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To check the humidifier’s operation, note the current setting and set the
Automatic Humidifier Control to the test mode when the furnace blower
motor is operating. Water will flow into the humidifier for 1 minute and
then it will turn off. This insures the unit is operating properly. Do not
leave the control in the test mode as it will not operate. Reset the control
to it’s original setting.
TABLE 3 – Outdoor-Indoor Relative Humidity
Model HUMD200A with Manual Mode:
(Automatic Humidifier Control – see pg 3)
Your new Humidifier is controlled by a humidifier control installed either in
the living area (typically near the thermostat) or in the cold air return. It is
important to anticipate a drop in outdoor temperature and reduce the setting
accordingly to avoid excessive condensation. For example, with an outdoor
temperature of 20°F the correct setting will be 35% relative humidity. If the
temperature is expected to fall to 0°F that evening, then merely reduce the
setting to 25% several hours prior to the temperature change.
The recommended settings on the humidifier control are based on years
of research (see Table 3) and experience as to what is best for the
average home. These settings represent a compromise between RH levels
that would be most desirable for comfort reasons and humidity levels that
are suitable for protection of your home. For example, a wintertime indoor
RH of 50% may be considered ideal by some, but unfortunately, it
probably would result in damage to your home. Observance of the
recommended RH levels on your humidistat, therefore, is an important
safeguard. Condensation of water on inside windows in the form of
fogging or frost is usually an indication of too high relative humidities.
This same condensation can take place in other areas in your home with
the possibility of damage resulting.
Outside Temperature Recommended RH+40°F 45%
+30°F 40%
+20°F 35%
+10°F 30%
0°F 25%
–10°F 20%
–20°F 15%
The humidistat is a precision instrument that can be used to determine
the RH accurately in your home during the winter. Turn the dial to the
lower setting, then reverse the dial direction slowly until a “click” is
heard. At this point, read the RH on the dial. This will be very close to the
actual RH in your home.