Sunlu Dryer Set and Forget Modification

This works well. The relays contacts are isolated, the contacts are wired in series so that both High RH% and low temp are required for the heater to be energized. The sensor fits under the heater.

There is about 3% RH and 3C hysteresis in the system because if it's mass.

This stops wasted energy the heater is only on when the RH% is high and the temp low. It is set and forget, not requiring the constant pushing of buttons to keep the heater energized.

When I set for 15%RH the heater is on a high percentage of time and hits the 50C max often.
When I set for 20%RH the heater is mostly off and does not go above 40C

If there is interest I will make pictures of the the modifications on the next Sunlu box I modify.

I made a replacement plate for the front of the Sunlu (below). It is notched to allow the wires to pass to the controller. The plate of the controller should also be notched to allow the wires to pass out the back and through my plate. The overlap should hide the wires when the controller is glued on using the same glue sheet used to glue glass to a flexplate..

I have settled on good values. I set the RH% to 15% and the Max temp to 47C. The overshoot will bring the initial temp up to 51C when a roll is initially put in the Sunlu. After a day the actual RH settles in at about 20% and the temp goes from 35C to 40C. This is big energy saver and small increases in %RH yield much lower temperatures after the roll RH has stabilized.

The second type of controller is the XK-W1099-24v (picture below).. This has simpler programming and functions. Perfect for the Sunlu, but the relay outputs are not isolated. Two PCB cuts (shown in red circles) and one PCB jumper (yellow) are required to convert the board. The input 24v is the center two wires (red and black) the output is the outside tow wires ((yellow and black).

The XK-W1099-24v uses 12v relays and so runs hotter than the ZFX-ST3022-24v. The does not show the overshoots in temp and RH that the ZFX-ST3022-24v does. I prefer the XK-W1099-24v. Either make life much simpler. It is interesting that the RH% has the capability to go lower when printing and the roll is rotating.