*Velocity in feet per minute = Duct airflow volume in cubic feet per minute / duct area in square feet.
Example: 1,200 cfm through 16” x 12” duct = 1,200/(12 x 16/144 sq. in./sq ft.) = 1,200/1.333 = 900 fpm
TABLE 3 – Absorption Distance (Minimum distance from dispersion tube downstream to any obstruction or bend in duct)
Humidifier
Output (gal/day)
Airflow Velocity*
70°F & 30% RH
Setpoint
70°F & 45% RH
Setpoint
65°F & 45% RH
Setpoint
45°F & 45% RH
Setpoint
Up to 16.0
300 fpm 13” 19” 23” 30”
600 fpm 6” 10” 12” 18”
1200 fpm 3” 5” 6” 13”
1800 fpm 2” 3” 4” 10”
20.5 – 25.0
300 fpm 15” 23” 28” 45”
600 fpm 6” 12” 13” 26”
1200 fpm 5” 6” 7” 19”
1800 fpm 3” 4” 5” 16”
25.0 – 35.0
300 fpm 24” 31” 36” 60”
600 fpm 17” 22” 26” 48”
1200 fpm 12” 15” 18” 25”
1800 fpm 10” 13” 15” 20”
INSTALLATION INSTRUCTIONS (CONTINUED)
Elevation
The preferred location for the dispersion tube is higher than the
humidifier so that the steam hose has a constant downward
slope of at least 2” per foot from the dispersion tube to the
humidifier. If hard pipe is used, the slope can be 1/4” per foot.
With the constant downward slope, any condensation that forms
in the steam hose will drain back into the steam canister. See
Figure 3.
FIGURE 3 – Dispersion Tube Mounted Above Humidifier
90-1521
90° long sweep
or two 45° elbows
Pitch*
Duct
Dispersion tube
Steam hose or pipe.
Insulate pipe with 1” fiberglass
to reduce steam loss.
* Pitch steam hose down from
dispersion tube to humidifier:
2"/ft (15%) minimum when
using steam hose.
1/4"/ft when using hard pipe.
7
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