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TABLE 3 – Outdoor-Indoor Relative Humidity
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Manual Mode: (Automatic Mode – see pg 4)
Your Aprilaire Humidifier is controlled by a Humidifier Control installed
either in the living area 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°
the correct setting will be 35% relative humidity. If the temperature is
expected to fall to 0° 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 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 for comfort, but unfortunately, it probably would
result in damage to your home. Observance of the recommended RH
levels on your Humidifier Control, therefore, is an important safeguard.
Condensation of water on inside windows in the form of fogging or frost
is usually an indication of too much relative humidity. 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%
If you would like to determine the RH in your home, follow these steps:
1. Activate the furnace blower by setting your thermostat to a higher
temperature.
2. Turn the control dial setting to the “Off” position. Then, slowly turn the
dial clockwise until you hear the solenoid valve”click on”. Next, slowly
turn the dial counter clockwise until you hear the solenoid valve “click
off”. This is the relative humidity in your home under existing
conditions.
3. Return the thermostat and the Humidifier Control to their original
settings.