Delonghi CF80E dehumidifier modification

[blackalex1952]

For those who have the electronic version of the Delonghi CF80E here is a simple mod I have worked out.The problem is that these units use electronic control for the functions. The supposed lowest setting is 50% RH. The humidity sensor is located at the exit point for the dry air from the machine and is not an indicator of the humidity in the space being dehumidified. The electronics are operated by momentary on switches which trigger the circuitry to switch relays within the control board which operates the machine.
So I want to switch the machine using an external humidity controller, with its sensor mounted at the opposite end of my dehumidification space-in my case, an underbench cupboard.
I have previously achieved 40% RH even on the 50% setting-it's just not that accurate, in fact it has gone to an unacceptable low level without constant supervision. The problem with these machines is that the external switch cannot operate on the input 240V supply because the unit switches itself off when power cuts and the momentary on switch on the front panel of the CF80E has to be actuated to get the whole thing to start again.
However, there is a microswitch in the water collecting tray that is activated when the tray is empty and switches the machine off when the tray is full. When a full tray is removed emptied and replaced, the machine starts up again without the on switch having to be reset.
The solution was simple! Bypass the water tray by installing an external drain hose(in my case, it goes thru a pipe thru a hole in the floor, under the building and out thru an external wall. The pipe has a wire strainer to prevent wasps from bogging it up-heaps of them here!) That means that the microswitch switch is permanently on because the water tray sits in the machine and never fills up with water. Then, connect the relay in the external humidity controller in series with the microswitch. I intend to put a switched connector socket on the side of the machine to connect the external switching to. When the external connector plug is removed, the unit returns to running on the water tank level microswitch. The switching voltage on the microswitch is 5V DC.That way, the machine can be run as a household dehumidifier as well should I need it by blocking off the drain hole and returning to water tray mode.See photos for where to connect.

[blackalex1952]

The humidity sensor is located at the exit point for the dry air from the machine and is not an indicator of the humidity in the space being dehumidified.

CORRECTION! The sensor is located on the air inflow side of the dehumidifier and measures the air going in of course. However it's not very accurate and so a higher quality external sensor will be better. I have modded the machine and placed a socket on the front panel, the kind used for 9v input to guitar pedals as I have heaps of them. If the system doesn't work all that well when the controller arrives in the mail, it will be due to the internal humidity sensor cutting the machine off before the target RH on the external controller. In which case, I will post how to bypass the internal humidity sensor.Hopefully the external sensor and switch will respond more accurately-Ross

[blackalex1952]

Here is an update on the project-this modification is simple and is working well using the ebay humidity control switch. Now all I need to do is source a small quantity of potassium carbonate salts for a budget price to calibrate all my hygrometers, which read all over the place! I just picked up an old Abbeon hygrometer, but it's reading 60% when the others read around 50%. So the project continues. In the meantime I'm forging ahead with a body assembly and guestimating....yeah, should be ok! Ross