Support at 1-800-334-6011 for additional information on absorption.
The dispersion tube must be mounted on a vertical surface with the tube angled up.
If the dispersion tube is mounted on insulated ductwork, make sure insulation is not more than 2” thick at tube location to prevent insulation
from blocking first steam outlet.
InSTallaTIon InSTRUCTIonSTable 2 – absorption Distance (Minimum distance from dispersion tube downstream to any obstruction or bend in duct)
Input
Power Humidifier
output airflow Velocity 70°f & 30% RH
Setpoint 70°f & 45% RH
Setpoint 65°f & 45% RH
Setpoint
120 V 11.5 gal/day
300 fpm 7" 11" 13"
600 fpm 3" 6" 7"
1200 fpm 2" 3" 3"
1800 fpm < 2" 2" 2"
208 V 20.5 gal/day
300 fpm 13" 19" 23"
600 fpm 6" 10" 12"
1200 fpm 3" 5" 6"
1800 fpm 2" 3" 4"
240 V 23.3 gal/day
300 fpm 15" 23" 28"
600 fpm 6" 12" 13"
1200 fpm 5" 6" 7"
1800 fpm 3" 4" 5"
5