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 and absorption Distance
The preferred location for the dispersion tube is in a supply duct because higher temperature air will absorb moisture more readily . The
dispersion tube must be in a straight section of duct far enough upstream of any obstruction or bends in the duct to allow the steam to be fully
absorbed, preventing condensation in the duct . The exact distance from obstructions in the duct depends on air temperature, RH set point, and
airflow velocity in the duct . Most installations can use an absorption distance between 24 and 36 inches, however if there are obstructions in
the ductwork use
Table 3
to determine the appropriate absorption distance .
Size absorption distance based on the lowest temperature,
lowest air velocity and highest humidity that the system will see.
When installing the humidifier in a system with variable speed blower,
determine absorption distance based on airflow at the lowest speed . Operation during AC calls is not recommended because of the potential for
condensation in the ductwork . If humidifier operation is needed during AC operation, make sure absorption distance is adequate . If absorption
distance is insufficient, configure controls to lock out humidifier during the AC calls and use the blower activation feature to allow the humidifier
to run with the blower only . Call Aprilaire Tech Support at 1-800-334-6011 for additional information on absorption .
The dispersion tube must be mounted with the plate on a vertical surface with the tube angled up as shown in
figure 3
. The steam outlets must
face up regardless of the airflow direction in the duct . The plate is labeled “UP”to indicate proper orientation . On horizontal duct runs install the
dispersion tube low in the duct, on vertical runs center the tube on the duct .
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 .
note:
If two dispersion tubes are installed in one duct, double the dispersion distances . If three dispersion tubes are installed, triple the
dispersion distance . Position dispersion tubes so one does not discharge directly onto another .
InSTallaTIon InSTRUCTIonS
CaUTIon
Each humidifier requires its own steam hose and dispersion tube. Do not connect steam hoses from more than one humidifier
together. Back-pressure from one humidifier can lower the water level in the canister in the other humidifier and cause
operational problems.
Do not install the dispersion tube in a duct with greater than 2 in. wg static pressure. High duct pressure can cause back-
pressure in the canister which can result in unstable unit operation.
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