Manual Versus Automatic Humidistat
The indoor humidity level needs to be set based on the outside temperature. This is to prevent water from running down the windows. The cool air near the windows can not hold the humidity and water will condense on the glass. To prevent this condensation, the indoor humidity level is sacrificed by lowering the humidistat.
An automatic humidistat (Aprilaire 60) adjusts the humidity by using an outside temperature sensor.
The Aprilaire manual humidistat as used in earlier Aprilaire humidifiers (Model 4655) requires adjusting the relative humidity based on the outside temperature. A manual humidistat needs to be set back as the season gets colder. The chart below shows the humidity setting for a range of outside temperatures.
When The Outdoor
Temperature is | This Relative Humidity
Should Be Maintained |
+40°F | 45% |
+30° | 40% |
+20° | 35% |
+10° | 30% |
0° | 25% |
-10° | 20% |
-20° | 15% |
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