One of the problems that affect many houses is mould caused by condensation forming on the windows. This can affect bedrooms where the humidity level increases during the night due to the exhaustion of moist air and the window temperature decreasing during the night.
Last year I bought a dehumidifier to decrease the humidity levels at night but found that I was waking up with a dry mouth and headache.
After setting up a monitoring station to collect the necessary data I found that the dehumidifier was reducing the humidity levels well below what was necessary to stop condensation forming on the window. What was needed was a dehumidifier that used the window temperature and humidity to calculate the point at which condensation would form on the window and keep the humidity level slightly lower than that point. The point at which moist is release from the air is called the dew point and can be calculated using temperature and humidity.
This instructable details how to modify a dehumidifier so it keeps the dew point just slightly above the window temperature, stopping condensation form on windows and keeping mould at bay.
Step 1: Disassemble Dehumidifier
Start by removing screws from the base of Dehumidifier
Remove Filter Covers
Remove the screw behind the water tray and split the case in half
Step 2: Remove Vent Cover
Remove Vent Caps and Foam filters
Split the case into the two halves
Step 3: Remove Heat Exchanger
Remove the two screws and the Heat Exchanger
Disconnect the PCB and remove the Fan and PCB
Step 4: Drill Out Hole for Sensor
Drill the exisiting hole out to 8mm to the deep of 5mm
Drill all the way through the shell with a 3mm drill in the center of the 8mm hole.
Step 5: Fit the New Fan
Step 6: Fit New Fan and PCB
Fit the new smart PCB with the sensor through the hole drilled out in a previous step
Build details here Github link for PCB
Refit the heat exchanger and connect the PCB up, install the HTU21D humidity sensor board in the intake channel and connect to PCB.
Step 8: Reassemble the Two Halves of the Shell
Reassemble both halves back together and the dehumidifier is now ready for use, make sure that the window temperature sensor hole is facing the centre of the window pane.
Below shows that the dehumidifier keeps the dew point just above the temperature of the window.
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