I purchased the SUNLU filament dryer and quickly discovered various problems.

1. When set to dry 70C, it would never reach the setpoint. The heaters stayed constantly on and the temperature reached a maximum of 68C 

2. I found that I had to open the SUNLU S2 occasionally to release moisture.

3. The SUNLU fan in the base of the unit is very noisy

Fixes to above.

1. I 3D printed an ABS panel that clips into the S2's rear wall. Behind this wall is some 1.5mm foam recovered from an insulated envelope. This reduced the temperature on the external wall by 10C. This reduction in heat lost allows the S2 to quickly reach the maximum 70C setpoint.

2. I added a type 4010 24volt fan. This fan has a split fan duct added. Approximately 8-10% of the fan air is directed outside the S2 to eject the moisture, the remaining fan air is used to help circulate the air inside the S2. The fan is connected to the lower heater element. So it cycles on and off with the heater power.

3. I unscrewed this SUNLU fan, I than sat the fan onto some Silicon Rubber, which when set held the fan in place, the fan noise is eliminated.